NSCP-2001.pdf

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NATIONAL STRUCTURAL CODE OF THE

PHILIPPINES 2001

VOLUME 1 BUILDINGS, TOWERS, AND OTHER VERTICAL STRUCTURES FIFTH EDITION

Telephone No. (+632) 411-8603, Tele/fax No. (+632) 411-8606 Emall: [email protected] Website: http://www.aseponline.org

••

F.OREWORD

For the protection of public life and property, the design of structures and the preparation of structural plans for their construction have to be controlled and regulated. For almost three decades now, this control has been exercised in this country by the National Structural Code ofthe Philippines with the initial publication by the ASEP of the National Structural Code for Buildings. The current publication of the 5th Edition of NSCP C101-01 for buildings and other vertical structures is the affirmation of the mandate of the ASEP to continuously update the National Structural Code of the Philippines with the latest technological developments. While attaining a legal status in its use as a referral code of the National Building Code, NSCP CI01-01 is a publication of high technical value in matters of structural concerns. The NSCP CI01-01 is not only completely new in its technical substance but also in its format. It has been a product of a sustained effort of ASEP spanning five years and the fruition of this endeavor has finally come to reality during my incumbency. It is therefore with a deep feeling of gratitude and pride that I commend the members of both the ASEP Codes and Publications Committees for their accomplishments. October 200 L

ROMEO A. ESTANERO, PhD, 1<'.ASEP, .'..PICE

President

Association of Structural Engineers of the Philippines 2001-2002

1

~1

l

Association of structural Engineers of the Philippines

/I

NATIONAL STRUCTURAL CODE OF THE PHILIPPINES (NSCP) CIO-Ol

Volume 1 Buildings, Towers, and Other Vertifal Structures Fifth Edition, 2001

Copyright @ 2001, The Association ofStructural Engineers ofthe Philippines, Inc. (ASEP)

All rights reserved. This publication or any part thereof must not be reproduced in any form without the written permission

or the Association Structural Engineers of the Philippines, Inc. (ASEP).

PUBLISHER Assodation of Structural Engineers of the Philippines, Ine. (ASEP) Suite 713 Future Point Plaza Condominium

112 Panay Avenue, Quezon City,

1100 Philippines

Telephone Nos, Facsimile No. E~mail address Website

(+632) 411-8603, (+632) 411-8606

(+632) 411-8606

: [email protected]

: http://.~,J~§.~P.Qruin~,.Q[g

The Association ofStrudllral Engineers of the Philippines. Inc:. (ASEP) is a professional

Association founded in September 1961 to represent the structural engineering community

nationwide. This document is published in keeping the association's objectives;

a.) b.) c.)

Maintenance of high ethical and professional standards in the practice of structural engineering;

Advancement of structural engineering knowledge; and

Promotion of good public and private clientele relationship,

Fellowship among structural engineers, and professional relations with other allied technical and scientific organizations.

Print History

First Edition, 1992 Second Edition, 1981 Third Edition, 1986 Fourth Edition, 1992 Fifth Edition, 2001

National Structural Code of the Philippines, Volume 1

III

PREFACE TO THE FIFTH EDITION

Ten (10) years have elapsed since the Fourth Edition has been published and it was deemed necessary to revise the Nationl Structural Code of tbe PbBippines (NSCP) to reflect the continuing rapid technological advances in structural engineering design and the latest seismic design practice for earthquake resistant structures. Tbe Fifth Edition has the following significant revisions. In Cbapter 1, General Design Requirements, major changes in this section include provisions where building owners are required to get the services of independent recognized structural engineers to perform design review for certain structures, and the installation of recording accelographs for every building over six stories (with floor area of S,SOOsq.m. or more), and every building over ten stories in height regardless offloor area. In Cbapter 2, Minimum Design Loads, revisions of load combinations were made to adopt the new strength-based seismic forces, and special load combinations to reflect the provisions of the 1997 Uniform Building Code (UBC). Near-source factors are specified in seismic zone 4 to recognize the amplified ground motions that occur close to known active faults. The Philippine Institute of Volcanology and Seismology (PHlVOLCS) is~ued the maps showing the active faults throughout the country as reference for determining near-source factors. Also, basic wind speeds are revised based on statistical studies and recommendations of the sub-committee on Design Loads and Lateral Forces and on the Electronic Industries Association (EIA) I Telecommunications Industry Association (TIA) 22E provisions. Cbapter 4, Structural Concrete, includes significant changes in several aspects of reinforced concrete design. Shear-governed concrete walls are designed for increased forces and special detailing requirements are clarified and improved, many of which reflect changes in American Concrete Institute (ACI318-99). Cbapter 5, Steel, recommendations to adopt AlSC's 1997 Edition of the Seismic Provisions for Structural Steel Buildings (AISC-Seismic '97) incorporates on-going development of seismic design and much of the current knowledge on design and quality assurance following intensive research and testing in the U.S. Significant issues associated with. moment frames and AlSC's Seismic Provisions are also addressed. Likewise, important issues and cdnsiderations on braced frames, eccentric brace frames, and truss moment frames following much research ahd development in recent years are also discussed. This publication of the Fifth Edition of the NSCP is a collective effort of the ASEP Board of Directors from 1997 to 2001 from ASEP's past presidents Engr. Nicanor M. Mayoralgo (1997-1998), Dr. Benito M. Pacbeco (/998-1999), Engr. Emilio Daniel G. Tible m (1999-2000), Engr. Alberto C. Caiiete (2000-2001), the current president Dr. Romeo A. Estaiiero, (2001-2002), the ASEP Codes Committee, without whose cooperation this publication wouldnet..1tave.been possible. The ASEP Codes Committee is indebted to all ASEP members and other users of the NSCP who have suggested improvements, identified errors, and recommended items for inclusion or omission. These suggestions have been carefully considered. Users of this Code are urged to communicate with the ASEP Codes Committee regarding all aspects ofthis publication for improvement.

Man

'ng Director

Co(es Committee (2001-2002)

Nationat Structural Code of the Philippines, Volume 1

Iv

Association of Structural Engineers of the Philippines, Inc.

National Structural Code Committee BENITO M. PACHECO, PhD Executive Chairman 1998-1999

NICANOR M. MAYORALGO Executive Chairman 1997-1998 ALBERTO C. CANETE Executive Chairman 2000-2001

EMILIO DANIEL G. TIBLE m Executive Chairman 1999-2000

ROMEO A. ESTANERO, PhD Executive Chairman 2001-2002

CODES COMMITTEE (1997-2002)

Anthony Vladimir C. Pimentel Managing Director, 2001-2002

Rico P. Gomez Assistant Managing Director, 2001-2002

GENERAL REQUIREMENTS

DESIGN LOADS AND LATERAL FORCES

Emilio Daniel G. nble HI (Chairman)

Dr. Benito M. Pacheco

(Chairman)

Angelico D. Andamon

Arman S. Rivera

Norman Daniel V. TibJe

(Members)

Silvestre M. Berso

Ronaldo S. bon

Carlos M. ViUaraza

(Members)

EXCAVATIONS & FOUNDATIONS

STRUCTURAL CONCRETE

Dr. Benjamin R. Buensuceso, Jr.

(Chairman)

Alfredo B. Juinio, Jr. Ulpiano P. Ignacio, Jr. (Co-Chairmen)

Dr. Salvador F. Reyes, Jr.

Dr. Alexis A. Acacio

Jorge P. Genota

(Members)

Dr. Romeo A. Estaiiero

Jorge P. Genota

Joseph Ramil I. Manalo

Anthony Vladimir C. Pimentel

(Members)

STEEL

WOOD

Romer S. Montoya

Adam C. Abinales

(Co-Chairmen)

Roberto P. Bernardo

(Chairman)

Dr. Romeo A. Estaiiero

Edna Grace A. Abinales

Artemio C. Bautista, Jr.

Rico P. Gomez

Ma. Teresa M. Montes

(Members)

Dr. Joaquin Siopongco Joseph Ramil L Manalo Renato R. Aguilar (Members)

MASONRY Eduardo C. Arrojado (Chairman) Edna P. Arrojado

Raynante S. Deapera

Ronaldo. S. bon

Anthony Vladimir C. Pimentel

(Members)

Association of Structural Engineers of the Philippines

v

ASEP

OFFICERS and DIRECTORS

2001-2002

ROMEO A ESTANERO, Ph. D Presitknt ADAM C. ABINALES Vice-President

MIRIAM LUSICA-TAMAYO Secretary RONALDO S. ISON Treasurer

RICO P. GOMEZ Director CESAR C. PABALAN Director JORGE P. GENOTA Director ROLEZA JEAN V. MARZAN Director JOSEPH RAMIL L MANALO Director ANTHONY VLADIMIR C. PIMENTEL Director

ALBERTO C. CANETE Immediate Past President


VI

TABLE OF CONTENTS

Chapter 1 GENERAL REQUIREMENTS 101102 103 104 105 -

Title, Pwpose and Scope ........ .... ....... Definitions ............................................ Classification of Buildings ................. Design Requirements ...... ........ ..... ........ Posting and Instrumentation ...............

1-1 1-2 1-3 1-4 1-6

106- Specifications, Drawings, and

Calculations ......... .............. ....... .... ..... 107- Structural Inspections and Tests ....... 108- Existing Structures .............. :.:............ 109 - Grading and Earthwork ... .................... /

1-6

1-8

1-13

1-14

Chapter 2 MINIMUM DESIGN LOADS AND LATERAL FORCES 20 t 202 203 204 -

General ........................................... ...... Definitions .... ..... ................................... Combinations of Loads .... ...... ...... ....... Dead Loads .......... .................................

2-1 2-1 2-3 2-4

205 206 207· 208-

Live Loads .... ........................ ................ Other Minimum Loads ............... ........ WindLoads ........................................ Earthquake Loads ...............................

2-7

2-12

2-14

2-35

305306 307 308.

Footings ................................................... Piles - General Requirements ................. Specific Pile Requirements .................... Foundation Construction-Seismic

Zone 4 ....................................................

Chapter 3 FOUNDATIONS AND EXCAVATIONS 301302 303 304-

General .................................................... Excavation and Fills .... .......................... Foundation Investigation ....... ................. Allowable Foundation and Lateral Pressures ...............................................

3-1 3-1 3-4 3-6

3-7

3-10

3-12

3-14

National structural Code of the Philippines, Volume 1

VIII

Chapter 4

STRUCTURAL CONCRETE

401402 403 404 405· 406407 408409 410411412 -

413 4'4-

Scope ..................................................... 4-1

Defmitions ............... ..... ........................... 4-1

Specifications for Tests and Materials ...... 4-4

Durability Requirements ...... ................... 4-9

Concrete Quality, Mixing and Placing .... 4... 11

Formwork. Embedded Pipes and

Construction Joints ................................ 4.16

Details of Reinforcement ....................... 4·18

Analysis and Design .............................. 4-24

Strength and Serviceability

Requirements ......................................... 4-27

Flexure and Axial Loads ....................... 4-33

Shear and Torsion ............ ............. ......... 4-41

Development and Splices of

Reinforcement ....................................... 4-54

Two-way Slab Systems ....... .................. 4-6]

Walls ..................................................... 4-68

.415 416 417 418 419420 421422 -

423 426 427 -

428-

Footings ................................................. 4-71

Precast Concrete ............ ............ ............ 4-73

Composite Concrete Flexural Members... 4-76

Prestressed Concrete .............................. 4-78

Shells and Folded Plates Members .......... 4-86

Strength Evaluation of Existing

Structures ............................................... 4-88

Special Provisions for Seismic

Design ............... ...................................... 4-90

Structural Plain Concrete .................. ... 4-106

Anchorage to Concrete ........................ 4-11 0

Alternate Design Method .. ...... ............. 4-112

Unified Design Provisions for

Reinforced and Prestressed Concrete

Flexural and Compres.<;ion Members 4-116

Alternative Load and Strength

Reduction Factors ................................ 4-118

Chapter 5

STRUCTURAL STEEL

501502 503 504505 506 .. 507 508509~

510511-

General Provisions .................. ............... Design Requirements .... ............... .......... Frames and Other Structures ................. Tension Members ................................. Columns and Other Compression

Members ............................ .................... Beam and Other Flexural Members ...... Plate Girders .... ............... ................. ..... Combined Stresses ............................... Composite Construction ....................... Connections, Joints and Fasteners ...... Special Design Considerations ...... ......

5-1

5-7

5-14

5.14

5-16

5-18

5-23

5-25

5-27

5-31

5-43

512 - Serviceability Design

Considerations ..... .............. ...... ........ ...... 513 -Fabrication. Erection

and Quality Control....... ..... ................. 514- Plastic Design ....................................... 515 - Seismic Provisions for Structural

Steel Buildings In Seismic

Zone 4 ................................................... 516 - Seismic Provisions for Structural

Steel Buildings In Seismic

Zone 2 ................................................... 517- Light Framed Wall Systems......... ....... 518 Inspection...... ... ...... ...... ...... ... ... ....

5-51

5-52

5-55

5-58

5-69

5-72

5-72


1)(

Chapter 6

WOOD

601602 603604 605 606 -

607 608 609610611-

General ............... ......................... .......... Definitions ........................................... ... Minimum Quality ................................... Design and Construction

Requirements .. ........... .................. ........ ... Decay and Termite Protection ... ..... , ... .. Wood Supporting Masomy or

Concrete ... .............................................. Wall Framing .......................................... Floor Franring .... .......... .............. ............. Exterior Wall Coverings ............ ............. Interior Paneling ..................... .............. Sheathing ................................... ...........

6-]

6-1

6-2

6-4

6-4

6-6

6-7

6-8

6-9

6-11

6-11

612 - Mechanically Laminated

Floors and Decks .......... ................... ...... 613 - Post-beam Connections ........................ 614- Wood Shear Walls and Diaphragms ..... 615- Stresses ................................................. 616 - Horizontal Member Design ............ ...... 617- Column Design ..................................... 618 - Flexural and Axial Loading

Combined .............................................. 619- Timber Connectors and Fasteners ....... 620- Conventional Light-frame

Construction Design Provisions ............. 621· Metal Plate Connected Wood

Truss Design ...... ............... ........... ..........

6-12

6-12

6-12

6-15

6-18

6-21

6-23

6·24

6-25

6-31

Chapter 7

MASONRY

701702703 704 705-

General ..................................................... Material Standards .................................. Mortar and Grout ............. ........... ....... ..... Construction ..... ...... ....... ............. ............ Quality Assurance ..................................

7-1

7-4

7-6

7-7

7-9

706707· 708709710-

General Design Requirements .............. Working Stress Design of Masomy ...... Strength Design ofMasomy ................. Empirical Design ofMasomy ............... Glass Masomy ......................................

National Structural Code of the PhiHppines, Volume 1

7-11

7-18

7-25

7,35

7-38

CHAPTER 1


TABLE OF CONTENTS

SECTION 101 - TITLE, PURPOSE, AND SCOPE ................................................................ 1-1

101.1 Title ................................................. 1·1 101.2 Purpose ............................................ 1-1 101.3 Scope ............................................... 1·1

101.4 Approval of Alternative

Systems ......................................... 1-1

SECTION 102 - DEFINTI'IONS ..•....•••••••.••••••.••.•••.••••••..••••••••••••..••.•...••.•...•..•..•..•..•.......•.••••••••• 1-2

SECTION 103 - CLASSIFICATION OF BUILDINGS ........................................................ 1-3

SECTION 104 - DESIGN REQUIR.EMENTS ....•••.•••.•••••••••.••••••.••..••••.•..••.••..•..•.....•..••.....•...• 1-4

104.1 Strength Requirement .................... 1-4 104.2 Serviceability Requirement ........... 1-4 104.3 Definitions and Other Requirements ................. ............... 1-4

104.4 104.5 104.6 104.7

Analysis........................... ....... .. ... .. ... Foundation Investigation .................. Design Review......... .................. Erection of Structural Framing .....

1-4

1-5

1-5

1-5

SECTION 105 - POSTING AND INSTRUMENTATION ................................................... 1-6

105.1 Posting of Live Loads ..................... 1-6

105.2 Earthquake Recording

Instrumentation ...... ....... ....... ..... ..... 1-6

SECTION 106 - SPECIFICATIONS, DRAWINGS, AND CALCULATIONS ......••..••.•••• 106.1 General ........................................... 1-6 106.2 Specifications ............. ....... ............. 1-6 106.3 Design Drawings ........................... 1-6

1~6

106.4 Calculations .................................... 1-7

106.5 As-Built Drawings ......................... 1-8


1-ii


SECTION 107 - STRUCTURAL INSPECTIONS, TESTS AND

STRUCTURAL OBSERVATIONS ............................................................................................. 1-8

107.1 General .. ........ ........ ....... ...... ..... ....... 107.2 Definitions ...................................... 107.3 Inspection Program ....................... 107.4 Structural Inspector ....................... lQ7.5 Types of Work for Inspection .........

1-8 1-8 1-9 1-9 1-9

107.6 Approved Fabricators .................... 107.7 PreFabricated Construction ............ 107.8 Nondestructive Testing .................. 107.9 Structural Observation ...................

1-11

1-12

1-12

1-12

SECTION 108 - EXISTING STRUCTURES ........................................................................ 1-13

108.1 108.2

General ......................................... 1-13 Maintainance .............. .................. 1-13

SECTION 109 - GRADING AND 109.1 General ......................................... 109.2 Hazards ........................................ 109.3 DefInitions .................................... , 109.4 Grading Pennit Requirements ......

108.3

Additions, Alterations or

Repairs ....................................... 1-13

108.4 Change in Use .............................. ~ 1-14

EARTHWO~

1-14 1-15 1-15

1-16

•••••••••••••••••••••••••••••••••••••••••••••••••••.•••••••. 1-14

109.5 Grading Inspection ...................... 1-17

109.6 Completion of Work ................... 1-17


TITLE, PURPOSE AND SCOPE

Sponsors of any system of design or construction within the scope of this code, the adequacy of which had been shown by successful use, by analysis and test, but which does not conform to or is not covered by this code, shall have the right to present the data on which their design is based to the building official or to a board of examiners appointed by the building official. This board shall be composed of competent structural engineers and shall have authority to investigate the data so submitted, to require tests, and to formulate rules governing design and construction of such systems to meet the intent of this code. These rules, when approved by the building official and promulgated shall be of the same force and effect ofthis code.

SECTION 101 - TITLE, PURPOSE AND SCOPE 101.1

TITLE

These regulations shall be known as the National Structural Code of the Philippines, may be cited as such and will be referred to herein as "this code. n

101.2

PURPOSE

The purpose of this code is to provide minimum standards to safeguard life or limb, property and public welfare by regulating and controlling the design, construction, quality of materials pertaining to the structural aspects of all buildings and structures within this jurisdiction.

101.3

SCOPE

The provisions of this code shall apply to the construction, alteration, moving, demolition, repair, maintenance and use of any building or structure within this jurisdiction, except work located primarily in a public way, public utility towers and poles, hydraulic flood control structures, and indigenous family dwellings. This Volume 1 of the code shall apply to buildings, towers and other vertical structures. The. latest edition of Volume 2 ofthis code shall apply to bridges. For additions, alterations, maintenance, and change in use ofbuildings and structures, see Section 108. Where, in any specific case, different sections of this code specify different materials, methods of construction or other requirements, the most restrictive provisions shall govern. Where there is a contlict between a general requirement and a specific requirement, the specific requirement sball be applicable. Wherever in this code reference is made to the appendix, the provisions in the appendix sball not apply unless specifically adopted.

101.4 APPROVAL OF ALTERNATIVE SYSTEMS The provisions of this code are not intended to prevent the use of any material, alternate design or method of construction not specifically prescribed by this co:ie, provided any alternate has been approved and its use authorized by the building official.

National Structural Code

1-1

of

the Philippines, Volume 1

GENERALREQUREMENTS

1-2

SECTION 102 - DEFINITIONS For the purpose of this code, certain terms, phrases, words and their derivatives shall be construed as specified in this chapter and elsewhere in this code where specific definitions are provided. Terms, phrases and words used in the singular include the plural and the plural, the singular. Terms, phrases and words used in the masculine gender include the feminine and the feminine, the masculine.

STRUCTURE is that which is built or constructed, an edifice or building of any kind, or any piece of work artificially built up or composed of parts joined together in some definite manner. STRUCTURAL ENGINEER is a registered Civil Engineer with special qualification in the practice of Structural Engineering as recognized by the Board of Civil Engineering of the Professional Regulation Commission or the Philippine Institute of Civil Engineers through the Association of Structural Engineers ofthe Philippines.

The following terms are defined for use in this chapter: ADDITION is an extension or increase in floor area or height of a building or structure. ALLOWABLE STRESS DESIGN is a method of proportioning structural elements such that computed stresses produced in the elements by the allowable stress load combinations do not exceed specified allowable stress (also called working stress design). ALTER or ALTERATION is any change, addition or modification in construction or occupancy. t

APPROVED as to materials and types of construction, refers to approval by the building official as the result of investigation and tests conducted by the building official, or by reason of accepted principles or tests by recognized authorities, technical or scientific organizations. BUILDING is any structure used or intended for supporting or sheltering any use or occupancy. BUILDING, EXISTING, is a building erected prior to the adoption of this'oode, or one for which a legal building permit has been issued. BUILDING OFFICIAL is the officer or other designated authority charged with the administration and enforcement of tttis code, or the building official's duly authorized representative.

WAD AND RESISTANCE FACTOR DESIGN (LRFD) METHOD is a method of proportioning structural elements using load and resistance factors such that no applicable limit state is reached when the structure is subjected to all appropriate load combinations. The term "LRFD" is used in the design of steel and wood structures. STRENGTH DESIGN is a method of proportioning structural elements such that the computed forces produced in the elements by the factored load combinations do not exceed the factored element strength. The term "strength design" is used in the design of concrete and masonry structures.


CLASSIFICATION OF BUILDINGS

SECTION 103 - CLASSIFICATION OF BlJILDINGS Buildings and other structures shall be classified, based on the nature of occupancy, according to Table 103-1 for purposes of applying wind and earthquake provisions in Chapter 2, and other. provisions. Each building or other structure shall be assigned to the highest applicable category. For buildings or other structures having multiple independent structural systems, each independent structural system shall be assigned to the highest applicable category based on the occupancy or functions dependent on the particular independent structural system. Table 103-1 - Occupancy Category OCCUPANCY CATEGORY

I

Essential Facilities

II Hazardous Facilities

III Special Occupancy Structures

OCCUPANCY OR FUNCTIONS OF STRUCTURE

Occupancies having surgery and emergency treatment areas, Fire and police stations, Garages and shelters for emergency vehicles and emergency aircraft, Structures and shelters in emergency preparedness centers, Aviation control towers, Structures and equipment in communication centers and other facilities required for emergency response, Standby power-generating equipment for Category I facilities, Tanks or other structures containing housing or supporting water or other fire-suppression material or equipment required for the protection of Category I, n or III structures. Occupancies and structures therein housing or supporting toxic or explosive chemicals or substances, Nonbuilding structures housing, supporting or containing quantities oftoxic or explosive substances. Buildings with an assembly room with an occupant capacity of 1,000 or more, Educational buildings with a capacity of 300 or more students, Buildings used for college or adult education with a capacity of 500 or more students, Institutional buildings ..ith 50 or more incapacitated patients, but not included in Category I,

III Special Occupancy Structures (Cont.)

Mental hospitals, sanitariums, jails, prison and other buildings where personal liberties of inmates are similarly restrained, All structures with an occupancy 5,000 or more persoos, Structures and equipment in powergenerating stations, and other public utility facilities not included in Category I or Category II above, and required for continued operation.

IV Standard Occupancy Structures

All structures housing occupancies or having functioned not listed in Category I, II or III above and Category V below.

IV Miscellaneous

Private garages, carports, sheds, agricultural buildings, and fences over 1.8 meters high.

Structures

1-4

SECTION 104 - DESIGN REQUIREMENTS 104.1

Table 104-2 Value of " l" for Table 104-1 ! Reinforced Wood I Concrete] Unseasoned Seasoned ~ ( l+SOpl) 1.0 0.5 I

STRENGTH REQUIREMENT

Buildings and other structures and all portions thereof shall be designed and constructed to sustain, within the limitations specified in this code, all loads set forth in Chapter 2 and elsewhere in this code, combined in accordance with Section 203. Design shall be in accordance with Strength Design, Load and Resistance Factor Design, Plastic Design or Allowable Stress Design methods, as permitted by the applicable materials chapters.

EXCEPTJON: Unless otherwise required by the building official, bUildings or portions thereof that are constructed in accordance with the conventional light-:framing requirements specified in thapter 6 of this code shall be deemed to meet the requirements ofthis section.

104.2

SERVICEABILITY REQUIREMENT

104.2.1 General. Structural systems and members thereof shall be designed to have adequate stiffness to limit deflections, lateral drifts, vibration, or any other deformations that adversely affect the intended use and performance o(~uildings and other structures. The design shall also consider durability, resistance to exposure to weather or aggressive environment, crack control, and other conditions that affect the intended use and performance of buildings and other structures. 104.2.2 Deflections. The deflection of any structural member shall not exceed the values set forth in Table 104 1, based on the factors set forth in Table 104-2. The deflection criteria representing the most restrictive condition shall apply. Deflection criteria for materials not specified shall be developed in a manner consistent with the provisions ofthis section. For concrete, see Section 409.5. Maximum Allowable Deflection for Structural Members1 Member Loaded Member Loaded with Live Load with Live Load Type of Member

Table 104-1

Only (L)

Roof member supporting plaster or floor member

I

WI.

I

1/360 ------'-

~.d 1

PI. (L+KD) Dead.

1/240

!

2

Steel

I

J ..J

I

0

Seasoned lumber is lumber having a moisture content of less than 16 percent at time of installation and used under dry conditions ofuse such as in covered structures. See also Section 104.3 for definitions and other requirements.

p'Shall be the value at midspan for simple and continuous spans, and at support for cantilevers. Time dependent factor A for sustained loads may be taken equal to: 2.0 ........ five (5) years or more 1.4 ........ twelve (12) months 1.2 ........ six (6) months 1.0 ........ three (3) months

104.3 DEFINITIONS AND OTHER REQUIREMENTS

I ~ ;.

pr A IS

b

d D

L

I

Span length of beam or one way slab, clear projection of cantilever, mm. Time dependent factor for sustained loads. = Multiplier for additional long time deflection. Reinforcement ratio for non-prestressed compression reinforcement, A's/ bd = Area of compression reinforcement, mm2 = Width of compression face of member,mm Distance from extreme compression fiber to centroid oftension reiforcement, mm Dead loads, or related internal moments and forces = Live loads, or related internal moments and forces.

104.4 ANALYSIS Any system or method of construction to be used shall be based on a rational analysis in accordance with well established principles of mechanics that take into account equilibrium, general stability, geometric compatibility and both short and long term material properties. Such analysis shall result in a system that provides a complete load path capable of transferring all loads and forces from their point of origin to the load resisting elements. The analysis shall include, but not be limited to, the provisions of Sections 104.4.1 through 104.4.4.

Sufficient slope or camber shall be pro,ided for flat rootS to avoid ponding.


DESIGN REQUIREMENT S

104.4.1 Distribution of Horizontal Shear. The total lateral foree shall be distributed to the various vertical elements of the lateral-foree-resisting system in proportion to their rigidities considering the rigidity of the horizontal bracing system or diaphragm. Rigid elements that are assumed not to be part of the lateral-foree-resisting system may be incorporated into buildings, provided that their effect on the action of the system is considered and provided for in the design. Provision shall be made for the increased forces induced on resisting elements of the structunu sys~em resulting from torsion due to eccentricity between the center of application of the lateral forees and the center of rigidity of the lateral foree-resisting system. For accidental torsion requirements for seismic design, see Section 208.5.6.

104.4.2 Stability against overturning. Every structure shall be designed to resist the overturning effects caused by the lateral forces specified in this chapter. See Section 206.6 for retaining walls, Section 201 for wind loading and Section 208 for seismic loading. 104.4.3 Self Straining Forces. Provisions shall be made for anticipated self-straining forces arising from differential settlement of foundations and from restrained dimensional changes due to temperature, moisture, shrinkage, creep and similar effects. 104.4.4 Anchorage. Anchorage of the roof to walls and columns, and of walls and columns to foundations shall be provided to resist the uplift and sliding forces that result from the application of the prescribed forces. Concrete and masonry walls shall be anchored to all floors, roofs and other structural elements that provide lateral support for the wall. Such anchorage shall provide a positive direct connection capable of resisting the horizontal forces specified in Chapter 2 but not less than the minimum forces in Section 206.4. In addition, in Seismic Zones 4, diaphragm to wall anchorage using embedded straps shall have the straps attached to or hooked around the reinforcing steel or otherwise terminated so as to effectively transfer forces to the reinforcing steel. Walls shall be designed to resist bending between anchors where the anchor spacing exceeds 1.2 meters. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall. See Sections 208.1, 208.8.2.1 and 208.8.2.8 for earthquake design requirements.

104.5 FOUNDATION INVESTIGATION Soil explorations shall be required for buildings falling under Categories I, II and III in accordance with Table 103

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1 or as required by the building official if the site specific conditions make the foundation investigation necessary. Detailed requirements for foundation investigations shall be in accordanee with Section 303 of this code.

104.6 DESIGN REVIEW The design calculations, drawings, specifications, and other design related documents for buildings and structures with Occupancy Categories I, II or III within Seismic Zone 4 shall be subject to a review by an independent recognized structural engineer to be employed by the owner. The structural engineer performing the review shall have comparable qualifications and experience as the structural engineer responsible for the design. The design review shall verify the general compliance with this code which shall include, but not be limited to, the review of the design load criteria, the 'design concept, mathematical model and techniques. The review shall also verify that there is no major error apparent in pertinent calculations, drawings and specifications The engineer of record shall submit with the plans and specifications, a statement by the structural engineer doing the review that the above review has been performed. See Section 208.6.6.3.2 for design review requirements when . nonlinear time-history analysis is used for earthquake, deSIgn. The design review shall not in any way transfer or diminish the responsibility ofthe design structural engineer.

104.7 ERECTION OF STRUCTURAL FRAMING Walls and structural framing shall be erected true and plumb in accordance with the design.

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SECTION 105 - POSTING AND INSTRUMENTATION

SECTION 106 - SPECIFICATIONS, DRAWINGS, AND CALClTLATIONS

105.1

106.1 GENERAL

POSTING OF LIVE LOADS

The live loads for which each floor or portion thereof of a commercial or industrial building has been designed shall have such design live loads conspicuously posted by the owner in that part of each story in which they apply, using durable metal signs, and it shall be unlawful to remove or deface such notices. The occupant of the building shall be responsible for keeping the actual load below the allowable limits.

Copies of design calculations, reports, plans, specifications, inspection program for all constructions shall bear the signature and the seal of the civil/structural engineer responsible for the structural design.

106.2 SPECIFICATIONS The specifications shall contain information covering the material and construction requirements. The materials and construction requirements shall conform to the specifications referred to in Chapters 3 to 7 of this Code.

105.2 EARTHQUAKE RECORDING INSTRUMENTATION 105.2.1 General. Unless waived by the building official, every building in Seismic Zone 4 over six (6) stories in height with an aggregate floor area of 5,500 square meters or more, and every building over ten (l0) stories in height r;gardless of floor area, shall be provided with not less than three approved recording accelerographs. The accelerographs shall be interconnected for common start and common timing. 105.2.2 Location. The instruments shall be located in the basement, midportion, and near the top of the building. Each instrument shall be located so that access is maintained at all times and is unobstructed by room contents. A sign stating MAINTAIN CLEAR ACCESS TO THIS INSTRLJ.M,ENT shall be posted in a conspicuous location. 105.2.3 Maintenance. Maintenance and service of the instruments shall be provided by the owner ofthe building, subject to the approval of the building official. Data produced by the instruments shall be made available to the building official or the Philippine Institute of Volcanology and Seismology on request.

106.3 DESIGN DRAWINGS 106.3.1 General. The design drawings shall be drawn to scale upon substantial paper or cloth and shall be of sufficient clarity to indicate the location, nature and extent of the work proposed. The drawings shall show a complete design with sizes, sections, relative locations and connection details of the various members. Floor levels, column centers and offsets shall be dimensioned.

106.3.2 Required Information. The design drawings shall contain, but not be limited to, the general information listed in Section 106.3.2.1 and material specific information listed in Sections 1063.2.2 and 106.3.2.3, as applicable. 106.3.2.1 1. 2.

General Information.

Name and date of issue of building code and supplements, if any, to which the design conforms. Strengths or designations of materials to be used.

3.

Design strengths of underlying soil or rock. The soil or rock profile, when available, shall be provided.

owners of existing structures selected by the jurisdiction authorities shall provide accessible space for the installation of appropriate earthquake-recording instruments. Location of said Instruments shall be determined by the jurisdiction authorities.

4. 5.

The jurisdiction authorities shall make arrangements to provide, maintain and service the instruments. Data shall be the property of the jurisdiction authorities, but copies of individual records shall be made available to the owner of the building and to the public on request and after the payment of an appropriate fee.

6.

Live loads and other loads used in design. Seismic design basis including the total base shear coefficient; a description of the lateral load resisting system; and the fundamental natural period in the design in each direction under consideration. Provisions for dimensional changes resulting from creep, shrinkage and temperature. Camber oftrusses, beams and girders, if required. Explanation or definition of symbols and abbreviations used in the drawings.

105.2.4

Instrumentation of Selected Buildiugs.

All

7. 8.

ASSOCiation of Structural Engineers of the Philippines

SPECIFICATIONS, DRAWINGS, CALCULATION

9.

Engineer's professional license number and expiration date of the current Professional Regulation Commi:::sion registration.

106.3.2.2 1.

Structural Concrete

Specified compressive strength of concrete at stated ages or stages of construction for which each part of structure is designed.

2.

Amount anchorage lengths or cutoff points of steel reinforcement; and location and length of lap splices.

3.

Type and location of welded splices and mechanical connections of reinforcement.

4.

Magnitude and location of prestressing forces.

5.

Minimum concrete compressive strength at time of post-tensioning. Stressing sequence for post-tensioned tendons.

6. 7.

Details and location of all contraction or isolation joints specified for plain concrete in Section 422.

8.

Statement if slab on grade is designed as a structural diaphragm, as specified in Section 421.8.3.4.

106.3.2.3 1. 2.

3. 4.

Structural Steel

Type or types of construction as defined in Section 501.2.2. Loads and design requirements necessary for preparation of shop drawings including shears, moments, and axial forces to be resisted by all members and their connections. The type of connection for joints using high strength bolts. Stiffener and bracing requirements.

5.

Description or explanation of welding and inspection symbols used on the design and shop drawings.

6.

Notes for joints in which welding sequence and technique of welding are required to be carefully controlled to minimize distortion.

106.4

1. 2. 3. 4. 5. 6.

7.

106.4.2 Basis of Design Summary. The calculations shall include a summary of the criteria and methodologies used in the design. This summary shall include, but need not be limited to, the following:

Name and date of issue of building code and supplements, if any, to which the design conforms. Strengths or designations of materials to be used for each component ofthe structure. Design strengths and other design parameters of the underlying soil or rock. Live loads and other loads used in design. The basis ofthe seismic and wind design forces. A description of the structure's gravity and lateral load resisting systems. A description of the roof, floor, foundation and other component systems shall also be provided. A description of the mathematical model and procedures used in the structural analysis. This shall include the section and material properties used, loading combinations considered, second-order effects considerations, and any simplifying assumptions made.

106.4.3 Computer Programs. Calculations may include the results from an electronic digital computer analysis. The following requirements apply to calculations which include such computer output. 1.

2.

3.

CALCULATIONS

106.4.1 General. Calculations pertinent to the structural design of structures and its component members shall be filed with the design drawings.

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4.

A drawing of the complete mathematical model used to represent the structure in the computer-generated analysis shall be provided. Design assumptions shaU be clearly described. A program description giving the program name, tqe version number, and the company which developed the program and its address shall be provided as part of the computation documentation. A program User's Guide shall also be made available, upon request, and shall contain the information to determine the nature and extent of the analysis, verify the input data, interpret the result, and determine whether the computations comply with the requirements ofthis code. Data provided. as computer input shall be clearly distinguished from those computed in the program. The information required in the output shall include date of processing, program identification, identification of structures being analyzed, all input data, units and final results. The first sheet of each computer run shall be signed and sealed by the engineer responsible for the structural design.

106.4.4 Model Analysis. Results from model analysis and experimental studies shall be permitted to supplement calculations. The results shall be accompanied by a description of the rational basis, set-up, methodology and other information required for the evaluation of the results.



106.5 AS-BUILT DRAWINGS As-built drawings shall be prepared by the permit holder or a person retained to provide such services to document the work as actually constructed. The as-built drawings shall be drawn to scale upon substantial paper or cloth and shall indicate the sizes, sections, relative locations, and connection details of the various structural members as actually constructed. Strengths of materials, based on required tests, shall also be indicated. Work items which required modifications of or are otherwise different from those shown in the design drawings filed with the building official shall be accordingly marked in the as-built drawings and provided with notes indicating the basis of such modifications or changes. The basis of modification or change shall include reference to supplemental design drawings, construction bulletins, or instructions from the owner, owner's representative or structural engineer authorizing such modifications or changes. The signature, name and professional license number of the structural inspector shall be included in the as-built drawings. Copies of the as-built drawings shall be provided to the owner, constructor, structural engineer and the building official.

SECTION 107 - STRUCTURAL

INSPECTIONS, TESTS AND

STRUCTURAL OBSERVATIONS

107.1

GENERAL

All construction or work for which a permit is required shall be subject to inspection throughout the various work stages. One or more structural inspectors shall be employed by the owner or the engineer of record acting as the owner's agent, who shall provide inspections during construction on the types of work listed under Section 107.5.

EXCEPTION: The building official may waive the requirement for the employment of a structural inspector if the construction is ofa minor nature. In addition to structural inspections, structural observations

shall be performed when required by Section 107.9.

107.2

DEFINITIONS

The following terms are defined for use in this section:

CONTINUOUS STRUCTURAL INSPECTION is a structural inspection where the structural inspector is on the site at all times observing the work requiring structural inspection. PERIODIC STRUCTURAL INSPECTION is a structural inspection where the inspections are made on a periodic basis and satisfy the requirements of continuous inspection, provided this periodic scheduled inspection is performed as outlined in the inspection program prepared by the structural engineer. STRUCTURAL INSPECTION is the visual observation by a structural engineer of a particular type of construction work or operation for general compliance to the approved plans and specifications and the applicable workmanship provisions of this code. STRUCTURAL OBSERVATION IS the visual observation of the structural system by the structural engineer responsible for the design (see Section 107.9.2), for general conformance to the approved plans and specifications, at significant construction stages and at completion of the structural system. Structural observation does not include or waive the responsibility for the structural inspections required by section 107.1 or other ·.sections of this code.


STRUCTURAL INSPECTIONS, TEST AND STRUCTURAL OBSERVATIONS

107.3

INSPECTION PROGRAM

EXCEPTIONS:

The structural engineer shall prepare an appropriate testing and inspection program that shall be submitted to the building official. The inspection program shall designate the portions of the work that require structural inspections and indicate the duties ofthe structural inspectors.

I.

When structural observation is required by Section 107.9, the inspection program shall describe the stages of construction at which structural observation is to occur.

2.

3. The inspection program shall include samples of inspection reports and provide time limits for submission of reports.

4.

107.4

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Concrete for foundations of residential buildings accommodating 10 or fewer persons, or buildings falling under Category V of Table 103-1, provided the building offiCial finds that a structural hazard does not exist. For foundation concrete, other than cast-in-place drilled piles or caissons, where the structural design is based on an Ie no greater than 17 MPa. Nonsfruch,ral slabs on grade, including prestressed slabs on grade when effective prestress in concrete is less than 1.0 MPa. Site work concrete flilly supported on earth and concrete where no special hazard exists.

STRUCTURAL INSPECTOR

107.4.1 Qualifications. The structural inspector shall be a registered civil engineer or a qualified person under the supervision of a registered civil engineer who shall demonstrate competence, to the satisfaction of the structural engineer, for inspection of the particular type of construction or operation requiring structural inspection. 107.4.2 Duties and Responsibilities. The structural inspector shall observe the work assigned for conformance to the approved design drawings and specifications. The structural inspector shall also verify that the as-built drawings (see Section 106.5) pertaining to the work assigned reflect the condition as constructed.

107.5.2. Bolts instaUed in concrete. Prior to and during the placement of concrete around bolts when stress increases permitted by Footnote 5 of Table 423-1 or Section 423 are utilized. 107.5.3 Special moment-resisting concrete frame. For moment frames resisting design seismic load in structures within Seismic Zone 4, the structural inspector shall provide reports to the person responsible for the structural design and shall provide continuous inspection of the placement of the reinforcement and concrete. 107.5.4 Reinforcing steel and prestressing steel tendons. 107.5.4.1 During all stressing and grouting of tendons iQ prestressed concrete.

The structural inspector shall furnish inspection reports to the building official, the structural engineer, and other designated persons. All discrepancies shall be brought to the immediate attention of the contractor for correction, then, if uncorrected, to the proper design authority and to the building official.

EXCEPTION:

The structural inspector shall submit a final signed report stating whether the work requiring structural inspection was, to the best of the inspector's knowledge, in conformance to the approved plans and specifications and the applicable workmanship provisions of this code.

The structural inspector need not be present continuously during placing of reiriforcing steel and prestressing tendons, provided the structural inspector has inspected for conformance to the approved plans prior to the closing of forms or the delivery ofconcrete to the jobsite.

107.5.4.2 During placing of reinforcing steel and prestressing tendons for all concrete required to have structural inspection by Section 107.5.1.

107.5.5

Structural welding

107.5 TYPES OF WORK FOR INSPECTION Except as provided in Section 107.1, the types of work listed below shall be inspected by a structural inspector. 107.5.1 Concrete. During the taking of test specimens and placing of reinforced concrete. See Section 107.5.12 for shotcrete.

107.5.5.1 GeneraL During the welding of any member or connection that is designed to resist loads and forces required by this code.

EXCEPTIONS: 1.

Welding done in an approved fabricator's shop in accordance with Section 107.6.



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2.

The structural inspector need not be continuously present during welding of the following items, provided the materials, qualifications of welding procedures and welders are verified prior to the start of work; periodic inspections are made of work in progress; and a visual inspection of all welds is made prior to completion or prior to shipment of shop welding:

a. Single-pass fillet welds not exceeding 8 mm in size. b. Floor and roofdeck welding. c. Welded studs when used for structural diaphragm or composite systems. d Welded sheet steel for cold-formed steel framing members such as studs andjoists. e. Welding ofstairs and railing systems. 107.5.5.2 Special moment-resisting steel frames. During the welding of special moment-resisting steel frames. In addition to Section 107.5.5.1 requirements, nondestructive testing as required by Section 107.8 of this code.

107.5.7

Structural masonry

107.5.7.1 For masonry, other than fully grouted open end hollow-unit masonry, during preparation and taking of any required prisms or test specimens, placing of all masonry units, placement of reinforcement, inspection of grout space, immediately prior to closing of cIeanouts, and during all grouting operations.

EXCEPTION:

For hollow-unit masonry where thefm is 110 more than 10 MPafor concrete 1mits or 18 MPafor clay units, structural inspection may be performed as required for fully grouted open-end hollow-unit masonry specified in Section 107.5.7.2.

107.5.7.2 For fully grouted open-end hollow-unit masonry during preparation and taking of any required prisms or test specimens, at the start of laying units, after the placement of reinforcing steel, grout space prior to each grouting operation, and during all grouting operations.

EXCEPTION: 107.5.5.3 Welding of reinforcing steel. During the welding of reinforcing steel.

EXCEPTION:

The structural inspector need not be continuously present during the welding of ASlM A 706 reinforcing steel not larger than 16 mm diameter bars used for embedments, provided. the materials, qualifications of welding procedures and welders are verified prior to the start of work; periodic inspections are made of work in progress; and a visual inspection oj all welds is made prior to completion or prior to shipment ofshop welding.

Stmctural inspection as required ill Sections 107.5. 7.1 and 107.5.7.2 need not be provided when design stresses have been a4justed as :.pecified ill Chapter 7 to permit noncontinuous inspection. 107.5.8 Reinforced gypsum concrete. When cast-in place Class B gypsum concrete is being mixed and placed. 107.5.9 Insulating concrete fill. During the application of insulating concrete fill when used as part of a structural system.

EXCEPT/ON: 107.5.6 High-strength bolting. The inspection of high strength A 325 and A 490 bolts shall be in accordance with approved nationally recognized standards and the requirements of this section. While the work is in progress, the structural inspector shall determine that the requirements for bolts, nuts, washers and paint; bolted parts; and installation and tightening in such standards are met. Such inspections may be performed on a periodic basis as defined in Section 107.2. The structural inspector shall observe the calibration procedures when such procedures are required by the plans or specifications and shall monitor the installation of bolts to determine that all plies of connected materials have been drawn together and that the selected procedure is properly used to tighten all bolts.

The structural inspections may be limited to all initial inspection to check the deck surface and placement of reinforcing. The structural inspector shall supenise the preparation of compression (est specimens during this initial inspection. 107.5.10 Spray-applied fire-resistive materials. During the application of spray-applied fire-resistive materials .. 107.5.11 Piling, drilled piers and caissons. During driving and testing of piles and construction of cast-in-place drilled piles or caissons. See Sections 107.5.1 and 1075.4 for concrete and reinforcing steel inspection. 107.5.12Shotcrete. During the taking of test specimens and placing of all shotcrete.


STRUCTURAL INSPECTIONS, TESTS AND STRUCTURAL OBSERVATIONS

EXCEPTION:

107.7 PREFABRICATED CONSTRUCTION

Shotcrete work fUlly supported on earth, minor repairs and when, in the opinion of the building official, no special hazard exists.

107.7.1

107.5.13 Special grading, excavation and filling. During earthwork excavations, grading and filling operations inspection to satisfy requirements of Chapter 3 and· Section 109.5. 107.5.14 Special cases. Work that, in the opinion of the structural engineer, involves unusual hazards or conditions. 107.5.15. Non-destructive Testing. In-situ non destructive testing program, in addition to the requirements of Section 107.8 that in the opinion of the structural engineer may supplement or replace conventional tests on concrete or other materials and assemblies.

107.6 APPROVED FABRICATORS Structural inspections required by this section and elsewhere in this code are not required where the work is done on the premises of a fabricator approved by the structural engineer to perform such work without structural inspection. The approved fabricator shall submit a certificate of compliance that the work was performed in accordance with the approved plans and specifications to the building official and to the engineer or architect of record. The approved fabricator's qualifications shall be contingent on compliance with the following: 1.

2.

3.

The fabricator has developed and submitted a detailed fabrication procedural manual reflecting key quality control procedures that will provide a basis for inspection control of workmanship and the fabricator plant Verification of the fabricator's quality control capabilities, plant and personnel as outlined in the fabrication procedural manual shall be by an approved inspection or quality control agency. Periodic plant inspections shall be conducted by an approved inspection or quality control agency to monitor the effectiveness of the quality control program

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General.

107.7.1.1 Purpose. The purpose of this section is to regulate materials and establish methods of safe . construction where any structure or portion thereof is wholly or partially prefabricated. 107.7.1.2 Scope. Unless otherwise specifically stated in this section, all prefabricated construction and all materials used therein shall conform to all the requirements of this code. (See Section 101.4.) 107.7.1.3

Definition.

PREFABRICATED ASSEMBLY is a structural unit, the integral parts of which have been built up or assembled prior to incorporation in the building.

107.7.2 Tests of Materials. Every approval of a material not specifically mentioned in this code shall incorporate as a proviso the kind and number of tests to be made during prefabrication. 107.7.3 Tests of Assemblies. The building official may require special tests to be made on assemblies to determine their durability and weather resistance. 107.7.4 Connections. Every device used to connect prefabricated assemblies shall be designed as required by this code and shall be capable of developing the strengtq of the members connected, except in the case of members forming part of a structural frame designed as specified in Chapter 2. Connections shall be capable of withstanding uplift forces as specified in Chapter 2. 107.7.5 Pipes and conduit. In structural design, due allowance shall be made for any material to be removed for the installation of pipes, conduits or other equipment. 107.7.6

Certificate and Inspection.

107.7.6.1 Materials. Materials and the assembly thereof shall be inspected to determine compliance with this code. Every material shall be graded, marked or labeled where required elsewhere in this code. 107.7.6.2 Certificate. A certificate of approval shall be furnished with every prefabricated assembly, except where the assembly is readily accessible to inspection at the site. The certificate of approval shall certify that the assembly in question has been inspected and meets all the requirements of this code.



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107.7.6.3 Certifying agency. To be acceptable under this code, every certificate of approval shall be made by an approved agency. 107.7.6.4 Field erection. Placement of prefabricated assemblies at the building site shall be inspected to determine compliance with this code. 107.7.6.5 Continuous inspection. If continuous inspection is required for certain materials where construction takes place on the site, it shall also be required where the same materials are used in prefabricated construction.

2.

3.

EXCEPTION: Continuous inspection will not be required during prefabrication if the approved agency certifies to the constructiOll andfumishes evidence ofcompliance.

107.8 NONDESTRUCTIVE TESTING 1~7.8.1 General. In Seismic Zone 4, welded, fully restrained connections between the primary members of ordinary moment frames and special moment-resisting frames shall be tested by nondestructive methods for compliance with approved standards and job specifications. This testing shall be a part of the structural inspection requirements of Section 107.5. A program for this testing shall be established by the person responsible for structural design and as shown on plans and specifications.

107.8.2 Testing Program. As a minimum, the testing program shall inclt,lde the following: 107.8.2.1 All complete penetration groove welds contained in joints and splices shall be tested 100 percent either by ultrasonic testing or by radiography.

107.8.2.2 Partial penetration groove welds when used in column splices shall be tested either by ultrasonic testing or radiography when required by the plans and specifications. For partial penetration groove welds when used in column splices, with an effective throat less than 20 mm thick, nondestructive testing is not required; for this welding, continuous structural inspection is required. 107.8.2.3 Base metal thicker than 40 rom, when subjected to through-thickness weld shrinkage strains, shall be ultrasonically inspected for discontinuities directly behind such welds after joint completion. Any material discontinuities shall be accepted or rejected on the basis of the defect rating in accordance with the (larger reflector) criteria of approved national standards. 107.8.3 Others. The structural engineer may accept or require in situ non-destructive testing of concrete or other materials and assemblies to supplement or replace conventional tests.

107.9 STRUCTURAL OBSERVATION 107.9.1 General. Structural observation shall be provided in Seismic Zone 4 when one of the following conditions exists:

EXCEPTIONS: 1.

continuous welds over 900 mm in length where the effective throat thickness is greater than 25 mm, each 150 mm of length or fraction thereof shall be considered one weld For complete penetration groove welds on materials less than 8 mm thick, nondestructive testing is not required; for this welding, cOlltirmous inspection is required. When approved by the building official and outlined in the project plans and specifications, this nondestntctive ultrasonic testing may be performed in the shop of ali approved fabricator utilizing qualified test techniques in· the employmem of the fabricator.

When approved, the nondestructive testing rate for an individual welder or welding operator may be reduced to 25 percent, provided the reject rate is demonstrated to be 5 percent or less of the welds tested for the welder or welding operator. A sampling of at least 40 completed welds for a job shall be made for SlIch reduction evaluation. Reject rate is defined as the number of welds containing rejectable defects divided by the number of welds completed For evaluating the reject rate of continuous welds over 900 mm in length where the effective throat thickness is 25 mm or less, each 300 mm increment or fractioll thereof shall be considered as one weld. For evaluating the reject rate on

1.

The structure is defined in Table 103-1 Occupancy Category I, II or III;

as

2.

The structure is in Seismic Zone 4, No as set forth in Table 208-4 is greater than one, and a lateral design is required for the entire structure;

EXCEPTION: One- alld two-story residential buildings accommodating 10 or fewer perSOIlS, or buildings falling under Category V


EXISTING STRUCTURES

of Table 103-1, and one- and two-story buildings for offices, for eating and drinking with an occupancy load of 50 persons or fewer, for factory and industrial occupancies, for the display and sale of merchandise, for storage, for open parking or repair garages, and aircraft hangars and helistops. 3.

When so designated by the structural engineer, or

4.

When such observation is specifically required by the building official.

107.9.2 Structural Observer. The owner shall employ the engineer responsible for the structural design, or another engineer designated by the engineer responsible for the structural design, to perform structural observation as defined in Section 107.2. Observed deficiencies shall be reported in writing to the , owner's representative, structural inspector, contractor and the building official. The structural observer shall submit to the building official a written statement that the site visits have been made and identifying any reported deficiencies that, to the best of the structural observer's knowledge, have not been resolved.

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SECTION lOS-EXISTING STRUCTURES 108.1 GENERAL Buildings in exiStence at the time of the adoption of this code may have their existing use or occupancy continued, if such use or occupancy was legal at the time of the adoption of this code, provided such continued use is not dangerous to life. Any change in the use or occupancy of any existing building or structure shall comply with the provisions of Sections 108.4 ofthis code.

108.2 MAINTENANCE All buildings and structures, both existing and new, and all parts thereot: shall be maintained in a safe condition.- The owner or the owner's designated agent shall be responsible for the maintenance of buildings and structures. To determine compliance with this subsection, the building official may cause a structure to be re-inspected.

108.3 ADDITIONS, ALTERATIONS OR REPAIRS

107.9.3 Construction Stages for Observations. The structural observations shall be performed at the construction stages prescribed by the inspection program prepared as required by Section 107.3.

108.3.1 General. Buildings and structures to which additions, alterations or repairs are made shall comply with all the requirements of this code for new facilities except as specifically provided in this section.

It shall be the duty of the person doing the work authorized by the permit to notify the structural observer that the described construction stages have been reached, and to provide access to and means for observing the components of the structural system.

108.3.2 When AUowed. Additions, alterations or repairs may be made to any building or structure without requiring the existing building or structure to comply with all the requirements of this code, provided the addition, alteration or repair conforms to that required for a new building or structure. Additions or alterations shall not be made to an existing building or structure that will cause the existing building or structure to become unsafe. An unsafe condition shall be deemed to have been created if an addition or alteration will cause any structural element of the existing building or structure to resist loads in excess of their capacity or cause a reduction of their load carrying capacity. Additions or alterations shall not be made to an existing building or structure when such existing building or structure is not in full compliance with the provisions of this code except when such addition or alteration will result in the existing building or structure being no more hazardous based on structural safety, than before such additions or alterations are undertaken.

National structlJRll Code of the Philippines, Volume 1


1·14

EXCEPTION: Alterations of existing structural elements, or additions of new structural elements, which are initiatedfor the purpose ofincreasing the lateral-force-resisting strength or stiffness of an existing structure, need not be designed for forces conforming . to these regulations provided that an engineering analysis is submitted to show that

No change in the character of occupancy of a building shall be made without a new certificate of occupancy regardless of whether any alterations to the building are required.

1.

The capacity of existing structural elements required to resist forces is not reduced,

2.

The lateral loading to required existing structural elements is not increased beyond their capacity,

SECTION 109 - GRADING AND EARTHWORK

3.

New structural elements are detailed and connected to the existing structural elements as required by the~ regulations,

109.1

4.

New or relocated nonstructural elements are detailed and connected to existing or new structural elements as required by these regulations.

108.3.3 Non-structural. Alterations or repairs to an existing building or structure that are nonstructural and do not adversely affect any structural member or any part of the building or structure having required fire resistance may be made with the same materials of which the building or structure is constructed. 108.3.4 Historic Buildings. Repairs, alterations and additions necessary for the preservation, restoration, rehabilitation or continued use of a building or structure may be made without conformance to all the requirements of this code when authorized by the building official, provided: 1.

2. 3.

108.4

The building or structure has been designated by official act!on of the legally constituted authority of this jurisdiction as having special historical or architectural significance. Any structurally unsafe conditions are corrected. The restored building or structure will be no more hazardous based on life safety than the existing building.

CHANGE IN USE

GENERAL

109.1.1 Permits Required. Except as specified in Section 109.1.2 of this section, no person shall do any grading without first having obtained a grading permit from the building official. 109.1.2 Exempted Work. A grading permit is not required for the following: 1.

2.

3. 4.

5. 6.

7. 8.

No change shall be made in the character of occupancies or use of any building unless the new or proposed use is less hazardous, based on life safety than the existing use. A change in use or occupancy of any building shall be allowed 0!1ly when the change in use or occupancy will not

I

cause any structural element of the eXlstmg building to resist loads, determined on the basis on this code and on the proposed use or occupancy, in excess of their capacity. Alterations to the existing building shall be permitted to satisfy this requirement.

9.

When approved by the building official, grading in an isolated, self-contained area if there is no danger to private or public property. An excavation below finished grade for basements and footings of a building, retaining wall or other structure authorized by a valid building permit. This shall not exempt any fill made with the material from such excavation or exempt any excavation having an unsupported height greater than 1.5 meters after the completion ofsuch structure. Cemetery graves. Refuse disposal sites controlled by other regulations. Excavations for wells or tunnels or utilities. Mining, quarrying, excavating, processing or stockpiling of rock, sand, gravel, aggregate or clay where established and provided for by law, provided such operations do not afIe..,"t the lateral support or increase the stresses in or pressure upon any adjacent or contiguous property. Exploratory excavations under the direction of geotechnical engineers or engineering geologists. An excavation that (1) is less than 600 mm in depth or (2) does not create a cut slope greater than 1.5 m in height and steeper than 1 unit vertical in 1Y2 units horizontal (66.7% slope). A fill less than 300 mm in depth and placed on natural terrain with a slope flatter than I unit vertical


GRADING AND EARTHWORK

in 5 units horizontal (20% slope), or less than 900 mm in depth, not intended to support structures, that does not exceed 40 m3 on anyone lot and does not obstruct a drainage course. Exemption from the permit requirements of this section shall not be deemed to grant authorization for any work to be done in any manner in violation of the provisions of this section or any other laws or ordinances ofthis jurisdiction.

109.2

HAZARDS

Whenever the building official determines that any existing excavation or embankment or fill on private property has become a hazard to life and limb, or endangers property, or adversely affects the safety, use or stability of a public way or drainage channel, the owner of the property upon which the excavation or fill is located, or other person or agent in control of said property, upon receipt of notice in writing from the building official, shall within the period specified therein repair or eliminate such excavation or embankment to eliminate the hazard and to be in conformance with the requirements of this code.

109.3 DEFINITIONS The following terms are defined for use in this section: APPROVAL shall mean that the proposed work or completed work conforms to this section in the opinion of the building official. AS GRADED is the extent of surface conditions on completion of grading. BEDROCK is in-place solid rock. BENCH is a relatively level step excavated into earth material on which fill is to be placed. BORROW is earth material acquired from an off-site location for use in grading on a site.

1-15

EARTH MATERIAL is any rock, natural soil or till or any combination thereof ENGINEERING GEOLOGIST is a licensed geologist experienced and knowledgeable in engineering geology. ENGINEERING GEOLOGY is the application of geologic knowledge and principles in the investigation and evaluation of naturally occurring rock and soil for use in the design of civil works. EROSION is the wearing away of the ground surface as a result of the movement of wind, water or ice. EXCAVATION is the mechanical removal of earth material.

FILL is a deposit of earth material placed by artificial means. GEOTECHNICAL ENGINEER is an engineer experienced and knowledgeable in the practice of geotechnical engineering. GEOTECHNICAL ENGINEERING is the application of the principles of soil and rock mechanics in the investigation, evaluation and design of civil works involving the use of earth materials and the inspection or testing of the construction thereof. GRADE is the vertical location of the ground surface. EXISTING GRADE is the grade prior to grading. FINISH GRADE is the final grade of the site that conforms to the approved plan. ROUGH GRADE is the stage at which the grade approximately conforms to the approved plan. GRADING is any excavating or filling or combination thereof.

KEY is a designed compacted fill placed in a trench

CIVIL ENGINEER is· a professional engineer licensed to practice in the field of civil engineering.

excavated in earth material beneath the toe of a proposed fill slope.

CIVIL ENGINEERING is the application of the knowledge of the forces of nature, principles of mechanics and the properties of materials to the evaluation, design and construction of civil works.

PROFESSIONAL INSPECTION is the inspection required by this code to be performed by the civil engineer, geotechnical engineer or engineering geologist. Such inspections include that performed by persons supervised by such engineers or geologists and shall be sufficient to form an opinion relating to the conduct of the work.

COMPACTION is the densification of a fill by mechanical means.


t

1-16


SITE is any lot or parcel of land or contiguous combination thereof, under the same ownership, where grading is performed or permitted.

address of the owner, and the person by whom they were prepared. The plans shall include the following information:

SLOPE is an inclined ground surface the inclination of which is· expressed as a ratio of vertical distance to horizontal distance. SOIL is naturally occurring superficial deposits overlying bedrock

1. 2.

3.

SOILS ENGINEER. See Geotechnical Engineer. SOILS ENGINEERING. See Geotechnical Engineering.

4.

TERRACE is a relatively level step constructed in the face of a graded slope surface for drainage and maintenance purposes.

109.4 GRADING PERMIT REQUIREMENTS 109.4.1 Except as exempted in Section 109.1.2 of this code, no person shall do any grading without first obtaining a grading permit from the building official. A separate permit shall be obtained for each site, and may cover both excavations and fills. 109.4.2 Grading Designation. Grading in excess of 4,000 m3 shall be performed in accordance with the approved grading plan prepared by a civil engineer, and shall be designated as "engineered grading." Grading involving less than 4,000 m3 shall be designated "regular grading" unless the permittee chooses to have the grading performed as engineered grading, or the building official determines that special conditions or unusual hazards exist, in which case grading shall conform to the requirements for engineered grading. 109.4.3 Engineered Grading Requirements. Application tor a grading permit shall be accompanied by two sets of plans and specifications, and supporting data consisting of a geotechni(;al engineering report and engineering geology report. Additionally, the application shall state the estimated quantities of work involved. The plans and specifications shall be prepared and signed by civil engineer licensed to prepare such plans or specifications when required by the building official. Specifications shall contain information covering construction and material requirements. Plans shall be drawn to scale upon substantial paper or cloth and shall be of sufficient clarity to indicate the nature and extent of the work proposed and show in detail that they will conform to the provisions of this code and all relevant laws, ordinances, rules and regulations. The first sheet of each set of plans shall give location of the work, the name and

5.

6.

7.

General vicinity map ofthe proposed site. Property limits and accurate contours of existing ground and details of terrain and area drainage. Limiting dimensions elevations or finish contours to be achieved by the grading, and proposed drainage channels and related construction. Detailed plans of all surface and subsurface drainage devices, walls, cribbing, dams and other protective devices to be constructed with, or as a part of, the proposed work, together with a map showing the drainage area and the estimated runoff of the area served by any drains. Location of any buildings or structures on the property where the work is to be performed and the location of any buildings or structures on land of adjacent owners that are within 4.5 m of the property or that may be affected by the proposed grading operations. Recommendations included in the geotechnical engineering report and the engineering geology report shall be incorporated in the grading plans or specifications. When approved by the building official, specific recommendations contained in the geotechnical engineering report and the engineering geology report, which are applicable to grading, may be included by reference. The dates of the geotechnical engineering and engineering geology reports together with the names, addresses and phone numbers of the fnms or individuals who prepared the reports.

109.4.4 Geotechnical Engineering Report. The geotechnical engineering report required by Section 109.4.3 shall include data regarding the nature, distribution and strength of existing soil, conclusions and recommendations for grading procedures and design criteria for corrective measures, including buttress fills, when necessary, and opinion on adequacy for the intended use of sites to be developed by the proposed grading as affected by geotechnical engineering factors, including the stability of slopes. 109.4;5 Engineering Geology Report. The engineering geology report required by Section 109.4.3 shall include an adequate description of the geology of the site, conclusions and recommendations regarding the effect of geologic conditions on the proposed development, and opinion on the adequacy for the intended use of sites to be developed by the proposed grading, as affected by geologic factors.


GRADING AND EARTHWORK

109.4.6 Regular Grading Requirements. Each application for a grading permit shall be accompanied by a plan in sufficient clarity to indicate the nature and extent of the work, and state the estimated quantities of work involved. The plans shall give the location of the work, the name of the owner and the name of the person who prepared the plan. The plan shall include the following information: 1. General vicinity map of the proposed site. 2. Limiting dimensions and depth of cut and fill. 3. Location of any buildings or structures where work is to be performed, and the location of any buildings or structures within 4.5 m ofthe proposed grading.

109.5 GRADING INSPECTION 109.5.1 General. Grading operations for which a permit is required shall be subject to inspection by the building official. Professional inspection of grading operations shall be provided by the civil engineer, geotechnical engineer and the engineering geologist retained to provide such services in accordance with Section 109.5.5 for engineered grading and as required by the building official for regular grading. 109.5.2 Civil Engineer. The civil engineer shall provide professional inspection within such engineer's area of technical specialty, which shall consist of observation and review as to the establishment of line, grade and surface drainage of the development area. If revised plans are required during the course of the work, they shall be prepared by the civil engineer. 109.5.3 Geotechnical Engineer. The geotechnical engineer shall provide professional inspection within such engineer's area of technical specialty, which shall include observation during grading and testing for required compaction. The geotechnical engineer shall provide sufficient observation during the preparation of the natural ground and placement and compaction of the fill to verify that such work is being performed in accordance with the conditions of the approved plan and the appropriate requirements of this chapter.

Revised recommendations relating to conditions differing from the approved geotechnical engineering and engineering geology reports shall be submitted to the permittee, the building official and the civil engineer. 109.5.4 Engineering Geologist. The engineering geologist shall provide professional inspection within such geologist's area of technical specialty, which shall include professional inspection of the bedrock excavation to determine if conditions encountered are in conformance with the approved report. Revised recommendations relating to conditions differing from the approved

1-17

engineering geology report shall be submitted to the geotechnical engineer. 109.5.5 Permittee. The permittee shall be responsible for the work to be performed in accordance with the approved plans and specifications and in conformance with the provisions of this code, and the permittee shall engage consultants, if required, to provide professional inspections on a timely basis. The permittee shall act as a coordinator between the consultants, the contractor and the building official. In the event of changed conditions, the permittee shall be responsible for informing the building official of such change and shall provide revised plans for approvaL 109.5.6 Building Official. The building official shall inspect the project at'the various stages of work requiring approval to determine that adequate control is being exercised by the professional consultants. 109.5.7 Notification of Noncompliance. If, in the course of fulfilling their respective duties under this chapter, the civil engineer, the geotechnical engineer. or the engineering geologist finds that the work is not being done in conformance with this chapter or the approved grading plans, the discrepancies shall be reported immediately in writing to the permittee and to the building official. 109.5.8 Transfer of Responsibility. If the civil engineer, the geotechnical engineer, or the engineering geologist of record is changed during grading, the work shall be stopped until the replacement has agreed in writing to accept their responsibility within the area of technical competence for approval upon completion of the work. It shall be the dl.¢Y of the permittee to notify the building official in writing of such change prior to the recommencement of such grading.

109.6 COMPLETION OF WORK 109.6.1 Final Reports. Upon completion of the rough grading work and at the final completion of the work, the following reports and drawings and supplements thereto are required for engineered grading or when professional inspection is performed for regular grading, as applicable: L

An as-built grading plan prepared by the civil engineer retained to provide such services in accordance with Section 109.5.5 showing original ground surface elevations, as-graded ground surface elev2tions, lot drainage patterns, and the locations and elevations of surface drainage facilities and of the outlets of subsurface drains. As-constructed locations, elevations and details of subsurface drains shall be shown as reported by the geotechnical engineer. Civil engineers shall state that to the best of their knowledge the work within their area of

National Structural Code of the Philippines, Volume '1


1-18

responsibility was done in accordance with the final

approved grading plan.

2.

A report prepared by the geotechnical engineer retained to provide such services in accordance with Section 109.5.3, including locations and elevations of field density tests, summaries of field and laboratory tests, other substantiating data, and comments on any changes made during grading and their effect on the recommendations made in the approved geotechnical engineering investigation report. Geotechnical engineers shall submit a statement that, to the best of their knowledge, the work within their area of responsibilities is in accordance with the approved geotechnical engineering report and applicable provisions of this section.

3.

A report prepared by the engineering geologist retained to provide such services in accordance with Section 109.5.3, including a final description of the' geology of the site and any new information disclosed during the grading and the effect of same on recommendations incorporated in the approved grading plan. Engineering geologists shall submit a statement that, to the best of their knowledge, the work within their area of responsibility is in accordance with the approved engineering geologist report and applicable provisions of this section.

4.

The grading contractor shall submit in a form prescribed by the building official a statement of conformance to said as-built plan and the specifications.

., 109.6.2 Notification of Completion. The permittee shall notify the building official when the grading operation is ready for final inspection. Final approval shall not be given until all work, including installation of all drainage. facilities and their protective devices, and all erosion-control measures have been completed in accordance with the final approved grading plan, and the required reports have been submitted.


C'HAPTER 2

MINIMUM DESIGN LOADS TABLE OF CONTENTS SECTION 201 - GENERAL ••.......••..........••...........•....•..........••........•••.......•..••......••......•..•........... 2-1

201.1

Scope ............................................... 2-1

201.2

Recognized Standards ...................... 2-1

SECTION 202 - DEFINITIONS •.••.••.....•••••......•••••.......••.................•••..................••......•..•.•.•....... 2-1

SECTION 203 - COMBINATIONS OF LOADS ....•••••.......•...........•.•.•....•.••......••......•••....•..•••• 2-3

203.1 General ........................................... 2-3 203.2 Notations ........................................ 2-3 203.3 Load Combinations Using Strength Design or Load and Resistance Factor Design ................... 2-3

203.4 203.5

Load Combination Using

Allowable Stress Design .............. 2-3

Special Seismic Load

Combination ..................... ;............. 2-4

SECTION 204 - DEAD LOADS •••••••••.•.••••••.••.•••••••.•••••••••.••••.•...•••••••..•..•••••••.••••••••••..•••••.•••••••••• 2-4

204.1 General ........................................... 2-4 204.2 Weights of Materials and

Construction ................................. 2-4

204.3

Partition Loads ...... ............................ 2-7

4

SECTION 205 - LIVE LOADS ................................................................................................... 2-7

205.1 General ........................................... 2-7 205.2 Critical Distribution ofLive Load ........................................................ 2-7 205.3 Floor Live Loads ............................. 2-7

205.4 205.5 205.6

Roof Live Loads ............................ 2-10

Reduction of Live Loads ............... 2-11

Alternative Floor Live Load

Reduction...................................... 2-11

SECTION 206 - OTHER M'lN'"WUM LOADS ••••••••.••••••.•..•.••••••.••••••••••..•.•••••••••••••••.•••.••••••.•. 2-12

206.1 206.2 206.3 206.4 206.5 206.6

General ......................................... Other Loads ............... ............ ....... Impact Loads ................................ Anchorage of Concrete and Masomy Walls ........................... Interior Wall Loads ...................... Retaining Walls ...........................

SECTION 207 - W'IN'D LOAD ••

2-12 2-12 2-12 2-12 2-12

2-12

206.7 206.8 206.9 206.10

Water Accumulation ..................... Hydrostatic Uplift ......................... Crane Loads ................................. Heliport and Helistop Landing

Areas ............................................

2-12

2-13

2-13

2-13

0 ••••••••••••••••••••••••••••••, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

207.1 General ......................................... 207.2 Definitions ............................. ...... 207.3 Symbols and Notations ................. 207.4 Calculation of Wind Loads ...........

2-14 2-14 2-15 2-15

207.5 Velocity Pressure .......................... 207.6 Gust Effect Factors ....................... 207.7 Pressure and Force Coefficients .... 207.8 FuUand Partial Loading ...............


2-14

2-18

2-20

2-20

2-20

2-ii

Structural Concrete

SECTION 208 - EARTHQUAKE DESIGN 208.1 208.2 208.3 208.4 208.5 208:6

General ......................................... Definitions .................................... Symbols and Notations ................. Criteria Selection .......................... Minimmn Design Lateral Forces

and Related Effects ........ ....... ..... Dynamic Analysis Procedures ......

2-35

2-35

2-37

2-38

2-43

2-49

...........................................................................

2-35

208.7 Lateral Forces on Elements of

Structures, Nonstructural

Components and Equipment

Supported by Structures ............ .

208.8 Detailed Systems Design

Requirements ............................ . 2-56

208.9 Non-building Structures .............. . 2-59

208.10 Site Categorization Procedure ..... . 2-60


GENERAL AND DEFINITIONS

SECTION 201 - GENERAL

2-1

SECTION 202 - DEFINITIONS The following terms are defined for use in this Chapter:

201.1

SCOPE

This chapter provides minimum design load requirements for the design of buildings and other vertical structures. Loads and appropriate load combinations, which have been developed to be used together, for strength design and allowable stress design are set forth.

201.2

RECOGNIZED STANDARDS

The standards listed below are recognized standards for wind loads. 1.

ASCE 7, Chapter 6, Minimum Design Loads for Buildings and Other Structures

2.

ANSI EIAITIA 222-E, Structural Standards for Steel Antenna Towers and Antenna Supporting Structures

3.

ANSIINAAMM FPIOOl, Guide Specifications for the Design Loads of Metal Flagpoles

ACCESS FLOOR SYSTEM is an assembly consisting of panels mounted on pedestals to provide an under-floor electrical, space for the installations of mechanical, communications or similar systems or to serve as an air supply or return-air plenum. AGRIClTLTURAL BUILDING is a structure designed to house farm implements, hay, grain, poultry, livestock or other horticultural products. The structure shall not be a place of human habitation or a place of employment where agricultural products are processed, treated, or packaged, nor shall it be a place used by the public. ALLOWABLE STRESS DESIGN METHOD IS a method of proportioning structural elements such that computed stresses produced in the elements by the allowable stress load combinations do not exceed specified allowable stress (also called working stress design). ASSEMBLY BUILDING is a building or portion of a building for the gathering together of 50 or more persons for such purposes as deliberation, education, instruction, worship, entertainment, amusement, drinking or dining, or awaiting transportation. AWNING is a shelter supported entirely from the exterior wall of a building. BALCONY, EXTERIOR, is an exterior floor system· projecting from a structure and supported by that structure, with no additional independent supports. DEAD LOADS consist of the weight of ali materials and fixed equipment incorporated into the building or other structure. DECK is an exterior floor system supported on at least two opposing sides by an adjoining structure and/or posts, piers, or other independent supports. ESSENTIAL FACILITIES are buildings and other structures that are intended to remain operational in the event of extreme environmental loading from wind or earthquakes. FACTORED LOAD is the product of a load specified in Sections 204 through 208 and a load factor. See Section 203.3 for combinations of factored loads. GARAGE is a building or portion thereof in which motor vehicle containing flammable or combustible liquids or gas in its tank is stored, repaired or kept.


2-2

MINIMUM DESIGN LOADS

GARAGE, PRIVATE, is a building or a portion of a building, not more than 90 m2 in area, in which only motor vehicles used by the tenants of the building or buildings on the premises are kept or stored.

EXTERIOR WALL is any wall or element of a wall, or any member or group of members. that defines the exterior boundaries or courts of a building and that has a slope of60 degrees or greater with the horizontal plane.

LIMIT STATE is a condition in which a structure or component is judged either to be no longer useful for its intended function (serviceability limit state) or to be unsafe (strength limit state).

NONBEARING WALL bearing wall.

LIVE LOADS are those loads produced by the use and occupancy of the building or other structure and do not include dead load, construction load, or environmental loads such as wind load, snow load, rain load, earthquake load or flood load.

PARAPET WALL is that part of any wall entirely above the roof line. RETAINING WALL is a wall designed to resist the lateral displacement of soil or other materials.

LOADS are forces or other actions that result from the weight of all building materials, occupants and their possessions, environmental effects, differential move ments, and restrained dimensional changes. Permanent loads are those loads in which variations over time are rare or ofsmall magnitude. All other loads are variable loads. LOAD AND RESISTANCE FACTOR DESIGN (LVD) MEmOD is a method of proportioning structural elements using load and resistance factors such that no applicable limit state is reached when the structure is subjected to all ,appropriate load combinations. The term "LRFD" is used in the design of steel and wood structures. MARQUEE is a permanent roofed structure attached to and supported by the building and projecting over public property.

OCCUPANCY is the purpose for that a building, or part thereof, is used or intended to be used. STRENGm DESIGN MEmOD is a method of proportioning structural elements such that the computed forces produced in the elements by the factored load combinations do not exceed the factored element strength. The term "strength design" is used in the design of concrete and masonry structures. WALLS BEARING WALL is any wall meeting either of the following classifications: 1. Any metal or wood stud wall that supports more than 0.5 kN per linear meter of superimposed load. Any masonry or concrete waH that supports more 2. than 1.0 kN per lineal meter superimposed loads, or any such wall supporting its own weight for more than one story.

L

is any wall that is not a


COMBINATIONS OF LOADS

SECTION 203 - COMBINATIONS OF LOADS

2-3

1.2D+1.0E+ hL 0.9 D ± (1.0 E or 1.3 W)

(203-5) (203-6)

Where:

203.1

GENERAL

h

Buildings and other structures and all portions thereof shall be designed to resist the load combinations specified in Section 203.3 or 203.4 and, where required by Section 208, or Chapters 3 through the special seismic load combinations of Section 203.5. The most critical effect can occur when one or more of the contributing loads are not acting. All applicable loads shall be considered, including both earthquake and wind, in accordance with the specified load combinations.

EXCEPTIONS: 1.

2.

3.

203.2

F H

Lr

P T

w

1.0 for floors in places of public assembly, for live loads in excess of 4.8 kPa, and for garage live load. 0.5 for other live loads.

Factored load combinations for structural concrete per Section 409.2. Factored load combinations of this section multiplied by 1. masonry where load combinations include seismic forces. Where other factored load combinations are specifically required by the provisions ofthis code.

NOTATIONS dead load.

earthquake load set forth in Section 208.5. L 1.

estimated maximum earthquake force that can be

developed in the structure as set forth in Section

208.5.1.1. load due to fluids. load due to lateral pressure of soil and water in soil.

live load, except roof live load, including any

permitted live load reduction.

roof live load, including any permitted live load reduction. ponding load. self-straining force and effects arising from resulting from contraction or expansion temperature change, shrinkage, moisture change, creep in component materials, movement due to differential settlement, or combinations thereof load due to wind pressure.

203.3.2 Other loads. Where F, H, P or T are to be considered in design, each applicable load shall be added to the above combinations factored as follows: 1.3F, 1.6H, 1.2P and 1.2T.

203.4 LOAD COMBINATIONS A\LLOWABLE STRESS DESIGN.

203.4.1 Basic load combinations. Where allowable stress design (working stress design) is used, structures and all portions thereof shall resist the most critical effects • resulting from the following combinations of loads: D

(203-7)

+L +LT D +(wor~) 1.4

203.3.1 Basic load combinations. Where Load and Resistance Factor Design is used, structures and all portions thereof shall resist the most critical effects from the following combinations of factored loads: I.4D

(203-1)

1.2 D + 1.6 L + 0.5 L,. 1.2 D + 1.6 LT + (Ii L or 0.8 W) I.2 D + 1.3 W fl L + 0.5 L,.

(203-2) (203-3) (203-4)

(203-8)

D

0.9D ±

203.3 LOAD COMBINATIONS USING LOAD AND STRENGTH DESIGN OR RESISTANCE FACTOR DESIGN.

USING

D

~ 1.4

+0.75 [L + LT +(worl~)J

(203-9)

(203-10) (203-11)

No increase in allowable stresses shall be used with these load combinations except as specifically permitted by Section 308.2.

203.4.2 Alternate basic load combinatioDS. In lieu of the basic load combinations specified in Section 203.4.1, structures and portions thereof shall be permitted to be designed for the most critical effects resulting from the following load combinations. wIien using these alternate basic load combinations, a one-third increase shall be

National Structural Code of 1he Philippines, Volume 1


2-4

permitted in allowable stresses for all combinations, including W or E.

SECTION 204 - DEAD LOADS

D+ L + Lr

(203-12)

204.1 GENERAL

D'+L+W

(203-13)

E

(203-14)

D +L + 1.4

EXCEPTIONS: Crane hook loads need not be combined with roof live load or with more than one halfofthe wind load

203.4.3 Other loads. Where F~ H, P or T are to be considered in design, each applicable load shall be added to the combinations specified in Sections 203.4.1 and 203.4.2. When using the alternate load combinations specified in Section 203.4.2, a one-third increase shall be permitted in allowable stresses for all combinations including Wor E.

203.5 SPECIAL COMBINATIONS

SEISMIC

Dead loads consist of the weight of all materials and fixed , equipment incorporated into the building or other structure, including but not limited to walls, floors, roofs, ceilings, stairways, built-in partitions, finishes, cladding and other similarly incorporated architectural and structural items, and fixed service equipment, including the weight of cranes.

204.2 WEIGHTS CONSTRUCTION

OF

LOAD

(203-17) (203-18)

Where: fl

AND

The actual weights of materials and constructions shaH be used in determining dead loads for purposes of design. In the absence of definite information, it shall be permitted to use the minimum values in Tables 204-1 and 204-2.

For both Allowable Stress Design and Strength Design, the following special load combinations for seismic design shall be used as specifically required by Section 208, or by Chapters 3 through 8.

I2D + flL + 10Em 0.9D± 1.0E",

MATERIALS

= 1.0

for floors in places of public assembly, for live loads in excess of 4.8 kPa, and for garage live load. 0.5 for other live loads.


DEAD LOADS

TABLE 204-1

2-5

Minimum Densities for Design Loads from Materials (kN/m3 )

Aluminum .............................. 26.7 BITUMINOUS PRODUCTS Asphaltum ........................... Graphite ..................... ......... Paraffin ..... ......... ... ..... .......... Petroleum, crude .................. Petroleum, refined ................ Petroleum, benzine ............. " Petroleum, gasoline .............. Pitch ................................... Tar ......................................

12.7 21.2 8.8 8.6 7.9 7.2 6.6 10.8 11.8

Brass ...................................... 82.6 Bronze . .......... ........... .............. 86.7 Cast-stone masonry (cement, stone, sand) .. .... ... .. .. ... .... .. . 22.6 Cement, portland, loose .......... 14.1 Ceramic tile ............................ 23.6 Charcoal ..... ........ .. ...... ........ ... . . l. 9 Cinder fill ................................ 9.0 Cinders, dry, in bulk ... ........ ..... 7.1 COAL Anthracite, piled ................... 8.2 Bituminous, piled . ... .... ......... 7.4 Lignite, piled ........................ 7.4 Peat, dry, piled ..................... 3.6

EARTH (not submerged) Clay, dry ............................. Clay, damp ......................... Clay and gravel, dry ........ .... Silt, moist, loose ................. Silt, moist, packed .............. Silt, flowing ........................ Sand and gravel, dry, loose .. Sand and gravel, dry, packed. Sand and gravel, wet............. EARTH (submerged) Clay .................................... Soil ..................................... Rivermud ........................... Sand or gravel . ... ........ ......... Sand or gravel and clay.......

Masonry grout ........................ 22.0 9.9 17.3 15.7 12.3 15.1 17.0 15.7 17.3 18.9

Particleboard .......................... Plywood ................................. 12.6 11.0 14.1 9.4 10.2

Glass ...................................... 25.1 Gravel, dry ............................. 16.3 Gypsum, loose ....... .... ..... ....... 11.0 Gypsum, wallboard ....... ......... 7.9 Ice ......................................... 9.0 IRON Cast .................................. Wrought ...........................

70.7 75.4

Lead ..................................... IlLS CONCRETE, PLAIN Cinder ................................. 17.0 Expanded-slag aggregate ..... 15.7 Haydite (burned-clay aggregate) ........................ 14.1 Slag ..................................... 20.7 Stone ................................... 22.6 Vermiculite and perlite aggregate, nonloadbearing ......................... 3.9-7.9 Other light aggregate, load bearing ..................... 11.0-16.5 CONCRETE, REThWORCED Cinder ................................. 17.4 Slag ..................................... 21.7 Stone, (including gravel) ..... 23.6 Copper ................................... 87.3 Cork, compressed ........ ........... 2.2

LIME Hydrated, loose ................... Hydrated, compacted ... .... .. .

MASONRY, RUBBLE STONE Granite ................................ 24.0 Limestone, crystalline ......... 23.1 Limestone, oolitic ................ 21.7 Marble ................................. 24.5 Sandstone .......................... " 21.5 Mortar, cement or lime .. ...... 20.4

5.0 7. 1

MASONRY, ASHLAR STONE Granite . ... ........ .. .............. ... 25.9 Limestone, crystalline ......... 25.9 Limestone, oolitic ............... 21.2 Marble ................................ 27.2 Sandstone ........................... 22.6 MASONRY, BRICK Hard (low absorption) 20.4 Medium (medium absorption) ....... ............... 18.1 Soft (high absorption) . ........ 15.7 MASONRY, CONCRETE (solid portion) Lightweight units ................ 16.5 Medium weight units .......... 19.6 Normal weight units ........... 2l.2

7.1 5.7

RIPRAP (not submerged) Limestone ........................... 13.0 Sandstone ............................ 14.1 SAND Clean and dry ...... ,.............. . 14.1 River, dry ........................... . 16.7 SLAG 1l.0 Bank Bank screenings ................. . 17.0 Machine ............................. . 15.1 Sand ............................ :...... . 8.2 Slate ....................................... 27.0 Steel, cold-drawn .................... 77.3 STONE, QUARRIED, P~ED Basalt, granite, gneiss .......... Limestone, marble, quartz ... Sandstone ... , '" ., ............ ,..... . Shale ................................... Greenstone, hornblende .......

15.1 14.9 12.9 14.5 16.8

TERRA COTTA, Architectural Voids filled ......................... 18.9 Voids unfilled ...................... 11.3 Tin .......................................... 72.1 WATER Fresh ...................................

9.8

Sea ...................................... 10.1 Wood (see Table 6.2 for relative densities for Philippine wood) Zinc, rolled sheet .................... 70.5



Table 204 -2

Minimum Design Dead Loads (kPa) (Use actual loads when available) Load

CEILINGS Acoustical Fiber Board ............ 0.05 Gypsum Board (per mm thickness) ............................ 0.008

Mechanical duct allowance ........ 0.20

Plaster on tile or concrete ........ 0.24

Plaster on wood lath ............... 0.38

Suspended steel channel

system ................................. 0.10 Suspended metal lath and cement plaster ... ....... ....... .. ... 0.72 Suspended metal lath and gypsum plaster ..................... 0.48 Wood furring suspension system .................................. 0.12

Waterproofing membranes: Bituminous, gravel-covered 0.26 Bituminous, smooth surface. 0.07 Liquid, applied .................... 0.05 Single-ply, sheet ................ 0.03 Wood Sheathing (per mm thickness) ............................ 0.0057 Wood shingles .......................... 0.14

FLOOR FILL Cinder concrete, per mm ........... 0.017 Lightweight concrete, per mm ... 0.015 Sand, per mm ............................ 0.015 Stone concrete, per mm ............. 0.023

FLOOR AND FLOOR FINISHES COVERINGS,

ROOF

AND

WALL Asphalt shingles .......................... 0.10 Cement tile .................................. O.77 Clay tile (for mortar add 0.48 kPa) Book tile, 50 mm ................... 0.57

Book tile, 75 mm .................... 0.96

Ludowici ................................ 0.48

Roman ................................... 0.57

Spanish .................................. 0.91

Composition: Three-ply ready roofing.......... 0.05 Four-ply felt and gravel... ....... 0.26 Five-ply felt and gravel .......... 0.29 Copper or tin ............................... 0.05 Corrugated asbestos-cement roofing ..................................... 0.19

Deck, metal 20 gage .................. 0.12

Deck, metal, 18 gage .................. 0.14

Fiberboard, 13 mm ..................... 0.04

Gypsum sheathing, 13 mm ......... 0.10

Insulation., roof boards (per mm thickness)

Cellular glass .................. 0.0013

Fibrous glass ................... 0.0021

Fiberboard ....................... 0.0028

Perlite ............ :................ 0.0015

polystyrene foam ............. 0.0004

Urethane foam with skin ." 0.0009

Plywood (per mm thickness) .. 0 ..0060 Rigid Insulation., 13 mm ......... 0.04 Skylight, metal frame, 10 mm wire glass .... ........ ..... ... ......... 0.3 8

Slate, 5 mm ............................. 0.34

Slate, 6 mm ............................. 0.48

Asphalt block (50 mm), 13 mm mortar ..................................... 1.44 Cement finish (25 mm) on stone-concrete fill ..................... 1.53 Ceramic or quarry tile (20 mm) on 13 mm mortar bed .............. 0.77 Ceramic or quarry tile (20 mm) on 25 mm mortar bed .............. 1.10 Concrete fill finish (per mm thickness) .............................. 0.023 Hardwood flooring, 22 mm ........ 0.19 Linoleum or asphalt tile, 6mm ..... 0.05 Marble and mortar on stoneconcrete fill ............................. 1.58 Slate (permm thickness) ........... 0.028 Solid flat tile on 25 mm mortar base ......................................... 1.10 Subflooring, 19 mm .................... 0.14 Terrazzo (38 mm) directly on slab .......................................... 0.91 Terrazzo (25 mm) on stoneconcrete fill ............................. 1.53 Terrazzo (25 mm), 50 mm stone concrete ................................... 1.53 Wood block (76 mm) on mastic, no fill ....................................... 0.48 Wood block (76 mm) on 13 mm mortar base .............................. 0.77

FLOORS, WOOD-JOIST (no plaster) Joist

I Joist Spacing

Sizes 1 300 (nun) i nun 5Ox150 0.30 50x200 0.30 50x250 0.35 50000 0.40

! 400

I nun 0.25 10.30 i 0.30 0.35

!

i 600

i

nun 0.25 0.25

Component

Load

FRAME PARTITIONS. Movable steel partitions.......... 0.19 Wood or steel studs. 13 mm gypsum board each side ....... 0.38 Wood studs, 50 x 100, unplastered .......................... 0.19 Wood studs 50 x 100, plastered one side ................................... 0.57 Wood studs 50 x 100, plastered two side .................................. 0.96

FRAME WALLS Exterior stud walls: 5Oxl00 mm @ 400 mm, 15 mm gypsum, insulated, 10 mm siding .......................... 0.53

5Ox150 mm @ 400 mm, 15 mm gypsum, insulated, 10 mm siding .......................... 0.57 Exterior stud wall with brick veneer ................................. 2.30 Windows, glass, frame and sash ..................................... 0.38 Clay brick wythes: 100 mm ........................... 1.87

200mm ........................... 3.80

300mm ........................... 5.50

400 mm ........................... 7.42 Hollow Concrete Masonry units (Unplastered, add 0.24 kPa for each face lastered

I 2.01

II 2.20

I 2.5i~._.

13.59

21.2 kNlm ~grout

800 600 400 Full

0.30


DEAD LOADS & LIVE LOADS

204.3 PARTmON LOADS

SECTION 205 - LIVE LOADS

Floors in office buildings and other buildings where partition locations are subject to change shall be designed to support, in addition to all other loads, a uniform1y distributed dead load equal to 1.0 kPa of floor area.

205.1

EXCEPTION:

Access floor systems shall be designed to support, in addition to all other loads, a uniformly distributed dead load not less than 0.5 kPa qffloor area.

2-7

GENERAL

Live loads shall be the maximum loads expected by the intended use or occupancy but in no case shall be less than the loads required by this section.

205.2 CRITICAL DISTRIBUTION OF LIVE LOADS Where structural members are arranged to create continuity, members shall be designed using the loading conditions, which would cause maximum shear and bending moments. This requirement may be satisfied in accordance with the provisions of Section 205.3.2 or 205.4.2, where applicable.

205.3

FLOOR LIVE LOADS

205.3.1 General. Floors shall be designed for the unit live loads as set forth in Table 205-1. These loads shall be taken as the minimum live loads in kilonewton per square meter of horizontal projection to be used in the design of buildings for the occupancies listed, and loads at least equal shall be assumed for uses not listed in this section but that create or accommodate similar loadings. Where it can be determined. in designing floors that the actual live load will be greater than the value shown in Table 205-1, the actual live load shall be used in the des~n of such buildings or portions thereof Special provisions shall be made for machine and apparatus loads. 205.3.2 Distribution of uniform floor loads. Where uniform floor loads are involved, consideration may be limited to full dead load on all spans in combination with full live load on adjacent spans and alternate spans. 205.3.3 Concentrated loads. Provision shall be made in designing floors for a concentrated load, L, as set forth in Table 205-1 placed upon any space 760 mm square, wherever this load upon an otherwise unloaded floor would produce stresses greater than those caused by the uniform load required therefore. Provision shall be made in areas where vehicles are used or stored for concentrated loads, L, consisting of two or more loads spaced 1. 5 meters nominally on center without uniform live loads. Each load shall be 40 percent of the gross weight of the maximum size vehicle to be accommodated. Parking garages for the storage of private or pleasure-type motor vehicles with no repair or refueling shall h~ a floor system designed for a concentrated lo~ of not less than 8.9 kN acting on an area of 0.013 m



2-8

TABLE 205-1 (continued) - MINIMUM UNIFORM AND CONCENTRATED LIVE LOADS

without uniform live loads. The condition of concentrated or uniform live load, combined in accordance with Section 203.3 or 203.4 as appropriate, producing the greatest stresses shall govern.

I

205.3.4 Special loads. Provision shall be made for the special vertical and lateral loads as set forth in Table 205-2.

USE OR OCCUPANCY

Uniform 1 Load

Category

Description

kPa

Concen trated Load kN

Basic floor area

1.9

0

I I

TABLE 205-1 MINIMUM UNIFORM AND CONCENTRATED LIVE LOADS 'fi ConcenU

-l

USE OR OCCUPANCY

Dl

orm

13. Residential

d

Access systems

floor

2.4

9.0)

Computer use

4.8

9.0 2

7.2

0

16. Roof decks

2.9

0

17. Schools

4.8

0

18. Sidewalks and driveways

4.8

0

Fixed seating

,

3. Assembly areas

Movable seating

Lobbies platforms

and auditorium and balconies

therewith

and !

7.2

Stag.es llreas

i 4.

t

Cornices and marquees Dining rooms and restaurants

6. -.Exit facilities ........ ..

-

4.8

5

7. Garages

8. Hospitals

I

4.8

0

21. 6

-

General storage and/or repair Prhllte or i pleasure-type motor vehicle .... storage and! Wards rooms

4.8

--

2.4

--

1.9

4.5 .:>

Laboratories & operating rooms

2.9

Reading rooms

i

7

4.5

2

2.9

4.5

2

Stack rooms

7.2

6.7 2

Light

6.0

9.0

Heavy

12.0

13.4)

-

2.4

9.0~

I

9. Libraries

I

2

10. Manufacturing

11. Offices

I 12. Printing plants

i

I 7.2

Press rooms Composing and linotype rooms

4.8

11.0 2 9.0 2

Pedestrian bridges and walkways

0

1.9

0

--

--

--

--

4.8

0

Same as area or served Occupancy

--

--

1.9

4.5

Public access

12.0

-- 7

Light

6.0 12.0

---

4.8

4.5 2

Wholesale

6.0

13.4

-

4.8

--

,

20. Stores

0

0

4

1.9

• Retail

0

2.9 4

Storage

19. Storage

~

3.6 4

. I

9

()fticeuse

2. Armories

3

14. Restrooms

15. Reviewing stands, grandstands, and Bleachers, folding and telescoping seating

_.

Exterior balconies

Decks

~~.~-.--.~~--_kPa~a~t:::-l Category Description kN 1.

8

6

2

2

NOTES FOR TABLE 205-1 See Section 205.5 for live load reductions. 2 See Section 205.3.3, first paragraph, for area of load application. 3 Assembly areas include such occupancies as dance halls, drill rooms, gymnasiums, playgrounds, plazas, terraces and similar occupancies that are generally accessible to the public. 4 For special-purpose roofs, see Section 205.4.4. 5 Exit facilities shall include such uses as corridors serving an occupant load of 10 or more persons, exterior exit balconies, stairways, fire escapes and similar uses. Individual stair treads shall be designed to support a 1.3 kN concentrated load placed in a position that would cause maximum stress. Stair stringers may be designed for the uniform load set forth in the table. See Section 205.3.3, second paragraph, for concentrated loads. See Table 205-2 for vehicle barriers. 8 Residential occupancies include private dwellings, apartments and hotel guest rooms. 9 Restroom loads shall not be less than the load for the occupancy with which they are associated, but need not exceed 2.4 kPa.

I


UVELOADS

TABLE 205-2 - SPECIAL LOADS 1

NOTES FOR TABLE 205-2

USE

Vertical Load

Lateral Load

Category

kPa

kPa

Walkway

7.2

-

Canopy

7.2

-

L

2.

Construction, public access at site (live load) Grandstands, reviewing, stands bleachers, and folding and telescoping seating' (live load)

4.

Followspot, . projection and ; control rooms

1

~

2.4

-

1.0

-

0.5 4

lover stages

5.

-

11.9

. CelTmg framIng . . stages (live load) • All uses except

Partitions and interior walls, 6. Elevators and dumbwaiters( dead and live loads)

I-

I 0.25

I - 2 x total loads

I

facilities an occupant load ~erthan50 •

Balcony railings and guardrails

!

Other than exit 1 facilities •

r- I Components

10. Vehicle barriers II. Handrails

I I

-

I

12. Storage racks

I

-

13.

Fire sprinkler structural support

I

0.75 7 kN/m

I

0.30 kN/m 7

-

I __

1.2 8

I - I See

27kN9 J

Over 2.4 meter high

Total ll loads

-

plus weight of water-

Ll

i

x

I

. Note 10

I

0.10 total 6 load

Exit

serving

-

x

1.25 total load'

Total load including impact increase

8. Cranes (dead and live loads)

9.

I

See Note 3

2

The tabulated loads are minimum loads. Where other vertical by this code or required by the design would cause greater stresses, they shall be used. Loads are in kPa unless otherwise indicated in the table. 2 Units is kN/m. 3 Lateral sway bracing loads of 350 N/m parallel and 145 N/m perpendicular to seat and footboards. 4 Does not apply to ceilings that have sufficient total access from below, such that access is not required within the space above the ceiling. Does not apply to ceilings if the attic areas above the ceiling are not provided with access. This live load need not be considered as acting simultaneously with other live loads imposed upon the ceiling framing or its supporting structure. S The impact factors included are for cranes with steel wheels riding on steel rails. They may be modified if substantiating technical data acceptable to the building official is submitted. Live loads on crane support girders and their connections shall be taken as the maximum crane wheel loads. For pendant-operated traveling crane support girders and their connections, the impact factors shall be 1.10. 6 This applies in the direction parallel to the runway rails (longitudinal). The factor for forces perpendicular to the rail is 0.20 x the transverse traveling loads (troiley, cab, hooks and lifted loads). Forces shall be applied at top of rail and may be disturbed among rails of multiple rail cranes and shall be distributed with due regard for lateral stiffness of the structures supporting these rails. 7 A load per lineal meter (kN/m) to be applied horizontally at right angles to the top rail. 8 Intermediate rails, panel fillers and their connections shall be capable of withstanding a load of 1.2 kPa applied horizontally at right angles over the entire tributary area, including openings and spaces between Pails. Reactions due to this loading need not be combined with those of Footnote 7. 9 A horizontal load in kilo newtons applied at right angles to the vehicle barrier at a height of 450 mm above the parking surface. The force may be distributed over a 300-millimeter-square are1\. 10 The mounting of handrails shall be such that the completed handrail and supporting structure are capable of withstanding a load of at least 890 N applied in any direction at any point on the rail. These loads shall not be assumed to act cumulatively with Item 9. 11 Vertical members of storage racks shall be protected from impact forces of operating equipment, or racks shall be designed so that failure of one vertical member will no cause collapse of more than the bay or bays directly supported by that member. 12 The 1.1 kN load is to be applied to any single fire sprinkler support point but not simultaneously to all support joints.. 1

I Catwalks

3. Stage accessories (live load)

1.75 kN/m

Seats and footboards

I See Note 10

1

. See Table 208-12

kN See Table

filled

I

i

2-9

pipeJ2

Nationaf Structural Code of the Philippines, Volume 1


2-10

205.4 ROOF LIVE LOADS

whenever this loading creates greater stresses than those caused by the uniform live load. The concentrated load shall be placed on the member over a length of 750 mm along the span. The concentrated load need not be applied to more than one span simultaneously. Water accumulation as prescribed in Section 206.7.

205.4.1 General Roofs shall be designed for the unit live loads, L r, set forth in Table 205-3. The live loads shall be assumed to act vertically upon the area projected on a horizontal plane. 3.

205.4.2 Distribution of loads. Where uniform roof loads are involved in the design of structural members arranged to create continuity, consideration may be limited to full dead loads on all spans in combination with full roof live loads on adjacent spans and on alternate spans. EXCEPTION: Alternate span loading need not be considered where the uniform rooflive load is 1 kPa or more.

For those conditions where light-gage metal preformed structural sheets serve as the support and finish of roofs, roof structural members arranged to create continuity shall be considered adequate if designed for full dead loads on all spans in combination with the most critical one of the following superimposed loads: 1. The uniform roof live load, L r, set forth in Table 205-3 on all spans. 2. A concentrated gravity load, L r, of 9 kN placed on an:! span supporting a tributary area greater than 18.5 m to create maximum stresses in the member,

205.4.3 Unbalanced loading. Unbalanced loads shall be used where such loading will result in larger members or connections. Trusses and arches shall be designed to resist the stresses caused by unit live loads on one half of the span if such loading results in reverse stresses, or stresses greater in any portion than the stresses produced by the required unit live load on the entire span. For roofs whose structures are composed of a stressed shell, framed or solid, wherein stresses caused by any point loading are distributed throughout the area of the shell, the requirements for unbalanced unit live load design may be reduced 50 percent. 205.4.4 Special roof loads. Roofs to be used for special purposes shall be designed for appropriate loads as approved by the building official. Greenhouse roof bars, purlins and rafters shall be designed to carry a 0.45 kN concentrated load, L,., in addition to the uniform live load.

Table 205-3 Minimum Roof Live Loads 1 METHOD 1 Tributary Area (mZ)

ROOF SLOPE

o to

18.5

METHOD 2

18.5 to 56

Over 56

Uniform Load (kPa)

• Uniform Load} . (kPa)

I

of Rate Reduction, r

Maximum Reduction R

(percenfaJ1;e)

(percentage)

1. Flaf or rise less than 4 units vertical in 12 units horizontal (33.3% slope). Arch and dome with rise less than one-eicllt of span. 2. Rise 4 units vertical to less than 12 units vertical in 12 units horizontal (33% to less than 100% slope). Arch and domes with rise one-eight of span to less than three-.eights of span. 3. Rise 12 units vertical in 12 units horizontal (100% slope) and greater. Arch or dome with rise three eights ofspan or greater

1.00

0.75

0.60

1.00

0.08

40

0.75

0.70

0.60

0.75

.0.06

25

0.60

0.60

0.60

0.60

4. Awnings except cloth covered.

0.25

0.25

·0.25

0.25

050

0.50

0.50

0.50

4

5. Green1iouses, lath houses and Agricultural buildings. 5 1

2

For special-purpose roofs, see Section 205.4.4 See Sections 205.5 and 205.6 for live-load reductions. The rate of reduction r in Equation 205-1 shall be as indicated in the table. The maximum reduction, R, shall not exceed the value indicated in the table.

3

4

S

No reduction permitted

A flat roof is any roof with a slope less than 1/4 unit vertical in 12 units horizontal (2% slope). The live load for flat roofs is in addition to the ponding load required by Section 206.7. See definition in Section 202. See Section 205.4.4 for concentrated load requirements for greenhouse roof members.


LNELOADS

205.5 REDUCTION OF LIVE LOADS The design live load deteffilined using the unit live loads as set forth in Table 205-1 for floors and Table 205-3, Method 2, for roofs mar be reduced on any member supporting more than 14 m , including flat slabs, except for floors in places of public assembly and for live loads greater than 4.8 kPa, in accordance with the following Equation: R

=

r (A - 14)

(205-1)

L

Lo

2-11

product of the span and the full flange width for a precast T -beam. reduced design live load per square meter of area supported by the member. unreduced design live load per square meter of area supported by the member (Table 205-1).

The reduced live load shall not be less than 50 percent of the unit live load Lo for members receiving load from one level only, nor less than 40 percent of the unit live load Lo for other members.

The reduction shall not exceed 40 percent for members receiving load from one level only, 60 percent for other members or R, as determined by the following Equation:

R

= 23.1

(1 + DIL)

(205-2)

Where: A

D

L

R r

= area

of floor or roof supported by the member, square meter. dead load per square meter of area supported by the member. = unit live load per square meter of area supported by the member. == reduction in percentage. 0,8'" rate of reduction equal to~ percent for floors. See Table 205-3 for roofs.

For storage loads exceeding 4.8 kPa, no reduction shall be made, except that design live loads on columns may be reduced 20 percent. The live load reduction shall not exceed 40 percent in garages for the storage of private pleasure cars having a capacity ofnot more than nine passengers per vehicle.

205.6 ALTERNATE REDUCTION

FLOOR

LIVE

LOAD

As an alternate to Equation (205-1), the unit live loads set forth in Table 205-1 may be reduced in accordance with Equation 205-3 on any member, including flat slabs, having an influence area of 37.2 m2 or more.

(205-3)

Where: AI

influence 1P"ea, in square meter. The influence area AI is four times the tributary area for a column, two

times the tributary area for a beam, equal to the panel area for a two-way slab, and equal to the



2·12

SECTION 206 - OTHER MINlMUM LOADS 206.1

GENERAL

206.5

In addition to the other design loads specified in this chapter, structures shall be designed to resist the loads specified in this section and the special loads set forth in Table 205-2. See Section 207 for design wind loads, and Section 208 for design earthquake loads.

206.2

OrnER LOADS

Buildings and other structures and portions thereof shall be designed to resist all loads due to applicable fluid pressures, F, lateral soil pressures, H, ponding loads, P, and self straining forces, T. See Section 206.7 for ponding loads for roofs.

206.3

•

using the greater of the wind or earthquake loads required 'by this chapter or a minimum horizontal force of 4.0 kN/m of wall, substituted for E.

INTERIOR WALL LOADS

Interior walls, permanent partitions and temporary partitions that exceed 1.8 meters in height shall be designed to resist all loads to which they are subjected but not less than a load, L, of 0.25 kPa applied perpendicular to the walls. The 0.25 kPa load need not be applied simul taneously with wind or seismic loads. The deflection of such walls under a load of 0.25 kPa shall not exceed ]/240 of the span for walls with brittle finishes and ]/120 of the span for walls with flexible finishes. See Table 208-12 for earthquake design requirements where such requirements are more restrictive. EXC'EPTION:

Flexible, folding or portable partitions are not required to meet the load and deflection criteria but must be anchored to the supporting structure to meet the provisions (?f this code.

IMPACT LOADS

The live loads specified in Sections 205.3 shall be assumed to include allowance for ordinary impact conditions. Provisions shall be made in the structural design for uses and loads that involve unusual vibration and impact forces. See Section 206.9.3 for impact loads for cranes, and Section 206.10 for heliport and helistop landing areas. 206.3.1 Elevators. All elevator loads shall be increased by 100% for impact. 206.3.2 Machi~ery. For the purpose of design, the weight of machinery and moving loads shall be increased as follows to allow for impact: 1. Elevator machinery .... ..... .. .. .. ... .... 100% 2. Light machinery, shaft- or motor-driven ................. ,.... ... 20010 3. Reciprocating machinery or power-driven units ................ 50% 4. Hangers for floors and balconies ..... ......... ............. .... 33%

206.6

RETAINING WALLS

Retaining walls shall be designed to resist loads due to the lateral pressure of retained material in accordance with accepted engineering practice. Walls retaining drained soil, where the surface of the retained soil is level, shall be designed for a load, H, equivalent to that exerted by a fluid weighing not less than 4.7 kPa per meter of depth and having a depth equal to that of the retained soil. Any surcharge shall be in addition to the equivalent fluid pressure. Retaining walls shall be designed to resist sliding by at least 1.5 times the lateral force and overturning by at least 1.5 times the overturning moment, using allowable stress design loads.

206.7 WATER ACCUMULATION All percentages shall be increased where specified by the manufacturer.

206.4 ANCHORAGE OF CONCRETE AND MASONRY WALLS

All roofs shall be designed with sufficient slope or camber to ensure adequate drainage after the long-term deflection from dead load or shall be designed to resist ponding load, P, combined in accordance with Section 203.3 or 203.4. Ponding load shall include water accumulation from any source due to deflection.

Concrete and masonry walls shall be anchored as required by Section 104.3.4. Such anchor:age shall be capable of resisting the load combinations of Section 203.3 or 203.4


OTHER MINIMUM LOADS

206.8

HYDROSTATIC UPLIFT

All foundations, slabs and other footings subjected to water pressure shall be designed to resist a uniformly distributed uplift load, F, equal to the full hydrostatic pressure.

206.10 HELIPORT LANDING AREAS

2-13

AND

HELISTOP

In addition to other design requirements of this chapter, heliport and helistop landing or touchdown areas shall be designed for the following loads, combined in accordance with Section 203.3 or 203.4:

206.9' CRANE LOADS 206.9.1 General. The crane load shall be the rated capacity of the crane. Design loads for the runway beams, including connections and support brackets, of moving bridge cranes and monorail cranes shall include the maximum wheel loads of the crane and the vertical impact, lateral, and longitudinal forces induced by the moving crane. 206.9.2 Maximum wheel load. The maximum wheel loads shall be the wheel loads produced by the weight of the bridge, as applicable, plus the sum of the rated capacity and the weight of the trolley with the trolley positioned on its runway where the resulting load effect is maximum.

1.

Dead load plus actual weight ofthe helicopter.

2.

Dead load plus a single concentrated impact load, L, covering 0.093 m2 of 0.75 times the fully loaded weight of the helicopter if it is equipped with hydraulic-type shock absorbers, or 1.5 times the_fully loaded weight of the helicopter if it is equipped' with a rigid or skid-type landing gear. The dead load plus a uniform live load, L, of 4.8 kPa. The required live load may be reduced in accordance with Section 205.5 or 205.6.

206.9.3 Vertical Impact force. The maximum wheel loads of the crane shall be increased by the percentages shown below to determine the induced vertical impact or vibration force: 1. Monorail cranes (powered) ............. 25% 2. Cab-operated or remotely operated bridge cranes (powered) ., ....... ... ....................... 25% 3. Pendant-operated bridge cranes (powered) .................................. 10% 4. Bridge cranes or monorail cranes with hand-geared bridge, trolley and hoist.......................... 0010 206.9.4 Lateral force. The lateral force on crane runway beams with electrically powered trolleys shall be calculated as 20% of the sum of the rated capacity of the crane and the weight of the hoist and troBey. The lateral force shall be assumed to act horizontally at the traction surface of a runway beam, in either direction perpendicular to the beam, and. sha11 be distributed with due regard to the lateral stiffness ofthe runway beam and supporting structure. 206.9.5 Longitudinal forces. The longitudinal forces on crane runway beams, except for bridge cranes with hand geared bridges, shall be calculated as 100/0 of the maximum wheel loads of the crane. The longitudinal force shall be assumed to act horizontally at the traction surface of a runway beam, in either direction parallel to the beam.


2-14


SECTION 207 - WIND LOAD 207.1 GENERAL Every building or structure and every portion thereof shall be designed and constructed to resist the wind effects determined in accordance with the requirements of this section. These provisions apply to the calculation of wind loads for main wind-force resisting systems and for individual structural components and cladding of buildings and other structures. Specific requirements are given for using wind-tunnel investigations to determine wind loading and structural response for buildings or other structures having irregular geometric shapes, response characteristics, or site locations with shielding or channeling effects that warrant specific investigation, or to establish more accurate wind loading. The provisions of this section do not apply to building and foundation systems in those areas subject to scour and water pressure by wind and wave action.

These conditions are expressed by the following equations: 1. Ao > 1.lOAoi 2. Ao > smaller of (0.5 m2 or O.OIAg), and Ao;lAg;:<; 0.20

where: Ao = the total area of openings in a wall that receives

positive external pressure, in square meters

Ag = the gross area ofthat wall in which Ao is identified,

in square meters Ao! = the sum of the areas of openings in the building envelope (walls and root) not including Ao, in square meters Agi the sum of the gross surface areas of the building envelope (walls and root) not including Ago in square meters BUILDING, LOW RISE is an enclosed or partially enclosed building which complies with the following conditions: 1. mean roof height, h, less than or equal to 18 meters. 2. mean roof height, h, does not exceed least horizontal dimension. COMPONENTS AND CLADDING are elements that do not qualify as part of the main wind-force resisting system.

207.2 DEFINITIONS The following definitions apply to the provisions of Section 207. BASIC WIND SPEED, V is a 3-second gust speed at 10 meters above the ground in Exposure C (see Section 207.5.3.1) and associated with an annual probability of 0.02 of being equaled or exceeded (50-year mean recurrence interval). Bun.DING, ENCLOSED is a building that does not comply with the requirements for open or partially enclosed buildings. Bun.DING, OPEN is a structure having all walls at least 80% open. BUILDING, PARTIALLY ENCLOSED is a building that complies with both ofthe following conditions: 1. the total area of openings in a wall that receives positive external pressure exceeds the sum of the areas of openings in the balance of the building envelope (walls and root) by more than 10%; and 2. the total area of openings in a wall that receives positive external pressure exceeds 0.5 m2 or 1% of the area of that wall, whichever is smaller, and the percentage of openings in the balance of the building envelope does not exceed 20%.

DESIGN FORCE, F, is the equivalent static force to be used in the determination of wind loads for open buildings and other structures. DESIGN PRESSURE, p, is the equivalent static pressure to be used in the determination of wind loads for buildings. The pressure is denoted as: pressure that varies with height in accordance pz with the velocity pressure qz evaluated at height Z, or pressure that is uniform with respect to height as determined by the velocity pressure qh evaluated at mean roof height h. EFFECTIVE WIND AREA is the area used to determined GCp • For components and cladding panels, the effective wind area in Figures 207-5 through 207-8 is the span length multiplied by an effective width that need not be less than one-third the span length. For cladding fasteners, the effective wind area shall not be greater than the area that is tributary to an individual fastener. FLEXmLE Bun.DINGS AND OTHER STRUC· TURES are slender buildings and other structures that have a fundamental natural frequency less than 1 Hz. Included are buildings and other structures that have a height, h, exceeding four times the least horizontal dimension.


WIND LOAD

v

velocity pressure exposure coefficient evaluated at height z. topographic factor. horizontal dimension of a building measured parallel to the wind direction, in meters. distance upwind of crest of hill or escarpment in Fig 207-2 to where the difference in ground elevation is half the height of hill or escarpment, in meters. larger dimension of sign, in meters. smaller dimension of sign, in meters. design pressure to be used in the determination of wind loads for buildings, in kilo newtons per square meters (kilopascals). h, in design pressure evaluated at height z kilopascals. wind pressure acting on leeward face in Figure 207-9. wind pressure acting on windward face in Figure 207-9. design pressure evaluated at height z above ground, in kilopascals. velocity pressure, in kilopascals. h, in velocity pressure evaluated at height z kilopascals. velocity pressure evaluated at height z above ground, in kilopascals. rise-to-span ratio for arched roofs. basic wind speed obtained trom Figure 207-1, in kilometers per hour. The basic \vind speed corresponds to a 3-sec. gust speed at 10 meters above ground in exposure category C and is associated with an annual probability of 0.02 of being equaled or exceeded. width of a building in Figures 207-5C and 207-7 A and width of span in Figures 207-6 and 207-7B, in meters. distance to center of pressure from windward edge in Table 207-6, in meters. distance upwind or downwind of crest in Figure 207-2 in meters. height above ground level, in meters. ratio of solid area to gross area for open sign, face or a trussed tower, or lattice structure. angle of plane of roof from horizontal, in degrees height-ta-width ratio for solid sign

207.4

CALCULATION OF WIND LOADS

IMPORTANCE FACTOR, I,,~ is a factor that accounts for the degree of hazard to human life and damage to property. MAIN WIND-FORCE RESISTING SYSTEM is an assemblage of structural elements assigned to provide support and stability for the overall structure. The system generally receives wind loading from more than one surface. RECOGNIZED LITERATURE are published research findings and technical papers that are approved by the authority having jurisdiction.

M N p

207.3 SYMBOLS AND NOTATION A a

Ar

B

cp 1)

J)'

G

Gr

H h

effective wind area, in square meters. width of pressure coefficient zone, in meters area of open buildings and other structures either normal to the surface or projected on a plane normal to the wind direction, in square meters. horizontal dimension of a building measured normal to wind direction, in meters. force coefficients to be used in the determination of wind loads for other structures. external pressure coefficient to be used in the

determination of wind loads for buildings.

diameter of a circular structure or member, in

meters. depth of protruding elements such as ribs and spoilers, in meters. gust effect factor. gust effect factor for main wind-force reslstmg systems of flexible buildings and other structures. product of external pressure coefficient and gust effect factor to be used in the determination of wind loads for buildings. product of equivalent external pressure coefficient and 'gust effect factor to be used in the determination of wind loads for main wind-force resisting system oflow-rise buildings. product of internal pressure coefficient and gust effect factor to be used in the determination of wind loads for buildings. height of hill or escarpment in Fig 207-2, in meters. mean roof height of a building or height of other structure, except that eave height shall be used for roof angle 0 ofless than or equal to 10°, in meters. importance factor. Kj, K2, multipliers in Figure 207-2 to obtain K:,.

velocity pressure exposure coefficient evaluated at

height z = h.

2-15

PI['

r

V

w

x x

o

20'7.4.1

GENERAL

207.4.1.1 Allowed procedures. The design wind loads for buildings and other structures as a whole or for individual components and cladding thereof shall be determined using one of the following procedures:


2-16

1. 2.


Analytical procedure in accordance with Section 207.4.2; or Wind-tunnel procedure in accordance with Section 207.4.3.

207.4.1.2 Minimum design wind loading. The wind load used in the design of the main wind-force resisting system shall be not less than 0.5 kPa multiplied by the area of the building or structure projected on a vertical plane normal to the wind direction. In the calculation of design wind loads for components and cladding for buildings, the algebraic sum of the pressures acting on opposite faces shall be taken into account. The design pressure for components and cladding of buildings shall be not less than 0.5 kPa acting in either direction normal to the surface. The design force for open buildings and other structures shall be not less than 0.5 kPa multiplied by the areaAf

t

207.4.2 ANALYTICAL PROCEDURE Design wind pressures and design wind forces shall be determined in accordance with the appropriate equations given in Table 207-1 using the following procedure: 1. A velocity pressure q (q~ or qh) is determined in accordance with the provisions of Section 207.5. A gust effect factor G is determined in accordance 2 with the provisions of Section 207.6. 3. Appropriate pressure or force coefficients are selected from the provisions of Section 207.7. The equations given in Table 207-1 are for determination of: 0) Wind loading on main wind-force resisting systems; and (2) wind. loading on individual components and cladding.' . 207.4.2.1 Limitations of analytical procedure. The provisions of Section 207.4.2 take into consideration the load magnification effect caused by gusts in resonance with along-wind vibrations of flexible buildings and other structures but do not include allowances for across-wind loading, vortex shedding, or instability due to galloping or flutter. The designer shall refer to recognized literature or documentation pertaining to wind load effects, or use the wind-tunnel procedure of Section 207.4.3, for site locations for which channeling effects or buffeting in the wake of upwind obstructions warrant special consideration, or for those buildings and other structures having unusual geometric shapes or response characteristics.

207.4.2.3 Application of pressures and forces. Design pressures, p, shall be assumed to act in a direction normal to the surface considered. Design forces, F, shall be assumed to act on the gross structure or components and cladding in accordance with Tables 207-6 through 207-10 and shall be considered to vary with respect to height in accordance with the velocity pressure qz. 207.4.3 WIND-TUNNEL PROCEDURE Wind-tunnel tests or similar tests employing fluids other than air shall be used for the determination of design wind loads in accordance with Section 207.4.3.1. 207.4.3.1 Test conditions. Tests for the determination of mean and fluctuating forces and pressures shall be considered to be properly conducted only if all of the following conditions are satisfied: I. The natural atmospheric boundary layer has been modeled to account for the variation of wind speed with height; 2. The relevant macro (integral) length and micro length scales of the longitudinal component of atmospheric turbulence are modeled to appro ximately the same scale as that used to model the building or other structure; 3. The modeled building or other structure and surrounding structures and topography are geome trically similar to their full-scale counterparts; 4. The projected area of the modeled building or other structure and surroundings is less than 8% of the test section cross-sectional area unless correction is made for blockage; 5. The longitudinal pressure gradient in the wind tunnel test section is accounted for; 6. Reynolds number effects on pressures and forces are minimized; and 7. Response characteristics of the wind tunnel instrumentation are consistent with the required measurements. 207.4.3.2 Dynamic response. Tests for the purpose of determining the dynamic response of a building or other structure shall be in accordance with Section 207.4.3.1. The structural model and associated analysis shall account for mass distribution, stiffhess, and damping.

207.4.2.2 Air-permeable cladding. Design pressures determined from Section 207.4.2 shall be used, unless approved test data or recognized literature demonstrate lower loads for the type of air-permeable cladding being considered.


2-17

WIND LOAD

TABLE 207-1

Design Wind Pressure, p (kPa), and Forces, F (kN)

I

Low-rise buildings

I

Open buildings and other structures

Buildings of all heights

1.::,5

P = q'II(G(~.rl - «iCpj )! Main wind-force resisting systems

iJ,,: at mean roof height using Exposure C for all terrain GCpi given in Fig. 207-4

GCp ;: given in Table 207-4

p = q GCp

-

qll (GCp ;) 1.2

s

ground

G: given in Sec. 207.6. I

Ci given in Tubles 207-6

through 207-10

Aj projected area normal

to ",ind-'

iI

p = qh [(GCp ) Components and cladding 4

h> 18meters

18 meters -

(GCp ;)1 i

iJ h: at mean roof height using Exposure C [or all terrain C.tp: given in Fig. 207-5, 207-6 and 207-7 GCpt: given in Table 207--1,

I

Open buildings and other structures

I 1

I

I

q 1«iL~) - (GCpi)) 1.6

P

F = q:GC"A f

q,: at height :: ubove

q: q= for windward wall at height z above ground., qh for leeward ,YalI, side wulls and roof at mean roof height G: given in Sec. 207.6.1 (~: given in Fig. 207-3

GCf)j: giyen in Table 207-4

Buildings h

II

I

q: q= for positive pressure at

I I

F = q:GCfAf q,' at height z above

ground G: given in Sec. 207.6.1 Lj. given in Tables 207-6 through 207-10 Ai projected area normal to "ind 3

height z above ground.. tfh for negative pressure at mean roof height Gel" given in Fig. 207-8 GLp,: given in Table 207-4

Flexible Buildings and Other Structures

(f< 1 Hz. Includes buildings and structures with heightlleast horizontal dimension> 4)

Buildings

II

-I

J

!

Other Structures

----~

qG~~l.::

p

(f q, for positiV'c pressurc at height z above ground. qh for negative pressure al menn roofheighL gl\,-~n in Fig 207-8 en in Tnbie 207-4_ _ _

nt height z abmc ground gi\-en in Sec. 207.6.1 giYen in Table 207-6 through 207-10 Ai pr~iecled area normnllo

Positive pressure acts toward surface and negative pressure acts away from surface; values of extemal and internal pressures shall be combined algebraically to determine most critical load. 2 Pressure shall be applied simultaneously on windward and leeward walls and on roof surfaces as shown in Figures 207·3 and 207-4. 3 AI is the projected area normal to the wind except where Ci is given for the surface area. 4 Major structural components supporting tributary area greater than 65 m2 shall be permitted to be designed using the provisions for main wind-force resisting systems. 1

5

~

_

_

_

_

_

_

~

_

~

I_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.L-_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _- L_ _

~

Components and cladding 4

_ _ _ _. _ _

~

q,: at height z above ground Gj obtaincd by rational analYSIS

Cf givcn in Table 207-6 207-10 normal to

~

height z above ground. tf if for leeward" all at menn roof height.

obtained by rationnl

q: q= for wind"ard waU at

Main wind..force resisting systems

___________ _

Low-rise buildings shaH be pernlitted to be designed in accordance with the provisions for buildings in Section 207.5.3.2.2. In the design of components and cladding for buildings having a mean roof height h, 18 meters < h < 27 meters, GCp values of Figures 207-5, 207-6 and 207-7 shall be used only if the height to-width ratio is 1 or less and '1 is taken as tJ.:; and Exposure C (see Section 207.5.3.3.1) is used for all terrain.

National Structural Code of the Philippines, Volume 1 "·-$~?ff!W@W&'-'Pf_"

I

Ai

2-18


207.5

VELOCITY PRESSURE

207.5.1 Procedure For Calculating Velocity Pressure. The velocity pressure qt, in kilopascals, shall be calculated from the equation: (207-1) where the basic wind speed V, in kmlhr, is selected in accordance with the provisions of Section 207.5.2, the importance factor I".. is set forth in Table 207-2, and the velocity pressure exposure coefficient K= is given in Table 207-3 in accordance with the provisions of Section 207.5.3. Provisions of Section 207.5.5 shall be used to determine Kzt where applicable, but K=t shall not be less than 1.0. The numerical coefficient, 47.3xlO.o, shall be used except where sufficient climatic data are available to justify the selection of a different value of this factor for a specific design application.

Table 207-2 Importance Factor, 1'1' (Wind L01,lds)

I Occupancy I Category "I. I

I

I

1----

1-.---. II

III •. --.....

I-

.. I DescriptIOn.

Iw

Essential

1.15

Hazardous

us

Spccial

\'

1.15

- - - '-.- r --- - -- -......-... - Occupancy

~

-

-~;-l-~t::~I- ¥,;-- ~

1 see

Table 103-1 for types of occupancy under each category.

207.5.2 Select.n of Basic Wind Speed. The basic wind speed ~. used in the determination of design wind loads on buildings and other structures shall be as given in Figure 207-1 except as provided in Sections 207.5.2.1 and 207.5.2,2. 207.5.2.1 Special wind regions. The basic wind speed shall be increased where records or experience indicate that the wind speeds are higher than those reflected in Figure 207-1, Mountainous terrain, gorges and special regions shall be examined for unusual wind conditions. The authority having jurisdiction shall, if necessary, adjust the values given in Figure 207-1 to account for higher local wind speeds. Such adjustment shall be based on meteorological information and an estimate of the basic wind speed obtained in accordance with the provisions of Section 207.5.2.2.

207-1 when: (l) approved extreme-value statistical-analysis procedures have been employed in reducing the data; and (2) the length of record, sampling error, averaging time, anemometer height, data quality, and terrain exposure have been taken into account. 207.5.2.3 Limitation. Extreme typhoons have not been considered. in developing the basic wind-speed distributions. .

Table 207-3 Velocity Pressure Exposure Coefficients 1, Kh and K·z Height

above

Exposure Category 2

Ground i

r

level, Z (m)

0-4.5

B 0.57

A 0.32

~~"---~

6 7.5 9 f--. 12 r-------... 15 18 21 24 27 30 36 42 48 54 60 75 90 105 120 135 ISO

! C 0.85 ------'0.90 .

D 1.03

r--1?l

0.36 0.62 0.39 0,94 0.66 0,98 0.42 0.70 0,76 0.47 1.04..-.0.51 0.81 1.09 0.55 0.85 1.13 0.59 0.89 1.17 --- i---0,62 0.92 1.20 0,65 0,95 1.23 ------0.68 0.98 1.26 0.73 1.04 1.31 0.77 1.08 1.35 i 0.82 1.12 1.39 .---0.86 1.16 1.43 0,89 1.46 1.20 0.98 1.28 1.53 LOS 1.35 1.59 1.12 1.41 1.64 --- - - - - - - _ . - f-Ll8 1.46 1.69 -1.23 ..1.51 1.73 - - - - - - f-1.29 1.56 1.77

1.12 1.16 1.22 1.27 1.31 1.34 1.37

.

lAO

1.43 1,48 1.52 1.55 1.58 1.61 1.68 1.73 1.78 1.82 1.86 1.89

f

--~---

----~

1 Unear

interpolation for intermediate values of height Z is

permissible. Alternatively. for values of height Z between 4.5

meters and the gradient height Zg. Kz may be calculated from

K: = 2.01(Yzg

fia

where.

a

and Zg are given in the following

table. ,-----r-----,-----.-----,-----~

2 Exposure

categories aie defined in Section 207.5.3.

207.5.2.2 Estimation of basic wind speeds from regional climatic data. Regional climatic data shall only be used in lieu of the basic wind speeds given in Figure


i

i

WIND LOAD

207.5.3

EXPOSURE CATEGORIES

207.5.3.1 General. An exposure category that adequately reflects the characteristics of ground surface irregularities shall be detennined for the site at which the building or structure is to be constructed. Account shall be taken of variations in ground surface roughness that arise from natural topography and vegetation as well as from constructed features. The exposure in which a specific building or other structure is sited shall be assessed as being one of the following categories:

Large city centers with at least 50% of Exposure A. the buildings having a height in excess of 21 meters. Use of this exposure category shall be limited to those areas for which terrain representative of Exposure A prevails in the upwind direction for a distance of at least I km or 10 times the height of the building or other structure, whichever is greater. Possible channeling effects or increased velocity pressures due to the building or structure being located in the wake ofadjacent buildings shall be taken into account. Exposure B. Urban and suburban areas, wooded areas, or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger. Use of this exposure category shall be limited to those areas for which terrain representative of Exposure B prevails in the upwind direction for a distance of at least 0.5 km or 10 times the height of the building or other structure, whichever is greater. Open terrain with scattered Exposure C. obstructions having heights generally less than 9 meters. This category includes flat open country and grasslands Exposure D. Flat, unobstructed areas exposed to wind flowing over open water for a distance of at least 2 km. This exposure shall apply only to those buildings and other structures exposed to the wind coming from over the water. Exposure D extends inland from the shoreline a distance of 0.5 km or 10 times the height of the building or structure, whichever is greater.

2·19

Exposure B for all wind directions, the appropriate multipliers as noted in Figure 207-4 and in Table 207-4 shall be used. . 207.5.3.3 Exposure category components and cladding.

for

design

of

207.5.3.3.1 Buildings with height h less than or equal to 18 meters. Components and cladding for buildings with a mean roof height of 18 meters or less shall be designed using a velocity pressure qh based on Exposure C. However, if the building is sited in Exposure B for all wind directions, the appropriate multipliers as noted in Figures 207-5 through 207-7, and in Table 207-4 shall be used. 207.5.3.3.2 Buildings with height h greater than 18 meters and other structures. Components and cladding for buildings with a mean roof height in excess of 18 meters and for other structures shall be designed on the basis of the most critical exposure category representative of the site as defined in Section 207.5.3.1, except that Exposure B shall be used for buildings and other structures sited in terrain representative of Exposure A, and Exposure C for terrain roofs indicated in Figure 207-8.

Table 207-4 Internal Pressure Coefficients for Buildings, GC· '0/ Condition

-

I I

Open Buildings

i

Partially enclosed buildings -~-"

•..

_

...

I

GCpi

0.00 +0.80 -0.30

4

Buildings satisfying the following conditions: I. sited in typhoon-prone regions having a basic wind speed greater than or equal to 175 kmIhr, and 2. having glazed openings in the lower 18 meters which are not designed to resist wind-borne debris or are not specifically

+0.80 -0.30

__ ._.~cted from.\'Iind-bo~ deb~~

207.5.3.2 Exposure category for desigu of main wind-force resisting systems.

All buildings except thos« listed above

+0.18 -0.18

NOTES:

207.5.3.2.1 Buildings and other structures. Wind loads for the design of the main wind-force resisting system, except as specified in Section 207.5.3.2.2, shall be based on the exposure categories defined in Section 207.5.3.1 for any given wind direction. 207.5.3.2.2 Low-rise buildings. Wind loads for the design of the main wind-force resisting systems for low-rise buildings shall use a velocity pressure qh based on Exposure C when external pressure coefficients GCpf given in Figure 207-4 are used. However, if the building is sited in

1. Plus and minus signs signify pressures acting toward and away from the internal surfaces. 2. Values of GCpi shall be used with qz or qh as specified in Table 207-1. 3. Two cases shall be considered to determine the critical load requirements for the appropriate condition: a positive value of GCP1 applied to all internal surfaces, and a negative value of GCp ; applied to all internal surfaces. 4. For buildings with mean roof height h :s; 18 meters and sited within Exposure S, calculated internal pressures shall be multiplied by 0.85. 5. If a building by definition complies with both the "Open" and 'Partially Enclosed" defintions, it shall be treated as an "Open" building.


2·20


207.5.4 Shielding. Where the provisions of Section 207.4.2 are used there shall be no reductions in velocity pressures due to apparent direct shielding afforded by buildings and other structures or terrain features. 207.5.5 Wind Speed-up over Hills and Escarpments. The provisions of this section shall apply to isolated hills or escarpments located in Exposure B, C, or D where the upwind terrain is free of such topographic features for a distance equal to 50H or lkm, whichever is smaller, as measured from the point at which H is determined. Wind speed-up over isolated hills and escarpments that constitute abrupt changes in the general topography shall be considered for buildings and other structures sited on the upper half of hills and ridges or near the edges of escarpments, illustrated in Figure 207-2, by using factor Kzt :

207.7 PRESSURE AND FORCE COEFFICIENTS. 207.7.1 General. Pressure and force coefficients are given in Figures 207-3 through 207-8 and Table 207-4 through 207-10. The values of the coefficients for buildings in Figures 207-4 through 207-8 and Table 207-4 include the gust effect factor; in these cases the pressure coefficient values and gust effect factor shall not be separated. 207.7.2

Roof Overhangs

207.7.2.1 Main wind-force resisting system. Roof overhangs shall be designed for a positive pressure on the bottom surface of windward roof overhangs corresponding to Cp = 0.8 in combination with the pressures indicated in Figures 207-3 and 207-4.

(207-2)

where K], K2 and K3 are given in Figure 207-2. The effect of wind speed-up shall not be required to be considered when HILh < 0.2, or when H < 4.5 meters for Exposure D, or H < 9 meters for Exposure C, or H < 18 meters for aU 'other exposures. '

207.7.2.2 Components and cladding. For all buildings, roof overhangs shall be designed for pressures determined from pressure coefficients given in Figure 207 5B.

207.8 207.6

GUST EFFECT FACTORS.

207.6.1 Values of Gust Effect Factors. For main wind-force resisting systems of buildings and other structures, and for components and cladding of open buildings and other structures, the value of the gust effect factor G shall be 0.8 for exposures A and B, and 0.85 for exposures C and D.

FULL AND PARTIAL LOADING

The main wind-force resisting system of buildings with mean roof height greater than 18 meters shall be designed for the torsional moments resulting from design wind pressures in Table 207-1 acting in the combinations indicated in Figure 207-9.

207.6.2 Flexible Buildings and Other Structures. Gust effect factor Gf for main wind-force resisting systems of flexible buildings and other structures shall be calculated by a rational analysis that incorporates the dynamic properties ofthe main wind-force resisting system. 207.6.3 Limitations. Where combined gust effect factors and pressure coefficients (GCp, GCpi and GCptJ are given in the figures and tables, gust effect factors shall not be determined separately.


WIND LOAD

2-21

External Pressure Coefficients for Arched Roofs, C

Table 207-5

Cp

Rise-to-span ratio, r

Condition

Windward quarter

Center half

-0.9

-0.7 - r

1.5r - 0.3 6r - 2.1

-0.7 - r

0 < r < 0.2

Roof on elevated structure

0.2

~

r < 0.3

or

._---- - - - - ' " - "

0.3

~

r

0 < r

Roof springing from ground level

0.6

2.75r - 0.7

0.6

lAr

~

~

NOTES 1. Values listed are for the determination of average loads on main windforce resisting systems. 2. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 3. For wind direyted parallel to the axis of the arch, use pressure coefficients from Figure 207-3 with wind directed parallel to ridge.

-0.5

4. For components and cladding: (1) At roof perimeter, use the external pressure coefficients in Figure 207-58 with 0 based on spring-line slope an~ 'ih based on Exposure C; and (2) for remaining roof areas, use external presure coefficients of this table multiplied by 0.87 and IJh based on Exposure C.

Table 207-6 Force Coefficients for Monoslope Roofs over Open Buildings, Cf Roof angle, Cf for L B values of: () .-~---

i

degrees

5

I

10

0.2

I

15

0.35

20 25

0.5

30

0.9

Roof angle, () degrees 10 to 20

0.7

i

3 0.25 OA5 0.6 0.8 1.0

.. r------'

2

. -- l----r-

1/2

--T'

I

I ''T'

-

-_..

0.3

OA5

0.55 -_.--......

0.5

0.7

0.85

0.9

0.85

0.75

0.9

1.0

0.95 ......

0.9

0.95

LIS

1.2

Location ~!rc{~e~a~!~r~~sure,

i

1.3

I

l.l

1.2

0.7 .

--L-.- 1.11.05

I

-

115

li3 - +--

0.75 ''---'-

....

0.95

- ......-.---- ....

1.0

i

XL'J

I !

2 to 5 1 ! lf5 to lI2 0.35

03

0.3

25

0.35

0.35

0.4

30

0.35

OA

OA5

.., ..

-~-~

_

.. ..... _..

_._._..

------.--.-~,

..-.-.

"~---""-'-~---'-----' -----.-~.

NOTES: 1. Wind forces act normal to the surface. Two cases shall be considered: (1) wind forces directed inward; and (2) wind forces directed outward. 2. Wind shall be assumed to deviate by ± 10 degrees from horizontal.

! 3. Notation: B Dimension of roof measured normal to wind direction, in meters. L Dimension of roof measured parallel to wind direction, in meters. X = Distance to center of pressure from windward edge of roof, in meters, and B = Angle of plane of roof from horizontal, in degrees.

=

=


2-22·


Table 207-7 Force Coefficients for Chimneys, Tanks, and Similar Struct es C-(

u"

r-

...

...

C, for hID Values of I 7 25

~--

Square

1.4

2.0

All

1.0

1.1

1.5

All

1.0

1.2

1.4

Moderately smooth

0.5

0.6

0.7

(D'ID",0.02'

0.7

0.8 I

O.~",

0.8

1.0

1.2

I 0.7

0.8

1.2

('wind alonll. diall.onal)

Hexagonal or

octagonal !

....

(D[ti; >0.17)

area, Ii

1.3

Square

Round

area to gross

All

(wind normal to mee)

I

•

Type of Surface

Cross-Section

Table 207-9 Force Coefficients for Open Signs and Lattice Frameworks, C·f, Cr Ratio of solid

i

RouSh~

!

...- r------

Very Rough fD 'ID '" 0.0&)

Round i

(D[ti; ~0.17)

All

< 0.1

NOTES: 1. The design wind force shall be calculated based on the area of the structure projected on a plane normal to the wind direction. The force shall be assumed to act parallel to the wind direction. 2. Linear interpolation is permitted for hID values other than shown. 3. Notation: D :: diameter of circular cross-sections and least horizontal dimension of square, hexagonal or octagonal cross sections at elevation under consideration, in meters; D' :: depth of protruding elements such as ribs and spoilers, in meters; h height of structure, in meters; and qz = velocity pressure evaluated at height z above ground, in

0.1 to 0.29 0.3 to 0.7

Flat-Sided Members

~(D~~:~~~I.~~mJ:~~~·o·.~;-J··

2.0 1.8

1.3

0.8 0.9

1.6

1.5

1.1

1.2

NOTES: 1. Signs with openings comprising 30% or more of the gross area shall be considered as open signs. 2. The calculation of tbe design wind forces shall be based on the area of all exposed members and elements projected on a plane normal to the wind direction. Forces shall be assumed to act parallel to the wind direction. 3. The area Ajconsistent with these force coefficients is the solid area projected normal to the wind direction. 4. Notation: c = ratio of solid area to gross area; D = diameter of a typical round member, in meters; and qz velocity pressure evaluated at heightz above ground, in kilopascals.

=

Table 207-10 Foree Coefficients for Trussed Towers, Cf Tower Cross Section

kPa.

4.0;' - 5.9 Ii + 4.0 3.4 ;. - 4.7 Ii + 3.4

-

Table 2078 Force Coeffic'e I I n ts for Solid Signsf C'f At Ground Level

1.2

~

10

20 30 ~40

, - - -..

..

Cr

V

3 5 --'-"'-"-' 8

Above Ground Level

Cf

6

1.2

10...

1.3..

16 20 40 60 .. 80

1.4

~

1.3

-~---

.__ ...-

1.4 1.5 1.75 1.85 2.0

---._._,----_.

....

1.5

..

I--.-----~

-~--

~

~~-

MIN

1.75 ._-_1.85 2.0 ..

NOTES: 1. Signs with openings comprising less than 30% of the gross area shall be considered as solid signs. 2. Signs for which the distance from the ground to the bottom edge is less than 0.25 times the vertical dimension shall be considered to be at ground level. 3. To allow for both normal and oblique wind directions, two cases shall be considered: a. resultant force acts normal to the face of the sign on a vertical line passing through the geometric center and b. resultant force acts normal to the face of the sign on a distance from a vertical line passing through the geometric centre equal to 0.2 times the average width ofthe sign.

1. For all wind directions considered, the area At consistent with the specified force coefficients shall be the solid area of a tower face projected on the pia ne of that face for the tower segment under consideration. 2. The specified force coefficients are for towers with structural angles or similar flat-sided members . 3. For towers containing rounded members, it is acceptable to multiply the specified force coefficients by the following factor when determining wind forces on such members:

(0.51 c 2 + 0.57), but not greater than 1.0 4. Wind forces shall be applied in the directions resulting in maximum member forces and reactions. For towers with square cross-sections, wind forces shall be multiplied by the following factor when the wind is directed along a tower diagonal: (1 + 0.75 c). but not greater than 1.2 5. Wind forces on tower appurtenances such as ladders, conduits, lights, elevators, etc., shall be calculated using appropriate force coefficients for these elements. 6. Notation: c = ratio of solid area to gross area of one tower face for the segment under consideration.

4. Notation:

v :: ratio of height to width;

M = larger dimension of sign, in meters; and

N =. smaller dimension of sign, in meters.


I i

WIND LOAD

118·

120·

122·

2-23

124

0

126°E

N 20·

18·

16'

ZONE II

v = SSm/s (200kph)

ZONE 1

v =70m/s (2S0kph

14°

12'

10'

ZONE III

v = 3Sm/s (12Skph)

6°

Wind Zone Map


2-24

WIND LOAD

Kl MULTIPLIER HILh

2-D Ridge

3-D Axisym. HiD

0.10 0.14 0.22 0.15 _._._..__ . 0.20 0.29 0.25 0.36 0.30 0.43 _._-- 0.35 0.51 ._-- - 0040 0.58 ._._------_...----_. _._<- 0.45 0.65 f-···...,----t---·-·--·- 0.50 0.72 ._.

__

0.11 0.16 0.17 0.21 0.21 0.26 0.26 0.32 0.30 0.37 _ - -0.34 - -.. ,--_.....0.42 0.38 0.47 - ..- - - / - . - - - - - - 1 0.43 0.53

Speed-up

~----

-~-

2-D Ridge or 3-D Axisymmetrical Hill z

K: MULTIPLIER x/LJr

2-D escarpment Downwind of Crest

/

All others Cases

,- Speed-up

0.00 1.00 1.00 ---_._+--------_.-+--- 0.50 0.88 0.67 1.00 0.75 0.33 0.00 0.00

~__~~------l-.---~~--_+-__ O.~--~

3.00 0.25 0.00 3.50 0.13 0.00 1---·----+----_·········-4--- 4.00 0.00 0.00

Kg MULTIPLIER 2-D Ridge

0.00

1.00

0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.50 2.00

0.74 0.55 0.41

0.09 0.07 0.05 0.01 0.00

2-D Escarpment

3-D Axisym. Hill

1.00 1.00 0.78 0.67 +._------!------ 0.61 0.45 0.47 0.30 0.20 ---t-- 0.14 0.09 7 0.06 0.04 0.14 0.03 0.11 0.08 0.02 0.00 0.02 0.00 0.00

FIGURE 207-2

Escarpment

NOTES: 1. For values of HIL", xiL" and zlL" other than those shown, linear interpolation is permitted. 2. For HIL" > 0.5, assume HILh :: 0.5, and substitute 2H for Lh in xiLh and zfLh. 3. Multipliers are based on the assumption that wind approaches the hill or escarpment along the direction of maximum slope. 4. Effect of Wind speed--up shall not be required to be accounted for when HIL" < 0.2 or when H < 4.5 meters for Exposure 0, or H < 9 meters for Exposure C, or H <18 meters for all other exposures. 5. Notation: H :: Height of hill or escarpment relative to the upwind terrain, in meters. ~ :: Distance upwind of crest to where the difference in ground elevation is half the height of hill or escarpment, in meters. K, :: Factor to account for shape of topographic feature and maximum speed-up effect. K:; :: Factor to account for reduction in speed-up with distance upwind or downwind of crest. KJ = Factor to account for reduction in speed-up with height above local terrain. X = Distance (upwind or downwind) from the crest to the building site, in meters. Z :: Height above local ground level, in meters.

Multipliers for Obtaining Topographic Factor, KrJ



2-26

Wall Pressure Coefficients, CD Surface

LIB

Cp

Windward Wall

All values

0.8

-"~------+------t-----,-

0-1 2

Wind

Leeward wall

Use with

--'------.. .

-0.5 -0.3 -0.2

~4

. - - - - -..~-+---,--+---.,-- --,,-------- All values Side walls qh -0.7 L ELEVATION

PLAN

Roof Pressure Coefficients, Cp , for Use with q" Wind Direction

hlL

~0.25

Nonnal to ridge for

10

15

20

25

30

35

-0.7

-0.5

-0.3

-0.2

-0.2

0.0"

0.0"

0.2

0.3

0.3

0.4

0.5

-0.7

-0.4

-0.3

-0.2

-0.2

0.0*

45

+-----4-----4------4-----4-----~----4_

0.5

-0.9

() ;;:: 10° ~

Normal to

ridge for () < 10° and Parallel to ridge for all ()

Leeward Angle, () (degrees)

Windward Angle, () (degrees)

LO

:::;0.5

;;:: LO

-1.3**

0.0" 0.2 0.2 0.3 0.4 ---r----+--·---+----+----l- -1.0 -0.7 -0.5 -0.3 -0.2 0.0* 0.0*

Horiz distance from windward edge o to hI2 hI2 to h h to 2h > 2h

o to hI2 >h12

-0.9

-0.9 -0.5 -0.3 -1.3** -0.7

0.2

----

10

15

om ()

-0.3

-0.5

..0.6

om ()

-0.5

-0.5

-0.6

~20

-0.7 -0.6 -0.6 0.2 0.3 om () " For slopes greater than 80°, use Cp =0.8.

* Value is provided for interpolation purposes.

*" Value can be reduced linearly with area over

which it is applicable as follows: Area

Reduction

(sq.m)

Factor

:::;10

LO 0.9 0.8

25 ;;:: 100

NOTES:

1. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 2. Unear Interpolation Is permitted for values of liB, hlL and 8 other than shown. Interpolation shall only be carried out between values of the same sign. Where no value of the same sign is given, assume 0.0 for interpolation purposes. 3. Where two values of Cp are listed, this indicates that the windward roof slope is subjected to either positive or negative pressures and the roof structure shall be designed for both conditions. Interpolation for intermediate ratios of hlL In this case shall only be carried out between Cp values of like sign. 4. For monoslope roofs, entire roof surface is either a windward or leeward surface.

5_ For flexible bundings use appropriate Gfas determined by rational analysis. 6. Refer to Table 207-5 for arched roofs. 7. Notation: B :; Horizontal dimension of building, in meter, measured normal to wind direction. L :; Horizontal dimension of building, in meter, measured parallel to wind direction. h :: Mean roof height in meter, except that eave height shall be used for O~ 10 degrees.

z :: Height above ground, inmeters.

G '" Gust effect factor.

q" qh :: Velocity pressure, in kilopascals, evaluated at

re$pective height.

o :; Angle of plane of roof from horizontal, in degrees.

FIGURE 207-3. External Pressure CoeffiCients, Cpt for Loads on Main Wind~ Force Resisting

Systems for Enclosed or Partially Enclosed Buildings of All Heights.


2-26

WIND LOAD

4E

6E

:.l

IE

rZa

5E

~~

~ Range

Range

CASE A

CASE A Roof Angle ()

CASE B

BUILDING SURFACE ZONE 1

2

3

4

1E

2E

3E

4E

0 5

0.40

-0.69

-0.37

-0.29

0.61

-1.07

-053

-0.43

20

0.53

-0.69

-0.48

-0.43

0.80

-1.07

-0.69

-0.64

30- 45

0.56

0.21

-0.43

-0.37

0.69

0.27

-0.53

-0.48

90

0.56

0.56

-0.37

-0.37

0.69

0.69

-0.48

-0.48

(degrees)

"i~k ~

CASEB

Roof Angle ()

BUILDING SURFACE ZONE

(degrees)

0-90

-0.45

2

3

4

5

6

1E

2E

3E

4E

5E

6E

-0.69

-0.37

-0.45

0.4

-0.29

-0.48

-1.07

-0.53

-0.48

0.61

-0.43

NOTES: 1. Case A and Case B are required as two separate loading conditions to generate the wind actions, including torsion, to be resisted by the main wind-force resisting system. 2. To obtain the critical wind actions, the bunding shall be rotated in 90" increments so that each comer in tum becomes the wind-ward comer while the loading patterns in the sketches remain fIXed. For the design of structural systems providiny lateral resistance in the direction parallel to the ridge line, Load Case A shall be based on 0= C!'. 3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 4. For case A loading the following restrictions apply: a. The roof pressure coefficient GCp" when negative in zone 2, shall be applied in zone 2 for a distance from the edge of roof equal to 0.5 times the horizontal dimension of the building measured perpendicular to the eave line or 2.5h, whichever is less; the remainder of one 2 extending to the ridge line shall use the pressure coefficient GCp, for zone 3.

b. Except for moment-resisting frames, the total horizontal shear shall not be less than that detemlined by neglecting wind forces on roof surfaces. 5. Combinations of external and internal pressures (see Tables 2074) shaH be evaluated as required to obtain the most severe loadings. 6. For buildings sited within Exposure B, calculated pressures shall be multiplied by 0.85. 7. For values of 0 other than those shown, linear interpolation is pemlitted. 8. Notation: a = 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4% of least horizontal dimension or 1 m. h = Mean roof height, in meters, except that eave height shall be used for e:!> 10". () ::: Angle of plane of roof from horizontal, in degrees.

FIGURE 207-4 External Pressure CoeffiCients, GCp/, for Loads on Main Wind-Force Resisting Systems for Enclosed or Partially Enclosed Low-Rise Buildings with Mean Roof Height, h, Less than or Equal to 18 m.

Association of Structural

En~lineers

of the Philippines


-2.0 I•1.4 1-.

l'

-1.1

2-27

I

!

I

I

-

'CD

-

(4)!~

-

-0.8

GCp

-0.5

-

I-

0.0

:,

0.5

,

1.0

-

@ &G)I

-

1.5 I

0.1

0.1

-

0.9 1.9 4.6 9.3 18.6 Eft'ective Wind Area

L

46.592.9

(square meters)

NOTES: 1. Vertical scale denotes GCp to be used with qh based on ExposureC. 2. Horizontal scale denotes effective wind area. in square

meters. 3. Plus and minus signs signify pressures acting toward and away from the surfaces. respectively. 4. Each component shall be designed for maximum positive and negative pressures. 5. Values of GCp for walls shall be reduced by 10% when 8'5. 10" 6. For buildings sited within Exposure B, calculated

pressures shall be multiplied by 0.85

7. Notation: a .: 10 percent of least horiZontal dimension or OAh, whichever is smaller, but not less than either 4% of least horiZontal dimension or 1m b = 1.51'11 Fig 207-5C. but not greater than 3J m h '" Mean roof height. in meters. except that eave height shall be used for a s; 10" hi = h, or ha in Fig 207-5C; h= hI + ha; hI?3 meters; hilh= 0.3 to 0.7. W = Building width in Figure 207-5C. Wi:: W, or W.:;>or W3in Figure207-5C' W= Wl + W2 or W,+ W2+ W3; WiIW=O.25toO.75. 8 :: Angle of plane of roof from horizontal, in degrees.

FIGURE 207-5A External Pressure Coefficients, GC" for Load$ on Building Components and Cladding for Enclosed or Partially Enclosed Buildings with Mean Roof Height h Less than or Equal to 18 m. Walls.

National Structural' Code of the Philippines, Volume 1

WIND LOAD

2·28

-3.7

- .....---. Roof Overhang -3.0

-2.5 -2.1

-2.5 ·2.2

GCp ·1.5

--------\-1.4

-0.9

-1.!

CD

P~===t===::::::==~·1.0 -O.!

F--":;;~--t-----';'---4-0.!

-0.5

0.0 I-------c-,-=~-----;-----I _~~~&~il~~~)__----_T--~03 .

05

k=g~®~l~&~b~,;;;::=;::i;;::::;t;:==::;;j

1-

0.1

0.9

1.9

4.6 9.3

0.9

41.5

ROOF SLOPE,

10° < (J .5 30°

4.6

9.3

a.!

46.5

Effective Wind Area (square meters)


(a)

1.9

ROOF SLOPE,

(b)

30°< (J.5 45°

-2.! -2.5 .1.8 ·1.7

"~-M-0

\..1) &

GCp ·1.0

~

.. -t-.. ,

.....

(i)

-0.5 0.0 0.3

0.2

0.9 1.9 4.6 9.3 Effective Wind Area (square meters)

0.1

(c) NOTES: 1. If a parapet equal to or higher than 1 meter is provided around the perimeter of the roof with 9 S; 1(1', Zone 3 shall be treated as Zone 2. 2. Values of GCp for roof overhangs inolude pressure

contributions from both upper and lower surfaces

3.

-1.1 -0.9 -0.8

ROOF SLOPE,

e .5

41.5

10°

For hipped roofs wittl10 < 9 S 3:1", edge/ridge strips and pressure coefficients for ridges of gabled roofs shall apply on each hip.

FIGURE 207-56. Gabled and Hipped Roofs (also see Notes on Figure 207-SA)


WIND LOAD

2-29

hI .::: 3 meters b = 1.5 hI b < 30m

h,lh = 0.3 to 0.7 W;lW

= 0.25 to

0.75

,

h I

~

_____________ Lj.I h2

NOTE:

1. On the lower level of flat, stepped roofs shown in Figure 207-5C, the zone designations and pressure coefficients shown in Figure 207-58 (e $10") shall apply, except that at the roof-upper wall intersection(s). Zone 3 shall be treated as Zone 2 and Zone 2 shall be treated as Zone 1.

2. Positive values of GCp equal to those for walls in Figure 207-5A shall apply on the cross-hatched areas shown in Figure 207-5C.

FIGURE 207-5C Stepped Roofs (also see Notes on Figure 207-5A)


2-30


I

I

-1"- -t--TI I I .F:::--+---!-----L

I I I I I I I I I I

I I I

....-Y. I

I I I I

-t'--r-I I

Multispan Gabled Roof

--t

-+a

1a __

Plan

Elevation

SINGLE-SPAN

MODULE

-2.7 -2.2

"'-_ _ _-1-1.7

-.;....---1-1.7

.1.15

- - - i - - - - l -1.4

" - - - - - 1 -1.1

-1.0

GCp -0.5 0.0 ~_-i-----1

0.4

0.6

W~~~

1.0

__--t---:j°·8

1.5 0.1

0.9

1.9

4.6

9.3

46.S

0.9

0.1

Effective Wind Area

(square meters)

(a) ROOF SLOPE,

10· <

1.9

4.6

9.3

46.5


(J

~

30°

NOTES: 1. Vertical scale denotes GCp to be used with qh based on ExposureC. 2. Horizontal scale denotes effective wind area A, in square meters. 3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 4. Each component shall be designed for maximum positive and negative pressures. 5. For ()s10", values of GCp from Figure 207-58 shall be used.

(b)

ROOF SLOPE,

30° <

(J

~

45°

6. For buildings sited within Exposure S, calculated

pressures shall be multiplied by 0.85.

7. Notation:

a = 10% of least horizontal dimension of a single-span

module or 0.411, whichever is smaller, but not less than either 4 percent of least horizontal dimension of a single-span module or 1 meter.

h = Mean roof height, in meters.

W = Building width, in meters.

() = Angle of plane of roof from horizontal, In degrees.

FIGURE 207...c; External Pressure Coefficients, GCp , for Loads on Building Components and Cladding for Multispan Gabled Roofs (with Two or More Spans) on Enclosed or Partially Enclosed Buildings with Mean Roof Height, h, Less than or Equal to 18 m.


2-31

WIND LOAD

(3:>

-2.6

G)

-1.8 -1.6 -1.3 -1.1

-......

i 2') (2 ')

~ 1

\J)

-1.6 -1.5 -1.2 -1.1

GCp -0.5

0.0

i i

0.3

0.2

All Zones

1.0

i 0.9

0.1

1.9

4.6

9.3

46.5

Effective Wmd Area (square meters)

(a)

-+j 23

l+

t '":_____________ 48

\Vi ,

-* a

I

•

I

I

I

I

01,

-2.0

CD Iz ~ ,,

I ,

I

,,

,, I '

~

.

_

,

,

:5 10°

i

I

: ...

(J

:

~ --~j

----I, t3'1 \:.),

3° <

ROOF SLOPE,

-1.2 -1.1

1 ,

-

-0.5

_________ I

0.0 1 - - - - - - - + - - - - - - + - - - - 1

0.41----.+----j---1- 0.3 All Zones

1.0 ~-----~--~-~~----~

0.1

0.9

1.9

4.6

9.3

46.5


(b)

ROOF SLOPE,

10° <

(J

S 300

Figure 207-7A External Pressure Coefficients, GCp • for Loads on Building Components and Cladding for Monoslope Roofs and Sawtooth Roofs with Two or More Spans on Enclosed or Partially Enclosed Buildings with Mean Roof Height, h. Less than or Equal to 18 meters. Monoslope. Roofs (refer to notes on Figure 207-7B)


2~2


-4.5 -4.1

-3.5 ·3.2

-2.6 -2.1

(i)(spanA)

G) 2a,

(i) (span BCD)!

CD

'1----/ -2.1

"i----i ·1.9

GCp

'i--.......j·1.6

-1.5

'j ieD i

"'!-_.......j·1.1

-1.0

-0.5 0.0

---w 0.1

0.9

1.9

4.6

9.3

46.S


ROOF SLOPE,

10° <

NOTES for Figures 207-7A and 207·7B: 1. Vertical scale denotes Gel' to be used with qh based on

2.

3. 4. 5.

Exposure C. Horizontal scale denotes effective wind area A, in square meters. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. Each component shall be designed for maximum positive and negative pressures. For (J~~ (Figure 207.7A) and 9 ~ 10" (Figure 207·78), values of Gel' from Figure 207-5B shall be used.

(J ~

30°

6. For buildings sited within Exposure B, calculated pressures shall be multiplied by 0.85. 7. Notation: a .. 10'lb of least horizontal dimension or 0.411, whichever Is smaller, but not less than either 4 percent of least horizontal dimension or 1 meter. h = Mean roof height, in meters, except that eave height shall be used for B 51cf. W ::: Building width, in meters. (J = Angle of plane of roof from horizontal, in degrees.

Figure 207-78 Sawtooth Roofs - Two or More Spans


WIND LOAD

2-33

,

a

r--

®f 1

i, ! a

Wall Elevation

Roof Plan -1.&

G)

-1.5

-2.3

-0.9

GC

fo.s

-us

CD

-1.4 I--=----i-__

-1.0

-0.9

4

-1.0

i-----j----.LJ..(J.7

0.0

0.5

_-.--,0.•

0.9 0.1

0.9 1.9

4.6 9.3

46.5


(a) ROOFS

e S 10·

NOTES: 1. Vertical scale denotes GCp to be used with appropriate qz orqh· 2. Horizontal scale denotes effective wind areaA, in square meters. 3. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. 4. Use q¥ with positive valUes of GCp and qh with negative values of GCp • 5. Each component shall be designed for maximum positive and negative pressures.

0.1

0.9 1.9

4.6 9.3

46.5


(b) WALLS

(all 9)

6. -Coefficients are for roofs with angle £15.10". For other roof angles and geometry,

use GCp values from Figure

207-58 and attendant qh based on Exposure C.

7. If a parapet equal to or higher than 1meter is provided around the perimeter of the roof, Zone 3 shall be treated as Zone 2. B. Notation: a = 10% of least horizontal dimension, but not less than 1 m. h '" Mean roof height, in meters. z = height above ground, in meters. (J = Angle of plane of roof from horizontal, in degrees.

FIGURE 207...s External Pressure Coefficients, GCp , for Loads on Building Components and Cladding for Enclosed or Partially Enclosed Buildings with Mean Roof Height, h, Greater than 18 m.

National Structural Code of the Philippines, Volwne 1


pw

PL Case 1 : Full design wind pressures acting on the projected area perpendicular to each principal axis of the structure considered separately.

Case 3. Wind pressure as defined in Case 1, but considered to act simultaneously at 75% of the specified values.

0.75p,.

O.25pw f

0.25pw

J.....- O.25PL ..:r-_ _

PL

t

Case 2. Wind pressure as defined in Case 1. but with a 25% reduction in pressure acting on 50% of the projected area bounded by the extreme projected edge of the building.

Case 4. Wind pressure as defined in Case 2, but considered to act simultaneously at 75% of the specified values in Case 2.

NOTES:

1. Design wind pressures for windward and leeward faces obtained in accordance with the provisions of Table '207-1 for main wind force resisting systems for buildings with mean roof height h greater than 18 meters. 2. Diagrams show plan view of building.

3. Notation: p",= Windward face design pressure PL '" Leeward face design pressure.

FIGURE 207-9 Wind Pressure Combinations for Full and Partial Loading of Main Wind Force Resisting Systems for Buildings with Mean Roof Height h Greater than 18 m.

Association of Structural Engineers of the Philippines, Inc.

EARTHQUAKE DESIGN

SECTION 208 - EARTHQUAKE DESIGN 208.1

GENERAL

Structures and 208.1.2 Minimum Seismic Design. portions thereof shall, as a minimum, be designed and constructed to resist the effects of seismic ground motions as provided in this section.

1

~

!

1 1 j

1

I

208.1.3 Seismic and Wind Design. When the code prescribed wind design produces greater effects, the wind design shall govern, but detailing requirements and limitations prescribed in this section and referenced sections shall be followed.

108.2

DEFINITIONS

BASE is the level at which the earthquake motions are considered to be imparted to the structure or the level at which the structure as a dynamic vibrator is supported. BASE SHEAR, V, is the total design lateral force or shear at the base of a structure.

j

BEARING WALL SYSTEM is a structural system with out a complete vertical load-carrying space frame. See Section 208.4.6.1.

I i

COMPONENT is a part or element of an architectural, electrical, mechanical or structural system. COMPONENT, EQUIPMENT, is a mechanical or electrical component or element that is part of a mechanical and/or electrical system.

208.1.1 Purpose. The purpose of the earthquake provisions herein is primarily to safeguard against major structural failures and loss of life, not to limit damage or maintain function.

I i

2-35

BOUNDARY ELEMENT is an element at edges of openings or at perimeters of shear walls or diaphragms. BRACED FRAME is an essentially vertical truss system of the concentric or eccentric type that is provided to resist lateral forces. BUILDING FRAME SYSTEM is an essentially com plete space frame that provides support for gravity loads. See Section 208.4.6.2. CANTILEVERED COLUMN ELEMENT is a column element in a lateral-force-resisting system that cantilevers from a fixed base and has minimal moment capacity at the top, with lateral forces applied essentially at the top. COLLECTOR is a member or element provided to transfer lateral forces from a portion of a structure to vertical elements of the lateral-force-resisting system.

National

COMPONENT, FLEXIBLE, is a component, including its attachments, having a fundamental period greater than 0.06 second. COMPONENT, RIGID, is a component, including its attachments, having a fundamental period less than or equal to 0.06 second. CONCENTRICALLY BRACED FRAME is a braced frame in which the members are subjected primarily to axial forces. DESIGN BASIS GROUND MOTION is that ground motion that has a 10 percent chance of being exceeded in 50 years as determined by a site-specific hazard analysis or may be determined from a hazard map. A suite of ground motion time histories with dynamic properties representative of the site characteristics shall be used to represent this ground motion. The dynamic effects of the Design Basis Ground Motion may be represented by the Design Response Spectrum. See Section 208.6.2. DESIGN RESPONSE SPECTRUM is an elastic response spectrum for 5 percent equivalent viscous damping used to represent the dynamic effects of the Design Basis Ground Motion for the design of structures in accordance with Sections 208.5 and 208.6. This response spectrum may be either a site-specific spectrum based on geologic, tectonic, seismological and soil characteristics associated with a specific site or may be a spectrum constructed in accordance with the spectral shape in Figure 208-3 using the site-specific values of Ca and C" and multiplied by the acceleration of gravity, 9.815 m/sec2 . See Section 208.6.2. DESIGN SEISMIC FORCE is the minimum total strength design base shear, factored and distributed in accordance with Section 208.5. DIAPHRAGM is a horizontal or nearly horizontal system acting to transmit lateral forces to the vertical-resisting elements. The term "diaphragm" includes horizontal bracing systems. DIAPHRAGM or SHEAR WALL CHORD is the boundary element of a diaphragm or shear wall that is assumed to take axial stresses analogous to the flanges of a beam.

Struc1luaJ Code of the Philippines, Vokne 1


DIAPHRAGM STRUT (drag strut, tie, collector) is the

ORDINARY MOMENT-RESISTING FRAME (OMRF)

element of a diaphragm parallel to the applied load that collects and transfers diaphragm shear to the vertical resisting elements or distributes loads within the diaphragm. Such members may take axial tension or compression.

is a moment-resisting frame not meeting special detailing requirements for ductile behavior.

ORTHOGONAL EFFECTS are the earthquake load

DRIFT. See "story drift."

effects on structural elements common to the lateral-force resisting systems along two orthogonal axes.

DUAL SYSTEM is a combination of moment-resisting

OVERSTRENGTH is a characteristic of structures where

frames and shear walls or braced frames designed accordance with the (;riteria of Section 208.4. 6.4.

the actual strength is larger than the design strength. The degree of overstrength is material-and system-dependent.

In

ECCENTRICALLY BRACED FRAME (EBF) is a steel-braced frame designed in conformance with Section 515.9.

PI).

ELASTIC RESPONSE PARAMETERS are forces and deformations determined from an elastic dynamic analysis using an unreduced ground motion representation, iIi accordance with Section 208.5.

SHEAR WALL is a wall designed to resist lateral forces

EFFECT is the secondary effect on shears, axial forces and moments of frame members induced by the vertical loads acting on the laterally displaced building system.

parallel to the plane of the wall (sometimes referred to as vertical diaphragm or structural wall).

SHEAR WALL-FRAME INTERACTIVE SYSTEM ESSENTIAL FACILITIES are those structures that are necessary for emergency operations subsequent to a natural disaster.

uses combinations of shear walls and frames designed to resist lateral forces in proportion to their relative rigidities, considering interaction between shear walls and frames on all levels.

FLEXffiLE ELEMENT or system is one whose deformation under lateral load is significantly larger than adjoining parts of the system. Limiting ratios for defining specific flexible elements are set forth in Section 208.5.6.

SOFT STORY is one in which the lateral stiffness is less than 70 percent of the stiffness of the story above. See Table 208-9.

HORIZONTAL BRACING SYSTEM is a horizontal

SPACE FRAME is a three-dimensional structural system,

truss system that serves the same function as a diaphragm.

without bearing walls, composed of members interconnected so as to function as a complete self contained unit with or without the aid of horizontal diaphragms or floor-bracing systems.

INTERMEDIATE MOMENT - RESISTING FRAME (IMRF) is a concrete frame designed in accordance with Section 421.10.

LATERAL-FORCE-RESISTING SYSTEM is that part of the structural system designed to resist the Design Seismic Forces.

SPECIAL CONCENTRICALLY BRACED FRAME (SCBF) is a steel-braced frame designed in conformance with the provisions of Section 515.8.

SPECIAL MOMENT-RESISTING FRAME (SMRF) is MOMENT-RESISTING FRAME is a frame in which members and joints are capable of resisting forces primarily by flexure.

a moment-resisting frame specially detailed to provide ductile behavior and comply with the requirements given in Chapter 4 or 5.

MOMENT-RESISTING WALL FRAME (MRWF) is

SPECIAL TRUSS MOMENT FRAME (STMF) is a

a masonry wall frame especially detailed to provide ductile behavior and designed in conformance with Section 708.2.6.

moment-resisting frame specially detailed to provide ductile behavior and comply with the provisions of Section 515.10.

ORDINARY BRACED FRAME (OBF) is a steel-braced

STORY is the space between levels. Story x is the story below Level x.

frame designed in accordance with the provisions of Section 515.7 or 516.5 or concrete-braced frame designed in accordance with Section 421.

STORY DRIFT is the lateral displacement of one level relative to the level above or below. STORY DRIFT RATIO is the story drift divided by the story height.


EARTHQUAKE DESIGN

STORY SHEAR, V,u is the summation of design lateral forces above the story under consideration.

F"

STRENGTH is the capacity of an element or a member to resist factored load as specified in Chapters 2, 3, 4, 5 and 7. STRUCTURE is an assemblage of framing members designed to support gravity loads and resist lateral forces. Structures may be categorized as building structures or nonbuilding structures. g

SUBDIAPHRAGM is a portion of a larger wood diaphragm designed to anchor and transfer local forces to primary diaphragm struts and the main diaphragm. VERTICAL LOAD-CARRYING FRAME is a space frame designed to carry vertical gravity loads. WALL ANCHORAGE SYSTEM is the system of elements anchoring the wall to the diaphragm and those elements within the diaphragm required to develop the anchorage forces, including subdiaphragms and continuous ties, as specified in Sections 208.8.2.7 and 208.8.2.8. f

WEAK STORY is one in which the story strength is less than 80 percent of the story above. See Table 208-9.

208.3 AB

E,EIf,

Ef/I> E"

F;, F""

1

SYMBOLS AND NOTATIONS =ground flnor area of structure in square meter to include area covered by all overhangs and projections. =the combined effective area, in square meter, of the shear walls in the first story of the structure. = the minimum cross-sectional area in any horizontal plane in the first story, in square meter of a shear wall. the torsional amplification factor at Level x. = numerical coefficient specified in Section 208.7 and set forth in Table 208-12. seismic coefficient, as set forth in Table 208 7. = numerical coefficient given in Section 208.5.2.2. = seismic coefficient, as set forth in Table 208 8. = dead load on a structural element. = the length, in meter, of a shear wall in the first .story in the direction parallel to the applied forces. earthquake loads set forth in Section 208.5.1.

2-37

=Design Seismic Force applied to Level i, 11 or x, respectively. =Design Seismic Forces on a part of the structure. =Design Seismic Force on a diaphragm. =that portion of the base shear, J'~ considered concentrated at the top of the structure in addition to F..,. = lateral force at Level i for use in Equation (208-10). =acceleration due to gravity. =9.815 m/sec"

=height in meter above the base to Level i, 11 or x, respectively. f =importance factor given in Table 208-1. =importance factor specified in Table 208-1 =Iive load on a structural element. level of the structure referred to by the Levell subscript i. "i =]" designates the first level above the base. Leveln =that level that is uppermost in the main portion of the structure. Level x =that level that is under design consideration. "x 1" designates the first level above the base. =maximum moment magnitude. M =near-source factor used in the determination of Ca in Seismic Zone 4 related to both the proximity of the building or structure to known faults with magnitudes as set forth in Tables 208-4 and 208-6. Nv =near-source factor used in the determination of c., in Seismic Zone 4 related to both the proximity of the building or structure to known faults with magnitudes as set forth in Tables 208-5 and 208-6. PI =plasticity index of soil determined in accordance with approved national standards. R =numerical coefficient representative of the inherent overstrength and global ductility capacity of lateral- force-resisting systems, as set forth in Table 208-11 or 208-13. r =a ratio used in determining p. See Section 208.5.1. SA. SB, Se. Sf), SE, SF = soil profile types as set forth in Table 208-2. T =elastic fundamental period of vibration, in seconds, of the structure in the direction under consideration. V =the total design lateral force or shear at the base given by Equation (208-4), (208-5), (208-6), (208-7) or (208-11). Vx =the design story shear in Story x. W =the total seismic dead load defined in Section 208.5.1.1.

National Structq.ral Code of the Philippines, Volume 1

2-38


that portion of W located at or assigned to Level i or x, respectively. = the weight of an element or component. = the weight of the diaphragm and the element tributary thereto at Level x, including applicable portions of other loads defined in Section 208.5.1.1. "" seismic zone factor as given in Table 208-3. = Maximum Inelastic Response Displacement, which is the total drift or total story drift that occurs when the structure is subjected to the Design Basis Ground Motion, including estimated elastic and inelastic contributions to the total deformation defined in Section 208.5.9. = Design Level Response Displacement, which is the total drift or total story drift that occurs when the structure is subjected to the design seismic forces. = horizontal displacement at Level i relative to the base due to applied lateral forces,/. for use in Equation (208-10). = RedundancylReliability Factor given by Equation (208-3). = Seismic Force Amplification Factor, which is required to account for structural overstrength and set forth in Table 208-11. =

z Ap.f

2'()8.4.2 OCCUPANCY CATEGORIES For purposes of earthquake-resistant design, each structure shaH be placed in one of the occupancy categories listed in Table 103-1. Table 208-1 assigns importance factors, I and I". and structural observation requirements for each category. Table 208-1 - Seismic Importance Factors Seismic Seismic I ! Importance 2 Occupancy Importance Category

I.

II. III.

Essential 3 Facilities Hazardous Facilities Special

Occupancy

Structures"4

I

Factor, I

Factor, Ip

1.25

1.50

1.25

1.50

1.00

1.00

1.00

1.00

!

IV. standard Occupancy Structures"4

I

V. Miscellaneous

-

1.00

1.00

structures 1 See Table 103-1 for occupancy category listing. 2 The limitation of Ip for panel connections in Section 208.8.2.3 shall be 1.0 for the entire connector. 3 Structural observation requirements are given in Section 107.9. 4 For anchorage of machinery and equipment required for life safety systems, the value of I p shall be taken as 1.5.

208.4 CRITERIA SELECTION 208.4.1 BASIS FOR DESIGN The procedures and the limitations for the design of structures shall be determined considering seismic zoning, site characteristics, occupancy, configuration, structural system and height in accordance with this section. Structures shall be designed with adequate strength to withstand the lateral displacements induced by the Design Basis Ground Motion, considering the inelastic response of the structure and the inherent redundancy, overstrength and ductility of the lateral-force- resisting system. The minimum design strength shall be based on the Design Seismic Forces determined in accordance with the static lateral force·procedure of Section 208.5, except as modified by Section 208.6.5.4. Where strength design is used, the .load combinations of Section 203.3 shall apply. Where Allowable Stress Design is used, the load combinations of Section 203.4 shall apply. Allowable Stress Design may be used to evaluate sliding or overturning at the soil-structure interface regardless of the design approach used in the design of the structure, provided load combinations of Section 203.4 are utilized.

208.4.3 SITE GEOLOGY AND SOIL CHARAC TERISTICS. Each site shall be assigned a soil profile type based on properly substantiated geotechnical data using the site categorization procedure set forth in Section 208.10 and Table 208-2. EXCEPTION: When the soil properties are 1I0t known in Sl(f(icient detail to determine the soil profile type, Type SD shall be used Soil Profile Type SE or SF need not he assumed unless the building qf(iciai determines that Type SE or SF may be present at the site or in the event that T}pe SE or SF is established by geotechnical data.

208.4.3.1 Soil profile type. Soil Profile Types Sl. SB. Se, So and SE are defined in Table 208-2 and Soil Profile Type SF is defined as soils requiring site-specific evaluation as follows: 1. Soils vulnerable to potential failure or collapse under seismic loading, such as liquefiable soils, quick and highly sensitive clays, and collapsible weakly cemented soils,


EARTHQUAKE DESIGN

Peats and/or highly organic clays, where the thickness of peat or highly organic clay exceeds 3.0 meters. Very high plasticity clays with a plasticity index, PI> 75, where the depth of clay exceeds 7.6 meters. Very thick soft/medium stiff clays, where the depth of clay exceeds 36 meters.

2.

3.

4.

208.4.4.2 Seismic Zone 4 near-sonrce factor. In Seismic Zone 4, each site shall be assigned near-source factors in accordance with Table 208-4 and 208-5 based on the Seismic Source Type as set forth in Section 208.4.4.4.

The value of Na used to determine Ca need not exceed 1.1 for structures complying with all the following conditions: 1. The soil profile type is SA" Ss, Sc or Sf>

2. 3.

The criteria set forth in the definition for Soil Profile Type SF requiring site-specific evaluation shall be considered. If the site corresponds to this criteria, the site shall be classified as Soil Profile Type SF and a site-specific evaluation shall be conducted.

4.

Table 208-2 - Soil Profile Types Average Soil Properties For Top Soil 30 m Of Soil Profile Profile Undrained Shear Wave SPT, N Name' Shear (blows' Generic j Velocity, V. Strength, Description (m/s) 300mm) (kPa)

Soil Profile Type

~ S4 ' I !

Hard Rock

I

SD'

.

Rock StitrSoil _ Profil,

Y 1--:- /'

> 50

-BID II "ID-

> 100

!

360

,0

!.

Except in single-story structures, residential building accommodating 10 or fewer persons, private garages, carports, sheds and agricultural buildings, moment frame systems designated as part of the lateral-force resisting system shall be special moment-resisting frames, The exceptions to Section 515.6.5 shall not apply, except for columns in one-story buildings or columns at the top story of multistory buildings. None of the following structural irregularities is present: Type 1,4 or 5 of Table 208-9, and Type 1 or 4 of Table 208-10,

208.4.4.4 Seismic source types. Table 208-6 defines the types of seismic sources. The location and type of seismic sources to be used for design shall be established based on approved geological data; see Figure 208-2A. Type A sources shall be determined from Figures 208 2B,C,D,E or the most recent mapping of active faults by the Philippine Institute of Volcanology and Seismology.

50 to

I

~

~J

Soft Soil < 180 < 15 Profile IS···. Soil Requiring Site-specific Evaluation. ~ F . See Section 208.43, I 1 Soil Profile Type SE also includes any soil profile with more than • E

= 1.0.

208.4.4.3 Seismic response coefficients. Each structure shall be assigned a seismic coefficient, Ca. in accordance with Table 208-7 and a seismic coefficient, C", in accordance with Table 208-8.

I

I

p

,

to I 760 Rock 1,500

Vel}' Dense I

Soil ad Soft . 360 to 760

. MFtI I

> 1,500

5,

-r-'

SBC.

S c:c.

!

2-39

.

3.0 meters of soft clay defined as a soil with plasticity index, P1>20, Wmc ~ 40 percent and Su < 24 kPa. The Plasticity Index, PI, and the moisture content, wmc , shall be determined in accordance with approved national standards,

Table 208-4 Near-Source Factor N/ Seismic Source Type

Closest Distance To

~~wn Sei!!!!Ilc~~u~~~_ ::;;; 5 km

208.4.4 SITE SEISMIC HAZARD CHARACTER ISTICS. Seismic hazard characteristics for the site shall be established based on the seismic zone and proximity of the site to active seismic sources, site soil profile characteristics and the structure's importance factor.

F

208.4.4.1 Seismic zone. Each site shall be assigned a seismic zone in accordance with Figure 208-1. Each structure shall be assigned a seismic zone factor Z. in accordance with Table 208-3,

Table 208-5 Near-Source Factor,

t-.

Table 208-3 Seismic Zone Factor Z j-iOijE . 2 I Z 0.20 L -_ _

~~

____

~

A

~-.----.-.-

..--- . - - - , - - -..

B

.-~--.----.---.-.--~

I

I I

Seismic Source Type

..

1.2

c..

I

..

~

10 _k_m_-l

1.0 -----.-~--

1.0

1.0

--'-~--.-.--------

I.

1.0

L

1.0

N/

Closest Distance To

._._ _ Known Seismic Source2

::;;; 5 km 10 km

---.:.,4_-----.J 0.40

__



2-40

Notes for Tables 208.4 and 208.5:

2

Table 208-6 - Seismic Source Types Seismic Source Type

I

I !

A

B

I

Table 208-8 - Seismic Coefficient, Cv _. __ ~ei!!mic Zo~_e_Fa~!1.,z~__ j Soil Profile type

The Near-Source Factor may be based on the linear interpolation of values for distances other than those shown in the table. The closest distance to seismic source shall be taken as the minimum distance between the site and the area described by the vertical projection of the source on the surface (i.e., surface projection of fault plane). The surface projection need not include portions of the source at depths of 10 km or greater. The largest value of the Near-Source Factor considering all sources shall be used for design.

f

C

1

Seismic Source Description Faults that are capable of producing large magnitude events and that have a high rate of seismic activity All faults other than TypesAandC Faults that are not capable of producing • large magnitude • earthquakes and that have a relatively low rate of seismic activity

Z=O.2

SA

O.32Nv

SB

0,20

0.40Nv

0.32

0,56N1

Sc .....

SD SE

1

1

Maximum Moment Magnitude, M

0.40 0,64

,-'- -' ----------

,,----~-

0,64Nv 0,96Nv ~.-~-.,--.,

..

Site-specific geotechnical investigation and dynamic site response analysis shall be performed to determine seismic coefficients.

208.4.5 CONFIGURAnON REQUIREMENTS Each structure shall be designated as being structurally regular or irregular in accordance with Sections 208,4,5.1 and 208.4.5.2.

M'C. 7.0

A,! < 6.5

I

T

,

~-"--.

See Footnote I

Seismic Source Definition

6.5:SM < 7.0

Z=O.4'

0,16

I

208.4.5.1 Regular structures. Regular structures have no significant physical discontinuities in plan or vertical configuration or in their lateral-foree-resisting systems such as the irregular features described in Section 208.4.5.2,

Sc

208.4.5.2 Irregular structures. 1, Irregular structures have significant physical discontinuities in configuration or in their lateral force-resisting systems, Irregular features include, but are not limited to, those described in Tables 208 9 and 208-10. All structures in occupancy Categories 4 and 5 in Seismic Zone 2 need to be evaluated only for vertical irregularities of Type 5 (Table 208-9) and horizontal irregularities of Type 1 (Table 208-10), 2, Structures having any of the features listed in Table 208-9 shall be designated as if having a vertical irregularity.

SD

EXCEPTION:

Subduction sources shall be evaluated on a site-specific basis.

Table 208-7 - Seismic Coefficient, Cll Soil Profile

e

Seismic Zone Factor, Z

.. -·

f---==~":'==-"L.[:":::--f---··z= ~i-z""o.-

SA

0.16

0.32N"

SB

0.20

0.40N"

SE SF

Where 110 story dr(ft ratio under de5ign lateral forces is greater thcUl 1.3 times the story drift raUo q{ the story above, the structure may be deemed to not have the stnlctllral irregularities of T)'1Je J or 2 ill Table 208-9. The story drift ratio for the top two stories need not be considered The slory drifts for this determination may be calculated neglecting torsional effects. 3.

Structures having any of the features listed in Table 208-10 shall be designated as having a plan irregularity.

208.4.6

STRUCTURAL SYSTEMS


OK JJ4S"J:').

EARTHQUAKE DESIGN

Structural systems shall be classified as one of the types listed in Table 208-11 and defined in this section. Bearing wall system. A structural system 208.4.6.1 without a complete vertical load-carrying space frame. Bearing walls or bracing systems provide support for all or most gravity loads. Resistance to lateral load is provided by shear walls or braced frames. Building frame system. A structural 208.4.6.2 system with an essentially complete space frame providin.g support for gravity loads. Resistance to lateral load IS provided by shear walls or braced frames. Moment-resisting frame system. A 208.4.6.3 structural system with an essentially complete space frame providing support for gravity loads. Moment-resisting frames provide resistance to lateral load primarily by flexural action of members.

Table 208-9 Vertical Structural Irregularities Irregularity Type and Definition

Refefence , Section

I

1. Stiffness Irregularity - Soft Story • A soft story is one in which the lateral stiffuess 208.4.8. 3 is less than 70 percent of that in the story above Item 2 or less than 80 percent of the average stiffuess of the three stories above. 2. Weight (J1\ass) Irregulari.ty

Mass irregularity shall be considered to exist 20M.8. where the effective mass of any story is more

3 than 150 percent of the effective mass of an Item 2 adjacent story. A roof that is lighter than the

floor below need not be considered. - - - - - + - - - - - 1 3. Vertical Geometric Irregularity

Vertical geometric irregularity shall be considered to exist where the horizontal 208.4.8. 3 dimension of the lateral-force-resisting system

in any story is more than l30 percent .of that in Item 2 an adjacent story. One-story penthouses need

not be considered.

4.In-Plane Discontinuity In Vertical Lateral

Force-Resisting Element. An in-plane offset 208.5.8. I of the lateral-load-resisting elements greater . than the length of those elements. . 5. Discontinuity In Capacity Weak Story A weak story is one in which the story strength

is less than 80 percent of that in the story above. 208.4.9. I The story strength is the total strength of all

seismic-resisting elements sharing the story for

~ direction under~co~ns~id~er~a~ti~o~n::...._ _ _ _ _~___ .~

1

208.4.6.4 Dual system. A structural system with the following features: 1.

2-41

2.

Resistance to lateral load is provided by shear walls or braced frames and moment-resisting frames (SMRF, IMRF, MMRWF or steel OMRF). The moment-resisting frames shall be designed to independently resist at least 2S percent of the design base shear.

3.

The two systems shall be designed to resist the total design base shear in proportion to their relative rigidities considering the interaction of the dual system at all levels.

208.4.6.5 Cantilevered column system. A structural system relying on cantilevered column elements for lateral resistance. 208.4.6.6 Undefined structural system. A structural system not listed in Table 208-11. 208.4.6.7 Nonbuilding structural system. A structural system conforming to Section 208.9.

Table 208-10

Plan Structural Irregularities : ReferenCe~1

Irregularity Type and Definition

. Section

1. Torsional Irregularity - To Be Considered When Diaphragms Are Not Flexible Torsional irregularly shall be considered to exist when the maximum story drift, computed including accidental torsion, at one end of the

structure transverse to an axis is more than 1.2

times the average of the story drifts of the two

ends of the structure.

2. Re-Entrant Corners Plan configurations of a structure and its lateral force-resisting system contain re-cntrant corners, where both projections of the structure beyond a re-entrant comer are greater than 15

percent of thc plan dimension of the structurc in

the given direction.

3. Diaphragm Discontinuity Diaphragms with abrupt discontinuities or variations in stiffuess, including those haying cutout or open areas greater than 50 percent of the gross enclosed area of the diaphragm, or

changes in effective diaphragm stiffuess of

more than 50 percent from one storv to the

i

208-8.2.8 Item 6

208.8.2.8

Items 6 and 7

208.8.2.iI

Ilem6

1

next. 4.0ut-Of-Plane Offsets 208.5.8.1 Discontinuities in a lateral force path, such as 208.82.11 Item (,: out-of-plane offsets of the vertical clements 515.7 i~ 5. Nonparallel Systems-----~--·----+-~-·~ The vertical lateral-load-rcsisting clements are 80 I 20 3'. not parallel to or symmetric about the major I orthogonal axes of the lateral-force~~_

An essentially complete space frame that provides support for gravity loads.

National Structural Code of the Philippines, Volume"

2-42


208.4.7 HEIGHT LIMITS. Height limits for the various structural systems in Seismic Zone 4 are given in Table 208-11.

3.

EXCEPTION: Regular structures may exceed these limits by not more than 50 percent for unoccupied structures, li'hich are not accessible to the general public. 208.4.8 SELECTION OF LATERAL-FORCE PROCEDURE Any structure may be, and certain structures defined below shall be, designed using the dynamic lateral-force procedures of Section 208.6.

4.

not described in Table 208-9 or 208-10, except as permitted by Section 208.5.4.1. Structures over five stories or 20 meters in height in Seismic Zones 4 not having the same structural system throughout their height except as permitted by Section 208.6.2. Structures, regular or irregular, located on Soil Profile Type Sf; that have a period greater than 0.7 second. The analysis shall include the effects of the soils at the site and shall conform to Section 208.6.2, Item 4.

208.4.9

SYSTEM LIM ITA TIONS

SIMPLIFIED STATIC. The simplified 208.4.8.1 static lateral-force procedure set forth in Section 208.5.2.3 may be used for the following structures of Occupancy Category IV or V:

208.4.9.1 Discontinuity. Structures with a discontinuity in capacity, vertical irregularity Type 5 as defined in Table 208-9, shall not be over two stories or 9 meters in height where the weak story has a calculated strength ofless than 65 percent of the story above.

1. Buildings of any occupancy (including single-family dwellings) t not more than three stories in height excluding basements, that use light-frame construction.

EXCEPTION:

2. Other buildings not more than two stories in height excluding basements.

Where the weak story is capable of resisting a tolal lateral seismic force of .Q, times the design force prescribed in Section 208.5.

208.4.8.2 STATIC. The static lateral force procedure of Section 208.5 may be used for the following structures: 1.

All structures, regular or irregular in Occupancy Categories IV and V in Seismic Zone 2.

2.

Regular structures under 75 meters in height with lateral force resistance provided by systems listed in Table 208-11, except where Section 208.4.8.3, Item 4, applies.

3.

Irregular structures not more than five stories or 20 meters in height.

4.

Structures having a flexible upper portion supported on a rigid lower portion where both portions of the structure considered separately can be classified as being regular, the average story stifIhess of the lower portion is at least 10 times the average story stifIhess of the upper portion and the period of the entire structure is not greater than 1.1 times the period of the upper portion considered as a separate structure fixed at the base.

208.4.8.3 DYNAMIC. The dynamic lateral-force procedure of Section 208.6 shall be used for all other structures, including the following: L Structures 75 meters or more in height, except as permitted by Section 208.4.8.2, Item L 2. Structures having a stifIhess, weight or geometric vertical irregularity of Type 1, 2 or 3, as defined in Table 208-9, or structures having irregular features

208.4.9.2 Undefined structural systems. For undefined structural systems not listed in Table 208-11, the coefficient R shall be substantiated by approved cyclic test data and analyses. The following items shall be addressed when establishing R: 1. Dynamic response characteristics, 2. Lateral force resistance, 3. Overstrength and strain hardening or softening, 4. Strength and stiffness degradation, 5. Energy dissipation characteristics, 6. System ductility, and 7.

Redundancy.

208.4.9.3 Irregular features. All structures having irregular features described in Table 208-9 or 208-10 shall be designed to meet the additional requirements of those sections referenced in the tables. 208.4.10 ALTERNATIVE PROCEDURES Alternative lateral-force procedures using rational analyses based on well-established principles of mechanics may be used in lieu ofthose prescribed in these provisions. 208.4.10.1" Seismic Isolation. Seismic isolation, energy dissipation and damping systems may be used in the design of structures when approved by the building official and when special detailing is used to provide results


EARTHQUAKE DESIGN

2-43

equivalent to those obtained by the use of conventional structural systems.

which occurs in any of the story levels at or below the two thirds height level of the building.

208.5 MINIMUM DESIGN LATERAL FORCES AND RELATED EFFECTS

For braced frames, the value of rj is equal to the maximum horizontal force component in a single brace element divided by the total story shear.

208.5.1 EARTHQUAKE LOADS AND MODELING REQUIREMENTS 208.5.1.1 Earthquake Loads. Structures shall be designed for ground motion producing structural response and seismic forces in any horizontal direction. The following earthquake loads shall be used in the load combinations set forth in Section 203: (208-1) (208-2)

Where: E = the earthquake load on an element of the structure resulting from the combination of the horizontal component, E", and the vertical component, E". Eh! the earthquake load due to the base shear, v~ as set forth in Section 208.5.2 or the design lateral force, Fp. as set forth in Section 208.7. Em = the estimated maximum earthquake force that can be developed in the structure as set forth in Section 208.5.l.1, and used in the design of specific elements of the structure, as specifically identified in this code. Ev = the load effect resulting from the vertical component of the earthquake ground motion and is equal to an addition of 0.5Ca I D to the dead load effect, D, for Strength Design, and may be taken as zero for Allowable Stress Design. no the seismic force amplification factor that is required to account for structural overstrength, as set forth in Section 208.5.3.1. p = ReliabilitylRedundancy Factor as given by the following equation:

P

2

6.1

(208-3)

r max the maximum element-story shear ratio. For a given direction of loading, the element-story shear ratio is the ratio of the design story shear in the most heavily loaded single element divided by the total design story shear.

AB= .t,be ground floor area of the structure in square meter For any given Story Level i, the element-story shear ratio is denoted as rio The maximum element-story shear ratio r,>IOX is defined as the largest of the element story shear ratios, rj,

For moment frames, rj shall be taken as the maximum of the sum of the shears in any two adjacent columns in a moment frame bay divided by the story shear. For columns common to two bays with moment-resisting connections on opposite sides at Level i in the direction under consideration, 70 percent of the shear in that column may be used in the column shear summation. For shear walls, rj shall be taken as the maximum value of the product of the wall shear multiplied by 3.01lw and divided by the total story shear, where lw is the length of the wall in meter. For dual systems, rj shall be taken as the maximum value of rj as defined above considering all lateral-load-resisting elements. The lateral loads shall be distributed to elements based on relative rigidities considering the interaction of the dual system. For dual systems, the value of p need not exceed 80 percent of the value calculated above. p shall not be taken less than 1.0 and need not be greater than 1.5. For special moment-resisting frames, except when used in dual systems, p shall not exceed 1.25. The number of bays of special moment-resisting frames shall be increased to reduce r. such that p is less than or equal to 1.25.

EXCEPTION: AB may be taken as the average floor area in the upper setback portion of the building where a larger base area exists at the groundfloor. When calculating drift, or when the structure is located in Seismic Zone 2, p shall be taken equal to 1. The ground motion producing lateral response and design seismic forces may be assumed to act nonconcurrentIy in the direction of each principal axis of the structure, except as required by Section 208.8.1. Seismic dead load, W; is the total dead load and applicable portions of other loads listed below. 1.

In storage and warehouse occupancies, a minimum of 25 percent of the floor live load shall be applicable.

2.

Where a partition load is used in the floor design, a load of not less than 0.5 kN/m2 shall be included.


2-44


Total weight of permanent equipment shall be included. 208.5.1.2 Modeling Requirements. The mathema tical model of the physical structure shall include all elements of the lateral-force-resisting system. The model shall also include the stiffness and strength of elements, which are significant to the distribution of forces, and shall represent the spatial distribution of the mass and stiffhess of the structure. In addition, the model shall comply with the following: L

Stiffness properties of reinforced concrete and masonry elements shall consider the effects of cracked sections.

2.

For steel moment frame systems, the contribution of panel zone deformations to overall story drift shall be included.

208.5.1.3 PA Effects. The resulting member forces and moments and the story drifts induced by PA effects shall be considered in the evaluation of overall structural frame stability and shall be evaluated using the forces producing the displacements of As. PA need not be considered when the ratio of secondary moment to primary moment does not exceed 0.10; the ratio may be evaluated for any story as the product of the total dead, and floor live loads, as required in Section 203, above the story times the seismic drift in that story divided by the product of the seismic shear in that story times the height of that story. In Seismic Zone 4, P L1 need not be considered when the story drift ratio does not exceed 0.02IR. 208.5.2

STATIC FORCE PROCEDURE

208.5.2.1 Design Base Shear. The total design base shear in a given direction shall be determined from the following equation: V

CvI W

RT

(208-4)

208.5.2.2 Structure Period. The value of T shall be determined from one ofthe following methods: 1.

Method A: For all buildings, the value T may be approximated from the following equation: #'

~

T = Ct (hnJ314

Where: Ct Ct

C1

(208-8)

0.0853 for steel moment-resisting frames. 0.0731 for reinforced concrete moment resisting frames and eccentrically braced frames. 0.0488 for all other buildings.

Alternatively, the value of C1 for structures with concrete or masonry shear walls may be taken as 0.0743 Ac in square meter.

/..[A:

with

The value of Ac shall be determined from the following equation: (208-9) The value of D./hn used in Equation (208-9) shall not exceed 0.9.

2.

Method B: The fundamental period T may be calculated using the structural properties and deformational characteristics of the resisting elements in a properly substantiated analysis. The analysis shall be in accordance with the requirements of Section 2085. 1.2. The value of T from Method B shall not exceed a value 30 percent greater than the value of T obtained from Method A in Seismic Zone 4, and 40 percent in Seismic Zone 2.

The fundamental period T may be computed by using the following equation:

The tot<\1 design base shear need not exceed the following:

v

= 2.5 ttl I W

R

The total design base shear shall not be less than the following: V

0.// Cal W

(208-6)

In addition, for Seismic Zone 4, the total base shear shall also not be less than the following: 0.8Z N"l W R

(208-10)

(208-5)

The values of j; represent any lateral force distributed approximately in accordance with the principles of Equations (208-13), (208-14) and (208-15) or any other rational distribution. The elastic deflections, 5;, shall be calculated using the applied lateral forces,};.

(208-7)


EARTHQUAKE DESIGN

208.5.2.3 Simplified Design Base Shear. Structures conforming to the requirements of Section 208.4.8.1 may be designed using this procedure. 208.5.2.3.1 Base shear. The total design base shear in a given direction shaH be determined from the foHowing equation:

v

3.0Ca W

seismic forces set forth in Section 20S.5. For both Allowable Stress Design and Strength Design, the Seismic Force Overstrength Factor, Q o, shall be taken from Table 208-1 L

208.5.3.2 Determination of R. The value for R shall be taken from Table 208-11.

(208-11)

R

where the value of Ca shall be based on Table 208-7 for the soil profile type. When the soil properties are not known in sufficient detail to determine the soil profile type, Type SD shall be used in Seismic Zone 4, and Type SE shall be used in Seismic Zones 2. In Seismic Zone 4, the Near-Source Factor, Na , need not be greater than 1.3 if none of the following structural irregularities are present: Type 1,4 or 5 of Table 208-9, or Type 1 or 4 of Table 208-10.

208.5.2.3.2 Vertical distribution. The forces at each level shall be calculated using the following equation: , 3.0

(208-12)

R where the value of Ca shall be determined as in Section 208.5.2.3.1.

208.5.2.3.3 Applicability. Sections 208.5.1.2, 208.5.1.3, 208.5.2.1, 208.5.2.2, 208.5.5, 208.5.9, 208.5.10 and 20S.6 shall not apply when using the simplified procedure. EXCEPTION: For bUildings with relatively flexible stntclural systems. the building official may require consideration of PO effects and drift ill accordance with Sections 208.5.1.3, 208.5.9 and 208.5.10. Os shall be determined using design seismic forces from Section 208.5.2.3.1.

Where used, /),M shall be taken equal to 0.01 times the story height of all stories. In Section 208.8.2.8, Equation (208 20) shall read Fpx

3.0Ca w R

px

2-45

and need not exceed 1.0

CWpx, but shall not be less than 0.5 Ca wpx. Rand Q" shall be taken from Table 208-11.

208.5.3 DETERMINATION OF SEISMIC FACTORS 208.5.3.1 Determination of QO" For specific elements of the structure, as specifically identified in this code, the minimum design strength shall be the product of the seismic force overstrength factor Oa and the design


2-46

Table 208-11


Structural Systems 1

'~~~~~~--------------------------------~-------r------'--=~--~

Basic Structural System2

I

Height

Lateral-Force-Resistiug System Description

R

!

I L~!f:r (m)

n.,

i

i

1. Light-Framed Walls with Shear Panels I a. Woo.·.·. . d. . struc . . rural panel walls for structures three stories. or less +-5~-Tl:~L.~·_]==- 20~= b. All o~ght-framed w a l l s _ 4.5 . . ~ _ 20 i

~~~e~o::~~ 1. Bearing Wall System

...

__

-.-~---

.

..__ .___

~=b~_ ~onqe~~=-___ _.. _-=~=~~_~

3. Moment-Resisting Frame Systems

~.~E±-....-H=F.8-~50'~·--

f-=---...,b:;:.:;._:Masoruy 4..5 2,lf"- --50- 3. Light Steel-Fram~ Bearing Walls. with tellSion-onlybracing -2~8 .. 2.2 20 .. 4. Braced Frames where Bracin ..J:arries (Jr-'a::..;v-'in:.l-.'. . :Loa=.::..::c=:d_____.__...-____---,..._____- .__ a. Steel b. Concr~te3 .---~- . . . r------"---::=:==~-::-------------- ..... - - . - . - - c. Heavy timber I. Steel Eccentrit,:ially Braced Frame (EBf}_ _ _ _ __

~_~ight-Frame(I}Valis with Shear Panels

6.5 2.8 20 ..'1.. Wood struc1:tJ!a.lpa.nel Willis fOI"~1!:Uc!UI'~J!lree~t<:!ties ().I"l~~ b. All other Ii t-framed walls 5.0 2.8 20 3. Shear Walls .... ...... .....- - a. ._-_ Concrete 5.5 2.8 75 ..... ..... --. 5.5

2.8 50 _ . . . b. Masoruy. ____ .._ ...... ____.... ___ .____ 4. _9!:.
5.6 a. Steel 2.2 50 --.. ·ii..... ConCrcte3 5.6 2.2 2.2 _--c:~Hea':itlID~-===--._~ __~~ial9>nce[ltrica1ly_Braced.£ram~_._ 6.4 75 a. Steel IL~ial MOIIlent~B-e.§i~~Er....m:n:~{SMNL . a. Steel N.L. ----.-~

2. Building Frame Systems

........

~Masoruy

_____

N.L.

Moment-Resisting Wall Frame (MMRWF) s i 3. Concrete Intermediate Moment-Resistin Frame (lMR.Ji)L.._ _ _4Jr~~_¥oIIlent:R~is~g~Fram~(QMREL a. Steel --b~ Concrete7- -..·-- ..-----

-5.S· -i!iI-TrusSMOmentFrames"Qrstet;f[stMFy-- 1. Shear Walls -a.concrete\Vith'-SMRF------'1). Concrete-With steel oMRF .. .- .-~-~.--.

--.. -"c: "-concrete -Wifuc-oncrete-WRFs- - ~

-

.~--

_~~lIs~[llY ~!!t_S¥RF

.---..

50 4.5 3.5 6.5

-----,

-~.

-----.~~~

-.-~-------

.... ____._

L.._~...MasOIIlY.~tl1s~e! o~_ -3-" 4. Dual Systems

~........L_ M!lSOI1l}'_~1th

concrete IMRf_ _ ... ___ ...

• ""g. Masonry with

masonry MMRWF

.

~. .§t~LE£centrt~~ly~r!..ced Fra!!l~ (BBn_

---~~-~~-:~t~~--

-

1

2.8 2.8 2.8 2.8.._-, 2.8 2.8 2.8

N.L. .'_ .... _ -

50 50 -- ---50 50

'-~-"--~--

.~'"~,-

---~

. -.. . -----.. _._.-_-.______._.~_-...J.

..3..: ... OrdinJl!Y..B..!.lIce(L.fr~J1l~_ ___

_

a. Steel with steel SMRF ---b:- sieeT"witli -steelOMRF ... " ----c-:- t-oncrete With concrcte'sMR:F3 •- d. Concrete with- coIlcretcIMR.FJ 4. -~~lal--:-<2~l!....CC[l~~i1!Y~j:!rac~{fr~es_" a. Steel with steel SMRF ----'b--:--SteefWlth steeCOMRF-·· . ------i Cantilevered column elements Concrete7

l

8.5 4.2 6.5 5.5 4.2 4.2 6.0


6.5 4.2 6.5 4.2

2.8 2.8 2.8 2.8 2.8 2.8 2.0

~.~~_}t_ - -"--

,

..

-

or

._.

-

-

N.L

50 106 50

EARTHQUAKE DESIGN

Notes for Table 208·11 N.L - no limit 1 See Section 208.5.4 for combination of structural systems. For Undefined Systems see Sections 208.4.6.6 and 208.4.9.2 2 Basic structural systems are defined in Section 208.4.6. ~ Prohibited in Seismic Zone 4. 4 Includes precast concrete conforming to Section 421.2.7. 5 Prohibited in Seismic Zone 4, except as permitted in Section 208.9.2. 6 Total height of the building including cantilevered columns. 7 Prohibited in Seismic Zones 2 and 4, See Section 208.8.2.6.

208.5.4 COMBINATIONS OF STRUCTURAL SYSTEMS. Where combinations of structural systems are incorporated into the same structure, the requirements of this section shall be satisfied.

2-47

50 ~eters in height. Only combinations of dual systems and speCial moment-resisting frames shall be used to resist seismic forces in structures exceeding 50 meters in height in Seismic Zone 4. 208.5.4.3 Combinations along the same axis. Where a combination of different structural systems is utilized to resist lateral forces in the same direction, the value of R used for design in that direction shall not be greater than the least value for any of the systems utilized in that same direction. 208.5.5 VERTICAL DISTRIBUTION OF FORCE The total force shall be distributed over the height of the structure in conformance with Equations (208-13), (208-14) and (208-15) in the absence ofa more rigorous procedure. n

208.5.4.1 Vertical combinations. The value of R used in the design of any story shall be less than or equal to the value of R used in the given direction for the story above.

The concentrated force Ft at the top, which is in addition to Fn, shall be determined from the equation:

EXCEPTION:

Fe

This requirement need not be applied to a story where the dead weight above that story is less than 10 percent of the total dead weight ofthe structure.

The value of T used for the purpose of calculating Fe shall be the period that corresponds with the design base shear as computed using Equation (208-4). Fe need not exceed 0.25Vand may be considered as zero where Tis 0.7 second or less. The remaining portion of the base shear shall be distributed over the height of the structure, including Level n, according to the following equation:

Structufes may be designed using the procedures of this section under the following conditions: 1.

The entire structure is designed using the lowest R of the lateral-force-resisting systems used, or

2.

The following two-stage static analysis procedures may be used for structures conforming to Section 208.4.8.2, Item 4.

2.1

The flexible upper portion shall be designed as a separate structure, supported laterally by the rigid lower portion, using the appropriate values of R and p.

2.2 The rigid lower portion shall be designed as a separate structure using the appropriate values of R and p. The reactions from the upper portion shall be those determined from the analysis of the upper portion amplified by the ratio of the (RIp) of the upper portion over (RIp) of the lower portion. 208.5.4.2 Combinations along different axes. In Seismic Zone 4 where a structure has a bearing wall system in only one direction, the value of R used for design in the orthogonal direction shall not be greater than that used for the bearing wall system. Any combinati6n of bearing wall systems, building frame systems, dual systems or moment-resisting frame systems may be used to resist seismic forces in structures less than

V

= Fe + I.E;

(208-13)

i~l

=

0.07 TV

(v -E;}w;ch;c n

(208-14)

(208-15~

I.w;}; i=l

At each level designated as x, the force shall be applied over the area of the building in accordance with the mass distribution at that level. Structural displacements and design seismic forces shall be calculated as the effect of forces and F t applied at the appropriate levels above the base. 208.5.6 HORIZONTAL DISTRIBUTION OF SHEAR The design story shear, V.r, in any story is the sum of the forces Ft and Fx above that story. V:r shall be distributed to the various elements of the vertical lateral-foree-resisting system in proportion to their rigidities, considering the rigidity of the diaphragm. See Section 208.8.2.3 for rigid elements that are not intended to be part of the lateral-force resisting systems. Where diaphragms are not flexible, the mass at each level shall be 1lssumed to be displaced from the calculated center of mass in each direction a distance equal to 5 percent of the building dimension at that level perpendicular to the direction of the force under consideration. The effect of


2-48


this displacement on the story shear distribution shall be considered.

20S.S.S.1 Systems-.

Diaphragms shall be considered flexible for the purposes of distribution of story shear and torsional moment when the maximum lateral deformation of the diaphragm is more than two times the average story drift of the associated story. This may be determined by comparing the computed midpoint in-plane deflection of the diaphragm itself under lateral load with the story drift of adjoining vertical resisting elements under equivalent tributary lateral load.

20S.S.S.L1 General. Where any portion of the lateral load-resisting system is discontinuous, such as for vertical irregularity Type 4 in Table 208-9 or plan irregularity Type 4 in Table 208-10, concrete, masonry, steel and wood elements supporting such discontinuous systems shall have the design strength to resist the combination loads resulting from the special .seismic load combinations of Section 203.5.

20S.S.7 HORIZONTAL TORSIONAL MOMENTS Provisions shall be made for the increased shears resulting from horizontal torsion where diaphragms are not flexible. The most severe load combination for each element shall be considered for design.

EXCEPTIONS: I. The quantity Em in Section 203.5 need not exceed the maximum force that can be transferred to the element by the lateral-force-resisting system. 2. Concrete slabs supporting light-frame wood shear wall systems or light-frame steel and wood structural panel shear wall systems.

The torsional design moment at a given story shall be the moment resulting from eccentricities between applied design lateral forces at levels above that story and the vertical-resisting elements in that story plus an accidental torsion. f

The accidental torsional moment shall be determined by assuming the mass is displaced as required by Section 208.5.6.

Where torsional irregularity exists, as defined in Table 208-10, the effects shall be accounted for by increasing the accidental torsion at each level by an amplification factor, Ax, determined from the following equation: 1. 2

A = x

Dmax [

(208-16)

1.2 Davg ]

2.

Where: Davg

Dmax

the average of the displacements at the extreme points of the structure at Level x. = the maximum displacement at Level x. =

The value of A x need not exceed 3.0. 3.

20S.S.S OVERTURNING Every structure shall be designed to resist the overturning effects caused by earthquake forces specified in Section 208.5.5. At any level, the overturning moments to be4. resisted shall be determined using those seismic forces (Ft and Fx) that act on levels above the level under5. consideration. At any level, the incremental changes of the design overturning moment shall be distributed to the various resisting elements in the manner prescribed in Section 208.5.6. Overturning effects on every element shall be carried down to the foundation. See Sections 207.1 and 208.8 for combining gravity and seismic forces.

L

Elements

Supporting

Discontinuous

For Allowable Stress Design, the design strength may be determined using an allowable stress increase of 1.7 and a resistance factor, ¢, of 1.0. This increase shall not be combined with the one- third stress increase permitted by Section 203.4, but may be combined with the duration of load increase permitted in Section 615.3.4.

20S.S.S.1.2 Detailing requirements in Seismic Zone 4. In Seismic Zone 4, elements supporting discontinuous systems shall meet the following detailing or member limitations: Reinforced concrete or reinforced masonry elements designed primarily as axial-load members shall comply with Section 421.4.4.5. Reinforced concrete elements designed primarily as flexural members and supporting other than light-frame wood shear wall system or light-frame steel and wood structural panel shear wall systems shall comply with Sections 421.3.2 and 421.3.3. Strength computations for portions of slabs designed as supporting elements shall include only those portions of the slab that comply with the requirements of these sections. Masonry elements designed primarily as axial-load carrying members shall comply with Sections 706.1.12.4, Item 1, and 708.2.6.2.6. Masonry elements designed primarily as flexural members shall comply with Section 708.2.6.2.5. Steel elements designed primarily as axial-load members shall comply with Sections 515.4.2 and 515.4.3. 6.

Steel elements designed primarily as flexural members or trusses shall have bracing for both top and bottom beam flanges or chords at the location of the support of the discontinuous system and shall comply with the requirements of Section 515.6.1.3.


EARTHQUAKE DESIGN

7.

Wood elements designed primarily as flexural members shall be provided with lateral bracing or solid blocking at each end of the element and at the connection location(s) of the discontinuous system.

EXCEPTIONS: 1.

208.5.8.2 At Foundation. See Sections 208.4.1 and 308.4 for overturning moments to be resisted at the foundation soil interface. 208.5.9 DRIFT Drift or horizontal displacements of the structure shall be computed where required by this code. For both Allowable Stress Design and Strength Design, the Maximum Inelastic Response Displacement, 6.u , of the structure caused by the Design Basis Ground Motion shall be determined in accordance with this section. The drifts corresponding to the design seismic forces of Section 208.5.2.1, 6.s, shall be determined in accordance with Section 208.5.9. L To determine 6..\f, these drifts shall be amplified in accordance with Section 208.5.9.2. 208.5.9.1 Determination of 6.s- A static, elastic analysis of the lateral force-resisting system shall be prepared using the design seismic forces from Section 208.5.2.1. Alternatively, dynamic analysis may be performed in accordance with Section 208.6. Where Allowable Stress Design is used and where drift is being computed, the load combinations of Section 203.3 shall be used. The mathematical model shall comply with Section 208.5.1.2. The resulting deformations, denoted as 1\" shall be determined at all critical locations in the structure. Calculated drift shall include translational and torsional deflections. 208.5.9.2 Determination of 6..v The Maximum Inelastic Response Displacement, 6.jf, shall be computed as follows: 6..1/ = 07 R 6.8

(208-17)

2-49

2.

These drift limits may be exceeded when it is demonstrated that greater drift can be tolerated by both structural elements and nonstructural elements that could affect life sqfety. The drift used in this assessment shall be based upon the Maximum Inelastic Response Displacement, LiM There shall be no drift limit in single-story steel framed structures whose primary use is limited to storage, factories or workshops. Minor accessory uses shall be allowed. Stnlctures on which this exception is used shall not have equipment attached to the structural frame or shall have such equipment detailed to accommodate the additional drift. Walls that are laterally supported by the steel frame shall be designed to accommodate the drift in accordance with Section 208.8.2.3.

208.5.10.2 Limitations. The design lateral forces

used to determine the calculated drift may disregard the

limitations of Equation (208-6) and (208-7) and may be

based on the period determined from Equation (208-10)

neglecting the 30 or 40 percent limitations of Section

208.5.2.2, Item 2.

208.5.11 VERTICAL COMPONENT.

The following requirements apply in Seismic Zone 4 only.

Horizontal cantilever components shall be designed for a

net upward force of 0.7 Cal Wp-

In addition to all other applicable load combination;, horizontal prestressed components shall be designed using not more than 50 percent of the dead load for the gravity load, alone or in combination with the lateral force effects.

208.6

DYNAMIC ANALYSIS PROCEDURES

EXCEPTION: Alternatively, LiM may he computed by nonlinear time history analysis in accordance with Section 208.6.6. The analysis used to determine the Maximum Inelastic Response Displacement 6.", shall consider P6. effects.

208.5.10 STORY DRIFT LIMITATION Story drifts shall be computed using the Maximum Inelastic Response Displacement, 6.,11' 208.5.10.1 Calculated. Calculated story drift using I\w shall not exceed 0.025 times the story height for structures having a fundamental period of less than 0.7 second. For structures having a fundamental period of 0.7 second or greater, the calculated story drift shall not exceed 0.020 times the story height.

208.6.1 GENERAL· Dynamic analyses procedures, when used, shall conform to the criteria established in this section. The analysis shall be based on an appropriate ground motion representation and shall be performed using accepted principles of dynamics. Structures that are designed in accordance with this section shall comply with all other applicable requirements of these provisions.

208.6.2 GROUND MOTION The ground motion representation shall, as a minimum, be one having a lO-percent probability of being exceeded in 50 years, shall not be reduced by the quantity R and may be one of the following:


2-50

I.

2.

3.


An elastic design response spectrum constructed in accordance with Figure 208-3, using the values of Ca and C" consistent with the specific site. The design acceleration ordinates shall be multiplied by the acceleration of gravity, 9.815 mlsec2 .

A site-specific elastic design response spectrum based on the geologic, tectonic, seismologic and soil characteristics associated with the specific site. The spectrum shall be developed for a damping ratio of 0.05, unless a different value is shown to be consistent with the anticipated structural behavior at the intensity of shaking established for the site. Ground motion time histories developed for the specific site shall be representative of actual earthquake motions. Response spectra from time histories, either individually or in combination, shall approximate the site design spectrum conforming to Section 208.6.2, Item 2.

4.

For structures on Soil Profile Type SF, the following requirements shall apply when required by Section 208.4.8.3, Item 4:

4.1

The ground motion representation shall be developed in accordance with Items 2 and 3.

4.2 Possible amplification of building response due to the effects of soil-structure interaction and lengthening of building period caused by inelastic behavior shall be considered. 5.

The vertical component of ground motion may be defined by scaling corresponding horizontal accelerations by a factor of two- thirds. Alternative factors may be used when substantiated by site specific data. Where the Near Source Factor, N,,, is greater than 1.0, site-specific vertical response spectra shall be used in lieu of the factor of two thirds.

208.6.3 MATHEMATICAL MODEL A mathematical model of the physical structure shall represent the spatial distribution of the mass and stiffness of the structure to an extent that is adequate for the calculation ofthe significant features of its dynamic response. A three dimensional model shall be used for the dynamic analysis of structures with highly irregular plan configurations such as those having a plan irregularity defined in Table 208-10 and having a rigid or semirigid diaphragm. The stiffuess properties used in the analysis and general mathematical modeling shall be in accordance with Section 208.5. 1.2.

208.6.4 DESCRIPTION OF ANALYSIS PROCEDURES. 208.6.4.1 Response spectrum analysis. An elastic dynamic analysis of a structure utilizing the peak dynamic response of all modes having a significant contribution to total structural response. Peak modal responses are calculated using the ordinates of the appropriate response spectrum curve which correspond to the modal periods. Maximum modal contributions are combined in a statistical manner to obtain an approximate total structural response. 208.6.4.2 Time-history analysis. An analysis of the dynamic response of a structure at each increment of time when the base is subjected to a specific ground motion time history. 208.6.5

RESPONSE SPECTRUM ANALYSIS.

208.6.5.1 Response spectrum representation and interpretation of results. The ground motion representation shall be in accordance with Section 208.6.2. The corresponding response parameters, including forces, moments and displacements, shall be denoted as Elastic Response Parameters. Elastic Response Parameters may be reduced in accordance with Section 208.6.5.4. 208.6.5.2 Number of modes. The requirement of Section 208.6.4.1 that all significant modes be included may be satisfied by demonstrating that for the modes considered, at least 90 percent of the participating mass of the structure is included in the calculation of response for each principal horizontal direction. Combining modes. The peak member 208.6.5.3 forces, displacements, story forces, story shears and base reactions for each mode shall be combined by recognized methods. When three- dimensional models are used for analysis, modal interaction effects shall be considered when combining modal maxima. 208.6.5.4 Reduction of Elastic Response Parameters for design. Elastic Response Parameters may be reduced for purposes of design in accordance with the following items, with the limitation that in no case shall the Elastic Response Parameters be reduced such that the corresponding design base shear is less than the Elastic Response Base Shear divided by the value of R 1.

For all regular structures where the ground motion representation complies with Section 208.6.2, Item I, Elastic Response Parameters may be reduced such that the corresponding design base shear is not less than 90 percent of the base shear determined in accordance with Section 208.5.2.


EARTHQUAKE DESIGN

2.

3.

For all regular structures where the ground motion representation complies with Section 208.6.2, Item 2, Elastic Response Parameters may be reduced such that the corresponding design base shear is not less than 80 percent of the base shear determined in accordance with Section 208.5.2. For al1 irregular structures, regardless of the ground motion representation, Elastic Response Parameters may be reduced such that the corresponding design base shear is not less than 100 percent of the base shear determined in accordance with Section 208.5.2.

The corresponding reduced design seismic forces shall be used for design in accordance with Section 203.

208.6.5.5 Directional effects. Directional effects for horizontal ground motion shall conform to the requirements of Section 208.5.1. The effects of vertical ground motions on horizontal cantilevers and prestressed elements shall be considered in accordance with Section 208.5.1l. Alternately, vertical seismic response may be determined by dynamic response methods; in no case shall the response used for design be less than that obtained by the static method. 208.6.5.6 Torsion. The analysis shall account for torsional effects, including accidental torsional effects as prescribed in Section 208.5.7. Where three-dimensional models are used for analysis, effects of accidental torsion shall be accounted for by appropriate adjustments in the model such as adjustment of mass locations, or by equivalent static procedures such as provided in Section 208.5.6. 208.6.5.7 Dnal systems. Where the lateral forces are resisted by a dual system as defined in Section 208.4.6.4, the combined system shall be capable of resisting the base shear determined in accordance with this section. The moment-resisting frame shall conform to Section 208.4.6.4, Item 2, and may be analyzed using either the procedures of Section 208.5.5 or those of Section 208.6.5. 208.6.6

TIME-HISTORY ANALYSIS.

208.6.6.1 Time history. Time-history analysis shall be performed with pairs of appropriate horizontal ground motion time- history components that shall be selected and scaled from not less than three recorded events. Appropriate time histories shall have magnitudes, fault distances and source mechanisms that are consistent with those that control the design-basis earthquake (or maximum capable earthquake). Where three appropriate recorded ground motion time-history pairs are not available, appropriate simulated ground-motion time-history pairs may be used to make up the total number required. For each pair of horizontal ground- motion components, the square root of

2-51

the sum of the squares (SRSS) of the 5 percent-damped site-specific spectrum of the scaled horizontal components shall be constructed. The motions shall be scaled such that the average value of the SRSS spectra does not fall below 1.4 times the 5 percent-damped spectrum of the design basis earthquake for periods from O.2T second to 1.51' seconds. Each pair of time histories shall be applied simultaneously to the model considering torsional effects. The parameter of interest shall be calculated for each time history analysis. If three time-history analyses are performed, then the maximum response ofthe parameter of interest shall be used for design. If seven or more time history analyses are performed, then the average value of the response parameter of interest may be used for design.

208.6.6.2 Elastic time-history analysis. Elastic time history shall conform to Sections 208.6.1, 208.6.2, 208.6.3, 208.6.5.2, 208.6.5.4, 208.6.5.5, 208.6.5.6, 208.6.5.7 and 208.6.6.1. Response parameters from elastic time-history analysis shall be denoted as Elastic Response Parameters. All elements shall be designed using Strength Design. Elastic Response Parameters may be scaled in accordance with Section 208.6.5.4. 208.6.6.3

Nonlinear time-history analysis.

208.6.6.3.1 Nonlinear time history. Nonlinear time-history analysis shall meet the requirements of Section 208.4.10, and time histories shall be developed and results determined in accordance with the requirements of Section 208.6.6.1. Capacities and characteristics of nonlinear elements shall be modeled consistent with test datal or substantiated analysis, considering the Importance Factor. The maximum inelastic response displacement shall not be reduced and shall comply with Section 208.5.1 O. 208.6.6.3.2 Design review. When nonlinear time history analysis is used to justifY a structural design. a design review of the lateral- force-resisting system shall be performed by an independent engineering team, including persons licensed in the appropriate disciplines and experienced in seismic analysis methods. The lateral~force resisting system design review shall include, but not be limited to, the following: 1.

Reviewing the development of site-specific spectra and ground-motion time histories.

2.

Reviewing the preliminary design of the lateral force-resisting system.

3.

Reviewing the final design of the lateral-force resisting system and all supporting analyses.

The engineer of record shall submit with the plans and calculations a statement by all members of the engineering


2-52


team doing the review stating that the above review has been performed.

208.7 LATERAL FORCE ON ELEMENTS OF STRUCTURES, NON STRUCTURAL COMPONENTS AND EQUIPMENT SUPPORTED BY STRUCTURES 208.7.1 GENERAL Elements of structures and their attachments, permanent nonstructural components and their attachments, and the attachments for permanent equipment supported by a structure shall be designed to resist the total design seismic forces prescribed in Section 208.7.2. Attachments for £1oor- or roof-mounted equipment weighing less than 1.8 kN, and furniture need not be designed. Attachments shall include anchorages and required bracing. Friction resulting from gravity loads shall not be considered to provide resistance to seismic forces.

•

When the structural failure of the lateral-force-resisting systems of nomigid equipment would cause a life hazard, such systems shall be designed to resist the seismic forces prescribed in Section 208.7.2. When permissible design strengths and other acceptance criteria are not contained in or referenced by this code, such criteria shall be obtained from approved national standards subject to the approval of the building official.

208.7.2 DESIGN FOR TOTAL LATERAL FORCE The total design lateral seismic force, Fl" shall be determined from the following equation: (208-18) Alternatively, equation: F p

may be calculated using the following

=QpCaIp (1+3 hx \.;: Rp

h,.)"P

(208-19)

Except that Fp shall not be less than 0.7CJpWp and need not be more than 4CJpWp

Where: hx is the element or component attachment elevation with respect to grade. hx shall not be taken less than 0.0. h, is the structure-roof elevation with respect to grade. is the in-structure Component Amplification Factor that varies from l.0 to 2.5.

l

A value for Qp shall be selected from Table 208-12. Alternatively, this factor may be determined based on the dynamic properties or empirical data of the component and the structure that supports it. The value shall not be taken less than 1.O. Rp is the Component Response Modification Factor that shall be taken from Table 208-12, except that Rp for

anchorages shall equal 1.5 for shallow expansion anchor bolts, shallow chemical anchors or shallow cast-in-place anchors. Shallow anchors are those with an embedment length-to-diameter ratio of less than 8. When anchorage is constructed of nonductile materials, or by use of adhesive, Rp shall equal 1.0. The design lateral forces determined using Equation (208 18) or (208-19) shall be distributed in proportion to the mass distribution of the element or component. Forces determined using Equation (208-18) or (208-19) shall be used to design members and connections that transfer these forces to the seismic-resisting systems. Members and connection design shall use the load combinations and factors specified in Section 203.3 or 203.4. The ReliabilitylRedundancy Factor, p, may be taken equal to 1.0. For applicable forces and Component Response Modification Factors in connectors for exterior panels and diaphragms, refer to Sections 208.8.2.3, 208.8.2.7, and 208.8.2.8. Forces shall be applied in the horizontal directions, which result in the most critical loadings for design.

208.7.3 SPECIFYING LATERAL FORCES Design specifications for equipment shall either specify the design lateral forces prescribed herein or reference these provisions. 208.7.4 RELATIVE MOTION OF EQUIPMENT ATTACHMENTS. For equipment in Categories I and IT buildings as defined in Table 103-1, the lateral-force design shall consider the effects of relative motion of the points of attachment to the structure, using the drift based upon /),M. 208.7.5 ALTERNATIVE DESIGNS Where an approved national standard or approved physical test data provide a basis for the earthquake-resistant design of a particular type of equipment or other nonstructural component, such a standard or data may be accepted as a basis for design ofthe items with the following limitations: l.

These provisions shall provide minimum values for the design of the anchorage and the members and


EARTHQUAKj: DESIGN

connections that transfer the forces to the seismic resisting system. 2.

The force, Fp, and the overturning moment used in the design of the nonstructural component shall not be less than 80 percent of the values that would be obtained using these provisions.

National structural Code of the Philippines. Voll.Dhe 1

2-53

2-54


T;tble 208-12 Horizontal Force Factors, Bp and Rp for Elements of Structures and· Nonstructural Components and Equipment Category

Element or Component

IJp

Footnote

Rp

L Walls including the following: -~

I

... - . -....

----------~.~

--.--,.~.-

2.5

a. Unbraced (cantilevered) parapets -.-----~-------

1. Elements of Structures

>

..

_.....•

~--

3.0 --_.

-.

1.0

3.0

2

c. All interior-bearing and non-bearing walls

1.0

3.0

2

3.0

J

2.5

2. Chimneys, stacks and trussed towers supported on or __projectingabove tl1<:.~~~._.>_._ a. Laterally braced or anchored to the structural frame at a point h<:~!! their ~~ of mass b. Laterally braced or anchored to the structural frame at above their -> - ....-_..'... centers _. - of mass .__ ._------ --

. _-

------

-

4. Storage racks (include contents) over 1.8 meters talL

1---5. Permanent floor-supported cabinets and book stacks more than 1.8 meters in height (include contents) 6. Anchorage and lateral bracing for suspended ceilings and light fi:,,:tures 7. Access floor systems 8. Masonry or concrete fences over 1.8 meters high

_ _-_ ......

........

_-

9. Partitions. 1. Tanks and vessels (include contents), including support

systems. bing equipment and associated- 2. Elec~cal, mechanical and oondwl ,nd doctwmk md p'pm,. ~ 3. Any fle~ble equipmen~ laterally bra~ed or anchored t~ the structural frame at a pomt below theIr center of mass TAnchorage of emergency power supply systems and-esscntial communications equipment. Anchorage and support systems . for battery racks and fuel tanks necessary for operation of emergen~ equi~ment. See also Section 208.7.2

t:'um

3. Equipment

5. Temporary containers with flammable or hazardous materials.

-- ---

4. Other Components

~-

~----.

2. Rigid components with nonductile material or attachments 3. Flexible components with ductile material and attachments. 4. Flexible components with nonductile material or attachments.

L

.. >.>.

'-"

1.0

- - .--.

-

3.0

2.5

3.0

.- .

.

2.5

4.0

4

1.0

3.0

5

1.0

3.0

3,6,7,8 4,5,9

1.0

I

3.0

1.0

I

3.0

1.0

3.0

1.0

3.0

I0 3.0 I . 25 30 . .

iT

I--':-r;

1. Rigid components with ductile material and attachments.

.

-

3.0 •..

3. Signs and billboards -~--

3.0

2.5

~

.

3

--~-

m .

1-"

-

4.0

1. Exterior and interior ornamentations and appendages.

Components

-------

b. Exterior walls at or above ground floor and parapets braced above their centers of gravity

2. Penthouse (except when framed by an extension of the structural frame) 3. Connections for prefabricated structural elements other walls. See also Section 208.7.2

2. Nonstructural

--

----

I0 .

I

!

30

~

13, 14, 15, 16 5, 10, 14,

15,16 17,18

._. 1.0

I

10, 11,12:"

!

I.

I

oJ.

-

1.0

3.0

19

3.0

1

..... ~.

1.5

1

I 2.5 3.0 1 I 2.5..~-F--_. -----·1 1.5 1 i


EARTHQUAKE DESIGN

FOOTNOTES FOR TABLE 208.12 See Section 208.2 for definitions of flexible components and rigid components. 2 See Section 208.8.2.3 and 208.8.2.7 for concrete and masonry walls and Section 208.7.2 for connections for panel connectors for panels. 3 Applies to Seismic Zones 2 and 4 only. 4 Ground supported steel storage racks may be designed using the provisions of Sections 208.9. Load and resistance factor design may be used for the design of cold-formed steel members, provided seismic design forces are equal to or greater than those specified in Section 208.7.2 or 208.9.2 as appropriate. 5 Only anchorage or restraints need be designed. Ceiling weight shall include all light fixtures and other equipment or partitions that are laterally supported by the ceiling. For purposes of determining the seismic force, a ceiling weight of not less than 0.2 kPa shall be used. Ceilings constructed of lath and plaster or gypsum board screw or nail attached to suspended members that support a ceiling at one level extending from wall to wall need not be analyzed, provided the walls are not over 15 meters apart. Light fixtures and mechanical services installed in metal suspension systems for acoustical tile and lay-in panel ceilings shall be independently supported from the structure above as specified in UBC Standard 25-2, Part III. Wp for access floor systems shall be the dead load of the access floor system plus 25 percent of the floor live load plus a 0.5 kPa partition load allowance. 10 Equipment includes, but is not limited to, boilers, chillers, heat exchangers, pumps, air-handling units, cooling towers, control panels, motors, switchgear, transformers and life safety equipment. It shall include major conduit, ducting and piping, which services such machinery and equipment and fire sprinkler systems. See Section 208.7.2 for additional requirements for determining ap for nonrigid or flexibly mounted equipment. 11 Seismic restraints may be omitted from piping and duct supports if all the following conditions are satisfied: 1U Lateral motion of the piping or duct will not cause damaging impact with other systems. 11.2 The piping or duct is made of ductile material with ductile connections. 11.3 Lateral. motion of the piping or duct does not cause impact of fragile appurtenances (e.g., sprinkler heads) with any other equipment, piping or structural member. 11.4 Lateral motion of the piping or duct does not cause loss of system vertical support. 11.5 Rod-hung supports of less than 300 mm in length have top connections that cannot develop moments. 11.6 Support members cantilevered up from the floor are checked for stability. 12 Seismic restraints may be omitted from electrical raceways, such as cable trays, conduit and bus ducts, if all the following conditions are satisfied: 12.1 Lateral motion of the raceway will not cause damaging impact with other systems. 12.2 Lateral motion of the raceway does not cause loss of system vertical support. 12.3 Rod-hung supports of less than 300 mm in length have top connections that cannot develop moments. 12.4 Support members cantilevered up from the floor are checked for stability.

13

14

15

16

17

18

19

Piping, ducts and electrical raceways, which must be functional foHowing an earthquake, spanning between diff~rent buildings or structural systems shall be sufficiently fleXIble to withstand relative motion of support points assuming out-of·phase motions. Vibration isolators supporting equipment shall be designed for lateral loads or restrained from displacing laterally by other means. Restraint shall also be provided which limits vertical displacement, such that lateral restr'aints do not become disengaged. ap and Rp for equipment supported on vibration isolators shall be taken as 2.5 and 1.5, respectively. except that if the isolation mounting frame is supported by shallow or expansion anchors, the design forces for the anchors calculated by Equation (208-18),or (208-19) (including limits), shall be additionally multiplied by factor of 2.0. Equipment anchorage shall not be designed such that loads are resisted by gravity friction (e.g., friction clips). Expansion anchors, which are required to resist seismic loads in tension. shall not be used where operational vibrating loads are present. Movement of components within electrical cabinets, rack and skid-mounted equipment and portions of skid-mounted electromechanical equipment that may cause damage to other components by displacing. shall be restricted by attachment to anchored equipment or support frames. Batteries on racks shall be restrained against movement in all direction due to earthquake forces. Seismic restraints may include straps, chains, bolts, barriers or other mechanisms that prevent sliding, falling and breach of containment of flammable and toxic materials. Friction forces may not be used to resist lateral loads in the restraints unless positive uplift restraint is provided which ensures that the friction forces act continuously.

National S1ructural Code of the Philippines, Volume 1


2·56

208.8 DETAll..ED SYSTEMS DESIGN

REQUIREMENTS

208.8.1 GENERAL All structural framing systems shall comply with the requirements of Section 208.4. Only the elements of the designated seismic-force-resisting system shall be used to resist design forces. The individual components shall be designed to resist the prescribed design seismic forces acting on them. The components shall also comply with the specific requirements for the material contained in Chapters 4 through 7. In addition, such framing systems and components shall comply with the detailed system design requirements contained in Section 208.8. All building components in Seismic Zones 2 and 4 shall be designed to resist the effects of the seismic forces prescribed herein and the effects of gravity loadings from dead and floor live loads. Consideration shall be given to design for uplift effects caused by seismic loads. 'In Seismic Zones 2 and 4, provision shall be made for the effects of earthquake forces acting in a direction other than the principal axes in each of the following circumstances:

1.

The structure has plan irregularity Type 5 as given in Table 208-10.

2.

The structure has plan irregularity Type I as given in Table 208-10 for both major axes.

3.

A column of a structure forms part of two or more intersecting lateral-force-resisting systems.

EXCEPTION:

If the axial load in the column due to seismic forces acting ill either direction is less than 20 percent of the column axial load capacity. The requirement that orthogonal effects be considered may be satisfied by designing such elements for 100 percent of the prescribed design seismic forces in one direction plus 30 percent of the prescribed design seismic forces in the perpendicular direction. The combination requiring the greater component strength shall be used for design. Alternatively, the effects of the two orthogonal directions may be combined on a square root of the sum of the squares (SRSS) basis. When the SRSS method of combining directional effects is used, each term computed shall be assigned the sign that will result in the most conservative result.

208.8.2 STRUCTURAL FRAMING SYSTEMS Four types of general building framing systems defined in Section 208.4.6 are recognized in these provisions and

shown in Table 208-11. Each type is subdivided by the types of vertical elements used to resist lateral seismic forces. Special framing requirements are given in this section and in Chapters 4 through 7.

208.8.2.1 Detailing for combinations of systems. For components common to different structural systems, the more restrictive detailing requirements shall be used. 208.8.2.2 Connections. Connections that resist design seismic forces shall be designed and detailed on the drawings. 208.8.2.3 Deformation compatibility. All structural framing elements and their connections, not required by design to be part of the lateral-foree-resisting system, shall be designed and/or detailed to be adequate to maintain support of design dead plus live loads when subjected to the expected deformations caused by seismic forces. Pl! effects on such elements shall be considered. Expected deformations shall be determined as the greater of the Maximum Inelastic Response Displacement, l!M, considering Pl! effects determined in accordance with Section 208.5.9.2 or the deformation induced by a story drift of 0.0025 times the story height. When computing expected deformations, the stiffening effect of those elements not part of the lateral-force-resisting system shall be neglected. For elements not part of the lateral-force-resisting system, the forces inducted by the expected deformation may be considered as ultimate or factored forces. When computing the forces induced by expected deformations, the restraining effect of adjoining rigid structures and nonstructural elements shall be considered and a rational value of member and restraint stiffness shall be used. Inelastic deformations of members and connections may be considered in the evaluation, provided the assumed calculated capacities are consistent with member and connection design and detailing. For concrete and masonry elements that are part of the lateral- force-resisting system, the assumed flexural and shear stiffness properties shall not exceed one half of the gross section properties unless a rational cracked-section analysis is performed. Additional deformations that may result from foundation flexibility and diaphragm deflections shall be considered. For concrete elements not part of the lateral-force-resisting system, see Section 421.9.

208.8.2.3.1 Adjoining rigid elements. Moment resisting frames and shear walls may be enclosed by or adjoined by more rigid elements, provided it can be shown that the participation or failure of the more rigid elements will not impair the vertical and lateral- load-resisting ability of the gravity load and lateral-force-resisting systems. The


EARTHQUAKE DESIGN

effects of adjoining rigid elements shall be considered when assessing whether a structure shall be designated regular or irregular in Section 208.4.5. 208.8.2.3.2 Exterior elements. Exterior non bearing, nonshear wall panels or elements that are attached to or enclose the exterior shall be designed to resist the forces per Equation (208-18) or (208-19) and shall accommodate movements of the structure based on AM and temperature changes. Such elements shall be supported by means of cast-in-place concrete or by mechanical connections and fasteners in accordance with the following provisions: 1.

Connections and panel joints shall allow for a relative movement between stories of not less than two times story drift caused by wind, the calculated story drift based on AM or 12.7 mm, whichever is greater.

2.

Connections to permit movement in the plane of the panel for story drift shall be sliding connections using slotted or oversize holes, connections that permit movement by bending of steel, or other connections providing equivalent sliding and ductility capacity.

3.

Bodies of connections shall have sufficient ductility and rotation capacity to preclude fracture of the concrete or brittle failures at or near welds.

4.

The body of the connection shall be designed for the force determined by Equation (208-19), where Rp = 3.0 and ap = 1.0.

5.

6.

All fasteners in the connecting system, such as bolts, inserts, welds .:md dowels, shall be designed for the forces determined by Equation (208-19), where Rp = 1.0 and ap = 1.0. Fasteners embedded in concrete shall be attached to, or hooked around, reinforcing steel or otherwise terminated to effectively transfer forces to the reinforcing steel.

208.8.2.4 Ties and continuity. All parts of a structure shall be interconnected and the connections shall be capable of transmitting the seismic force induced by the parts being connected. As a minimum, any smaller portion of the building shall be tied to the remainder of the building with elements having at least a strength to resist 0.5 Cel times the weight of the smaller portion. A positive connection for resisting a horizontal force acting parallel to the member shall be provided for each beam, girder or truss. This force shall not be less than 0.3 Cel times the dead plus live load. 208.8.2.5 Collector elements. Collector elements shall be provided that are capable of transferring the

2-57

seismic forces originating in other portions of the structure to the element providing the resistance to those forces. Collector elements, splices and their connections to resisting elements shall resist the forces determined in accordance with Equation (208-20). In addition, collector elements, splices, and their connections to resisting elements shall have the design strength to resist the combined loads resulting from the special seismic load of Section 203.5.

EXCEPTION: [n stntctures, or portions thereC?f. braced entirely by light frame wood shear walls or light-frame steel and wood stntctural panel shear wall systems, collector elements, splices and connections to resisting elements need ollly be designed to resist forces in accordance with Equation (208-20). The quantity EM need not exceed the maximum force that can be transferred to the collector by the diaphragm and other elements of the lateral-force-resisting system. For Allowable Stress Design, the design strength may be determined using an allowable stress increase of 1.7 and a resistance factor, <», of 1.0. This increase shall not be combined with the one-third stress increase permitted by Section 203.4, but may be combined with the duration of load increase permitted in Section 615.3.4. 208.8.2.6 Concrete frames. Concrete frames required by design to be part of the lateral-force-resisting system shall conform to the following: 1.

In Seismic Zone 4 they shall be special momentresisting frames.

2.

In Seismic Zone 2 they shall, as a minimum, be intermediate moment-resisting frames.

208.8.2.7 Anchorage of concrete or masonry walls. Concrete or masonry walls shall be anchored to all floors and roofs that provide out-of-plane lateral support of the wall. The anchorage shall provide a positive direct connection between the wall and floor or roof construction capable of resisting the larger of the horizontal forces specified in this section and Sections 206.4 and 208.7. In addition, in Seismic Zone 4, diaphragm to wall anchorage using embedded straps shall have the straps attached to or hooked around the reinforcing steel or otherwise terminated to effectively transfer forces to the reinforcing steel. Requirements for developing anchorage forces in diaphragms are given in Section 208.8.2.8. Diaphragm deformation shall be considered in the· design of the supported walls. 208.8.2.7.1 Out-of-plane wall anchorage to flexible diaphragms. This section shall apply in Seismic


2-58


Zone 4 where flexible diaphragms, as defined in Section 208.5.6, provide lateral support for walls. 1.

3.

Design seismic forces for flexible diaphragms providing lateral supports for walls or frames of masonry or concrete shall be determined using Equation (208-20) based on the load determined in accordance with Section 208.5.2 using a R not exceeding 4.

4.

Diaphragms supporting concrete or masonry walls shall have continuous ties or struts between diaphragm chords to distribute the anchorage forces specified in Section 208.8.2.7. Added chords of subdiaphragms may be used to form subdiaphragms to transmit the anchorage forces to the main continuous crossties. The maximum length-to-width ratio of the wood structural subdiaphragm shall be 2Y2: l.

5.

Where wood diaphragms are used to laterally support concrete or masonry walls, the anchorage shall conform to Section 208.8.2.7. In Seismic Zone 2 and 4, anchorage shall not be accomplished by use of toenails or nails subject to withdrawal, wood ledgers or framing shall not be used in cross grain bending or cross-grain tension, and the continuous ties required by Item 4 shall be in addition to the diaphragm sheathing.

6.

Connections of diaphragms to the vertical elements in structures in Seismic Zone 4, having a plan irregularity of Type 1, 2, 3 or 4 in Table 208-10, shall be designed without considering either the one third increase or the duration of load increase considered in allowable stresses for elements resisting earthquake forces.

7.

In structures in Seismic Zone 4 having a plan irregularity of Type 2 in Table 208·10, diaphragm chords and drag members shall be designed considering independent movement of the projecting wings of the structure. Each of these diaphragm elements shall be designed for the more severe ofthe following two assumptions:

a.

Motion of the projecting wings in the same direction.

b.

Motion of the projecting wings directions.

Elements of the wall anchorage system shall be designed for the forces specified in Section 208.7 where Rp = 3.0 and ap = 1.5. In Seismic Zone 4, the value of Fp used for the design of the elements of the wall anchorage system shall not be less than 6.1 kN per lineal meter of wall substituted for E.

See Section 206.4 for minimum design forces in other seismic zones.

t

2.

When elements of the wall anchorage system are not loaded concentrically or are not perpendicular to the wall, the system shall be designed to resist all components ofthe forces induced by the eccentricity.

3.

When pilasters are present in the wall, the anchorage force at the pilasters shall be calculated considering the additional load transferred from the wall panels to the pilasters. However, the minimum anchorage force at a floor or roof shall be that specified in Section 208.8.2.7.1, Item l.

4.

The strength design forces for steel elements of the wall anchorage system shall be 1.4 times the forces otherwise required by this section.

5.

The strength design forces for wood elements of the wall anchorage system shall be 0.85 times the force otherwise required by this section and these wood elements shall have a minimum actual net thickness of63.5 mm. Diaphragms.

208.8.2.8 l.

The deflection in the plane of the diaphragm shall not exceed the permissible deflection of the attached elements. Permissible deflection shall be that deflection that will permit the attached element to maintain its structural integrity under the individual loading and continue to support the prescribed loads.

2.

Floor and roof diaphragms shall be designed to resist the forces determined in accordance with the following equation:

Fpx

in opposing

EXCEPTION:

=

_-lI--,-i:::o=X=-- W

px

(208-20)

The force Fpx determined from Equation (208-20) need not exceed 1.0C)Wpx> but shall not be less than 0.5C)Wpr

This requirement may be deemed satisfied if the procedures of Section 208.6 in conjunction with a three-dimensional model have been used to determine the lateral seismic forces for design..

When the diaphragm is required to transfer design seismic forces from the vertical-resisting elements above the diaphragm to other vertical-resisting elements below the diaphragm due to offset in the placement of the elements or to changes in stiffuess in the vertical elements, these forces shall be added to those determined from Equation (208-20).

208.8.2.9 Framing below the base. The strength and stiffness of the framing between the base and the foundation shall not be less than that of the superstructure. The special detailing requirements of Chapters 4, 5 and 7, as appropriate, shall apply to columns supporting

LW

i

i=x


EARTHQUAKE DESIGN

discontinuous lateral-force-resisting elements and to SMRF, IMRF, EBF, STMF and MMRWF system elements below the base, which are required to transmit the forces resulting from lateral loads to the foundation. 208.8.2.10 Buildiug separations. All structures shall be separated from adjoining structures. Separations shall allow for the displacement D.M. Adjacent buildings on the same property shall be separated by at least P-''MT where

(208-21 ) and AMI and AMl are the displacements of the adjacent buildings. When a structure adjoins a property line not common to a public way, that structure shall also be set back from the property line by at least the displacement AM of that structure. EXCEPTION:

Smaller separations or property line setbacks may be permitted when justified by rational analyses based 011 maximum expected ground motions.

208.9 208.9.1

NONBUILDING STRUCTURES GENERAL.

208.9.1.1 Scope. Nonbuilding structures include all self- supporting structures other than buildings that carry gravity loads and resist the effects of earthquakes. Nonbuilding structures shall be designed to provide the strength required to resist the displacements induced by the minimum lateral forces specified in this section. Design shall conform to the applicable provisions of other sections as modified by the provisions contained in Section 208.9. 208.9.1.2 Criteria. The minimum design seismic forces prescribed in this section are at a level that produce displacements in a fixed base, elastic model of the structure, comparable to those expected of the real structure when responding to the Design Basis Ground Motion. Reductions in these forces using the coefficient R is permitted where the design of nonbuilding structures provides sufficient strength and ductility, consistent with the provisions specified herein for buildings, to resist the effects of seismic ground motions as represented by these design forces.

. When applicable, design strengths and other detailed design criteria shall be obtained from other sections or their referenced standards. The design of nonbuilding structures shall use the load combinations or factors specified in

2-59

Section 203.3 or 203.4. For nonbuilding structures designed using Section 208.9.3, 208.9.4 or 208.9.5, the ReliabilityfRedundancy Factor, p, may be taken as 1.0. When applicable design strengths and other design criteria are not contained in or referenced by this code, such criteria shall be obtained from approved national standards. 208.9.1.3 Weight W. The weight, W. for nonbuilding structures shaH include all dead loads as defined for buildings in Section 208.5.1.1. For purposes of calculating design seismic forces in non building structures, W shall also include all normal operating contents for items such as tanks, vessels, bins and piping. 208.9.1.4 Period. The fundamental period of the structure shall be determined by rational methods such as by using Method B in Section 208.5.2.2. 208.9.1.5 Drift. The drift limitations of Section 208.5.1 0 need not apply to nonbuilding structures. Drift limitations shall be established for structural or nonstructural elements whose failure would cause life hazards. PA effects shall be considered for structures whose calculated drifts exceed the values in Section 208.5.1.3. 208.9.1.6 Interaction effects. In Seismic Zone 4, structures that support flexible nonstructural elements whose combined weight exceeds 25 percent of the weight of the structure shall be designed considering interaction effects between the structure and the supported elements. , 208.9.2 LATERAL FORCE. Lateral-force procedures for nonbuilding structures with structural systems similar to buildings (those with structural systems which are listed in Table 208-11) shall be selected in accordance with the provisions of Section 208.4. EXCEPTION:

Intermediate moment-resisting frames (IMRF) may be used in Seismic Zone 4 for nonbuilding stnlctures in Occupancy Categories III and IV if (1) the structure is less than 15 meterd in height and (2) the value R used in reducing calculated member forces and moments does not exceed 2.8.

208.9.3 RIGID STRUCTURES

Rigid structures (those with period Tless than 0.06 second)

and their anchorages shall be designed for the lateral force

obtained from Equation (208-22) .

V

0.7CJW

Nationaf Structural Code of the Philippines, Volume 1

(208-22)

1 I

I


The force V shall be distributed according to the distribution of mass and shall be assumed to act in any horizontal direction.

particular type of nonbuilding structure covered by this section, such a standard may be used, subject to the limitations in this section:

208.9.4 TANKS WITH SUPPORTED BOTTOMS Flat bottom tanks or other tanks with supported bottoms, founded at or below grade, shall be designed to resist the seismic forces calculated using the procedures in Section 208.7 for rigid structures considering the entire weight of the tank and its contents. Alternatively, such tanks may be designed using one of the two procedures described below:

The seismic zones and occupancy categories shall be in conformance with the provisions of Sections 208.4.4 and 208.4.2, respectively,

1.

A response spectrum analysis that includes consideration of the actual ground motion anticipated at the site and the inertial effects of the contained fluid.

The values for total lateral force and total base overturning moment used in design shall not be less than 80 percent of the values that would be obtained using these provisions.

Table 208-13 Rand n." Factors For Nonbuilding Structures STRUCTURE TYPE

I

R

n." •

2.

A design basis prescribed for the particular type of tank by an approved national standard, provided that the seismic zones and occupancy categories shall be in conformance with the provisions of Sections 208.4.4 and 208.4.2, respectively.

1.08.9.5 OTHER NONBUILDING STRUCTURES Nonbuilding structures that are not covered by Sections 208.9.3 and 208.9.4 shall be designed to resist design seismic forces not less than those determined in accordance with the provisions in Section 208.5 with the following additions and exceptions:

1. Vessels, including tanks and pressurized spheres, on braced or unbraced legs. 2, Cast-in-place concrete silos and chimneys having walls continuous to the foundations ~, Distributed mass cantilever structures such as stacks, chimneys, silos and skirt-

supported vertical vessels.

4. Trussed towers (freestanding or

guyed stacks and

•

The factors Rand n." shall be as set forth in Table 208-13. The total design base shear determined in accordance with Section 208.5.2 shall not be less than the following:

Additionally, for Seismic Zone 4, the total base shear shall also not be less than the following: f' =

2,

1.6ZNJ W R

(208-24)

The vertical distribution of the design seismic forces in structures covered by this section may be determined by using the provisions of Section 208.5.5 or by using the procedures of Section 208,6,

EXCEPTION: For irregular sln/cfures aSSigned fo Occupancy Categories J and II that cannot be modeled as a Single mass, the procedures ofSection 208.6 shall be used 3.

l

3,6

2,0

2.9

2.0

2.9

2.0

5. Cantilevered column-type

2.2

2.0

6. Cooling towers.

3.6

2.0

7. Bins and hop unbraced legs.

~.

2.0

8. Storage racks.

3.6

2.0

9. Signs and billboards.

3.6

2.0

2.2

2.0

2.9

2.0

(208-23)

V=0.56C"lW

T

2,0

.1..

structures.

1.

2.2

Where an approved national standard provides a basis foc the earth(juake-resistant design of a

10. Amusement structures and - _ .monuments. _ - _...__.._._.._.. II. All other self-supporting structures not otherwise covered.

-I

208.10 SITE CATEGORIZATION PROCEDURE 208.10.1 SCOPE This section describes the procedure for determining Soil Profile Types 4 through 5Fas defined in Table 208-2.

5:

208.10.2 DEFINITIONS Soil profile types are defined as follows: Hard rock with measured shear wave velocity, Vs > 1500 mls.


EARTHQUAKE DESIGN

~

SB

Rock with 760 mls < Vs

Sc

Very dense soil and soft rock with 360 mls < Vs ~ 760 mls or with either N > 50 or s" ~ 100 kPa.

SD

Stiff soil with 180 mls ~ Vs ~ 360 mls or with 15 ~ N ~ 50 or 50 kPa ~ su ~ 100 kPa.

2~1

208.10.2.2 N, Average Field Standard Penetration Resistance and Net" Average Standard Penetration Resistance For Cobesionless Soil Layers. N and NCH shall be determined in accordance with the following equation:

1500 mls.

(208-26)

A soil profile with Vs < 80 mls or any profile with more than 3 meters of soft clay defined as soil with PI> 20, W me ~ 40 percent and < 25 kPa.

SE

Su

d

N eH -s- - " d.

' 2:N

SF

Soils requiring site-specific evaluation:

1.

Soils vulnerable to potential failure or collapse under seismic loading such as liquefiable soils, quick and highly sensitive clays, collapsible weakly cemented soils. Peats andlor highly organic clays (H > 3 meters of peat and/or highly organic clay where H thickness of soil). Very high plasticity clays (H> 7.5 meters with PI> 75). Very thick soft/medium stiff clays (H> 36 meters).

i=l

2.

3. 4.

(208-27)

i

Where: d; thickness ofLayer i in millimeter do = the total thickness of cohesionless soil layers in the top 30 meters.

the standard penetration resistance of soil layer in

accordance with approved nationally recognized

standards.

208.10.2.3 su, Average Undrained Shear Strength. shall be determined in accordance with the following equation:

SIt

EXCEPTION: de

When the soil properties are not known in sufficient detail to determine the soil profile type, T:;pe SD shall be used 5,'0;,' r,,'.!~le Type SE need not be aSSloned unless the huilding offiCial determines that Soil Profile Type SE may be present at the site or ill the event that Type SE is established by geotechnical data.

The criteria set forth in the definition for Soil Profile Type SF requiring site-specific evaluation shall be considered. If the site corresponds to this criteria, the site shall be classified as Soil Profile Type SF and a site-specific evaluation shall be conducted. 208.10.2.1 v., Average Shear Wave Velocity vs shall be determined in accordance with the following equation:

(208-25)

vs

Where: ~ 115i

thickness ofLayer i in mcter. shear wave velocity in Layer i in mlsec.

S" =--d- n .

(208-28)

2:-'

1=1 SUi

Where: de

I

the total thickness (100 - ds) of cohesive soil layers in the top 30 meters. the undrained shear strength in accordance with approved nationally recognized standards, not to exceed 250 kPa.

208.10.2.4 Soft Clay Profile, SEe The existence of a total thickness of soft clay greater than 3 meters shall be 24 investigated where a soft clay layer is defined by SIt kPa, WI/Ie.::: 40 percent and PI > 20. If these criteria are met, the site shall be classified as Soil Profile Type SE. 208.10.2.5 Soil Profiles So SD and SEe Sites with Soil Profile Types Sc, SD and SF; shall be classified by using one of the following three methods with vs , N and Su computed in all cases as specified in Section 20810.2. 1. v, for the top 30 meters (v, method). 2. N for the top 30 meters (N method). 3. NCl! for cohesionless soH layers (PI < 20) in the top 30 meters and average s" for cohesive soil layers (PI > 20) in the top 30 meters (s" method).


2-62


208.10.2.6 Rock Profiles, SA and SB' The shear

wave velocity for rock, Soil Profile Type Ss, shall be either

measured on site or estimated by a geotechnical engineer,

engineering geologist or seismologist for competent rock

with moderate fracturing and weathering. Softer and more

highly fractured and weathered rock shall either be

measured on site for shear wave velocity or classified as

Soil Profile Type Sc.

The hard rock, Soil Profile Type SA, category shall be

supported by shear wave velocity measurement either on

site or on profiles of the same rock type in the same

formation with an equal or greater degree of weathering and

fracturing. Where hard rock conditions are known to be

continuous to a depth of 30 meters, surficial shear wave

velocity measurements may be extrapolated to assess Vs.

The rock categories, Soil Profile Types 5.4 and Ss, shall not

be used if there is more than 3 meters of soil between the

rock surface and the bottom of the spread footing or mat

foundation.

t

L

The definitions presented herein shall apply to the upper 30

meters of the site profile. Profiles containing distinctly

different soil layers shall be subdivided into those layers

designated by a number from 1 to 11 at the bottom, where

there are a total of 11 distinct layers in the upper 30 meters.

The symbol i then refers to anyone of the layers between 1 and ll.



118°

120·

122·

2-63

124°

126°E

N 20°

-

•

o

18°

16°

ZONE 4 14°

12°

10'

ZONE 2

6'

",-.

Figure 208-1 • Seismic Zone Map of the Philippines

National Structural Code of the Philippines. Volume 1

MINIMlIM DESIGN LOADS

2-64

2000'

Distribution 9f~c~ive Faults in the Philippines PFZ: Bangui Fa~Sy$tam t.~

f

P ,

" 1,1 , , '

",

Dummon River Faun SysIem

"

I'

Legend Active Fault: Solid line- tmce certain;

1600'

dashed line- InIce approximate; IIpJlrOlCimaIe offshofe projection

, , Faun Zone(PFZ): Oigdig Faun

1800'

o

lila Fault

100

200

Kilometers '1Ir+------lPFZ: Gabaldon Faull

PFZ: Guinyangan Fault

Valley Fault sr.-n-----Hi-:

Central MaOnduqe Faull Lake Bato Uneament

1400'

Southern Mindoro Faull--:;----;--~iI1r"j._~~

1200'

TablasFault

west Panay Faull 1000'

/ t

~

/r

East Sohal Fau,It-----t--=:,,~rl__#:J'f_~~1'"

Central Mindanao Fault System MF: Western Mindanao Ext~ion

-------..:~~--tC~

800'

Zamboanga Peninsula Faull System_ _-J......"

PFl: Mati Fault

600'

Davaa River Faull Tangbulan Faull Mindanao Fault(MF): Oagurna Ext 123 00' 12500'

Figure 208-2A - Type A Seismic Sources


12700'

2-65

EARTHQUAKE DESIGN

1800'

1700'

1600'

Legend - '

Active Fault: solid line- onlMd;

dashed line- offshore @ Capital CityfTown 2S

Kilometers

1500'

Figure 208-28 - Type A Seismic Sources

National 8tn.Jct9ra1 Code of 1he Philippines, VohDne 1

50


2-66

12400'

12500'

12600'

Figure 208-2C - Type A Seismic Sources


EARTHQUAKE DESIGN

2-67

"?~:' \.

Dasi)

-~,--

lOW

Active Fault: solid line- onland;

dashed line- offshore (';) Capital City/Town e _

..

50 ;

Kjl0meters

Active Faults in West Central Phili 11000'

).:100'

J:200

Figure 208-20- Type A Seismic Sources


!~ \


2-68

(\

1000'

.d ~

~-/.

~J .

,I

~~

F

SiqUi~

, I

~g

)

~.

'"'

Pro~~

""'~'~-.o

') ~

(

1!)."alaybelay

800'

~

/ {

~.

V'(\

\.....

~

.

~ - - , Active Fault: solid line- onland; dashed line- offshore 1!iJ Capital CityfTown o

__ .~'H

15

-,

,. _ _ _

wlorrw:tters-

50

._5

""l, .

I

@Mag.noy

/

~lI.ulan

T\

Dig

~

'I." "",,_

//l

),..{t~Alabel

~_.~j

'

~

\

\{

J

600'

I

C~

~

Active Faults inSouthern.cPhilippines 12500'

700'

~

GeneraLSantos

'6, ~,

Ma:~'.i. "\:a

( /'

\\

U

~

1,

'l

~\ .-~.

~

\

U'-J

12~

Figure 208-2E- Type A Seismic Sources Association of Structural Engineers of the Philippines

00'

--------------------------------............

r

EARTHQUAKE DESIGN

~

2-69

Control Periods

2.5Ga

Ts

I I

To

= Cv12.5Ca =0.2Ts

Gill

1

2

3

Period (TIT s )

F~gure

208-3 - Design Response Spectra

National Structural Code of the Philippines, Vol\ime 1

4

5

1 I

CHAPTER 3

EXCAVATIONS AND FOUNDATIONS

TABLE OF CONTENTS SECTION 301 - GENERAL ....................................................................................................... 3-1

30l.1 - Scope ........................................................... 3-1 301.2 - Quality and Design ..................................... 3-1

301.3 - Al1owab1e Bearing Pressures ....................... 3-1

SECTION 302 - EXCAVATIONS AND FaLS ........ 302.1 - General... ......................................................... 3-1 302.2 - Cuts ................................................................. 3-1 302.3 - Fi1ls .. ........ ..... ...................... ..... ................... 3-2

ao •••••••••••••••••••••••••••••••••••••••••••••••••••••••••

3-1

302.4 - Setbacks ......... .......... ......... .................. ........ 3-3

302.5 - Drainage and Terracing .............................. 3-3

302.6 - Erosion Control ....... ......... ............... ........... 3-4

SECTION 303 - FOUNDATION mvESTIGATION ................................................................ 3-4

•

303.1 303.2 303.3 303.4 303.5

-

Genera1 ............................................................ 3-4 Soil Classification ........................................... 3-4 Liquefaction Study..................................... 3-4 Expansive Soil ............................................ 3-4 Reports ....................................................... 3-5

303.6 - Liquefaction Potential and Soil Strength

Loss................................................. ·.............. 3-5

303.7 - Adjacent Loads ..................................... ,....... 3-5

303.8 - Drainage .................. ............ .......... ........ ...... 3-5

SECTION 304 - ALWWABLE FOUNDATION AND LATERAL PRESSURES............... 3-6

SECTION 305 - FOOTINGS 305.1 305.2 305.3 305.4 305.5

~ -

...................................................................................................

General ....................................................... Footing Design .......................................... Bearing Walls ............................................ Stepped Foundations .......~.. .......... .............. Footings On Or Adjacent to Slopes ........

3-7 3-7 3-7 3-7 3-7

305.6 306.7 305-8 305.9

-

Foundation Plates or Sills ........................ Designs Employing Lateral Bearing ......... Grillage Footings ....... ............... ............ ..... Bleacher Footings ......................................


3-7

3-8

3-8

3-9

3-9

3-ij


SECTION 306 - PILES - GENERAL REQUIREMENTS .............................................. 3-10

306.1 306.2 306.3 306.4 306.5 306.6 306.7

- General... ................. .......... .......... ........ ..... 3-10 - Interconnection ......................................... 3-10 - Determination of Allowable Loads ........ 3-10 - Static Load Test ..... .... ................ ....... ...... 3-10 - Dynamic Load Test .... ..... ....... ... ............. 3-10 - Column Action ........................................ 3-10 - Group Action ........................................... 3-10

306.8 - Piles in Subsiding Areas ...................... 306.9 - Jetting ..................................................... 306.10 - Protection of Pile Materials .................. 3U6.11 - Allowable Loads .................................... 306.12 - Use of Higher Allowable Pile

Stresses ...................................................

3-11

3-11

3-11

3-11

3-11

SECTION 307 - PILES - SPECIFIC REQUIREMENTS ................................................ 3-12

307.1 307.2 307.3 307.4

- Round Wood Piles .................................. - Uncased Cast-i'n-Place Concrete Piles .... - Metal-Cased Concrete Piles .................... - Precast Concrete Piles ...... ........... ..... .......

3-12 3-12 3-12 3-12

307.5 - Precast Prestressed Concrete Piles

(Pretensioned) .......................................... 307.6 - Structural Steel Piles ............................... 307.7 - Concrete-Filled Steel Pipe Piles ..............

3-13

3-13

3-13

SECTION 308 - FOUNDATION CONSTRUCTION FOR

SEISMIC ZONE 4 ...................................................................................... 3-14

308.1 - General ..................................................... 3-14 308.2 - Soil Capacity ........... ..... .... ............ ........... 3-14 308.3 - Superstructure to Foundation Connection ......................................... ...... 3-14

'<,

l

308.4 - Foundation-Soil Interface ........................ 308.5 - Special Requirements for Piles and

Caissons ...................................................

i

Association of Structural Engineers of the

Philippine~

3-14

3-14

GENERAL & EXCAVATION AND FILLS

SECTION 301 - GENERAL 301.1

QUALITY AND DESIGN

The quality and design of materials used structurally in excavations, fills, footings and foundations shall conform to the requirements specified in Chapters 4,5,6 and 7.

301.3

SECTION 302 - EXCAVATION AND FILLS

SCOPE

This chapter sets forth requirements for excavations, fills, footings and foundations for any building or structure.

301.2

3-1

ALLOWABLE BEARING PRESSURES

Allowable stresses and design formulas provided in this chapter shall be used with the allowable stress design load combinations specified in Section 203.4.

302.1

GENERAL

Excavation or fills for bui!~jngs or structures shall be constructed or protected that they do not endanger life or property. Reference is made to Section 109 of this code for requirements governing excavation, grading and earthwork construction, including fills and embankments.

302.2

CUTS

302.2.1 General. Unless otherwise recommended in the approved geotechnical engineering or engineering geology report, cuts shall conform to the provisions of this section. In the absence of an approved geotechnical engineering report, these provisions may be waived (or minor cuts not intended to support structures. 302.2.2 Slope. The slope of cut surfaces shall be no steeper than is safe for the intended use and shall be no steeper than 1 Wlit vertical in 2 units horizontal (50% slope) unless a geotechnical engineering or an engineering geology report, or both, stating that the site has been investigated and giving an opinion that a cut at a steeper slope will be stable and not create a hazard to public or private property, is submitted and approved.

,

302.2.3 Existing footings or foundations which may be affected by any excavation shall be underpinned adequately or otherwise protected against settlement and shall be protected against lateral movement. 302.2.4 Protection of adjoining property. The requirement for protection of adjacent property and the depth to which protection is required shall be defined by prevailing law. Where not defined by law, the following shall apply: 1.

Any person making or causing an excavation to be made to a depth of3.5 meters or less below the grade shall protect the excavation so that the soil of adjoining property will not cave in or settle, but shall not be liable for the expense of underpinning or extending the foundation of buildings on adjoining properties where his excavation is not in excess of 3.5 meters in depth.

2.

Before commencing the excavation, the person making or causing the excavation to be made shall notify in writing the owners of adjoining building not less than 10 days before such excavation is to be



3·2

Top of Slope P~* i Hl5 but i ~ 0.60m !

. min. ant . 1 '/ 1

i 3 m max. : 7

Toe of

PA*

Slipe

!< HI~ but O.6m ~

i =~=~ I

1

;

I

.. h Natu\ral or Flms Grade

Cut or Fill Slope B

Natural or Finish Grade * Permit Area Boundary

FIGURE 302-1

SETBACK DIMENSIONS FOR CUT AND FILL SLOPES

made and that the adjoining building should be protected. 3.

The owners of the adjoining property shall be given access to the excavation for the purpose of protecting such adjoining buildings.

4.

Any person making or causing an excavation to be made exceeding 3.5 meters in depth below the grade shall protect the excavation so that the adjoining soil will not cave in or settle and shall extend the foundation of any adjoining buildings below the depth of 3.5meters below grade at his own expense. The owner of adjoining buildings shall extend the foundation of these buildings to a depth of3.5 meters below grade at his own expense, as provided in the preceding paragraph.

302.3

Fills to be used to support the foundations of any building or structure shall be placed in accordance with accepted engineering practice. A geotechnical investigation report and a report of satisfactory placement of fill, both acceptable to the building official, shall be submitted when required by the building official. No fill or other surcharge loads shall be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional vertical and horizontal loads caused by the fill or surcharge. Fill slopes shall not be constructed on natural slopes steeper than 1 unit vertical in 2 units horizontal (50% slope)

302.3.2 Preparation of Ground. The ground surface shall be prepared to receive· fill by removing vegetation, non-complying fill, topsoil and other unsuitable materials, and by scarifying to provide a bond with the new filL.

FILLS

302.3.1 General. Unless otherwise recommended in the approved geotechnical engineering report, fills shall conform to the provisions of this section. In the absence of an approved geotechnical engineering report, these provisions may be waived for minor fills not intended to support structures.

Where the natural slopes are steeper than 1 unit vertical in 5 units horizontal (20% slope) and the height is greater than 1.5 meters, the ground surface shall be prepared by benching into sound bedrock or other competent material as determined by the geotechnical engineer. The bench under the toe of a fill on a slope steeper than 1 unit vertical in 5 units horizontal (20% slope) shall be at least 3 meters wide.


EXCAVATION AND FILLS

The area beyond the toe of fill shall be sloped for sheet overflow or a paved drain shall be provided. When fill is to be placed over a cut, the bench under the toe of fill shall be at least 3 meters wide but the cut shall be made before placing the fill and acceptance by the geotechnical engineer as a suitable foundation for filL 302.3.3 FiJI Material. Detrimental amounts of organic· material shall not be permitted in fills. Except as ~itted by the geotechnical engineer, no rock or similar irreducible material with a maximum dimension greater than 300 mm shall be buried or placed in fills.

EXCEPTION: The placement qf larger rock may be permitted when the geotechnical engineer properly devises a method of placement, and continuously inspects its placement and approves the fill stability. The follOWing conditions shall also apply: 1.

Prior to issuance of the grading permit, potential rock disposal areas shall be delineated on the grading plan

2.

Rock sizes greater than 300 mm ill maximum dimension shall be 3 meters or more ,below grade, measured vertically.

3.

Rocks shall he placed so as to assure filling of all voids with well-graded soil.

302.3.4 Compaction. All fills shall be compacted to a minimum of 90 percent of maximum density as determined by ASTM Standard D-698, or D-1551. In-place density shall be determined in accordance with ASTM D-1556, D 2161, D-2922, D-3011 or equivalent. 302.3.5 Slope. The slope of fill surfaces shall be no steeper than is safe for the intended use. Fill slopes shall be no steeper than 1 unit vertical in 2 units horizontal (50% slope) unless substantiating data justifying steeper slopes are submitted and approved.

302.4

SETBACKS

302.4.3 Toe of FiU Slope. The toe of fill slope shall be. made not nearer to the site boundary line than one ~ the height of the slope with a minimum of 0.6 meter and a maximum of 6 meters. Where a fill slope is to blil localQd near the site boundary and the adjacent off-site propertY is developed, special precautions shall be incorporated in the work as the building official deems necessary to protect the adjoining property from damage as a result of such grading. These precautions may include but are not limited to: 1.

Additional setbacks.

2.

Provision for retaining or slough walls.

3.

Mechanical or chemical treatment of the fill slope surface to minimize erosion.

4.

Provisions for the control of surface waters.

302.4.4 Modification of Slope Location. The building official may approve ,alternate setbacks.' The build~ official may require an investigation and recommendation by a qualified geotechnical engineer to demonstrate that the intent ofthis section has been satisfied. '

302.5

DRAINAGE AND TERRACING

301.7.1 General. Unless otherwise indicated on the approved grading plan, drainage facilities and terracing shall conform to the provisions of this section for (11t or fill slopes steeper than 1 unit vertical in 3 units horizontal (33.3% slope). 302.3.2 Terrace. Terraces at least 2 meters in width sha'J.I be established at not more than 10 meters vertical intervals on all cut or fill slopes to control surface drainage and debris except that where only one terrace is required, it shall be at midheight. For cut or fill slopes greater than 20 meters and up to 40 meters in vertical height, one terrace at approximately midheight shall be 4 meters in width. Terrace widths and spacing for cut and fill slopes greater than 40 meters in height shall be designed by the civil engineer and approved by the building official. Suitable access shall be provided to permit proper cleaning and maintenance.

302.4.1 General. Cut and fill slopes shall be set back from site boundaries in accordance with this section unless an alternate setback is approved by the building official (see Section 302.4.4). Setback dimensions shall be horizontal distances measured perpendicular to the site boundary. Setback dimensions shall be as shown in Figure 302-1

Swales or ditches on terraces shall have a minimum gradient of 5 percent and must be paved with reinforced concrete not less than 75 mm in thickness or an approved equal paving. They shall have a minimum depth at the deepest point of 0.3 meter and a minimum paved width of 1.5 meters.

302.4.2 Top of Cut Slope. The top of cut slopes shall not be made nearer to a site boundary line than one fifth of the vertical height of cut with a minimum of 0.6 meter and a maximum of 3 meters. The setback may need to be increased for any required interceptor drains.

A single run of swale or ditch shall not collect runoff from a tributary area exceeding 1,000 m2 (projected area) without discharging into a down drain.


3-4


302.5.3 Subsurface Drainage. Cut and fill slopes shall be provided with subsurface drainage as necessary for stability.

SECTION 303 - FOUNDATION INVESTIGATION

302.5.4 Disposal. All drainage facilities shall be designed to carry waters to the nearest practicable drainage way approved by the building official or other appropriate jurisdiction as a safe place to deposit such waters. Erosion of ground in the area of discharge shall be prevented by installatio~ of non-erosive down drains or other devices.

303.1

Building pads shall have a drainage gradient of 2 percent toward approved drainage facilities, unless waived by the building official.

EXCEPTION:

The gradient from the building pad may be 1 percent if all

of the following conditions exist throughout the permit

area:

No proposed fills are greater thall 3 meters in 1. maximum depth. No proposed finish cut or fill slope faces have a 2. vertical height in excess of 3 meters. No existing slope faces steeper than 1 unit vertical in 3. 10 units horizontal (10% slope) have a vertical height in excess of 3 meters. 302.5.5 Interceptor Drains. Paved interceptor drains shall be installed along the top of all cut slopes where the tributary drainage area above slopes toward the cut and has a drainage path greater than 12 meters measured horizontally. Interceptor drains shall be paved with. a minimum of 7';>, mm of concrete or gunite and reinforced. They shall have a minimum depth of 300 mm and a minimum paved width of 750 mm measured horizontally across the drain. The slope of drain shall be approved by the building official.

GENERAL

Foundation investigation shall be conducted at each huilding site when required by the building official. The building official may require that the interpretation and evaluation of the results of the foundation investigation be made by a registered civil engineer experienced and knowledgeable in the field ofgeotechnical engineering.

303.2

SOIL CLASSIFICATION

For the purposes of this chapter, the definition and classification of soil materials for use in Table 304-1 shall be according to ASTM D-2487. Soil classification shall be based on observation and any necessary tests of the materials disclosed by borings or excavations made in appropriate locations. Additional studies may be necessary to evaluate soil strength, the effect of moisture vanatlon on soil-bearing capacity, compressibility, liquefaction and expansiveness.

303.3

LIQUEFACTION STUDY

The building official may require a geotechnical evaluation in accordance with Section 303.6 when, during the course of the foundation investigation, all of the following conditions are discovered: 1.

Shallow ground water, 15 meters or less.

2.

Unconsolidated saturated sandy alluvium.

3.

Seismic Zone 4.

EXCEPTION:

302.6

EROSION CONTROL

302.6.1 Slopes. The faces of cut and fill slopes shall be prepared and maintained to control against erosion. This control may consist of effective planting. The protection for the slopes shall be installed as soon as practicable and prior to calling for final approval. Where cut slopes are not subject to erosion due to the erosion-resistant character of the materials. such protection may be omitted. 302.6.2 Other Devices. Where necessary, chec\<: dams, cribbing, riprap or other devices or methods shall be employed to control erosion and provide safety.

The bUilding official may waive this evaluation upon receipt ofwritten opi11ion ofa qualified geotechnical engineer that liquefaction is llOt probable.

303.4

EXPANSIVE SOIL

When the expansive characteristics of a soil are to be determined, the procedures shall be in' accordance with ASTM D-4546 or D-4829 and the soil shall be classified according to Table 303-1. Foundations for structures resting on soils with an expansion index greater than 20 shall require special design consideration. If the soil expansion index varies with depth, the variation is to be included in


FOUNDATION fNVESTIOATION

the engineering analysis of the expansive soil effect upon the structure. Table 303-1 Classification of Expansive s oil

Expansion Index

Potential Expansion

0- 20

Very Low

21 - 50

Low

f--

..

.....- - 1 -____..

51 - 90

I

Medium

91 - 130

High

Above 130

Very High

303.5 REPORTS The soil classification and design-bearing capacity shall be shown on the plans, unless the foundation conforms to Table 305-1. The building official may require submission of a written report of the investigation, which shall include, but need not be limited to, the following information:

estimation of differential settlement, lateral movement or reduction in foundation soil-bearing capacity, and discuss mitigating measures. Such measures shall be given consideration in the design of the building and may include, but are not limited to, ground stabilization, selection of appropriate foundation type and depths, selection of appropriate structural systems to accommodate anticipated displacements, or any combination of these measures. The potential for liquefaction and soil strength loss shall be evaluated for a site peak ground acceleration that, as a minimum, conforms to the probability of exceedance specified in Section 208.6.2. Peak ground acceleration may be determined based on a site-specific study taking into account soil amplification effects. In the absence of such a study, peak ground acceleration may be assumed equal to the seismic zone factor in Table 208-3.

303.7 ADJACENT LOADS Where footings are placed at varying elevations, the effect of adjacent loads shall be included in the foundation design.

1.

A plot is showing the location of all test borings and/or excavations.

2.

Descriptions and classifications of the materials encountered.

303.8

3.

Elevation ofthe water table, if encountered.

Provisions shall be made for the control and drainage of surface water around buildings. (See also Section 305.5.5.)

4.

Recommendations for foundation type and design criteria, including bearing capacity, provisions to mitigate the effects of expansive soils, provisions to mitigate the effects of liquefaction and soil strength, and the effects of adjacent loads.

5.

Expected total and differential settlement.

DRAINAGE

When expansive soils are present, the building official may require that special provisions be made in the foundation design and construction to safeguard against damage due to this expansiveness. The building official may require a special investigation and report to provide these design and construction criteria.

303.6 LIQUEFACTION POTENTIAL AND SOIL STRENGTH LOSS When required by Section 303.3, the potential for soil liquefaction and soil strength loss during earthquakes shall be evaluated during the geotechnical investigation. The geotechnical evaluation shall assess potential consequences of any liquefaction and soil strength loss, including


of the

Philippines, Volume 1

3-6


SECTION 304 - ALLOWABLE FOUNDATION AND LATERAL PRESSIJRES The allowable foundation and lateral pressures shall not exceed the values let forth in Table 304-1 unless data to substantiate the use of higher values are submitted. Table 304-1 may be used for design of foundations on rock or non-expansive soil for buildings that do not exceed three stories in height or for structures that have continuous footings having a load of less than 30 kN/m and isolated footings with loads ofless than 250 kN. Allowable bearing pressures provided in Table 304-1 shall be used with the allowable stress design load combinations specified in Section 203.4.

Table 304-1 Allowable Foundation and Lateral Pressure t

2

Class of Materials

AUowable Foundation Pressure3 (kPa)

Lateral Bearing Below Natural

Lateral Sliding 1

Grade4

(kPalm of

CoefficientS

Resistance (kPa)

0.70

-

depth)

200

1. Massive Crystalline Bedrock

200

6

. ._..._

2. Sedimentary and Foliated Rock

100

60

-

0.35

I --_._.._.......

3. Sandy Graver and lor Gravel(GW & GP)

100

3

Lateral bearing and lateral sliding resistance may be combined. For soil classification OL, OH and PT (i.e., organic clays and peat), a foundation investigation shall be required. All values of allowable foundation pressure are for footings having a minimum width of 300 mm and a minimum depth of 300 mm into natural grade. Except as in Footnote 7 below, increase of 20 perce~ is allowed for each additional 300 mm of width and/or depth to a maximum value of three times the designated value.

25

75

----"--'-'~'-'-'----'-

0.25

-

- - - - - - - - - - 1-

5. Clay, Sandy Clay, Silty Clay and Clayey Silt (CL, ML, MH, andCH) 1

-

0.35 ----

4. Well-graded Sand, Poorly-graded Sand, Silty Sand, Clayey Sand, Silty Gravel 'and Clayey Gravel (SW, SP, SM, SC, GM and GC)

2

30

50

7

15

-

7

The amount of the designated value may be increased for each additional 300 mm of depth to a maximum of 15 times the designated value. Isolated poles for uses such as flagpoles or signs and poles used to support buildings which are not adversely affected by a 12 mm motion at ground surface due to short term lateral bearing values equal to two times the tabulated values. S Coefficient to be multiplied by the dead load. 6 Lateral sliding resistance value to be multiplied by the contact area. In no case shall the lateral sliding resistance exceed one half the dead load. 7 No increase for width is allowed.

4


FOOTINGS

3·7

SECTION 305 - FOOTINGS

305.3

305.1

Bearing walls shall be supported on masonry or concrete foundations or piles or other approved foundation system that shall be of sufficient size to support all loads.

GENERAL

Footings and foundations shall be constructed of masonry, concrete or treated wood in conformance with Chapter 4,6 and 7. Footings of concrete and masonry shall be of solid material. Foundations supporting wood shall extend at least 150 mm above the adjacent finish grade. Footings shall have a minimum depth as indicated in Table 305-1, unless another depth is recommended by a foundation investigation. The provisions of this section do not apply to building and foundation systems in those areas subject to scour and water pressure by wind and wave action. Buildings and foundations subject to such loads shall be designed in accordance with approved national standards.

Where a design is not provided, the minimum foundation requirements for stud bearing walls shall be as set forth in Table 305-1, unless ~xpansive soils of a severity to cause differential movement are known to exist.

EXCEPTIONS: 1.

A one-story wood or metal-frame bUilding not used for human occupancy and not over -10 m:' il1 floor area may be cOllstmcted with walls supported all a wood foundation plate when approved by the bUilding official.

2.

The support ofbuildings by posts embedded in earth shall be designed as specified in Section 305.7. Wood posts or poles embedded in earth ,shall be pressure treated with an approved presenJative. Steel posts or poles shall be protected as specified ;n Sectioll 306.10.

TABLE 305-1 - Foundations for Stud Bearing Walls - Minimum Requirements 1,2,3 Number of

Thickness of Foundation Wall

Floors Supported (mm) by'be Unit Foundations Concrete

Width Thickness of of Footing Footing (mm)

(mm)

150

2

200

3

250

Depth DeID,,' Undisturbed

Ground Surface

150

300

150

300

200

375

175

450

250

450

200

600

_._._...

Where unusual conditions are found, footings and foundations shall be as required in Section 305.1. 2 The ground under the floor may be excavated to the elevation of the top of the footing. S Foundation may support a roof in addition to the stipulated number of floors. Foundations supporting roofs only shall be as required for supporting one floor. 1

305.2

305.4

STEPPED FOUNDATIONS

Masonry

1

BEARING WALLS

Foundations for all buildings where the surface of the ground slopes more than 1 unit vertical in 10 units horizontal (10010 slope) shall be level or shall be stepped so that both top and bottom of such foundation are level.

305.5 FOOTINGS ON OR ADJACENT TO SLOPES 305.5.1 Scope. The placement ofbuildings and structures on or adjacent to slopes steeper than 1 unit vertical in 3 units horizontal (33.3% slope) shall be in accordance with this section.

FOOTING DESIGN

Except for special provisions of Section 307 covering the design of piles, all portions of footings shall be designed in accordance with the structural provisions of this code and shall be designed to minimize differential settlement when necessary and.the effects of expansive soils when present Slab:-an-grade and mat-type footings for buildings located on expansive soils may b~ designed in accordance with the geotechnical recorrunendation as approved by the building officiaL

305.5.1 Building clearance from ascending slopes. In general, buildings below slopes shall be set a sufficient distance from the slope to provide protection from slope drainage, erosion and shallow failures. Except as provided for in Section 305.5.6 and Figure 305-1, the following criteria will be assumed to provide this protection. Where the existing slope is steeper than 1 unit vertical in 1 unit horizontal (100% slope), the toe of the slope shall be assumed to be at the intersection of a horizontal plane drawn from the top of the foundation and a plane drawn tangent to the slope at an angle of 45 degrees to the horizontal. Where a retaining wall is constructed at the toe

Nationai Structural Code of the Philippines, Volume 1

3-8


Face of Fooling

...->:

I

~

:

.Y

T('P of Slope

/'><....",

'-.''

Face of Structure

i

:<

~:

~

~

IIi:! but nct"d not

-, ~i

C',.Cl'l'U

4.')11l

ma\.

I IF, hut nl'.:d n.)[ e:w.:eu

FIGURE 305-1

I~

m

SETBACK DIMENSIONS FOR BUILDING CLEARANCE FROM SLOPES

of the slope, the height of the slope shall be measured from the top of the wall to the top of the slope.

of slope. slope gradient load characteristics of slope material.

305.5.3 Footing setb2ck from descending slope surface.

305.6

Footings on or adjacent to slope surfaces shall be founded intfinn material with an embedment and setback from the slope surface sufficient to provide vertical and lateral support for the footing without detrimental settlement. Except as provided for in Section 305S6 and Figure 305-1, the following setback is deemed adequate to meet the criteria, Where the slope is steeper than ! unit vertical in I unit horizontal (100% slope), the required setback shall be measured from an imaginary plane 45 degrees to the horizontal, projected upward from the toe of the slope.

305.5.4

Pools. The setback between pools rebrulated by this code and slopes shall be equal to one half the building footing setback distance required by this section. That portio~ of the pool wall within a horizontal distance of 2 meters from the top of the slope shall be capable of supporting the water in the pool without soil support. 305.5.5

FOV~DATION

intensifY and erosion

PLATES OR SILLS

Wood plates or sills shall be bolted to the toundatlOll or tounda.ion wall Steel holts with a minimum nominai diameter l,f 11 mm shall be USt'd in Sci'>mic Zone 1 Stet; bolts with a minimum nomma! diameter of If, mm shall h,· used in Se!!'.mic lone 4. Bolts shaH be embedded at lea< i 180 mm into the concrete or masonry and shaH he ;,pacc:l not more than 2 meters aparr. There ~hall hi:' a minimum \,' t\110 bolts per piece with one bolt located Pot more than" Ii: mm or less than "even bolt diameters from each end of tlw piece A properly sized nut and ~\asher "hall be tightened on each holt 10 the plate. Foundation plates and sills shall bt~ the kind of wood specified in Cbapt~r 6

305.7

DESIGNS

l~!\1PL()\'ING

LATERAL

BEARP\G

Foundation elevation. On graded sires. the top of any exterior foundation shaH extend above the elevation of the street gutter at point of discharge or the inlet of an approved drainage device a minimum of 300 mm plus 2 percent. The building official may approve aliernate elevations, provided it can be demonstrated that required drainage to the point of discharge and away from the stmcture is provided at all locations on the site

305.7.1 General Construc1ion employing posts or poles as columns embedded in earth or embedded in concrel": footings in the earth rna\' be used In resist both axial and lateral loads. The depth to resist lateral load~ shall be determined by means of the design criteria e~tahli:"hed herein or other methods approved by the building otTicial.

305.5.6

305.7.2.1 l'onconstrained. The following f,1nTlllia may be used in determining the depth \)f embedment required to resist later,,! loads where no constraint i" provided at the ground surface. such a~ rigid Hoor or ngid ground surface pavement

Alternate setback and clearance. The building official may approve alternate setbacks and clearances. The building official may require an investigation and recommendation of a qualified engineer to demonstrate that the intent of this section has been satisfied Such an investigation shall include consideration of materiaL heigh:

305.7.2

Oesign C"iteria


FOOTINGS

(305-1)

Where:

.t4 h

d

h p

=

2.3 P SIb

diameter of round post or footing or diagonal dimension of square post or footing, meters. depth of embedment in earth in meters but not over 3.5 meters for purpose of computing lateral pressure. distance in meters from ground surface to point of application of"P." applied lateral force in kilonewtons . allowable lateral soil-bearing pressure as set forth in Table 304-1 based on a depth of one third the depth of embedment (kPa), allowable lateral soil-bearing pressure as set forth in Table 304-1 based on a depth equal to the depth of embedment (kPa).

305.7.2.2 Constrained. The following formula may be used to determine the depth of embedment required to resist lateral loads where constraint is provided at the ground surface, such as a rigid floor or pavement

(305-2)

3-9

305_7.4.1 The frictional resistance for retaining walls and slabs on silts and clays shall be limited to one half of the normal force imposed on the soil by the weight of the footing or slab. 305.7.4.1 Posts embedded in earth shall not be used to provide lateral support for structural or nonstructural materials such as plaster, masonry or concrete unless bracing is provided that develops the limited deflection required.

305.8

GRILLAGE FOOTINGS

When grillage footings of structural steel shapes are used on soils, they shall be completely embedded in concrete. Concrete cover shall be at least 150 mm on the bottom and at least 100 mm at all other points.

305.9

BLEACHER FOOTINGS

Footings for open-air seating facilities shall comply with Chapter 3.

EXCEPTIONS: Temporary open-air portable bleachers may be supported upon wood sills or steel plates placed directly upon the ground suiface, provided soil pres:'1.l1'e does not exceed 50 kPa.

305.7.2.3 Vertical load. The resistance to vertical loads is determined by the allowable soil-bearing pressure set forth in Table 304-1. 305.7.3 Backfill. The backfill in the annular space around column not embedded in poured footings shall be by one of the following methods:

I.

Backfill shall be of concrete with an ultimate strenhrth of 15 MPa at 28 days. The hole shall not be less than 100 mm larger than the diameter of the column at its bottom or 100 mm larger than the diagonal dimension of a square or rectangular column.

2.

Backfill shall be of clean sand. The sand shall be thoroughly compacted by tamping in layers not more than 200 mm in depth.

305.7.4 Limitations. The design procedure outlined in this section shall be subject to the following limitations:


3·10


SECTION 306 - PILES - GENERAL REQUIREMENTS 306.1

GENERAL

Pile foundations shall be designed and installed on the basis of a foundation investigation as defined in Section 303 where required by the building official. The investigation and report provisions of Section 303 shall be expanded to include, but not be limited to, the following: 1.

Recommended pile types and installed capacities.

2.

Driving criteria.

3.

Installation procedures.

4.

Field inspection and reporting procedures (to include procedures for verification of the installed bearing capacity where required).

5.

Pile load test requirements.

The use of piles not specifically mentioned in this chapter shall be permitted, subject to the approval of the building ~fficial upon submission of acceptable test data, calculations or other information relating to the properties and load-carrying capacities of such piles.

306.4

STATIC LOAD TEST

Static axial compressive pile load test shall be in accordance with ASTM Standard D-1143. The building official may require that the test be conducted under the supervision of a registered civil engineer experienced and knowledgeable in the practice of static pile load testing When the allowable axial compressive load of a single pile is determined by a static load test, one of the following methods shall be used: Method 1. It shall not exceed 50 percent of the yield point under test load. The yield point shall be defined as that point at which an increase in load produces a disproportionate increase in settlement. Method 2. It shall not exceed one half of the load, which causes a net settlement, after deducting rebound, of 0.03mm/kN of test load, which has been applied for a period of at least 24 hours. Method 3. It shall not exceed one half of that load under which, during a 40-hour period of continuous load application, no additional settlement takes place.

306.5 DYNAMIC LOAD TEST 306.2

INTERCONNECTION

Individual pile caps and caissons of every structure subjected to seismic forces shall be interconnected by ties. Such ties shall be capable of resisting, in tension or compression, a,minimum horizontal force equal to 10 percent of the largest column vertical load.

High-strain dynamic load test may be used to determine the bearing capacity of piles, in accordance with ASTM Standard D-4945. The building official may require that the test be conducted by a registered civil engineer experienced and knowledgeable in the practice of dynamic load testing.

306.6

EXCEPTION: Other approved methods may be used where it can be demonstrated that eqUivalent restraint can be provided

306.3 DETERMINATION OF ALLOWABLE LOADS The allowable axial and lateral loads on piles shall be determined by an approved formula, by a foundation investigation or by load tests. Static axial compressive pile load test shall be in accordance with ASTM Standard D· 1143, and lateral load testing of piles shall conform with ASTM Standard D·3966. Dynamic pile tests shall be in accordance with ASTM Standard D-4945. Static axial tensile load testing to determine the uplift capacity of pile soil systems shall be in accordance with ASTM Standard D-3689.

COLUMN ACTION

All piles standing unbraced in air, water or material not capable of lateral support shall conform with the applicable column formula as specified in this code. Such piles driven into firm ground may be considered fixed and laterally supported at 1.5 meters below the ground surface and in soft material at 3 meters the ground surface unless otherwise prescribed by the building official after a foundation investigation by an approved agency.

306.7 GROUP ACTION Consideration shall be given to the reduction of allowable pile load when piles are placed in groups. Where soil conditions make such load reductions advisable or necessary, the allowable axial load determined for a single pile shall be reduced by any rational method or formula approv€\d by the building official.


PILES - GENERAL REQUIREMENTS

306.8

PILES IN SUBSIDING AREAS

Where piles are driven through subsiding fills or other subsiding strata and derive support from underlying firmer materials., consideration shall be given to the downward frictional forces, which may be imposed on the piles by the subsiding upper strata. Where the influence of subsiding fills is considered as imposing loads on the pile, the allowable stresses specified in this chapter may be increased if satisfactory substantiating data are submitted.

306.9

306.12 USE OF HIGHER ALLOWABLE PILE STRESSES Allowable compressive stresses greater than those specified in Section 307 shall be permitted when substantiating data justifying such higher stresses ,are submitted to and approved by the building official. Such substantiating data shall be included in the foundation investigation report in accordance with Section 306.1.

JETTING

Jetting shall not be used except where and as specifically permitted by the building officiaL When used, jetting shall be carried out in such a manner that the carrying capacity of existing piles and structures shall not be impaired. After withdrawal of the jet, piles shall be driven down until the required resistance is obtained.

306.10 PROTECTION OF PILE MATERIALS Where the boring records of site conditions indicate possible deleterious action on pile materials because of soil constituents, changing water levels or other factors, such materials shall be adequately protected by methods or processes approved by the geotechnical engineer. The effectiveness of such methods or processes for the particular purpose shall have been thoroughly established by satisfactory service records or other evidence, which demonstrates the effectiveness of such protective measures.

306.11

3-11

ALLOWABLE LOADS

The allowable loads based on soil conditions shall be established in accordance with Section 306. EXCEPTION: Any uncased cast-in-place pile may be assumed to develop a frictional resistance equal to one sixth of the bearing value of the soil material at minimum depth as set forth in Table 305-1 but not to exceed 25 kPa unless a greater value is allowed by the building official qfter a foundation investigation as specified in Section 303 is submitted Frictional resistance and bearing resistance shall not be assumed to act Simultaneously unless recommended after a foundation investigation as specified in Section 303.


3·12


SECTION 307 - PILES - SPECIFIC REQUIREMENTS 307.1

ROUND WOOD PILES

307.1.1 Material. Except where untreated piles are permitted, wood piles shall be pressure treated. Untreated piles may be used only when it has been established that the cutoff will be below lowest groundwater level assumed to exist during the life ofthe structure. 307.1.2 Allowable stresses. The allowable unit stresses for round woodpiles shall not exceed those set forth in Chapter 6. The allowable values listed in, for compression parallel to the grain at extr~e fiber in bending are based on load sharing as oc~urs an a pile cluster. For piles which support their own specific load, a safety factor of 1.25 shall be applied to compression parallel to the grain values and 1.30 to extreme fiber in bending values.

307.2 UNCASED CAST-IN-PLACE CONCRETE PILES 307.2.1 Material. Concrete piles cast in place against earth in drilled or bored holes shall be made in such a manner as to ensure the exclusion of any foreign matter and to secure a full-sized shaft. The length of such pile shall be limited to not more than 30 times the average .diameter. Concrete shall have a specified compressive strengthf'c of not less than 17.5 MFa.

307.3.2 Installation. Every metal casing for a concrete pile shall have a sealed tip with a diameter of not less than 200 mm. Concrete piles cast in place in metal shells shall have shells driven for their full length in contact with the surrounding soil and left permanently in place. The shells shall be sufficiently strong to resist collapSe and sufficiently watertight to exclude water and foreign material during the placing of concrete. Piles shall be driven in such order and with such spacing as to ensure against distortion of or injury to piles already in place. No pile shall be driven within tour and one-half average pile diameters of a pile filled with concrete less than 24 hours old unless approved by the geotechnical engineer.

307.3.3 Allowable stresses. Allowable stresses shall not exceed the values specified in Section 307.2.2, except that the allowable concrete stress may be increased to a maximum value of O.4Q{'c for that portion of the pile meeting the following conditions: 1.

The thickness of the metal casing is not less than 1.7 mm (No. 14 carbon sheet steel gage).

2.

The casing is seamless or is provided with seams of equal strength and is of a configuration that will provide confinement to the cast-in-place concrete.

3.

The specified compressive strength f'c shall not exceed 35 MFa and the ratio of steel minimum specified yield strength Fy to concrete specified compressive strengthf'c shall not be less than 6.

4

The pile diameter is not greater than 400 mm.

EXCEPTION: The length of pile may exceed 30 times the diameter provided the design and installation of the pile foundation is in accordance with an approved foundation investigation report. 307.2.2 Allowable stresses. The allowable compressive stress in the concrete shall not exceed 0.33f'c. The allowable compressive stress of reinforcement shall not exceed 34 percent of the yield strength of the steel or 175 MFa.

307.3

METAL-CASED CONCRETE PILES

307.3.1 Material Concrete used in metal-cased concrete piles shall have a specified compressive strength f'c of not less than 17.5 MFa.

307.4 PRECAST CONCRETE PILES 307.4.1 Materials. Precast concrete piles shall have a specified c~mpressive strengthf'c of not less than 20 MFa, and shall develop a compressive strength of not less than 20 MFa before driving. 307.4.2 Reinforcement ties. The longitudinal reinforcement in driven precast concrete piles shall be laterally tied with steel ties or wire spirals. Ties and spirals shall not be spaced more than 75 mm apart, center to center, for a distance of 600 mm from the ends and not more than 200 mm elsewhere. The gage of ties and spirals shall be as follows: 1.

For piles having a diameter of 400 mm or less, wire shall not be smaller than 5.5 mm (No.5 B.W.gage).


PILES • SPECIFIC REQUIREMENTS

2.

For piles, having a diameter of more than 400 mm and less than 500 mm, wire shall not be smaller than 6 mm (No.4 B.W.gage).

3.

For piles having a diameter of 500 mm and larger, wire shall not be smaller than 6.5 mm (No.3 B.W. gage).

3·13

The compressive stress in the concrete due to externallv applied load shall not exceed: .

.fc

307.4.3 Allowable stresses. Precast concrete piling shall be designed to resist stresses induced by handling and driving as well as by loads. The allowable stresses shall not exceed the values specified in Section 307.2.2.

= O.3~f'c

- 0.27fpc

(307-1 )

Where:

hc

= effective

prestress stress on the gross section.

Effective prestress shall be based on an assumed loss of200 MPa in the prestressing steeL The allowable stress in the prestressing steel shall not e.xceed the values specified in Section 418 5

307.5 PRECAST PRESTRESSED CONCRETE PILES (PRETENSIONED)

307.6

307.5.1 Materials. Precast prestressed concrete piles shall have a specified compressive strength Fe of not less than 35 MPa and shall develop a compressive strength of not less than 27 MPa before driving.

307.6.1 Material. Structural steel piles, steel pipe piles and fully welded steel piles fabricated from plates shall conform to one of the material specifications listed in Section 501.3.

307.5.2

Reinforcement

307.5.2.1 Longitudinal reinforcement. The longitudinal reinforcement shall be high-tensile seven-wire strand conforming to ASTM Standards. Longitudinal reinforcement shall be laterally tied with steel ties or wire spirals. . 307.5.2.2 Transverse reinforcement. Ties or spiral . reinforcement shall not be spaced more than 75 mm apart, center to center, for a distance of 600 mm from the ends and not more than 200 mm elsewhere.

At each end of the pile, the first five ties or spirals shall be spaced 25 mm center to center.

307.6.2 Allowable stresses. The allowable axial stresses shall not exceed 0.35 of the minimum specified yield strength f~, or 85 MPa, whichever is less.

EXCEPTION: When just!fied ill accordance with Section 306.12, the allowable axial stress may be increased above 85 MPa and O.35F>, but shall/WI exceed O.5F;. 307.6.3 Minimum dimensions. Sections of driven. H piles shall comply with the following:

1.

The flange projection shall not exceed 14 times the minimum thickness of metal in either the tlange or the web, and the flange widths shall not be less than 80 percent of the depth of the section.

2.

The nominal depth in the direction of the web shall not be less than 200 mm.

3.

Flanges and webs shall have a minimum nominal thickness oflO mm.

For piles having a diameter of 600 mm or less, wire shan not be smaller than 5.5 mm (No.5 B. W. gage). For piles having a diameter greater than 600 mm but less than 900 mm, wire shall not be smaller than 6 mm (No.4 B.W.gage). For piles having a diameter greater than 900 mm, wire shall not be smaller than 6 mm (No.3 B.W.gauge). 307.5.3 Allowable stresses. Precast prestressed piling shall be designed to resist stresses induced by handling and driving as well as by loads. The effective prestress in the pile shall not be less than 2.5 MPa for piles up to 10 meters in length, 4 MPa for piles up to 15 meters in length. and 5 MPa for piles greater than 15 meters in length.

STRUCTURAL STEEL PILES

Sections of driven pipe piles shall have an outside diameter of not less than 250 mm and a minimum thickness of not less than 6 mm.

307.7 CONCRETE-FrLLED STEEL PIPE PILES 307.7.1 Material The steel pipe of concrete-filled steel pipe piles shall conform to one of the material specifications listed in Section 501.3. The concrete in

Nationai Struct.ural Code of the Philippines, Volume 1

3-14


concrete-filled steel pipe piles shall have a specified compressive strengthf'c of not less than 17.5 MPa. 307.7.2 Allowable stresses. The allowable axial stresses shall not exceed 0.35 of the minimum specified yield strength ~. of the steel plus 0.33 of the specified compressive strength f'c of concrete, provided Fy shall not be assumed greater than 250 MPa for computational purposes. EXCEPTION:

SECTION 308 - FOUNDATION CONSTRUCTION-SEISMIC ZONE 4 308.1

GENERAL

In Seismic Zones 4, the further requirements of this section shall apply to the design and construction of foundations, foundation components and the connection of superstructure elements thereto. See Section 421.9 for additional requirements for structural concrete foundations resisting seismic forces.

When justified in accordance with Section 306.12. the allowable stresses may be increased to 0.50 Fy 307.7.3 Minimum dimensions. Driven piles of unifurm section shall have a nominal outside diameter of not less than 200 mm.

308.2

SOIL CAPACITY

The foundation shall be capable of transmitting the design base shear and overturning forces prescribed in Chapter 2 from the structure into the supporting soil. The short term dynamic nature of the loads may be taken into account in establishing the soil properties.

308.3 SUPERSTRUCTURE TO FOUNDATION CONNECTION. The connection of superstructure elements to the foundation shall be adequate to transmit to the foundation the forces for which the elements were required to be designed.

II

308.4

FOUNDATION-SOIL INTERFACE.

For regular buildings, the force F t as provided in Section 208.5.5 may be omitted when determining the overturning moment to be resisted at the foundation-soil interface.

308.5 SPECIAL REQUIREMENTS FOR PILES AND CAISSONS. 30S.S.1 General. Piles. caissons and caps shall be designed according to the provisions of Chapter 2, including the effects of lateral displacements. Special detailing requirements as described in Section 308.5.2 shall apply for a length of piles equal to 120 percent of the flexural length. Flexural length shall be considered as a length of pile from the first point of zero lateral deflection to the underside of the pile cap or grade beam. 30S.S.2 Steel Piles, Nonprestressed Concrete Piles and Prestressed Concrete Piles. 30S.S.2.1 Steel piles. Piles shall conform to width thickness ratios of stiffened, unstiffened and tubular compression elements as specified in Chapter 5.

Association of Structural Engineers of the Philippines d

FOUNDATION CONSTRUCTION - SEISMIC ZONE 4

308.5.2.2 Nonprestressed concrete piles. Piles shall have transverse reinforcement meeting the requirements of Section 421.5 EXCEPTION: Transverse reinforcement need not exceed the amount determined by Equation 421-2 for spiral and circular hoop reinforcement, or by Equation 421-4 for rectangular hoop reinforcement.

308.5.2.3 Prestressed concrete piles. Piles shall have a minimum volumetric ratio of spiral reinforcement no less than 0.021 for 350 mm square and smaller piles, and 0.012 for 600 mm square and larger piles unless a smaller value can be justified by rational analysis. lnterpolation may be used between the specified ratios for intermediate sizes.


3-15

CHAPTER 4

CONCRETE

TABLE OF CONTENTS SECTION 401 - GENERAL ........................................................................................................ 4-1

401. 1 Scope ............................................... 2-1

SECTION 402 - DEFINITIONS .................................................................................................. 4-1

SECTION 403 - SPECIFICATIONS FOR TESTS AND MATERIALS ................................ 4-4

403.1 403.2 403.3 403.4

Notation .......................................... 4-4 Tests of Materials ........................... 4-4 Cement ................................................. 4-4 Aggregates ...................................... 4-4

403.5 403.6 403.7 403.8

Water .................................................. Steel Reinforcement ........................... Adnrixtures ......................................... Storage of Materials ............................

4-5

4-5

4-7

4-7

SECTION 404 - DURABILITY REQlllREMENTS .................................................................. 4-9

404.1 Notation .......................................... 4-9 404.2 Water-Cementitious Materials Ratio ............................................... 4-9 404.3 Special Exposure Conditions............. 4-9

404.4 404.5

Sulfate Exposure................................ 4-9

Corrosion Protection of

Reinforcement... ...... ........................ 4-9

SECTION 405 - CONCRETE, QUALITY, MIXING AND PLACING ................................ 4-11

405.1 Notations ... ...... ... ..................... 405.2 General ..... ... ............ . ..................... 405.3 Selection of Concrete Proportions ................................. 405.4 Proportioning on the Basis of Field Experience and Trial Mixtures, or both ........................ 405.5 Proportioning without field experience or trial mixtures ........... 405.6 Average Strength Reduction ............ ~

~

~

~~.

~

4-11 4-11 4-11

405.7 Evaluation and Acceptance of

Concrete ........................................ 405.8 Preparation of Equipment and

P1ace ofDeposiL.......................... 405.9 Mixing ......... .,. .......... .................... 405.10 Conveying ............ " ................ "' ........ 405.11 Depositing .... ............................... 405.12 Curing ............. _.. . ............... , .......... 405.13 Hot Weather Requirements ........... ~

~

4-11

~

~

~

~

4-13 4-13


~

4-13

4-14

4-14

4-15

4-15

4-15

4-15

TABLE OF CONTENTS

4-ii

SECTION 406 - FORMWORK, EMBEDDED PIPES AND CONSTRUCTION

JOINTS ............................................................................................................ 4-16

406.1 Design of Formwork .................... 4-16 406.2 Removal of Forms, Shores and Reshoring...................................... 4-16

406.3 406.4

Conduits and Pipes Embedded ........ 4-16

Construction Joints .......... ................ 4- I 7

SECTION 407 - DETAILS OF REINFORCEMENT ............................................................. 4-18

Notations ........... .. ..................... Standard Hooks ...... .................... Minimum Bend Diameters .............. Bending of Reinforcement... ............ Surface Conditions of Reinforcement. .............................. 407.6 Placing Reinforcement .................... 407.7 Spacing Limits for

Reinforcement. .............................. ,407.8 Concrete Protection for Reinforcement 407. I 407.2 407.3 407.4 407.5

~

~

~.

~

~

~

~

••••••• * ••••••••••••••••••••

<'Ii

iii

4-18 4-18 4-18 4-18 4-18 4-18 4-19 4-20

407.9

Special Reinforcement Details for

Colulnns........... ............................. 4~21

407.10 Connections..................................... 4~21

407.11 Lateral Reinforcement for

Compression Members ................. 4-21

407.12 Lateral Reinforcement foe

Flexural Members. ........................ 4-22

407.13 Shrinkage and Temperature

ReinforcemenL............................. 4-22

407.14 Requirements for Structural

Integrity......................................... 4-23

SECTION 408 - ANALYSIS AND DESIGN ........................................................................... 4-24

408.1 408.2 408.3 408.4 408.5

Notations .................................. ....... Design Methods............................... Loading ........................................... Methods of Analysis ... .... ...... ........ Redistribution of Negative Moments in Continuous NonPrestressed Flexural Members ........ ....... ... ..... ............ ....

4-24 4-24 4-24 4-24

4-25

408.6 408.7 408.8 408.9 408.10 408.11 408.12 408.13

Modulus of Elasticity....................... Stiffness........................................... Span Length .............................. ...... Columns .... ..... ......... ..... ........... ........ Arrangement of Live Load .............. T-Beam Construction ...................... Joist Construction ............................ Separate Floor Finish.......................

4-25

4-25

4-25

4-26

4-26

4-26

4-26

4-27

SECTION 409 - STRENGTH AND SERVICEABILITY REQlJIREMENTS....................... 4-27

409.1 409.2 409.3 409.4

Notations ........... ... .... ............... ........ General............................................ Required Strength............................ Design Strength ...............................

4-27 4-28 4-28 4-29

409.5 409.6

Design Strength for

Reinforcement... . .. ... .. . ... ... ... ... 4-29

Control of Deflections ..................... 4-30


TABLE OF CONTENTS

4 • Iii

SECTION 410 - FLEXURE AND AXIAL LOADS................................................................... 4-33

410.1 410.2 410.3 410.4 410.5

410.6 410.7

410.8 410.9

Notations ......................................... Scope ............................................... Design Assumptions ........................ General Principles and Requirements ................................ Distance between Lateral Supports of Flexural Members ......

Minimum Reinforcement of Flexural Members ......................... Distribution of Flexural Reinforcement in Beams and One-way Slabs .............................. Deep Flexural Members .................. Design Dimensions for Compression Members .................

4-33 4-34 4-34

410.10 Limits for reinforcement of Compression Members ................. 4-36 410. J 1 Slenderness Effects in Compression Members ................. 4-37

4-34 4-35

4-35

4-35 4-36 4-36

410.12 Magnified Moments-General ........... 410.13 Magnified Moments-Non-sway Frames .......................................... 410.14 Magnified Moments-Sway Frmnes .......................................... 410.15 Axially Loaded Members Supporting Slab System ................ 410.16 Transmission of Column Loads through Floor System .................... 410.17 Composite Compression Melnbers ....................................... 410.18 Bearing Strength ..............................

4-37 4-37 4-38 4-39 4-39 4-39 4-40

SECTION 411 - SHEAR AND TORSION ................................................................................. 4-41

411.1 411.2 411.3 411.4

411.5

411.6

Notations ......................................... Shear Strength ................................. Lightweight Concrete ...................... Shear Strength Provided by Concrete for Nonstressed Members ....................................... Shear Strength Provided by Concrete for Prestressed Members ....................................... Shear Strength provided by Shear Reinforcement. ..............................

4-41 4-42 4-43

411.7 411.8 411.9 411.10

4-43

4-44

411.11 411.12 411.13

Design for Torsion ........................... Shear Friction .................................. Special Provisions for Deep Flexural Members ......................... Special Provisions for Brackets and Corbels ................................... Special Provisions for Walls ............ Transfer of Moments to Columns .... Special Provisions for Slabs and Footings ........................................

4-46 4-48 4-49 4-49 4-50 4-51 4-51

4-44

SECTION 412 - DEVELOPMENT AND SPLICES OF REINFORCEMENT ...................... 4-54

412.1 Notations ......................................... 412.2 Development of Reinforcement General ......................................... 412.3 Development of Deformed Bars and Deformed Wire in Tension ..... 412.4 Development of Deformed Bars in Compression ............................. 412.5 Development ofBundled Bars.........

4-54 4-54 4-54 4-55 4-56

Development of Standard Hooks

in Tension ..................................... 412.7 Mechanical Anchorage.................... 412.8 Development of Welded Deformed Wire Fabric in Tension ......................................... 412.9 Development of Welded Plain

Wire Fabric in Tension ................. 412.10 Development of Prestressing Strand.... ....... ..... ...... ......... ............. 412.6

NatIOnal Structural Code of the Philippines, Volume 1

4-56

4-56

4-56

4-57

4-57

TABLE OF CONTENTS

4-iv

SECTION 413 -TWO-WAY SLAB SYSTEM ..•...••.••.•..•...•......••....••..•••.••••..•....•..•.•...........•.••... 4-61

413.1 413.2 413.3 413.4

Notation........................................... Scope.............. ................................. Definitions....................................... Slab Reinforcement .........................

4-61 4-62 4-62 4-62

413.5 413.6 413.7 413.8

Openings in Slab System ......... ........ Design Procedures........................... Direct Design Method ..................... Equivalent Frame Method ..... .........

4-63

4-63

4-64

4-66

SECTION .414- WALLS................................................................................................................. 4-68

414.1 414.2 414.3 414.4 414.5

NotatioIl ........................................... Scope ............................................... General ............................................ Minimum Reinforcement ................ Walls Designed as Compression

Members ........ ...... ..................... ....

4-68 4-68 4-68 4-68

414.6 414.7 414.8 414.9

Empirical design Method................. Non-Bearing Walls.......................... Wa11s as Grade Beams ..................... Alternate Design of Slender Walls..

4-69

4-69

4-69

4-69

4-68

SECTION 415- FOOTmGS .......................................................................................................... 4-71

415.1 415.2 415.3 415.4

415.5 415.6

Notation ........................................... Scope ............................................... Loads and Reactions........................ Footings Supporting Circular or Regular Polygon-Shaped Columns or Pedestals.................... Moment in Footings ........................ Shearin Footings .............................

4-71 4-71 4-71

4-71 4-71 4-71

415.7

Development of Reinforcement in

Footings ................................... ..... 415.8 Minimum Footing Depth ......... ........ 415.9 Transfer of Force at base of

Column, Wall or Reinforced

Pedestal......................................... 4 I 5. to Sloped or Stepped Footings............. 415.11 Combined Footings and Mats .......... 415.12 Plain Concrete Pedestals and

Footings ................... ......... .........

4-72

4-72

4-72

4-73

4-73

4-73

SECTION 416- PRECAST CONCRETE..................................................................................... 4-73

416.1 416.2 416.3 416.4 416.5 416.6

Notation ........................................... Scope............................................... General ............................................ Distribution of Forces Among Members ....................................... Member Design ............................... Structural Integrity ..........................

4-73 4-73 4-73 4-73 4-74 4-74

416.7 416.8

Connection and Bearing Design ...... Items Embedded After Concrete

Placelnent ..................................... 416.9 Marking and Identification .............. 416.10 Handling .......................................... 416.11 Strength Evaluation of Precast

Construction ................................


4-74

4-75

4-72

4-75

-t.-75

TABLE OF CONTENTS

4-v

SECTION 417- COMPOSITE CONCRETE FLEXURAL MEMBERS .................................. 4-76

417.1 4J 7.2 417.3 417.4

Notation........................................... Scope............................................... General............................................ Shoring ............................................

4-76 4-76 4-76 4-76

417.5 417.6 417.7

Vertical Shear Strength .................... 4-76

Horizontal Shear Strength ................ 4-76

Ties for Horizontal Shear................. 4-77

SECTION 418 - PRESTRESSED CONCRETE ........................................................................ 4-78

418.1 418.2 418.3 418.4 418.5

Notations ......................................... Scope ............................................... General ............................................ Design Asswnptions ........................ Permissible Stresses in Concrete Flexural Members ......................... 418.6 Permissible Stress in Prestressing Tendons ........................................ 418.7 Loss of Prestress .............................. 418.8 Flexural Strength ............................. 418.9 Limits for Reinforcement of Flexural Members ......................... 418.10 Minimum Bonded Reinforcement ... 418.11 Statically Indeterminate Structures ...................................... 418.20 Protection for Prestressing Tendons ........................................ 418.21 Application and Measurement of Prestressing Forces .......................

4-78 4-78 4-78 4-79 4-79 4-79 4-79 4-80 4-80 4-80 4-81 4-85

418.12 Compression Members-Combined

Flexure and Axial Loads ............... 418.13 Slab Systems.................................... 418.14 Post-tensioned Tendon Anchorage

Zones ............................................ 418.15 Design of Anchorage Zones for

Mono-Strand or Single 16 mm

Diameter Bar Tendons .... :............. 418.16 Design of Anchorage Zones for

Multi-Strand Tendons ................... 418.17 Corrosion protection for

Unbonded Prestressing Tendons ... 418.18 Post-tensioning Ducts ...................... 418.19 Grout for Bonded Prestressing

Tendons ........................................ 418.22 Post-tensioning Anchorages and

Couplers ........................................ 418.23 External Post-Tensioning.................

4-82

.4-82

4-82

4-84

4-84

4-84

4-85

4-85

4-86

4-86

4-85

SECTION 419- SHELLS AND FOLDED PLATE MEMBERS ................................................ 4-86

419.1 419.2 419.3

Notation............................... ............ 4-86 Scope and DefInitions...................... 4-86 Analysis and Design .................... .... 4-86

419.4 419.5 419.6

Design Strength of materials............ 4-87

Shell Reinforcement ........................ 4-86

Construction .................................... 4-86

SECTION 420- STRENGTH EVALUATION OF EXISTING STRUCTURES ...................... 4-88

420.1 Notation........................................... 4-88 420.2 Strength Evaluation - General......... 4-88 420.3 Determination of Required Dimensions and Material Properties...................................... 4-89 420.4 Load Test Procedure........................ 4-89

420.5 420.6 420.7 420.8

Loading Criteria......................... ..... Acceptance Criteria......................... Provisions for Lower Load

Rating........................................... Safety ..................... ............... ..........


4-89

4-89

4-90

4-90

TABLE OF CONTENTS

4·vl

SECTION 421- SPECIAL PROVISIONS FOR SEISMIC DESIGN ........................................ 4-90

421.1 421.2 421.3 421.4 421.5

Notation........................................... Definitions....................................... General Requirements ...... ....... ........ Flexural Members of Frames........... Special Moment Frame Members Subjected to Bending and Axial Load... ............ 421.6 Joints of Special Moment Frames................... ..... ..................

4-90 4-91 4-92 4-95

4-96 4-98

421.8

Structural Diaphragms and

Trusses ....................................... 4-101

421.9 Foundations................................... 4-103

421.10 Frame Members not

Proportioned to Resist Forces

induced by Earthquake

Motions ...................................... 4-104

421.11 Requirements for Intennediate Moment

Frames, Seismic Zone 2 .. ....... .... 4-104

421.7 Special Reinforced Concrete

Structural Walls and Coupling

Beams ........................................... 4-99

SECTION 422- STRUCTURAL PLAIN CONCRETE............................................................. 4-106

f

'!i

~:

422.1 Notation......................................... 4-106 422.2 Scope............................................. 4-106 422.3 Limitations .................................... 4-106 422.4 Joints ............................................. 4-106 422.5 Design Method.............................. 4-107 422.6 Strength Design............................. 4-107

422.7 422.8 422.9 422.10 422.11

Walls ............................................. Footings......................................... Pedestals........... ............. ................ Precast Members ........................... Plain Concrete in Earthquake Resisting Structures ....................

4-108

4-108

4-109

4-109

4-109

SECTION 423- ANCHORAGE TO CONCRETE .................................................................... 4-110

423.1 Service Load Design...................... 4-110

423.2 Strength Design ............................. 4-110

423.3 Strength of Anchors....................... 4-110

SECTION 424- ALTERN'ATE DESIGN METHOD................................................................. 4-112

424.1 Notation......................................... 4-112 424.6 Flexure........................................... 4-113

424.2 Scope............................................. 4-112 424.7 Compression Members with or

without Flexure........................... 4-113

424.3 General .......................................... 4-112 424.4 Permissible Service Load Stresses. 4-112

424.8 Shear and Torsion.......................... 4-114

424.5 Development and Splices of Reinforcement...... .................... ... 4-112


TABLE OF CONTENTS

2-vii

SECTION 425- UNIFIED DESIGN PROVISIONS FOR REINFORCED AND PRESTRESSED CONCRETE FLEXURAL AND COMPRESSION MEMBERS.......................................................................... 4-116

425.1 Scope ...................................... 4-116 425.408.5 Redistribution of Negative Moments in Continuous Flexural Members ................... 4-116 425.409.4 Design Strength ....................... 4- 116

425.418.9

Limits for Reinforcement

of Flexural Members ..... 4-117

425.418.11.4 Redistribution of Negative

Moments in Continuous

Prestressed Flexural

Members...... ........... ........... 4-117

SECTION 426- ALTERNATIVE LOAD AND STRENGTH REDlJCTION FA(~TORS ...................................•.•..........................•.......•. » •••••••••••••••••••••••••••••• 4~lt8 426. ,

General.......................................... 4-118

National Structural Code of the Philippines. Vok.une 1

CONCRETE

4-1


SECTION 402 - DEFINIT10NS

401.1

The following terms are defined for general use in this chapter. Specialized definitions appear in individual sections.

SCOPE

401.1.1 This chapter provides minimum requirements for the design and construction of structural concrete elements of any buil ding or other structure. 401.1.2 This chapter shall govern in all matters pertaining to the design, construction, and material properties of structural concrete elements wherever this chapter is in conflict with requirements contained in other standards referenced in this chapter. 401.1.3 For special structures, such as arches, tanks, reservoirs, bins and silos, blast-resistant structures, and chimneys, provisions of this chapter shall govern where applicable. 401.1.4 This chapter does not govern design and installation of portions of concrete piles' and drilled piers embedded in ground except tor structures in regions of high . seismic risk or assigned to high seismic performance or design categories. See Section 421.9.4 for requirements for concrete piles, drilled piers, and caissons in structures ill regions of high seismic risk or assigned to high seismic performance or design categories .. 401.1.5 This chapter does not govern design and construction of soil-supported slabs, unless the slab transmits vertical loads from other portions of the structure to the soil. 401.1.6

Concrete On Steel Form Deck

401.1.6.1 Design and construction of structural concrete slabs cast on stay-in-place, noncomposite steel form deck are governed by this chapter. 401.1.6.2 This chapter does not govern the design of structural concrete slabs cast on stay-in-place, composite steel form deck Concrete used in the construction of such slabs shall be governed by Sections 401 to 407 of this chapter, where applicable.

401.1.7 Special Provisions For Earthquake Resistance 401.1.7.1 In regions of moderate (seismic zone 2) or high seismic risk (seismic zone 4), provisions of Section 421 shall be satistied. See Section 421.3.].

ADMIXTURE is material other than water, .aggregate, or hydraulic cement used as an ingredient of concrete and added to concrete before or during its mixing to modify its properties. AGGREGATE is granular material, such as sand, gravel, crushed stone and iron blast-furnace slag, and when used with a cementing medium forms a hydraulic cement concrete or mortar. AGGREGATE, LIGHTWEIGHT, is aggregate with a dry, loose weight of 1120 kg/m3 or less. AIR-DRY WEIGHT is the unit weight of a lightweight concrete specimen cured for seven days with neither loss nor gain of moisture at 15°C to 2~C and dried for 21 days in 50 ± 7 percent relative humidity at 23°C 1. 1°C. ANCHORAGE DEVICE in post-tensioning is a device used to anchor tendons to concrete member; in pretensioning, a device used to anchor tendons during hardening of concrete. ANCHORAGE ZONE in post-tensioned members is the portion of the member through wr..ich the concentra\ed prestressing force is transferred to the concrete and distributed more uniformly across the section. Its extent is equal to the largest dimension of the cross section. For intermediate anchorage devices, the anchorage zone includes the disturbed regions ahead of and behind the anchorage devices. BASIC MONOSTRAND ANCHORAGE DEVICE is an anchorage device used with any single strand or a single 16 mm or smalley diameter bar that satisfies section 418.22.1 and the anchorage device requirements of the Post-Tensioning Institute'S "Specification for Unbonded Single Strand Tendons". BASIC MULTISTRAND ANCHORAGE DEVICE is an anchorage device used with multiple strands, bars or wires, or single bars larger than 16 mm diameter, that satisfies Section 418.22.1 and the bearing stress and minimum plate stiffness requirements of AASHTO Bridge Specifications, Division I, Sections 9.21.7.2.2 through 9.21.7.2.4. BONDED TENDON is a prestressing tendon that bonded to concrete either directly or through grouting.


IS

4-2

DEFINITIONS

CEMENTITIOUS MATERIALS are materials as specified in Section 403 which have cementing value when used in concrete either by themselves, such as portland cement, blended hydraulic cements and expansive cement, or such materials in combination with fly ash, raw or other calcined natural pozzolans, silica fume, or ground granulated blast-furnace slag.

DEVELOPMENT LENGTH is the length of embedded reinforcement required to develop the design strength of reinforcement at a critical section. See Section 409.4.3.

COLUMN is a member with a ratio of height-to-Ieast lateral dimension of 3 or greater used primarily to support axial compressive load.

EFFECTIVE DEPTH OF SECTION (d) is the distance measured from extreme compression fiber to centroid oftension reinforcement.

COMPOSITE CONCRETE FLEXURAL MEMBERS are concrete flexural members of precast and cast-in-place concrete elements, or both, constructed in separate place ments but so interconnected that all elements respond to loads as a unit.

EFFECTIVE PRESTRESS is the stress remammg in prestressing tendons after all losses have occwred, excluding effects of dead load and superimposed load.

COMPRESSION-CONTROLLED SECTION is a cross section in which the net tensile strain in the extreme tension steel at nominal strength is less than or equal to the ,compression-controlled strain limit. COMPRESSION-CONTROLLED STRAIN LIMIT is the net tensile strain at balanced strain conditions. See Section 410A.2. CONCRETE is a mixture of portland cement or any other hydraulic cement, fine aggregate, coarse aggregate and water, with or without admixtures. CONCRETE, SPECIFIED COMPRESSIVE STRENGTH OF (f'e), is the compressive strength of concrete used in design and evaluated in accordance with provisions of Section 405, expressed in megapascals (MPa). Whenever the quantity Pc is under a radical sign, square root of numerical value only is intended, and result has units of megapascaIs. CONCRETE, STRUCTURAL LIGHTWEIGHT, is concrete containing lightweight aggregate that conforms to Section 403.4 and has an air-dry unit weight as determined by "Test Method for Unit Weight of Structural Lightweight Concrete" (ASTM C 567) not exceeding 1840 kg/m3 . In this code, a lightweight concrete without natural sand is termed "all-lightweight concrete" and lightweight concrete in which all fine aggregate consists of normal-weight sand is termed "sand-lightweight concrete." CONTRACTION JOINT is a formed, sawed, or tooled groove in a concrete structure to create a weakened plane and regulate the location of cracking resulting from the dimensional change ofdifferent parts ofthe structure. CURVATURE FRICTION is friction resulting from bends or curves in the specified prestressing tendon profile.

DEFORMED REINFORCEMENT is deformed reinforcing bars, bar and rod mats, deformed wire, welded smooth wire fabric and welded deformed wire fabric.

EMBEDMENT LENGTH is the length of embedded reinforcement provided beyond a critical section. EXTREME TENSION STEEL js the reinforcement (prestressed or nonprestressed) that is the farthest from the extreme compression fiber. ISOLATION JOINT is a separation between adjoining parts of a concrete structure, usually a vertical plane, at a designed location such as to interfere least with performance of the structure, yet such as to allow relative movement in three directions and avoid formation of cracks elsewhere in the concrete and through which all or part of the bonded reinforcement is interrupted. JACKING FORCE is the temporary force exerted by device that introduces tension into prestressing tendons in prestressed concrete. WAD, DEAD, is the dead weight supported by a member, as defined by Section 204 (without load factors). LOAD, FACTORED, is the load, multiplied by appropriate load factors, used·to proportion members by the strength design method of this chapter. See Sections 408.2.1 and 409.3. WAD, LIVE, is the live load specified by Section 205 (without load factors). LOAD, SERVICE, is the load specified by Sections 204 to 207 (without load factors). MODULUS OF ELASTICITY is the ratio of normal stress to corresponding strain for tensile or compressive stresses below proportional limit of material. See Section 408.6.


CONCRETE

NET TENSILE STRAIN is the tensile strain at nominal strength exclusive of strains due to effective prestress, creep, shrinkage and temperature. PEDESTAL is an upright compression member with a ratio of unsupported height to average least lateral dimension not exceeding of 3. PLAIN CONCRETE is structural concrete with no reinforcement or with less reinforcement than the minimum amount specified for reinforced concrete. PLAIN REINFORCEMENT is reinforcement that does not conform to definition of deformed reinforcement. POST-TENSIONING is a method of prestressing in which tendons are tensioned after concrete has hardened. PRECAST CONCRETE is a structural concrete element cast in other than its final position in the structure. PRESTRESSED CONCRETE is structural concrete in which internal stresses have been introduced to reduce potential tensile stresses in concrete resulting from loads. PRETENSIONING is a method of prestressing in which tendons are tensioned before concrete is placed. REINFORCED CONCRETE is structural concrete reinforced with no less than the minimum amounts of prestressing tendons or nonprestressed reinforcement specified in this chapter. REINFORCEMENT is material that conforms to Section 403.5.1, excluding prestressing tendons unless specifically included. RESHORES are shores placed snugly under a concrete slab or other structural member after the original forms and shores have been removed from a larger area., thus requiring the new slab or structural member to deflect and support its own weight and existing construction loads applied prior to the installation of the reshores. SHEATHING is a material encasing a prestressing tendon to prevent bonding the tendon with the surrounding concrete, to provide corrosion protection, and to contain the corrosion inhibiting coating. SHORES are vertical or inclined support members designed to carry the weight of the formwork, concrete and construction loads above. SPAN LENGTH. See Section 408.8.

........

SPECIAL ANCHORAGE DEVICE is an anchorage device that satisfies Section 418.20.1 an.d the standardized acceptance tests of AASHTO "Standard Specifications for Highway Bridges", Division n, Section 10.3.2.3. SPIRAL REINFORCEMENT is continuously wound reinforcement in the form of a cylindrical helix. SPLITTING TENSILE STRENGTH (fcJ is the tensile strength of concrete determined in accordance with ASTM C 496 as described in "Specifications for Lightweight Aggregate for Structural Concrete" (ASTM C 330). See Section 405.2.4. STIRRUP is reinforcement used to resist shear and torsion stresses in a structural member; typically bars, wires, or welded wire fabric (plain or deformed) bent into L, U or rectangular shapes and located perpendicular to or at an angle to longitudinal reinforcement. (The term "stirrups" is usually applied to lateral reinforcement in flexural members and the term "ties" to those in compression members.) See also "tie." STRENGTH, DESIGN, is the nominal strength multiplied by a strength-reduction factor, fj). See Section 409.4. STRENGTH, NOMINAL, is the strength of a member or cross section calculated in accordance with provisions and assumptions of the strength design method of this chapter before application of any strength-reduction factors. See Section 409. 4 .1. STRENGTH, REQUIRED, is the strength of a member or cross section required to resist factored loads or related internal moments and forces in such combinations as are stipulated in this chapter. See Section 409.2.1. STRESS is the intensity of force per unit area. STRUCTURAL CONCRETE is all concrete used for structural purposes, including plain and reinforced concrete. TENDON is a steel element such as wire, cable, bar, rod or strand, or a bundle of such elements, used to impart prestress forces to concrete. TENSION-CONTROLLED SECTION is a cross section in which the net tensile strain in the extreme tension steel at nominal strength is greater than or equal to 0.005. TIE is a loop of reinforcing bar or wire enclosing longi tudinal reinforcement. A continuously wound bar or wire in the form of a circle, rectangle or other polygon shape without re-entrant comers is acceptable. See "stirrup. "


1 4-4

SPECIFICATIONS FOR TESTS AND MATERIALS & DEFINITIONS

TRANSFER is the act of transferring stress in prestressing tendons from jacks or pretensioning bed to concrete member.

SECTION 403 - SPECIFICATIONS FOR TESTS AND MATERIALS

UNBONDED TENDON is a tendon that is permanently prevented from bonding to the concrete after stressing.

403.1

specified yield strength of nonprestressed reinforcement in megapascals (MPa).

WALL is a member, usually vertical, used to enclose or separate spaces. WOBBLE FRICTION in prestressed concrete, is friction caused by unintended deviation of prestressing sheath or duct from its specified profile. YIELD STRENGTH is the specified rmmmum yield strength or yield point of reinforcement in megapascals (MFa). Yield strength or yield point shall be determined in tension according to applicable ASTM standards as modified by Section 403.6 of this code.

NOTATION

403.2

TESTS OF MATERIALS

403.2.1 The engineer may require the testing of any materials used in concrete construction to determine if materials are of quality specified. 403.2.2 Tests of materials and of concrete shall be made in accordance with the standards listed in Section 403.9. 403.3.3 A complete record of tests of materials and of concrete shall be available for inspection during progress of work and for two (2) years after completion of the project, and shall be preserved by the inspecting engineer or architect for that purpose.

403.3

CEMENT

403.3.1 Cement shall conform to one of the following specifications: 1.

2.

3.

"Specifications for Portland Cement" (ASTM C150). "Specifications for Blended Hydraulic Cements" (ASTM C 595M), excluding Types S and SA which are not intended as principal cementing constituents of structural concrete. "Specifications for Expansive Hydraulic Cement" (ASTM C 845).

403.3.2 Cement used in the work shall correspond to that on which selection of concrete proportions waS" based. See Section 405.3.

403.4 AGGREGATES 403.4.1 Concrete aggregates shall conform to one of the fullowing specifications: 1. "Specifications for Concrete Aggregates"

(ASTMC 33),

l


CONCRETE

2.

"Specifications for Lightweigl¢ Aggregates for StructuratConcrete" (ASTM C 330)

Aggregates failing to meet the above specifications but which have been shown by special test or actual service to produce concrete of adequate strength and durability may be used where authorized by the engineer. 403.4.2 The nominal maximum size of coarse aggregate shall not be larger than: L One fifth (l/5) the narrowest dimension between sides of forms, or 2. One third (1/3) the depth of slabs, or 3. Three fourths (3/4) the minimum clear spacing between individual reinforcing bars or wires, bundles ofbars, or prestressing tendons or ducts.

These limitations may be waived if, in the judgment of the engineer, workability and methods of consolidation are such that concrete can be placed without honeycomb or voids.

403.5 WATER. 403.5.1 Water used in mixing concrete shall be clean and free from injurious amounts of oils, acids, alkalis, salts, organic materials or other substances deleterious to concrete or reinforcement. 403.5.2 Mixing water for prestressed concrete or for concrete that will contain aluminum embedments, including that portion of mixing water contributed in the form of free moisture on aggregates, shall not contain deleterious amounts ofchloride ions. See Section 404.5.1. 403.5.3 Non-potable water shall not be 1Jsed in concrete unless the following are satisfied: 403.5.3.1 Selection of concrete proportions shall be based on concrete mixes using water from the same source. 403.5.3.2 Mortar test cubes made with nonpotable mixing water shall have 7-day and 28-day strengths equal to at least 90 percent of strengths of similar specimens made with potable water. Strength test comparison shall be made on mortars, identical except for the mixing water, prepared and tested in accordance with "Test Method for Compressive Strength of Hydraulic Cement Mortars (using 50-mm Cube Specimens)" (ASTM C 109).

403.6 STEEL REINFORCEMENT 403.6.1 Reinforcement shall be deformed reinforcement, except that plain reinforcement may be used for spirals or

k........

4-5

tendo~, and reinforcement consisting of structural steel,

steel pIpe or steel tubing may be used as specified in this chapter. 403.6.2 Welding of reinforcing bars shall conform to "Structural Welding Code - Reinforcing Steel", ANSIIAWS D1.4 ofthe American Welding Society. Type and location of welded splices and other required welding of reinforcing bars shall be indicated on the design drawings or in the project specifications. ASTM reinforcing bar' specifications, except for ASTM A 706, shall be supplemented to require a report of material properties necessary to conform to requirements in ANSIIAWS DL4. 403.6.3

Deformed Reinforcements

403.6.3.1 Deformed reinforcing bars shall conform to one ofthe following specifications: L "Specifications for Deformed and Plain Billet Steel Bars for Concrete Reinforcement" (ASTM A 61 SM). 2. "Specifications for Rail-Steel Deformed and Plain Bars for Concrete Reinforcement" including Supplementary Requirement SI (ASTM A 616M including S1). 3. "Specifications for Axle-Steel Deformed and Plain Bars for Concrete Reinforcement" (ASTM A 617M). 4. "Specifications for Low-Alloy Steel Deformed Bars for Concrete Reinforcement" (ASTM A 706M). 4u3.6.3.2 Deformed reinforcing bars with a specified yield. strength.l;. exceeding 415 MPa shall be permitted, proVided h shall be the stress corresponding to a strain of 0.35 percent and the bars otherwise conform to one of the ASTM specifications listed in 403.6.3.1. See Section 409.5. 403.6.3.3 Bar mats for concrete reinforcement shall conform to "Specifications for Fabricated Deformed Steel Bar Mats for Concrete Reinforcement" (ASTM A 184). Reinforcing bars used in bar mats shall conform to one of the specifications listed in 403.6.3.1. 403.6.3.4 Deformed wire for concrete reinforcement shall conform to "Specifications for Steel Wire, Deformed, for Concrete Reinforcement" (ASTM A 496). except that wire shall not be smaller than size D4, and for wire with a specified yield strength h exceeding 415 MPa,1, shall be the stress corresponding to a strain of 0.35 perc:nt, if the yield strength specified in design exceeds 415 MPa. 403.6.3.5 Welded plain wire fabric for concrete reinforcement shall conform to "Specifications for Steel Welded Wire, Fabric, Plain for Concrete Reinforcement"


SPECIFICATIONS FOR TESTS AND MATERIALS

4-6

(ASTM A 185), except that for wire with a specified yield strength h exceeding 415 MPa, h shall be the stress corresponding to a strain of 0.35 percent, if the yield strength specified in design exceeds 415 MPa. Welded intersections shall not be spaced farther apart than 300 mm in direction of calculated stress, except for wire fabric used as stirrups in accordance with Section 412.14.2. 403.6.3.6 Welded deformed wire fabric for concrete reinforcement shall conform to "Specifications for Steel Welded Wire Fabric, Deformed, for Concrete Reinforcement" (ASTM A 497), except that for wire with a specified yield strength/y exceeding 415 MPa,/y shall be the stress corresponding to a strain of 0.35 percent, if the yield strength specified in design exceeds 415 MPa. Welded intersections shall not be spaced farther apart than 400 mm in direction of calculated stress, except for wire fabric used as stirrups in accordance with Section 412.14.2 403.6.3.7 Galvanized reinforcing bars shaH comply with "Specifications for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement" (ASTM A 767M). Epoxy-coated reinforcing bars shall comply with "Specification for Epoxy-Coated Reinforcing Steel Bars" (ASTM A 175M) or with "Specifications for Epoxy-Coated Prefabricated Steel Reinforcing Bars" (ASTM A 934M). Galvanized or epoxy-coated reinforcement shall conform to one of the specifications listed in 403.6.3.1. "

403.6.3.8 Epoxy-coated wires and welded wire fabric shall comply with "Standard Specification for Epoxy Coated Steel Wire and Welded Wire Fabric for Reinforcement" (ASTM A 884M). Epoxy-coated wires shall conform to Section 403.6.3.4 and epoxy-coated welded wire fabric shall conform to Section 403.6.3.5 or 403.6.3.6. 403.6.4

2.

3.

4.

403.6.4.2 Plain wire for spiral reinforcement shall ·tonform to "Specifications for Steel Wire, Plain, for Concrete Reinforcement" (ASTM A 82), except that for wire with a specified yield strength h exceeding 415 MPa, {" shall be the stress corresponding to a strain of 0.35 .~ercent, if the yield strength specified in design exceeds 415 MPa.

403.6.6

Structural Steel, Steel Pipe or Tubing

403.6.6.1 Structural steel used with reinforcing bars in composite compression members meeting requirements of Section 410.17.7 or 410.17.8, shall conform to one of the following specifications: 1. 2.

3.

4.

"Specifications for Structural Steel" (ASTM A 36M). "Specifications for High-Strength Low-Alloy Structural Steel" (ASTM A 242M). i "Specifications for High-Strength Low-Alloy Columbium-Vanadium Steels of Structural Quality" (ASTM A 572M). "Specifications for High-Strength Low-Alloy Structural Steel with 345 MPa minimum yield point to 100mm thick" (ASTM A 588M).

403.6.6.2 Steel pipe or tubing for composite compression members composed of a steel-encased concrete core meeting requirements of Section 410.17.6 shall conform to one of the following specifications: 1.

2.

3.

Prestressing Tendons

Wire conforming to "Specifications for Uncoated Stress-Relieved Steel Wire for Prestressed Concrete" (ASTM A 421). Low-relaxation wire conforming to "Specifications for Uncoated Stress-Relieved Steel Wire for Prestressed Concrete" including Supplement "Low Relaxation Wire" (ASTM A 421) Strand conforming to "Specifications fel Steel Strand, Uncoated Seven-Wire for Prestressed Concrete" (ASTM A 416M). Bar conforming to "Specifications for Uncoated High-Strength Steel Bar for Prestressing Concrete" (ASTMA 722)

403.6.5.2 Wire, strands, and bars not specifically listed in ASTM A 416, A 421 and A 722 are allowed, provided they conform to minimum requirements of these specifications and do not have properties that make them less satisfactory than those listed in these specifications.

Plain Reinforcement

403.6.4.1 Plain bars for spiral reinforcement shall conform to one of the following specification: ASTM A615, A 616 and A 617.

403.6.5

1.

Grade B of "Specifications for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated Welded and Seamless" (ASTM A 53). "Specifications for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes" (ASTM A 500). "Specifications for Hot-Formed Welded and Seamless Carbon Steel Tubing" (ASTM A 501)

403.6.5.1 Tendons for prestressed reinforcement shall conform to one of the following specifications:


CONCRETE

4-7

403.8.2 Any material that has deteriorated or has been contaminated shall not be used for concrete

403.7 ADMIXTURES 403.7.1 Admixtures to be used in concrete shall be subject to prior approval by the engineer. 403.7.2 An admixture shall be shown capable of maintaining essentially the same composition and performance throughout the work as the product used in establishing concrete proportions in accordance with Section 405.3. 403.7.3 Calcium chloride or admixtures containing chloride from other than impurities from admixture ingredients shall not be used in prestressed concrete, in concrete containing embedded aluminum, or in concrete cast against stay-in-place galvanized steel forms. See Sections 404.4.2 and 404.5.1. 403.7.4 Air-entraining admixtures shall conform to "Specifications for Air-Entraining Admixtures for Concrete" (ASTM C 260). 403.7.5 Water-reducing admixtures, retarding admixtures, accelerating admixtures, water-reducing and retarding admixtures, and water-reducing and accelerating admixtures shall conform to "Specifications for Chemical Admixtures for Concrete" (ASTM C 494) or "Specification for Chemical Admixtures for Use in Producing Flowing Concrete" (ASTM C 1017). 403.7.6 Fly ash or other pozzolans used as admixtures shall conform to "Specifications for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete" (ASTM C 618).

403.9 STANDARDS CITED IN TmS CHAPTER 403.9.1 Standards of the American Society for Testing and Materials (ASTM) referred to in this chapter are listed below with their serial designations, including year of adoption or revision, and are declared to be part of this code as iffully set forth herein: A 36M-96 A 53-97

A 82-97 A 184-96

A 185-97

A 242M-93a A 416M-96 A 421-91 A 496-97

403.7.7 Ground granulated blast-furnace slag used as an admixture shall conform to "Specifications for Ground Granulated Blast-furnace Slag for Use in Concrete and Mortars" (ASTM C 989).

A 497-97 A 500-96

403.7.8 Admixtures used in concrete containing ASTM C845 expansive cements shall be compatible with the cement and produce no deleterious effects. 403.7.9 Silica fume used as an admixture shall conform to "Specification for Silica Fume for Use in Hydraulic-Cement Concrete and Mortar" (ASTM C 1240).

A 501-96

A 572-97

A 588M-97

403.8 STORAGE OF MATERIALS 403.8.1 Cementitious materials and aggregate shall be stored in such manner as to prevent deterioration or intrusion of foreign matter.

A 615M-96a A 616M-96a

Standard Specifications for Carbon Structural Stee.! Standard Specifications for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated Welded and Seamless Standard Specifications for Steel Wire, Plain, for Concrete Reinforcement Standard Specifications for Fabricated Deformed Steel Bar Mats for Concrete Reinforcement Standard Specifications for Steel Welded Wire Fabric, Plain, for Concrete Reinforcement Standard Specifications for High-Strength Low-Alloy Structural Steel Standard Specifications for Steel Strand, Uncoated Seven-Wire for Prestressed Concrete Standard Specifications for Uncoated Stress-Relieved Steel Wire for Prestressed Concrete Standard Specifications for Steel Wire, Deformed, for Concrete Reinforcement Standard Specifications for Steel Welded Wire Fabric, Deformed, for Concrete Reinforcement Standard Specifications for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes Standard Specifications for Hot-Formed Welded and Seamless Carbon Steel Structural Tubing Standard Specifications for High-Strength bew--AHoy Columbium-Vanadium Structural Steels Standard Specifications for High-Strength Low-Alloy Structural Steel with 345 MPa minimum yield point to 100 mm thic'!< Standar(i Sp~cifications for Deformed and Plain Billet-Steel Bars for Concrete Reinforcement Standard Specifications tor Rail-Steel Deformed and Plain Bars for Concrete


4-8

A 617M-96a

A 706M-96b

A 722-97

A 767M-97

A 775M-97 A 884M-96a

A 934M-97 C 31-96M C 33-93 C 39-96 C 42-94

~.'

i

\11:

r"

'Ii

C 94-96

'I

C109M-95

"11'

" ,.::: 'I :1

1

C 144-93 C 150-97

l 1,

~i!

C 172-90 C 192M-95 C 260-95 C 330-89 C 494-92 C496-96 C 567-91

l

SPECIFICATIONS FOR TESTS AND MATERIALS

Reinforcement, including Supplementary Requirement S 1 Standard Specifications for Axle-Steel Deformed and Plain Bars for Concrete Reinforcement Standard Specifications for Low-Alloy Steel Deformed Bars for Concrete Reinforcement Standard Specifications for Uncoated High-Strength Steel Bar for Prestressing Concrete Standard Specifications for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement Standard Specifications for Epoxy-Coated Reinforcing Steel Bars Standard Specifications for Epoxy-Coated Steel Wire and Welded Wire Fabric for Reinforcement Standard Specifications for Epoxy-Coated Prefabricated Steel Reinforcing Bars Standard Practice for Making and Curing Concrete Test Specimens in the Field Standard Specifications for Concrete Aggregate Standard Test Method for Compressive of Cylindrical Concrete Strength Specimens Standard Method of Obtaining and Testing Drilled Cores and Sawed Beams of Concrete Standard Specifications for Ready-Mixed Concrete Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 50-mm Cube Specimens) Standard Specifications for Aggregate for Masomy Mortar Standard Specifications for Portland Cement Standard Method of Sampling Freshly Mixed Concrete Standard Method of Sampling Freshly Mixed Concrete Standard Specifications for AirEntraining Admixtures for Concrete Standard Specifications for Lightweight Aggregates for Structural Concrete Standard Specifications for Chemical Admixtures for Concrete Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimens Standard Test Method for Unit Weight of Structural Lightweight Concrete

C 595M-97 C 618-97

C 685-95a

C 845-96 C 989-95

C 1017-92

C 1218M-97 C1240-97

Standard Specifications for Blended Hydraulic Cements Standard Specifications for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture on Portland Cement Concrete Standard Specifications for Concrete Made by Volumetric Batching and Continuous Mixing Standard Specifications for Expansive Hydraulic Cement Standard Specifications for Ground Granulated Blast-Furnace Slag for Use in Concrete and Mortars Standard Specifications for Chemical Admixtures for Use in Producing Flowing Concrete Standard Test Method for Water Soluble Chloride in Mortar and Concrete Standard Specifications for Silica Fume for Use in Hydraulic-Cement Concrete and Mortar

403.9.2. "Structural Welding Code - Reinforcing Steel" (ANSIIAWS D1.4-98) of the American Welding Society is declared part of this code as if fully set forth herein. 403.9.3 Section 2.3 Combining Loads Using Strength Design 'of "Minimum Design Loads for Buildings and Other Structures" (ASCE 7-95) is declared part of this code as if fully set forth herein, for the purposes cited in Sections 409.4.1.1 and 426. 403.9.4 "Specification for Unbonded Single Strand Tendons", July 1993, of the Post-Tensioning Institute is declared part of this code as iffully set forth herein. 403.9.5 Sections 9,21.7.2 and 9.21.7.3 of Division I and Section 10.3.2.3 of Division II of AASHTO "Standard Specification for Highway Bridges" (AASHTO 16th Edition, 1996) are declared to be part of this code as if fully set forth herein.


CONCRETE

404.4

SECTION 404 - DURABILITY REQUIREMENTS

4-9

SULFATE EXPOSURE

fc = specified compressive strength of concrete, (MFa).

404.4.1 Concrete to be exposed to sulfate-containing solutions or soils shall conform to the requirements of Table 404-2 or shall be concrete made with a cement that provides sulfate resistance and that has a maximum water cementitious materials ratio and minimum compressive strength set forth in Table 404-2.

404.2 WATER-CEMENTITIOUS MATERIALS RATIO

404.4.2 Calcium chloride as an admixture shall not be used in concrete to be exposed to severe or very severe sulfate-containing solutions, as defined in Table 404-2.

404.1

NOTATION

The water-cementitious materials ratios specified in Tables 404-1 and 404-2 shall be calculated using the weight of cement meeting ASTM C 150, C 595M or C 845 plus the weight offly ash and other pozzolans meeting ASTM C 618, slag meeting ASTM C 989, and silica fume meeting ASTM C 1240, if any.

404.3

404.5 CORROSION PROTECTION OF REINFORCEMENT 404.5.1 For corrosion protection of reinforcement in concrete, maximum water soluble chloride ion concentrations in hardened concrete at ages from 28 to 42 days contributed from the ingredients, including water, aggregates, cementitious materials and admixtures shall not exceed the limits of Table 404-3. When testing is performed to determine water soluble chloride ion content, test procedures shall conform to ASTM C 1218.

SPECIAL EXPOSURE CONDmONS

Concrete that will be subject to the exposure given in Table 404-1 shall conform to the corresponding maximum water cementitious materials ratios and minimum specified concrete compressive strength requirements of that table.

404.5.2 If concrete with reinforcement will be exposed to chlorides from salt, salt water, brackish water, sea water or spray from these sources, requirements of Table 404-1 for water-cementitious materials ratio and concrete strength and the minimum concrete cover requirements of Section 407.8 shall be satisfied. In addition, see Section 418.15 {or unbonded prestressed tendons.

Table 404-1 Requirements for Special Extposure emf' 0 ItlOns

Exposure Condition

Maximum WaterCementitious Materials Ratio, by weight,

Normal Weight

Aggregate

Minimum I'" NormalWeight and Lightweight Aggregate Concrete, MPa

Concrete Concrete intended to have low permeability when exposed to water

0.50

28

For corrosion protection for reinforced concrete exposed to chlorides from salts, saltwater, brackish water, seawater or smav from these sources

0.40

35 i


4-10

Table 404-2

Sulfate Exposure

R

uirements for Concrete Exposed to Minimumf'c,

Water-Soluble Sulfate (S04) in Soil, Percent by Weight

Sulfate (S04) in Watel', ppm

Nom1al-Weight and i .1i!-hl\\eigbt Aggregate Concrete,

Cement Type

Mpa

~~··--------~~----------~-----~------+-------------i~~~~~·:~~~'~_~L_------

Negligible

0.00 - 0.10

0- 150

Moderate1

0.10-0.20

150 1,500

0.20 - 2.00

1,500 - 10,000

OA5

over 10,000

0.45

Very Severe

II, IP(MS), rS(MS), P(MS), ItPM)(MS), I(SM)(MS)

oso

Pozzolan that has been determined by test or service record to improve sulfate resistance when used in concrete containing Type V cement.

1 A lower water-cementitious materials ratio or higher strength may be required for low permeability or for protection against corrosion of embedded items (Table 404-1). 2 Seawater

Table 404-3 - Maximum Chloride Ion Content

for Corrosion Protection Reinforcement

Maximum

Water-Soluble

Chloride Jon

(CI) in Concrete, Percentage by weight of ccmcnlitious

TYPE OF MEMBER

__----~

matcr.~~L-j I

0.06 " ~::

I

L -_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _~_ _ _ _ _ _ _ _ ~


CONCRETE

405 - CONCRETE ALITY, MIXING AND PLACING

specified compressive strength of concrete, MFa. = required average compressive strength of oncrete used as the basis for selection of concrete proportions, MFa. average splitting tensile strength of lightweight aggregate concrete. MFa. standard deviation, MFa.

=

GENERAL

405.2.2 Requirements for f'e shall be based on tests of cylinders made and tested as prescribed in Section 405.7.3. 405.2.3 Unless otherwise specified, f'e shall be based on 28-day tests. If other than 28 days, test age for f'e shall be as indicated in design drawings or specifications. 405.2.4 Where design criteria in Sections 409.6.2.3, 411.3; and 412.3.4, provide for use of a splitting tensile strength value of concrete, laboratory tests shall be made in accordance with "Specification for Lightweight Aggregates for Strucutural Concrete (ASTM C 330) to establish value ofiel corresponding to specified values off'c. 405.2.5 Splitting tensile strength tests shall not be used as a basis for field acceptance of concrete.

405.3 SELECTION OF CONCRETE PROPORTIONS 405.3.1 Proportions of materials for concrete shall be established to provide:

2.

Conformance with strength test requirements of Section 405.7.

405.3.3 Concrete proportions, including water cementitious materials ratio, shall be established on the basis of field experience and/or trial mixtures with materials to be employed (see Section 405.4), except as permitted in Section 405.5 or required by Section 404.

405.4 PROPORTIONING ON THE BASIS OF FIELD EXPERIENCE AND TRIAL MIXTURES, OR BOTH

405.2.1 Concrete shall be proportioned to provide an average compressive strength as prescribed in Section 405.4.2, as well as satisfY the durability criteria of Section 404. Concrete shall be produced to minimize frequency of strengths belowf'c as prescribed in Section 405.7.3.3.

1.

3.

405.3.2 Where different materials are to be used for different portions of proposed work, each combination shall be evaluated.

NOTATIONS

405.2

4·11

405.4.1 Standard Deviation

Where a concrete production facility has 405.4.1.1 test records, a standard deviation shall be established. Test records from which a standard deviation is calculated: 1. Must represent materials, quality control procedures and conditions similar to those expected, and changes in materials and proportions within the test records shall not have been more restricted than those for proposed work. 2. Must represent concrete produced to meet a specified strength or strengths f'e within 7 MFa of that specified for proposed work. . 3. Must consist of at least 30 consecutive tests or two groups of consecutive tests totaling at least 30 tests as defined in Section 405.7.2.4, except as provided in Section 405.4.1.2.

.

405.4.1.2 Where a concrete production facility does not have test records meeting requirements of Section 405.4.1.1, but does have a record based on 15 to 29 consecutive tests, a standard deviation may be established as the product of the calculated standard deviation and the modification factor of Table 405-1. To be acceptable, the test record must meet the requirements of Section 405.4.1.1, Items 1 and 2, and represent only a single record of consecutive tests that span a period of not less than 45 calendar days.

Workability and consistency to permit concrete to be worked readily into forms and around reinforcement under conditions of placement to be employed without segregation or excessive bleeding. Resistance to special exposures as required by Section 404.


CONCRETE, QUALITY, MIXING AND PLACING

4-12

Table 405-1 Modification Factor for Standard Deviation When Less Than 30 Tests are Available Modification Factor for Number of Tests I Standard Deviation]

I

!

i

i

Use Table 405-2

Less than 15 15

i I

1.16

20

I

1.08

I

25

1.03

30 or more

1.00

i

i

!

'Interpolate for intermediate number of tests. Modified standard deviation to be used to determine required average strength!,,, from Section 405.4.2.1

2

405.4.2

405.4.3.2 When an acceptable record of field test results is not available, concrete propOltions established from trial mixtures meeting the following restrictions shall be permitted:

Required Average Strength

405.4.2.1 Required average compressive strength 1'cr used as the basis for selection of con..:rete proportions shall be the larger of Equation (405-1) or (405-2) using a standard deviation calculated in accordance with Section ,405.4.1.1 or 405.4.1.2.

1'er

=

1'c +

1.34 s

(405-1)

1'er

=

1'e +

2.33 s - 3.5

(405-2)

405.4.3.1 When test records are used to demonstrate that proposed co.ncrete proportions will produce the required average strength 1'er (see Section 405.4.2), such records shall represent materials and cor,ditions similar to those expected. Changes in materials, conditions and proportions within the test records shall not have been more restricted than those for proposed work. For the purpose of documenting average strength potential, lest records consisting of less than 30 but not less than 10 consecutive tests may be used, provided test records encompass a period of time not less than 45 days. Required concrete proportions may be established by interpolation between the strengths and proportions of two or more test records each of which meets other requirements of this section.

1.

Combination of materials shall be those for proposed work.

2.

Trial mixtures having proportions and consistencies required for proposed work shall be made using at least three different water-cementitious materials ratios or cementitious materials contents that will produce a range of strengths encompassing the required average strengthf'er. Trial mixture shall be designed to produce a slump within ±20 mm of maximum permitted, and for air entrained concrete, within ±0.5 percent of maximum allowable air content.

or

405.4.2.2 When a concrete production facility does not have field strength test records for calculation of standard deviation meeting requirements of Section 405.4.l.l or 405.4.1.2, required average strength 1'er shall be determined from Table 405-2 and documentation of average strength shall be in accordance with requirements of Section 405.4.3.

3.

4.

For each water-cementitious materials ratio or cementitious materials content, at least three test cylinders for each test age shall be made and cured in accordance with "Method of Making and Curing Concrete Test Specimens in the Laboratory" (ASTM C 192). Cylinders shall be tested at 28 days or at test age designated for determination of1'c

5.

From results of cylinder tests, a curve shall be plotted showing relationship between water cementttlOus materials ratio or cementItlOus materials content and compressive strength at designated test age.

6.

Maximum water-cementitious materials ratio or minimum cementitious materials coritent for concrete to be used in proposed work shall be that shown by the curve to produce the average strength required by Section '405.4.2, unless a lower water-cementitious materials ratio or higher strength is required by Section 404.

.::;::

Table 405-2 Required Average Compressive Strength When Data are not Available to Establish a Standard Deviation Specified Compressive Strength, /,,,,

Required Average Compressive Strength, /,,,,,

MPa

MPa f'c

+ 7.0

21 to 35

f'c

+

OYer 35

f'c

+ 10.0

Less than 21 MPa

II

i

8.5

I

405.4.3 Documentation of average strength. Documentation that proposed concrete proportions will produce an average compressive strength equal to or greater than required average compressive strength (see Section 405.4.2) shall consist of a field strength test record, several strength test records, or trial mixtures.

I


4-13

405.5 PROPORTIONING WITHOUT FIELD EXPERIENCE OR TRIAL MIXTURES If data required by Section 405.4 are not available, concrete proportions shall be based upon other experience or infonnation, if approved by the engineer. The required average compressive strength 1'er of concrete produced with materials similar to those proposed for use shall be at least 8.5 MPa greater than the specified .. compressive strength,1'e. This alternative shall not be used for specified compressive strength greater than 28 MPa.

405.7.2.2 On a given project, if the total volume of concrete is such that the frequency of testing required by Section 405.7.2.1 would provide less than five strength tests for a given class of concrete, tests shall be made from at least five randomly selected batches or from each batch if fewer than five batches are used. 405.7.2.3 When total quantity of a given class of concrete is less than 40 m3, strength tests are not required when evidence of satisfactory strength is submitted to and approved by the engineer.

405.5.2 Concrete proportioned by Section 405.5 shall confonn to the durabilit~1 requirements of Section 404 and to compressive strength test criteria of Section 405.7

405.7.2.4 A strength test shall be the average of the strengths of two cylinders made from the same sample of concrete and tested at 28 days or at test age designated for detennination of1'e.

405.6

405.7.3

AVERAGE STRENGTH REDUCTION

As data become available during construction, it shall be permitted to reduce the amount by which 1'er must exceed the specified value oU~, provided: 1.

2.

3.

Thirty or more test results are available and average of test results exceeds that required by Section 405.4.2.1, using a standard deviation calculated in accordance with Section 405.4.1.1, or Fifteen to 29 test results are available and average of test results exceeds that required by Section 405.4.2.1, using a standard deviation calculated in accordance with Section 405.4.1.2, and Special exposure requirements of Section 404 are met.

Laboratory-Cured Specimens

Samples for strength tests shall be taken in 405.7.3.1 accordance with "Method of Sampling Freshly Mixed Concrete" (ASTM C 172). 405.7.3.2 Cylinders for strength tests shall be molded and laboratory cured in accordance with "Practice for Making and Curing Concrete Test Specimens in the Field" (ASTM C 31) and tested in accordance with "Test Method for Compressive Strength of Cylindrical Concrete Specimens" (ASTM C 39). 405.7.3.3 Strength level of an individual class of concrete shall be considered satisfactory if both the following requirements are met: 1.

Every arithmetic average of any three consecutive strength tests equals or exceeds 1'C' No individual strength test (average of two cylinders) falls below1'c by more than 3.5 MPa.

405.7 EVALUATION AND ACCEPTANCE

OF CONCRETE

2.

405.7.1 Concrete shall be tested in accordance with the requirements of Section 405.7.2 through 405.7.5. Qualified field testing technicians shall perform tests on fresh concrete at the job site, prepare specimens required for curing under field conditions, prepare specimens required for testing in the laboratory, and record the temperature of the fresh concrete when preparing specimens for strength tests. Qualified laboratory technicians shall perfonn all required laboratory tests.

405.7.3.4 If either of the requirements of Section 405.7.3.3 are not met, steps shall be taken to increase the average of subsequent strength test results. Requirements of Section 405.7.5 shall be observed if the requirement of Item 2 of Section 405.7.3.3 is not met.

405.7.2

Frequency of Testing

405.7.2.1 Samplf.')s for strength tests of each class of concrete placed each day shall be taken not less than once a day, or not less than once for each 120 m3 of concrete, or not less than once for each 500 m2 of surface area for slabs or walls.

405.7.4

Field-Cured Specimens

If required by the building official, results 405.7.4.1 of strength tests of cylinders cured under field conditions shall be provided. 405.7.4.2 Field-cured cylinders shall be cured under field conditions, in accordance with "Practice for Making and Curing Concrete Test Specimens in the Field" (ASTM C 31).


4-14

CONCRETE, QUALITY, MIXING AND PLACING

405.7.4.3 Field-cured test cylinders shall be molded at the same time and from the same samples as laboratory cured test cylinders. 405.7.4.4 Procedures for protecting and curing concrete shall be improved when strength of field-cured cylinders at test age designated for determination of 1'c is less than 85 percent of that of companion laboratory-cured cylinders. The 85 percent limitation shall not apply if field cured strength exceeds1'c by more than 3.5 MPa. 405.7.5 Investigation of Low-Strength Test Results 405.7.5.1 If any strength test (see Section 405.7.2.4) of laboratory cured cylinders falls below specified values of 1'c by more than 3.5 MPa (see Section 405.7.3.3, Item 2) or if tests of field-cured cylinders indicate deficiencies in protection and curing (see Section 405.7.4.4), steps shall be taken to ensure that load-carrying capacity of the structure is not jeopardized. 405.7.5.2 lfthe likelihood of low-strength concrete is confirmed and calculatiOns indicate that load-carrying capacity is significantly reduced, tests of cores drilled from f the area in question in accordance with "Method of Obtaining and Testing Drilled Cores and Sawed Beams of Concrete" (ASTM C 42) shall be permitted. In such case, three cores shall be taken for each strength test more than 3.5 MPa below specified value of1'c.

,.11'

'II ~ :;

405.7.5.3 If concrete in the structure will be dry under service conditions, cores shall be air dried (temperatures 15°C to 25°C, relative humidity less than 60 percent) for seven days before test and shall be teste.d dry. If concrete in the structure will be more than superficially wet under service conditions, cores shall be immersed in water for at least 40 hours and be tested wet.

;: :: ~:

405.7.5.4 Concrete in an area represented by core tests shall be considered structurally adequate if the average ofthree cores is equal to at least 85 percent of1'o and if no single core is less than 75 percent of1'o. Additional testing of cores extracted from locations represented by erratic core strength results shall be permitted. 405.7.5.5 If criteria of Section 405.7.5.4 are not met, and if structural adequacy remains in doubt, the responsible authority shall be permitted to order a strength evaluation in accordance with Section 420 for the questionable portion of the structure, or take other appropriate action.

405.8 PREPARATION OF EQUIPMENT AND PLACE OF DEPOSIT 405.8.1 Preparation before concrete placement shall include the following: tran~porting

1.

All equipment for mixing and shall be clean.

2.

All debris shall be removed from spaces to be occupied by concrete.

3.

Forms shall be properly coated.

4.

Masonry filler units that will be in contact with concrete shall be well drenched.

5.

Reinforcement shall be thoroUghly clean of dele terious coatings.

6.

Water shall be removed from place of deposit before concrete is placed unless a tremie is to be used or unless otherwise permitted by the engineer.

7.

All laitance and other unsound material shall be removed before additional concrete is placed against hardened concrete.

405.9

concrete

MIXING

405.9.1 All concrete shall be mixed until there is a uniform distribution of materials and shall be discharged completely before mixer is recharged. 405.9.2 Ready-mixed concrete shall be mixed and delivered in accordance with requirements of "Specifications for Ready-Mixed Concrete" (ASTM C 94) or "Specifications for Concrete Made by Volumetric Batching and Continuous Mixing" (ASTM C 685). 405.9.3 Job-mixed concrete shall be mixed in accordance with the following: 1. Mixing shall be done in a batch mixer of an approved type. 2. Mixer shall be rotated at a speed recommended by the manufacturer. 3. Mixing shall be continued for at least 1-1/2 minutes after all materials are in the drum, unless a shorter time is shown to be satisfactory by the mixing, uniformity tests of "Specifications for Ready-Mixed, Concrete" (ASTM C 94). 4. Matedals handling, bat ching and mixing conform to applicable provisions of "SJ)eciflc:atioll!I,' for Ready-Mixed Concrete" (ASTM C 94).

Association Of Structural Engineers of the Philippines

CONCRETE

4-15

405.12 CURING Number of batches produced; Proportions of materials used; Approximate location of final deposit in structure; .4 Time and date of mixing and placing.

CONVEYING 1 Concrete shall be conveyed from mixer to place deposit by methods that will prevent separation or materials.

405.12.1 Concrete (other than high-early-strength) shall be maintained above 10°C and in a moist condition for at least the first seven days after placement, except when cured in accordance with Section 405.12.3. 405.12.2 High-early-strength concrete shall be maintained above 10°C and in a moist condition for at least the first three days, except when cured in accordance with Section 405.12.3. 405.12.3

0.2 Conveying equipment shall be capable of a supply of concrete at site of placement without of ingredients and without interruptions to· permit loss of plasticity between successive

DEPOSITING Concrete shall be deposited as nearly as racllcable in its final position to avoid segregation due to HUlD(lImg or flowing. Concreting shall be carried on at such a rate that conCI'ete is at all times plastic and flows readily into spaces .bl::tw4llen reinforcement. 405.11.3 Concrete that has partially hardened or been cointamlllat€ld by foreign materials shall not be deposited in

Accelerated Curing

405.12.3.1 Curing by high-pressure stearn, steam at atmospheric pressure, heat and moisture or other accepted processes, may be employed to accelerate strength gain and reduce time of curing. 405.12.3.2 Accelerated curing shall provide a compressive strength of the concrete at the load stage considered at least equal to required design strength at that load stage. 405.12.3.3 Curing process shall be such as to produce concrete with a durability at least equivalent to the curing method of Section 405.12.1 or 405.12.2. 405.12.4 When required by the engineer, supplementary strength tests in accordance with Section 405.7.4 shall be performed to assure that curing is satisfactory.

405.13 HOT WEATHER REQUIREMENTS 1.4 Re-tempered concrete or concrete that has been re-mixed after initial set shall not be used unless approved by the engineer. 405.11.5 After concreting is started, it shail be carried on as a continuous operation until placing of a panel or section, as defined by its boundaries or predetermined joints, is completed, except as permitted or prohibited by Section

During hot weather, proper attention shall be given to ingredients, production methods, handling, placing, protection and curing to prevent excessive concrete temperatures or water evaporation that may impair required strength or serviceability ofthe member or structure.

406.4.

405.11.6 Top surfaces of vertically formed lifts shall be generally level. 405.11.7 When construction Jomts are required, joints shall be made in accordance with Section 406.4. 405.11.8 All concrete shall be thoroughly consolidated by suitable means during placement and shall be thoroughly worked around reinforcement and embedded fixtures and into corners offorms.

National S1ructuraI Code of the Philippines, Volume 1

r""

..

_~"_'_M_~-~-.--~-~

4-16

..

----~.-.---'-

FORMWORK. EMBEDDED PIPES AND CONSTRUCTION JOINTS

SECTION 406 - FORMWORK, EMBEDDED PIPES AND CONSTRUCTION JOINTS

1.

2.

406.1

DESIGN OF FORMWORK

406.1.1 Forms shall result in a final structure that conforms to shapes, lines and dimensions of the members as required by the design drawings and specifications. 406.1.2 Forms shall be substantial and sufficiently tight to prevent leakage of mortar. 406.1.3 Forms shall be properly braced or tied together to maintain position and shape. 406.1.4 Forms and their supports shall be designed so as not to damage previously placed structure. 406.1.5 Design of formwork shall include consideration of the following factors: 1. 2. 3. ~"

Rate and method of placing concrete. Construction loads, including vertical, horizontal and impact loads. Special form requirements for construction of shells, folded plates, domes, architectural concrete or similar types of elements.

406.1.6 Forms for prestressed concrete members shall be designed and constructed to permit movement of the member without damage during application of prestressing force.

406.2 REMOVAL OF FORMS, SHORES AND RESHORING 406.2.1 Removal of forms. Forms shall be removed in such a manner as not to impair safety and serviceability of the structure. Concrete to be exposed by form removal shall have sufficient strength not to be damaged by removal operation. 406.2.2 Removal of shores and reshoring. The provisions of Section 406.2.2.1 through 406.2.2.3 shall apply to slabs and beams except where cast on the ground. 406.2.2.1 Before starting construction, the contractor shall develop a procedure and schedule for removal of shores and installation of reshores and for calculating the loads transferred to the structure during the process.

3.

The structural analysis and concrete strength data used in planning and implementing form removal and shoring shall be furnished by the contractor to the building official when so requested. No construction loads shall be supported on, or any shoring removed from, any part of the structure under construction except when that portion of the structure in combination with remaining forming and shoring system has sufficient strength to support safely its weight and loads placed thereon. Sufficient strength shall be demonstrated by structural analysis considering proposed loads, strength of forming and shoring system and concrete strength data. Concrete strength data may be based on tests of field-cured cylinders or, when approved by the engineer, on other procedures to evaluate concrete strength.

406.2.2.2 No construction loads exceeding the combi nation of superimposed dead load plus specified live load shall be supported on any unshored ponion of the structure under construction, unless analysis' indicates adequate strength to support such additional loads. 406.2.2.3 Form supports for prestressed concrete members shall not be removed until sufficient prestressing has been applied to enable prestressed members to carry their dead load and anticipated construction loads.

406.3 CONDUITS AND PIPES EMBEDDED IN CONCRETE 406.3.1 Conduits, pipes and sleeves of any material not harmful to concrete and within limitations ofthis subsection may be embedded in concrete with approval of the engineer. provided they are not considered to replace structurally the displaced concrete. 406.3.2 Conduits and pipes of aluminum shall not be embedded in structural concrete unless effectively coated or covered to prevent aluminum-concrete reaction or electrolytic action between aluminum and steel. 406.3.3 Conduits, pipes and sleeves passing through a slab, wall or beam shall not impair significantly the strength of the construction. 406.3.4 Conduits and pipes, with their fittings, embedded within a column shall not displace more than 4 percent of the area of cross section on which strength is calculated or which is required for fire protection. 406.3.5 Except when plans for conduits and pipes are approved by the structural engineer, conduits and pipes

As$ociation of Structural Engineers of the Philippines

l

CONCRETE

;Y;emb1edc1ed within a slab, wall or beam (other than those . merely passing through) shall satisfy the following: 406.3.5.1 They shall not be larger in outside dimension than one third the overall thickness of slab, wall or beam in which they are embedded. They shall be spaced not closer than three diameters or widths on center. 406.3.5.3 They shall not impair significantly the strength ofthe construction. 406.3.6 Conduits, pipes and sleeves may be c;onsidered as replacing structurally in compression the displaced concrete, provided:

406.4

4-17

CONSTRUCTION JOINTS

406.4.1 Surface of concrete construction joints shall be cleaned and laitance removed. 406.4.2 Immediately before new concrete is placed, all construction joints shall be wetted and standing water removed.. 406.4.3 Construction joints shall be so made and located as not to impair the strength of the structure. Provision shall be made for transfer of shear and other forces through construction joints. See Section 411.8.9.

They are not exposed to rusting or other

406.4.4 Construction joints in floors shall be located within the middle third of spans ofslabs, beams and girders. Joints in girders shall be offset a minimum distance of two times the width of intersecting beams.

406.3.6.2 They are of uncoated or galvaniZed iron or steel not thinner than standard Schedule 40 steel pipe..

406.4.5 Beams, girders or slabs supported by columns or walls shall not be cast or erected until concrete in the vertical support members is no longer plastic.

406.3.6.1 deterioration.

406.3.6.3 They have a nominal inside diameter not over 50 mm and are spaced not less than three diameters on centers.

406.4.6 Beams, girders, haunches, drop panels and capitals shall be placed monolithically as part of a slab system, unless otherwise shown in design drawings or specifications.

406.3.7 Pipes and fittings shall be designed to resist effects of the material, pressure and temperature to which. they will be subjected. 406.3.8 No liquid, gas or vapor, except water not exceeding 30. oC or 0.3 MPa pressure, shall be placed in the pipes until the concrete has attained its design strength. 406.3.9 In solid slabs, piping, unless it is used for radiant heating or snow melting, shall be placed between top and bottom reinforcement. . 406.3.10 Concrete cover for pipes, conduit and fittings shall not be less than 40 mm for concrete exposed to earth or weather, or less than 20 mm for concrete not exposed to weather or in contact with ground. 406.3.11 Reinforcement with an area not less than 0.002 times the area of concrete section shall be provided normal to the piping. 406.3.12 Piping and conduit shall be so fabricated and installed that cutting, bending or displacement of reinforcement from its proper location will not be required.

National Structqral Code of the Philippines, Volume 1

DETAILS OF REINFORCEMENT

4-18

SECTION 407 - DETAILS OF REINFORCEMENT 407.1

Table 407-1 - Minimum Diameters of Bend Minimum Diameter Bar Size

NOTATIONS

d

distance from extreme compression fiber to centroid of tension reinforcement, mm. nominal diameter of bar, wire or prestressing strand, mm. compressve strength of concrete at time of initial prestress, MPa. specified yield strength of non-prestressed reinforcement, MPa. development length, mm. See Section 412.

db·

lei 1;. Ld

407.2

other wires. Bends with inside diameter of less than 8db shall not be less than 4db from nearest welded intersection.

STANDARD HOOKS

No. 10 through No 25

6db

No 28, 32 and 36 mm diameter

8db

407.4

BENDING OF REINFORCEMENT

407.4.1 All reinforcement shall be bent cold, unless otherwise permitted by the engineer. 407.4.2 Reinforcement partially embedded in concrete shall not be field bent, except as shown on the design drawings or permitted by the engineer.

"Standard hook" as used in this code is one of the following:

, 407.2.1 180-degree bend plus 4db extension, but not less than 60 mm at free end of bar. 407.2.2 bar.

90-degree bend plus 12db extension at free end of

407.2.3 For stirrup and tie hooks: 16 mm diameter bar and smaller, 90-degree bend 1. plus 6db extension at free end of bar, or 20 and 25 mm diameter bar, 90-degree bend, plus 2. 12db extension at free end of bar, or 3.

25 mm diameter bar and smaller, 13 5-degree bend plus 6db extension at free end of bar.

::::::::

407.2.4

407.3

Seismic hooks as defined in Section 421.2

MINIMUM BEND DIAMETERS

407.3.1 Diameter of bend measured on the inside of the bar, other than for stirrups and ties in sizes 10 mm diameter through 16 mm diameter, shall not be less than the values in Table 407-1. 407.3.2 Inside diameter of bends for stirrups and ties shall not be less than 4db for 16 mm diameter bar and smaller. For bars larger than No. 16, diameter of bend shall be in accordance with Table 407-1. 407.3.3 Inside diameter of bends in welded wire fabric (plain or deformed) for stirrups and ties shall not be less than 4db for deformed wire larger than D6 and 2db for all

L

407.5 SURFACE CONDITIONS OF REINFORCEMENT 407.5.1 At the time concrete is placed, reinforcement shall be free from mud, oil or other nonmetallic coatings that decrease bond. Epoxy coatings of steel reinforcement in accordance with Section 403.6.3.7 and 403.6.3.8 shall be permitted. 407.5.2 Reinforcement, except prestressing tendons, with rust, mill scale or a combination of both, shall be considered satisfactory, provided the minimum dimensions (including height of deformations) and weight of a hand wire-brushed test specimen comply with applicable ASTM specifications referenced in Section 403.6. 407.5.3 Prestressing tendons shall be clean and free of oiL dirt, scale, pitting and excessive rust. A light coating of rust shall be permitted.

407.6

PLACING REINFORCEMENT

407.6.1 Reinforcement, prestressing tendons and ducts shall be accurately placed and adequately supported before concrete is placed, and shall be secured against displacement within tolerances of this section. 407.6.2 Unless otherwise specified by the engineer, reinforcement, prestressing tendons and prestressing ducts shall be placed within the following tolerances:


CONCRETE

Tolerance for depth d. and mlfllmum cover in flexural members, walls and compression shall be as follows: Tolerance on d

I

Tolerance on Minimum Concrete Cover

::;; 200 mm

± 10mm

-lOmm

> 200 mm

mm

-12mm

that tolerance for the clear distance to formed soffits be minus 6 mm and tolerance for cover shall not minus one third (1/3) the minimum concrete cover ~~~n.r<>r1 by the approved plans or specifications. Tolerance for longitudinal location of bends and ends of reinforcement shall be ±50 mm except at discontinuous ends of members where tolerance shall be ±12 mm. Welded wire fabric (with wire size not greater than W5 or D5) used in slabs not exceeding 3 meters in span shall be permitted to be curved from a point near the top of slab over the support to a point near the bottom of slab at midspan, provided such reinforcement is either continuous over, or securely anchored at, support. 407.6.4 Welding of crossing bars shall not be permitted for assembly of reinforcement.

Ey:ceptions: 1.

Reinforcing steel bars are not required by design.

2.

When specifically approved by the engineer, welding of crossing bars for assembly purposes in Seismic Zone 2 may be permitted, prov;ded that data are submitted to the engineer to show that there is no detrimental effect on the action qf the structural member as a result ofwelding ofthe crossing bars.

407.7 SPACING LJMITS FOR REINFORCEMENT 407.7.1 The minimum clear spacing between parallel bars in a layer shall be db but not less than 25 mm. See also Section 403.4.2.

I I

4-19

407.7.3 In spirally reinforced or tied reinforced compression members, clear distance between longitudinal bars shall not be less than 1.5dh or less than 40 mm. See also Section 403.4.2. 407.7.4 Clear distance limitation between bars shall apply also to the clear distance between a contact lap splice and adjacent splices or bars. 407.7.5 In walls and slabs other than concrete joist construction, primary flexural reinforcement shaH not be spaced farther apart than three times the wall or slab thickness, nor farther than 450 mm. 407.7.6

Bundled Bars

407.7.6.1 Groups of parallel reinforcing bars bundled in contact to act as a unit shall be limited to four bars in onl' bundle. 407.7.6.2 Bundled bars shall be enclosed within stirrups or ties. 407.7.6.3 Bars larger than 36 mm diameter shall not be bundled in beams. 407.7.6.4 Individual bars within a bundle terminated within the span of flexural members shall terminate at different points with at least 40db stagger. 407.7.6.5 Where spacing limitations and minimum concrete cover are based on bar diameter d". a unit of bundled bars shall be treated as a single bar of a diamet~r derived from the equivalent total area. 407.7.7

Prestressing tendons and ducts

Center-to-center spacing of pretensioning 407.7.7.1 tendons at each end of a member shall not be less than 5dh for wire, nor 4db for strands, except that if concrete strength at transfer of prestress,!,e; is 30 MPa or more, minimum center to center spacing of strands shall be 45 mm for strands of 12 mm nominal diameter or smaller and 50 mm for strands of 15 mm nominal diameter. See also Section 403.4.2. Closer vertical spacing and bundling of tendons shall be permitted in the middle portion of a span. 407.6.7.2 Bundling of post-tensioning ducts shall be permitted if it is shown that concrete can be satisfactorily placed and if provision is made to prevent the tendons, when tensioned, from breaking through the duct.

407.7.2 Where parallel reinforcement is placed in two or more layers, bars in the upper layers shall be placed directly above bars in the bottom layer with clear distance between layers not less than 25 mm.

National structural Code of the Philippines. Volume 1

4-20

DETAILS OF REINFORCEMENT

407.8.1 Cast-in-place concrete _ (nonprestressed). The following minimum concrete cover shall be provided for reinforcement: Minimum Cover 1. Concrete cast against and permanently exposed to earth ..................................... 75 mm 2.

Concrete exposed to earth or weather: 20 mm through 36 rom diameter bar ....... . 50 rom 16 rom diameter bar, W31 or D31 wire, and smaller ................................. . 40 rom

3.

Concrete not exposed to weather or in contact with ground: a. Slabs, walls, joists: 45 and 60 mm diameter bars ... ........ ..... 40 mm 20 mm 36 mm diameter bar and smaller b. Beams, columns: Primary reinforcement, ties, stirrups, spirals ................................... 40 mm c. Shells, folded plate members: 20 mm diameter bar and larger 20 rom 16 mm diameter bar, W31 or D31 wire, and smaller ................................ 12 mm

~ IIIIII~I

III

407.8.2 Precast concrete (manufactured under plant control conditions). The following minimum concrete cover shall be provided for reinforcement: Minimum Cover Concrete exposed to earth or weather: 1. a. Wall panels: 45 mm and 60 mm diameter bars 40mm 20mm 36 mm diameter bar and smaller b. Other members: 45 mm and 60 rom diameter bars ...... 50 mm 20 rom through 36 mm diameter bar 40 mm 16 mm diameter bar W31 or D31 wire, and smaller ........................................... 30 rom

2.

Concrete not exposed to weather or in contact with ground: a. Slabs, walls, joists: 45 rom and 60 rom diameter bars ........ 30 mm 36 rom diameter bar and smaller ...... 15 mm b. Beams, columns: Primary reinforcement ................. db but not less than 15 mm and need not exceed 40 mm Ties, stirrups, spirals ......................... 10 rom c. Shells, folded plate members: 20 mm diameter bar and larger 15 mm 16 mm diameter bar, W31 or D31 wire, and smaller ........................... 10 mm

407.8.3

Prestressed conrrete.

407.8.3.1 The following minimum concrete cover shall be provided for prestressed and nonprestressed reinforcement, ducts and end fittings, except as provided in Sections 407.8.3.2 and 407.8.3.3. Minimum Cover 1. Concrete cast against and permanently exposed to earth 75mm 2.

Concrete exposed to earth or weather: Wall panels, slabs, joists ......................... 25 mm Other members ....................................... 40 mm

3.

Concrete not exposed to weather or in contact with ground: a. Slabs, walls, joists ............................. 20 mm

b. Beams, columns: Primary reinforcement Ties, stirrups, spirals

40 rom 25mm

c. Shells, folded plate members: 16 mm diameter bars, W31 or D31 wire, and smaller .................. 10 mm Other reinforcement ......... .. ........... db but not less than 20 mm

407.8.3.2 For prestressed concrete members exposed to earth, weather or corrosive environments, and in which permissible tensile stress of Section 418.5.2, Item 3, is exceeded, minimum cover shall be increased 50 percent. 407.8.3.3 For prestressed concrete members manufactured under plant control conditions, mlmmum concrete cover for nonprestressed reinforcement shall be as required in Section 407.8.2. 407.8.4 Bundled bars. For bundled bars, mIDImum concrete cover shall be equal to the equivalent diameter of the bundle, but need not be greater than 50 mm; except for concrete cast against and permanently exposed to earth, minimum cover shall be 75 mm. 407.8.5 Corrosive environments. In corrosive environments or other severe exposure conditions, amount of concrete protection shall be suitably increased, and denseness and nonporosity of protecting concrete shall be considered, or other protection shall be provided. 407.8.6 Future extensions. Exposed reinforcement, inserts and plates intended for bonding with future extensions shall be protected from corrosion. 407.8.7 Fire protection. When a thickness of cover for fire protection greater than the minimum concrete


CONCRETE

in Section 407.8 is required, such greater shall be used.

SPECIAL REINFORCEMENT AILS FOR COLUMNS Offset bars. Offset bent longitudinal bars shall to the following: •1.1 Slope of inclined portion of an offset bar axis ofcolumn shall not exceed 1 in 6.

4-21

the footing by compression in the concrete and by reinforcement.

407.10 CONNECTIONS 407.10.1 At connections of principal framing. elements (such as beams and columns), enclosure shall be provided for splices of continuing reinforcement and for anchorage of reinforcement terminating in such connections . 407.10.2 Enclosure at connections may consist of external concrete or internal closed ties, spirals or stirrups .

. 1.2 Portions of bar above and below an offset be parallel to axis ofcolumn.

Horizontal support at offset bends shall be by lateral ties, spirals or parts of the floor Horizontal support provided shall be designed resist one and one-half times the horizontal component of computed force in the inclined portion of an offset bar. ties or spirals, if used, shall be placed not more than 50 mm from points of bend. .9.1.4 Offset bars shall be bent before placement the forms. See Section 407.4. 9.1.5 Where a column face is offset 75 mm or longitudinal bars shall not be offset bent. Separate lap spliced with the longitudinal bars adjacent to offset column faces, shall be provided. Lap splices shall conform to Section 412.18. ....;,;

407.11 LATERAL REINFORCEMENT FOR COMPRESSION MEMBERS 407.11.1 Lateral reinforcement for compression members shall conform to the provisions of Sections 407.11.4 and 407.11.5 and, where shear or torsion reinforcement is required, .shall also conform to provisions of Section 411. 407.11.2 Lateral reinforcement requirements for composite compression members shall conform to Section 410.17. Lateral reinforcement requirements for prestressing tendons shall conform to Section 418.12. 407.11.3 It shall be permitted to waive the lateral reinforcement requirements of Sections 407.11, 410.17 and 418.12 where tests andstructural analyses show adequate strength and feasibility ofconstruction.

~

407.9.2 Steel cores. Load transfer ill structural steel cores . of composite compression members. ~ha.ll be provided by the following:

407.11.4

Spirals. Spiral reinfprcement for compression

members·shal~.confOrn1"'to Bection 410.10.3 and to the

following:

.9.2.1 Ends of structural steel cores shall be .;tCcurately finished to bear at end-bearing splices, with positive provision for alignment of one core above the other in concentric contact.

407.11.4.1 Spirals shall consist of evenly spaced continuous bar or wire of such size and so assembled as to permit handling and placing without distortion from designed dimensions.

407.9.2.2 At end-bearing splices, bearing shall be considered effective to transfer not more than 50 percent of the total compressive stress in the steel core.

407.11.4.2 For cast-in-place construction, size of spirals shall not be less 10 mm diameter.

407.9.2.3 Transfer of stress between column base and footing shall be designed in accordance with Section 415.9.

407.11.4.3 Clear spacing between spirals shall not exceed 75 mm or be less than 25 mm. See also Section 403.4.2.

407.9.2.4 Base of structural steel section shall be designed to transfer the total load from the entire composite member to the footing; or, the base may be designed to transfer the load from the steel core only, provided ample concrete section is available for transfer of the portion of the total load carried by the reinforced concrete section to

407.11.4.4 Anchorage of spiral reinforcement shall be provided by one and one-half extra turns of spiral bar or "vire at each end ofa spiral unit. . 407.11.4.5 Spiral reinforcement shall be spliced, if needed, by anyone ofthe following methods:


DETAilS OF REINFORCEMENT

4-22

a)

b)

Lap splices not less than the larger of 300 mm and the length indicated in one of (1) through (5) below: (I) deformed uncoated bar or wire ........ 48 db

(2) plain uncoated bar or wire ............. ... 72 db

(3) epoxy-coated deformed bar or wire... 72 dh (4) plain uncoated bar or wire with a standard stirrup or tie hook in accordance with Section 407.2.3 at ends of lapped spiral reinforcement. The hooks shall be embedded within the core confined by the spiral reinforcement ............................... 48 db (5) epoxy-coated deformed bar or wire with a standard stirrup or tie hook in accordance with Section 407.2.3 at ends of lapped spiral reinforcement. The hooks shall be embedded within the core confined by the spiral reinforcement ................................. 48 db Full mechanical or welded splices in accordance with Section 412.15.3.

407.11.4.6 Spirals shall extend from top of footing or slab in any story to level of lowest horizontal reinforcement in members supported above. 407.11.4.7 Where beams or brackets do not frame into all sides of a column, ties shall extend above termination of spiral to bottom of slab or drop panel. 407.11.4.8 In columns with capitals, spirals shall extend to a level at which the diameter or width of capital is two times that of the column. 407.11.4.9 true to line.

Spirals shall be held firmly in place and

407.11.5 Ties. Tie reinforcement for members shall conform to the following:

compresslon

407.11.5.1 All nonprestressed bars shall be enclosed bv lateral ties, at least 10 mm diameter in size for l~ngitudinal bars 32 mm diameter or smaller, and at least 12 m; diameter in size for 36 diameter bars and bundled longitudinal bars. Deformed wire or welded wire fabric of equivalent area shall be permitted. 407.11.5.2 Vertical spacing ofties shall not exceed 16 longitudinal bar diameters, 48 tie bar or wire diameters, or least dimension ofthe compression member.

angle of not more than 135 degrees and a bar shall be not farther than 150 mm clear on each side along the tie from such a laterally supported bar. Where longitudinal bars are located around the perimeter of a circle, a complete circular tie shall be permitted. 407.11.5.4 Ties shall be located vertically not more than one half a tie spacing above the top of footing or slab in any story and shall be spaced as provided herein to not more than one half a tie spacing below the lowest horizontal reinforcement in slab or drop panel above. 407.11.5.5 Where beams or brackets frame from four directions into a column, termination of ties not more than 75 mm below reinforcement in shallowest of such beams or brackets shall be permitted. 407.11.5.6 Column ties shall have hooks as specified in Section 407.2.3.

407.12 LATERAL REINFORCEMENT FOR FLEXURAL MEMBERS 407.12.1 Compression reinforcement in beams shall be

enclosed by ties or stirrups satisfying the size and spacing

limitations in Section 407.11.5 or by welded wire fabric of

equivalent area. Such ties or stirrups shall be provided

throughout the distance where compression reinforcement

is required.

407.12.2 Lateral reinforcement for flexural members subject to stress reversals or to torsion at supports

shall consist of closed ties, closed stirrups, or spiral extending around the flexural reinforcement.

407.12.3 Closed ties or stirrups may be formed in

piece by overlapping standard stirrup or tie end around a longitudinal bar, or formed in one or two

lap spliced with a Class B splice (lap of 131J ), or <>nr·hrof·P.I

in accordance with Section 412.14.

407.13 SHRINKAGE AND TEMPERATURE REINFORCEMENT 407.13.1 Reinforcement for shrinkage and +"'n'npr~T1l stresses normal to flexural reinforcement shall be in structural slabs where the flexural reinforcement in one direction only.

Shrinkage and temperature rei shall be provided in accordance with either 407.l3.2 or 407.13.3 below.

407.13.1. 1

407.11.5.3 Ties shall be arranged such that every comer and alternate longitudinal bar shall have lateral support provided by the comer of a tie with an included


CONCRETE

407.13.1.2 Where shrinkage and temperature movements are significantly restrained, the requirements of Sections 408.3.4 and 409.3.7 shall be considered. 407.13.2 Deformed reinforcement conforming to Section 403.6.3 used for shrinkage and temperature reinforcem~nt shall be provided in accordance with the following: 407.13.2.1 Area of shrinkage and temperature reinforcement shall provide at least the following ratios of reinforcement area to gross concrete area, but not less than 0.0014:

1. 2.

3.

Slabs where Grade 275 or 345 deformed bars are used .......................... 0.0020 Slabs where Grade 415 deformed bars or welded wire fabric (smooth or deformed) are used ................................ 0.0018 Slabs where reinforcement with yield stress exceeding 415 MPa measured at a yield strain of 0.35 percent is used ................................................ .0.0018 x415

h 407.13.2.2 Shrinkage and temperature reinforcement shall be spaced not farther apart than five times the slab thickness, or 450 mm. 407.13.2.3 At all sections where required, reinforcement for shrinkage and temperature stresses shall develop the specified yield strength h in tension in accordance with Section 412. 407.13.3 Prestressing tendons conforming to Section 403.6.5 used for shrinkage and temperature reinforcement shall be provided in accordance with the following: 407.13.3.1 Tendons shall be proportioned to provide a minimum average compressive stress of 1 MPa ori gross concrete area using effective prestress, after losses, in accordance with Section 418.7. 407.13.3.2 Spacing of prestressed tendons shall not exceed 1.8 meters. 407.13.3.3 When the spacing of prestressed tendons exceeds 1.4 meters, additional bonded shrinkage and temperature reinforcement conforming with Section 407.13.2 shall be provided between the tendons at slab edges extending from the slab edge for a distance equal to the tendon spacing.

4-23

407.14 REQUIREMENTS FOR STRUCTURAL INTEGRITY 407.14.1 In the detailing of reinforcement and connections, members of a structure shall be effectively tied together to improve integrity ofthe overall structure. 407.14.2 For cast-in-place construction, the following shall constitute minimum requirements: 407.14.2.1 In joist construction, at least one bottom bar shall be continuous or shall be spliced over the support with a Class A tension splice and at non-continuous supports be terminated with a standard hook. 407.14.2.2 Beams at the perimeter of the structure shall have at least one sixth of the tension reinforcement required for negative moment at the support and one quarter of the positive moment reinforcement required at midspan made continuous around the perimeter and tied with closed stirrups or stirrups anchored around the negative moment reinforcement with a hook having a bend of at least 135 degrees. Stirrups need not be extended through any joints. When splices are needed, the required continuity shall be provided with top reinforcement spliced at midspan and bottom reinforcement spliced at or near the support with Class A tension splices. 407.14.2.3 In other than perimeter beams, when closed stirrups are not provided, at least one-quarter of the positive moment reinforcement required at midspan shaIl be continuous or shall be spliced over the support with a Class A tension splice and at non continuous supports be terminated with a standard hook. 407.14.2.4 413.4.8.5.

For two-way slab construction, see Section

407.14.3 For precast concrete construction, tension ties shall be provided in the transverse, longitudinal, nori vertical directions and around the perimeter of the stt1lcturt to effectively tie elements together. The provisions 0[' Section 416.6 shall apply. 407.14.4 For lift-slab copstruction, see Sections 413.4 /S.U and 418.13.6.


A.NAL YSIS AND DESIGN

4-24

SECTION 408 - ANALYSIS AND DESIGN 408.1 As A'$ b d

Ee Es

Fe h In

Ve we' Wu

111 tt p

NOTATIONS

area of nonprestressed tension reinforcement, mm.

area of compression reinforcement, square millimeters. width of compression face of member, mm. distance from extreme compression fiber to centroid oftension reinforcement, mm. modulus of elasticity of concrete, megapascals. See Section 408.6.1. modulus of elasticity of reinforcement, megapascals. See Sections 408.6.2 and 408.6.3. spscified compressive strength of concrete, megapascals. specified yield strength of nonprestressed reinforcement, megapascals. clear span for positive moment or shear and average of adjacent clear spans for negative moment. nominal shear strength provided by concrete. unit weight of concrete, kilograms per cubic meter. . factored load per unit length of beam or per unit area of slab. factor defined in Section 410.3.7.3. net tensile strain in extreme tension steel at nominal strength. ratiQofnonprestressed tension reinforcement.

A/bd p'

ratio of nonprestressed compression reinforcement.

Ph

A'/bd rei~f'o~cement ratio producing balanced strain

¢

. conditions, See Section 410.4.2. .strength-reduction factor. See Section 409.4.

" :_:~08.2 DESIGN METHODS 408.1.1 In design of structural concrete, members shall be propori.io~ed· . for adequate strength in accordance with provisions Of this chapter, using load factors and strength reduction factors ¢ specified in Section 409. 408.2.2 Nonprestressed reinforced concrete members shall be pernlltted to be designed using the provisions of Section 426. 408.2.3 Design of reinforced concrete using Section 425 shall be permitted.

408.3

LOADING

408.3.1 Design provisions of this code are based on the assumption that structures shall be designed to resist all applicable loads. 408.3.2 Service loads shall be in accordance with Chapter 2 with appropriate live load reductions as permitted therein. 408.3.3 In design for wind and earthquake loads, integral structural parts shall be designed to resist the total lateral loads. 408.3.4 Consideration shall be given to effects of forces due to prestressing, crane loads, vibration. impact, shrinkage, temperature changes, creep, expansion of shrinkage-compensating concrete and unequal settlement of supports.

408.4

METHODS OF ANALYSIS

408.4.1 All members of frames or continuous construction shall be designed for the maximum effects of factored loads as determined by the theory of elastic analysis, except as modified by Section 408.4. It is permitted to simplifY the design by using the assumptions specified in Sections 408.7 through 408.10. 408.4.2 Except for prestressed concrete, approximate methods of frame analysis may be used for buildings of usual types of construction, spans and story heights, 408.4.3 As an alternate to frame analysis, the following approximate moments and shears shall be permitted to be used in design of continuous beams and one-way slabs (slabs reinforced to resist flexural stresses in only one direction), provided: 1.

There are two or more spans,

2.

Spans are approximately equal, with th~ larger of two adjacent spans not greater than the shorter by more than 20 percent,

3.

Loads are uniformly distributed,

4.

Unit live load does not exceed three times unit dead load, and

5,

Members are prismatic.


CONCRETE

POSITIVE MOMENT: End spans w" 1/11 I Discontinuous end unrestrained Discontinuous end integral with support ,. ... ,. ................................ w"I/1I4

Interior spans ,. ,. ........................ ,. ...... .

NEGATIVE MOMENT: at exterior face of first interior support Two spans .. ,........................................ w,J/19 More than two spans .......................... wuln21I0 at other faces of interior supports ............ at face of all supports for: slabs with spans not exceeding 3 meters; and beams where ratio of sum of column stiffnesses to beam stiffness exceeds eight at each end of the span .................. at interior face of exterior support for

members built integrally with

supports:

where support is a spandrel beam ....... where support is a column ..................

wJn2111

wJ/124

w,//116

408.5 REDISTRIBUTION OF NEGATIVE MOMENTS IN CONTINUOUS NONPRESTRESSED FLEXURAL MEMBERS 408.5.1 Except where approximate values for moments are used, it is permitted to increase or decrease negative moments calculated by elastic theory at supports of continuous flexural members for any assumed loading arrangement by not more than

.

\.

Ph

percent

j

408.5.2 The modified negative moments shall be used for calculating moments at sections within the spans. 408.5.3 Redistribution of negative moments shall be made only when the section, at which moment is reduced, is so designed that P or (P PI is not greater than 0.50 {lb, where

Pb

= 0.85Pl f' c

Iv

( 600 l600+ f"

J

National

408.6

for

MODULUS OF ELASTICITY

408.6.1 Modulus .of elasticity Ec for concrete s~all be permitted to be taken as w/ 50.043..Jf'c (in MPa) for values of We between 1,500 and 2,500 kg/m 3 For normal. weight concrete, Ec shall be permitted to betaken as 4700 ..J f ' c ' . 408.6.2 Modulus of elasticity Es for nonprestressed reinforcement shall be permitted to be taken as 20'0,000 MPa. 408.6.3 Modulus of elasticity Es for prestressing tendons shall be determined by tests or supplied by the manufacturer.

408.7

at face of first interior support .............. 1. 15 w"l j2

at face of all other supports ........................ wulj2

( ~I·'\

408.5.4 For criteria on moment redistribution prestressed concrete members, see Section418.1IA.

"';i",

wJ/!l2

SHEAR:

20.1

4-25

STIFFNESS

408.7.1 Use of any set of reasonable assumptions shall be permitted for computing relative flexural and torsional stiffnesses of columns, walls, floors and roof systems. The assumptions adopted shall be consistent throughout· ., analysis. 408.7.2 Effect of haunches shall be considered both in determining moments and in design of memb.ers.

408.8

SPAN LENGTH

408.8.1 Span length of members not built integrally with supports shall be considered the clear span plus depth of member, but need not exceed distance between centers of . . l~" supports. 408.8.2 In analysis of frames or continuous construction for determination of moments, span length shall be taken as the distance center to center of supports. 408.8.3 For beams built integrally with supports, design on the basis of moments at faces of support' shall be permitted. 408.8.4 It shall be permitted to analyze solid or ribbed slabs built integrally with supports, with clear spans not more than 3 meters, as continuous slabs on knife edge supports with spans equal to the clear spans of the slab and width of beams otherwise neglected.

(408-1 )

Stru.ctur~

Code of the Philippine!! Volume 1

ANALVSIS AND DESIGN

4-26

408.9

408.11.3 For beams with a slab on one side only, the effective overhanging flange width shall not exceed:

COLUMNS

408.9.1 Columns shall be designed to resist the axial forces from factored loads on all floors or roof and the maximum moment from factored loads on a single adjacent span of the floor or roof under consideration. Loading condition giving the maximum ratio of moment to axial load shall also be considered. 408.9.2 In frames or continuous construction, consi deration shall be given to the effect of unbalanced floor or roof loads on both exterior and interior columns and of eccentric loading due to other causes. 408.9.3 In computing gravity load moments in columns, it shall be permitted to assume far ends of columns built integrally with the structure to be fixed.

t

408.9.4 Resistance to moments at any floor or roof level shall be provided by distributing the moment between columns immediately above and below the given floor in proportion to the relative column stiffnesses and conditions of restraint.

408.10 ARRANGEMENT OF LIVE LOAD 408.10.1 It is permissible to assume that: I. 2.

the live load is applied only to the floor or roof under consideration, and the far ends of columns built integrally with the structure are considered to be fixed.

408.10.2 It is permitted to assume that the arrangement of live load is limited to combinations of: I. Factored dead load on all spans with full-factored live load on two adjacent spans, and 2.

Factored dead load on all spans with full-factored live load on alternate spans.

408.11

T-BEAM CONSTRUCTION

408.10.1 In· T-beam construction, the flange and web shall be built integrally or otherwise effectively bonded together. ..f08.11.2 Width of slab effective as a T-beam flange shall not exceed one fourth the span length of the beam, and the etfective overhanging slab width on each side of the web shall not exceed: Eight times the slab thickness, or One haif the clear distance to the next web.

1. 2.

3.

One twelfth the span length ofthe beam, Six times the slab thickness, or One half the clear distance to the next web.

408.11.4 Isolated beams, in which the T-shape is used to provide a flange for additional compression area, shall have a flange thickness not less than one half the width of web and an effective flange width not more than four times the width of web. 408.11.5 Where primary flexural reinforcement in a slab that is considered as a T-beam flange (excluding joist construction) is parallel to the beam, reinforcement perpendicular to the beam shall be provided in the top of the slab in accordance with the following: 408.11.5.1 Transverse reinforcement shall be designed to carry the factored load on the overhanging slab width assumed to act as a cantilever. For isolated beams, the full width of overhanging flange shall be considered. For other T-beams, only the effective overhanging slab width need be considered. 408.11.5.2 Transverse reinforcement shall be spaced not farther apart than five times the slab thickness or 450 mm.

408.12 JOIST CONSTRUCTION 408.12.1 Joist construction consists of a monolithic combination of regularly spaced ribs and a top slab arranged to span in one direction or two orthogonal directions. 408.12.2 Ribs shall not be less than 100 mm in width and shall have a depth of not more than three and one-half times the minimum width of rib. 408.12.3 mm.

Clear spacing between ribs shall not exceed 750

408.12.4 Joist construction not meeting the limitations of Sections 408.12.1 through 408.12.3 shall be designed as slabs and beams . 408.12.5 When permanent burned clay or concrete tile fillers of material having a unit compressive strength at least equal to that of the specified strength of concrete in the joists are used: 408.12.5.1 For shear and negative-moment strength computations, it shall be permitted to include the vertical

Association of Structural Enaineers of the Philippines

CONCRETE

shells of fillers in contact with ribs. Other portions of fillers shall not be included in strength computations. 408.12.5.2 Slab thickness over permanent fillers shall not be less than one twelfth the clear distance between ribs nor less than 40 mm. 408.12.5.3 In one-way joists, reinforcement normal to the ribs shall be provided in the slab as required by Section 407.13.

4-27

SECTION 409 - STRENGTH AND SERVICEABILITY REQUIREMENTS 409.1

Ag gross area of section, mm2 A's = area of compression reinforcement, mm 2 . b

width of compression face of member, mm distance from extreme compression fiber to neutral axis in millimeters. D dead loads, or related internal moments and forces. d = distance from extreme compression fiber to centroid of tension reinforcement, mm. d' = distance from extreme compression fiber to centroid of compression reinforcement, mm. d, = distance from extreme tension fiber to centroid of tension reinforcement, mm. dt distance from extreme compression fiber to extreme tension steel, mm. E = load effects of earthquake, or related internal moments and forces. Ec = modulus of elasticity of concrete, MPa. See Section 408.6.1 F loads due to weight and pressures of fluids with well defined densities and controllable maximum heights, or related internal moments and forces. Pc = specified compressive strength of concrete, MPa.

c

408.12.6 When removable forms or fillers not complying with Section 408.12.5 are used: 408.12.6.1 Slab thickness shall not be less than one twelfth the clear distance between ribs, or less than 50 mm. 408.11.6.2 Reinforcement normal to the ribs shall be provided in the slab as required for flexure, considering load concentrations, if any, but not less than required by Section 407. 13. 408.12.7 Where conduits or pipes as permitted by Section 406.3 are embedded within the slab, slab thickness shall be at least 25 mm greater than the total overall depth of the conduits or pipes at any point. Conduits or pipes shall not impair significantly the strength of the construction. 408.12.8 For joist construction, contribution of concrete to shear strength Vc is permitted to be 10 percent more than that specified in Section 411. It shall be permitted to increase shear strength using shear reinforcement or by widening the ends of the ribs.

=

~f' c = square root of specified compressive strength of

let /r

.h 408.13 SEPARATE FLOOR FINISH 408.13.1 A floor finish shall not be included as part of a structural member unless placed monolithically with the floor slab or designed in accordance with requirements of Section 417. 408.13.2 It shall be permitted to consider all concrete floor finishes may be considered as part of required cover or total thickness for non structural considerations

NOTATIONS

H

=

h Ier

Ie

!" L /

In

Al" !t.4cr =

concrete, MPa. average splitting tensile strength of lightweight i ag.,.gregate concrete, MPa. modulus ofrupture of concrete, MPa. specified yield strength of nonprestressed reinforcement, MPa. loads due to weight and pressure of soil, water in soil, or other materials, or related internal moments and forces. overall thickness of member, mm. moment of inertia of cracked section transformed to concrete, mm4. effective moment of inertia for computation of deflection, mm4 moment of inertia of b'TOSS concrete section about 4 centroidal axis, neglecting reinforcement, mm live loads, or related internal moments and forces. span length of beam or one-way slab, as defined in Section 408.8; clear projection of cantilever, mm. length of clear span in long direction of two-way construction, measured face to face of supports in slabs without beams and face to face of beams or other supports in other cases. maximum moment in member at stage deflection is computed. cracking moment. See Equation (409-8).


STRI;NGTH AND SERVICEABIUTY REQUIREMENTS

4-28

"

"

:::::

'hi,

,,',

nominal axial load strength at balanced strain

conditions. See Section 41004.2.

nominal axial load strength at given eccentricity.

P" cumulative effects of temperature, creep, shrinkage, T differential settlement and shrinkage compensating concrete. required strength to resist factored loads or related U internal moments and forces. wind load, or related internal moments and forces. W weight of concrete, kg/m3 . distance from centroidal axis of gross section, neglecting reinforcement, to extreme fiber in tension. ratio ot flexural stiffness of beam section to flexural a stiffness of a width of slab bounded laterally by center line of adjacent panel (if any) on each side of beam~ See Section 413. average value of (l': for all beams on edges of a panel. ratio of clear spans in long-to-short direction of two-way slabs. = time-dependent factor for sustained load. See Section 409.6.2.5. ~ = net tensile strain in extreme tension steel at nominal strength. A = multiplier for additional long-time deflection as defined in Section 409.6.2.5. p ratio of nonprestressed tension reinforcement, A/bd. p' reinforcement ratio for nonprestressed compression reinforcement, A '/bd Ph reinforcement ratio producing balanced strain conditions. See Section 423.10.3.2.

¢ ~ strength-reduction factor. See Section 409.4.

409.2

GENERAL

409.2.1 Structures and structural members shall be designed to have design strengths at all sections at least equal to the required strengths calculated for the factored loads and forces in such combinations as are stipulated in this code. 409.2.2 Members also shall meet all other requirements of this code to ensure adequate performance at service load levels.

409.3

409.3.2 If resistance to structural effects of a specified wi.nd load W are included in design, the following combinations of D, L and W shall be investigated to determine the greatest required strength U: U = 0.75 (lAD -+ 1.7 L + 1.7 W)

(409-2)

where load combinations shall include both full value and zero value of L to determine the more severe condition, and U

0.9D -+ 1.3 W

(409-3)

but for any combination ofD, L and W, required strength U shall not be less than Equation (409-1). 409.3.3 If resistance to specified earthquake loads or forces E are included in design, the following combinations ofD, L and E shall be investigated to determine the greatest required strength U:

U

=

l.3D + 1.1L + 1.1E

(409-4)

where load combinations shall include both full value and zero value of L to determine the more severe condition, and

U

0.9D + 1.1E

(409-5)

but for any combination of D, L and E, required strength U shall not be less than Equation (409-1). 409.3.4 If resistance to earth pressure H is included in design, required strength U shall be at least equal to U

lAD+1.7L+1.7H

(409-6)

except that where D or L reduces the effect of H, 0.9D shall be substituted for lAD and zero value of L shall be used to determine the greatest required strength U. For any combination of D, L and H, required strength U shall not be less than Equation (409-1). 409.3.5 If resistance to loadings due to weight and pressure of fluids with well-defined densities and controllable maximum heights F is included in design, such loading shall have a load factor of 1.4 and be added to all loading combinations that include live load. 409.3.6 If resistance to impact effects is taken into account in design, such effects shall be included with live load L.

REQUIRED STRENGTH

409.3.1 Required strength U to resist dead load D and live load L shall be at least equal to: U 104 D + 1.7 L (409-1)

409.3.7 Where structural effects T of differential settlement, creep, shrinkage, expansion of shrinkage compensating concrete or temperature change may be significant in design, required strength U shall be at least equal to


CONCRETE

U=0.75(I.4D + l.4T+ l.7L)

(409-7)

but required strength U shall not be less than

U

1.4 (D + 7)

(409-8)

Estimations of differential settlement, creep, shrinkage, expansion of shrinkage-compensating concrete or tempe rature change shall be based on a realistic assessment of such effects occurring in service.

409.3.8 Load Factors. For post-tensioned anchorage zone design, a load factor of 1.2 shall be applied to the maximum tendon jacking force.

409.4:.1 Design strength provided by a member, its connection to other members and its cross sections, in terms of flexure, axial load, shear and tension, shall be taken as the nominal strength calculated in accordance with requirements and assumptions of this chapter, multiplied by a str~ngth-reduction factor ¢; in Sections 409.4.2 and 409.4.4. If the structural framing includes primary 409.4.1.1 members of other materials proportioned to satisfy the load factor combinations of Section 2.4 of ASCE 7, it shall be permitted to proportion the concrete members using the set of strength-reduction factors, ¢;, listed in Section 425 and the load-factor combinations in ASCE 7.

409.4.2 Strength-reduction factor. Strength-reduction factor ¢; Shall be as follows: Flexure, without axial load

than 0.70, ¢; shall be permitted to be increased linearly to 0.90 as ¢; Pn decreases from 0.10 /,c Ag to zero. For other reinforced members, ¢; shall be permitted to be increased linearly to 0.90 as ¢; P" decreases from O.lO/,c A~ or ¢;Pb , whichever is smaller, to zero.

409.4.2.3 Shear and torsion (See also Section 409.4.4 for shear walls and frames in Seismic Zones 4) ................................................. 0.85 409.4.2.4 Bearing on concrete (except for post-tensioning anchorage zones) ......................... 0.70 409.4.2.5

Post-tensioned anchorage zones .. 0.85

409.4.3 Development lengths specified in Section 412 do not require a ¢; factor.

409.4 DESIGN STRENGTH

409.4.2.1

4-29

......

0.90

Axial load and axial load with flexure. (For 409.4.2.2 axial load with flexure, both axial load and moment nominal strength shall be multiplied by appropriate single value of ¢;.) Axial tension and axial tension with flexure .........

0.90

Axial compression and axial compression with flexure: with spiral reinforcement Members conforming to Section 410.10.3 ........ .......... 0.75 Other reinforred members 0.70

409.4.4 In Seismic Zone 4, strength-reduction factors ¢; shall be as given above except for the following: 409.4.4.1 The shear strength-reduction factor shall be 0.6 for the design of walls, topping slabs used as diaphragms over precast concrete members and structural framing members, with the exception of joints, if t~eir nominal shear strength is less than the shear correspondmg to development of their nominal flexural strength. .The nominal flexural strength shall be detemuned corresponding to the most critical factored axial lo~ds including earthquake effects. The shear strength reductIOn factor for joints shall be 0.85. 409.4.4.2 Reinforcement used for diaphragm chords or collectors placed in topping slabs over precast concrete members shall be designed using a strength-reduction factor of 0.6. 409.4.5 Strength reduction factor ¢; for flexure, compression, shear and bearing of structural plain concrete in Section 422 shall be 0.65.

409.5 DESIGN STRENGTH FOR REINFORCEMENT Designs shall not be based on a yield strength of reinforcement J;, in excess of 550 MPa, except for prestressing tendons.

except that for low values of axial oompression, ¢; shall be t>ermitted to be increased in accordance with the following: For members in which h does not exceed 415 MPa, with sYlllmetric reinforcement, and with (h - d' - dJIh not less


STRENGTH AND SERVICEABILITY REQUIREMENTS

4-30

409.6 CONTROL OF DEFLECTIONS

where

409.6.1 Reinforced concrete members subject to flexure shall be designed to have adequate stiffness to limit deflections or any deformations that affect strength or serviceability ~f a structure adversely.

Mcr=

y,

(409-10)

and for normal-weight concrete

f, 409.6.2

f,I g

O.'l{"?c

(409-11)

One-Way Construction (nonprestressed).

Minimum thickness stipulated in Table 409.6.2.1 409-1 shall apply for one-way construction not supporting or attached to partitions or other construction likely to be d;nnaged by large deflections, unless computation of deflection indicates a lesser thickness may be used without adverse effects.

Table 409-1 - Minimum Thickness of Nonprestressed Beams or One-Way Slabs Unless Deflections are Computed Minimum Thickness. h Simply Supported

Member

One end continuous

Both ends continuous

Cantilever

Members not supporting or attached to partitions or other construction likely to be damaged by large deflections

_I 20

Solid oneway slabs

_I 24

-.L 28

-' 10

Beams or _I _I _I ribbed one 21 18.5 8 16 way slabs Values given shaH be used directly for members with normal weight concrete (we = 2,300 kgfm~ and Grade 415 reinforcement. For other conditions, the values shall be modified as follows: a) For structural lightweight concrete having unit weight in the range 1,500-2,000 kg.m 3 , the values shall be multipfied by (1.65 - 0.0003we) but not less than 1.09, 3 where We is the unit weight in kgfm • b) For h other than 415 MPa, the values shall be multiplied by (0.4 + f/700)

409.6.2.2 mere deflections are to be computed, deflections that occur immediately on application of load shall be computed by usual methods or formulas for elastic deflections, considering effects of cracking and reinforcement on member stiffness. 409.6.2.3 Unless stiffness values are obtained by a more comprehensive analysis, immediate deflection shall be computed with the modulus of elasticity for concrete as specified in Section 408.6.1 (normal-weight .or lightweight concrete) and with the effective moment of inertia as follows, but not greater than I g •

I,

~ (~: JI, +[.- (~: J}

(409-9)

When lightweight aggregate concrete is used, one of the following modifications shall apply: 1.

2.

Whenfct is specified and boncrete is proportioned in accordance with Section 405.3, f, shall be modified by substituting 1.8!ct fo~c but the value of 1.8/ct shall not exceechJ7c When!ct is not specified, Ir shall be multiplied by 0.75 for "all-lightweight" concrete, and 0.85 for "sand-lightweight" concrete. Linear interpolation shall be permitted to be used when partial sand replacement is used.

409.6.2.4 For continuous members, effective moment of inertia shall be permitted to be taken as the, average of values obtained from Equation (409-9) for the critical positive and negative moment sections. For prismatic members, effective moment of inertia shall be permitted to be taken as the value obtained from Equation (409-9) at midspan for simple and continuous spans, and at support for cantilevers. 409.6.2.5 Unless values are obtained by a more . comprehensive analysis, additional longtime deflection resulting from creep and shrinkage of flexural members (normal-weight or lightweight concrete) shall be determined by multiplying the immediate deflection caused by the sustained load considered, by the factor A,

=

1 + 50p'

(409-12)

where p' shall be the value at midspan for simple and continuous spans, and at support for cantilevers. It is permitted to assume the time-dependent factor .; for sustained loads to be equal to Five years or more ........ .,..... 2.0

12 months ...................... .,.... 1.4

Six months ............................. 1.2

Three months ... .,....................... 1.0

409.6.2.6 Deflection computed in accordance with this section shall not exceed limits stipulated in Table 409-2. 409.6.3

Two-Way Construction (non prestressed)

This section shall govern the minimum 409.6.3.1 thickness of slabs or other two-way construction designed


CONCRETE

accordance with the proVISIOns of Section 413 and "Co·nfonn'tng with the requirements of Section 413.7.1.2. thickness of slabs without interior beams sparming between the supports on all sides shall satisfy the reaUlnlmE:nts of Section 409.6.3.2 or 409.6.3.4. Thickness slabs with beams spanning between the supports on all shall satisfy the requirements of Section 409.6.3.3 or 409.6.3.4. For slabs without interior beams sparming 409.6.3.2 between the supports and having a ratio of long to short span not greater than 2, the minimum thickness shall be in accordance with the provisions of Table 409-3 and shall not be less than the following values: 1. Slabs without drop panels as defined in Sections 413.4.7.1 and 413.4.7.2 ...... 125 mm 2. Slabs with drop panels as defined in Sections 413.4.7.1 and413.4.7.2 .............. 100mm 409.6.3.3 For slabs with beams spanning between the supports on all sides, the minimum thickness shall be as follows: 1. For a", equal to or less than 0.2, the provisions of Section 409.6.3.2 shall apply.

. 2.

For a", greater than 0.2 but not greater than 2.0, the thickness shall not be less than

J

h

In [ 0.8 . + -fy 1500 .

- .

Tabl e 4092

Ii

4-31

but not less than 125 mm. 3.

For a", greater than 2.0, the thickness shall not be less than

In h ==

4.

[O.S + ~J 1500

(409-14)

36+9p

but not less than 90 mm. At discontinuous edges, an edge beam shall be provided with a stifihess ratio a not less than 0.80; or the minimum thickness required by Equation (409-13) or (409-14) .shall be increased by at least 10 percent in the panel with a discontinuous edge.

409.6.3.4 Slab thickness less than the minimum thickness required by Sections 409.6.3.1, 409.6.3.2 and 409.6.3.3 shall be permitted to be used if shown by computation that the deflection will not exceed the limits stipulated in Table 409-2. Deflections shall be computed taking into account size and shape of the panel, conditions of support, and nature of restraints at the panel edges. The modulus of elasticity of concrete Ec shall be as ~ecified in Section 408.6.1. The effective moment of inertia shall be that given by Equation (409-9); other values shall be permitted to be used if they result in computed deflections in reasonable agreement with the results of comprehensive tests. Additional long-term deflection shall be computed in accordance with Section 409.6.2.5.

(409-13)

MaXlmum p ermissl· bl e C omputed Deflectlons

Type of Member

Deflection to be considered

Deflection Limitation

i

Flat roofs not supporting or attached to nonstructural elements likely to be damaged by large deflections Floors not supporting or attached to non-structural elements likely to be damaged by large deflections Roof or floor construction supporting or attached to non-structural elements likely to be damaged by large deflections Floor or floor construction supporting or attached to non-structural elements not likely to be damaged by large deflections 1

Immediate deflection due to live load, L • Immediate deflection due to live load, L That part of the total deflection occurring after attachment of nonstructural elements (sum of the long-term deflection due to all sustained loads and the immediate deflection due to any additional live load) 2

Limit not intended to safeguard against ponding. Ponding should be checked by suitable calculations of deflection, including added deflections due to ponded water. and considering long camber. construction term effects of all sustained loads. tolerances. and reliability of provisions for drainage. Long term deflection shall be determined in accordance with 409.6.2.5 or 409.6.4.2. but may be reduced by amount of deflection calculated to occur before attachment of nonstructural elements. The amount shaH be determined on basis of accepted engineering data relating to time-deflection characteristics of members similar to those being considered.

3

4

I

J

180 I

360

L

480 I

4

240

Umit may be exceeded if adequate measures are taken to prevent damage to supported or attached elements. But not greater than tolerance provided for nonstructural elements. Limit may be exceeded if camber is provided so that total deflection minus camber does not exceed Hmit.

National Structural Code of ilia Philippines. Volume 1

u:n

.. t,

STRENGTH AND SERVICEABILITY REQUIREMENTS .

4-32

Table 409-3 - Minimum Thickness of Slabs

Without Interior Beams

Without drop panels] With drop panels 2

i

Yield strength

fy MPa]

E,.1erior panels

beam

In 33

In 36

Ln

I. 33

Ln

415

In 30

520

In

2 3

with edge

without edge beam

275

1

Interior panels

28

i I

l

In

TI

l

I

In 36

36

I

I

in

40

i

I i

In 40

i

In 33

33 Ln 31

In 36

In 36

l

l

For values of reinforcement yield strength between the values given in the table, minimum thickness shall be determined by linear interpolation. Drop panels is defined in 413.4.7.1 and 413.4.7.2 Slabs with beams between columns along exterior edges. The value of a for the edge beam shall not be less than O.S.

408.6.4

In

a prestressed

409.6.5.2 Unsbored construction. If the thickness of a nonprestressed precast flexural member meets the requirements of Table 409-1, deflection need not be computed. If the thickness of a nonprestressed composite member meets the requirements of Table 409-1, it is not required to compute deflection occurring after the member becomes composite, but the long-time deflection of the precast member shall be investigated for magnitude and duration of load prior to beginning of effective composite action.

Interior panels

Exterior panels without With edge edge beam . beam'

!

components, and of axial creep effects concrete member.

I

409.6.5.3 Deflection computed in accordance with this section shall not exceed limits stipulated in Table 409 2.

Prestressed Concrete Construction

409.6.4.1 For flexural members designed in accordance with provisions of Section 418, immediate deflection shall be computed by usual methods or formulas for elastic deflections, and the moment of inertia of the gross concrete section shall be permitted to be used for uncracked sections. 409.6.4.2 Additional long-time deflection of prestressed concrete members shall be computed taking into account stresses in' concrete and steel under sustained load and including effects of creep and shrinkage of concrete and relaxation of steel.

Deflection computed in accordance with this section shall not exceed limits stipulated in Table 409

409.6.4.3 2.

409.6.5 . Composite Construction

Shored construction. If composite flexural members are supported during construction so that, after removal of temporary supports, dead load is resisted by the full composite section, it shall be permitted to consider the composite member equivalent to a monolithically cast member for computation of deflection. For nonprestressed members, the portion of the member in compression shall determine whether values in Table 409-1 for normal-weight or lightweight concrete shall apply. If deflection is computed, account shall be taken of curvatures resulting from differential shrinkage of precast and cast-in-place

409.6.5.1


CONCRETE

SECTION 410 - FLEXURE AND .AXIAL LOADS 410.1 NOTATIONS a

=depth of equivalent rectangular stress block as defined in Section 410.3.7.1, mm. =area of core of spirally reinforced compression member measured to outside diameter of spiral, mm2 . · =gross area 0f SectIOn, mm2 =area of nonprestressed tension reinforcement, square millimeters. = minimum amount of flexural reinforcement, mm2. See Section 410.6. =area of skin reinforcement per unit height in one side face, mm2 1m. See Section 410.7.7. =total area of lon~itudinal reinforcement (bars or steel shapes), mm . = area of structural steel shape, pipe or tubing in a • • 2 compOSIte SectiOn, mm .. 2 = loaded area, mm . = the area of the lower base of the largest frustum of a pyramid, cone, or tapered wedge contained wholly within the support and having for its upper base the loaded area, and having side slopes of 1 unit vertical in 2 units horizontal (50% slope), ,

mrn2 . width of compression face of member, mm. web width, mm. = distance from extreme compression fiber to neutral axis, mm. = clear cover from the nearest surface in tension to the surface of the flexural tension reinforcement, mm. = a factor relating actual moment diagram to an equivalent uniform moment diagram. = distance from extreme compression fiber to centroid oftension reinforcement, mm. = thickness of concrete cover measured from extreme tension fiber to center of bar or wire located closest thereto, mm. distance from extreme compression fiber to extreme tension steel, mm. = modulus of elasticity of concrete, MPa See Section 408.6.1. modulus of elasticity of reinforcement, MPa. See Sections 408.6.2 and 408.6.3. = flexural stiffiless of compression member. See Equation (410-12) and (410-13). = specified compressive strength of concrete, MPa calculated stress in reinforcement at service loads, MPa. specified yield strength of nonprestressed reinforcement, MPa.. =

d

EI

h

4-33

h

=

Q

= =

overall dimension of member in direction of action considered, mm. Ig = moment of inertia of gross concrete section about centroidal axis, neglecting reinforcement, mm4 I.e = moment of. inertia.of reinforcement about centroidal axis of member cross section, mm4 1/ moment ofinertia of structural steel shape, pipe or tubing about centroidal axis of composite member cross section, mm4. k = effective length factor for compression members. Ie = length ofa compression member in a frame, measured from center to ,center of the joints in the frame. lu = unsupported length of compression member. Me factored moment to be used for design of compression member. M. moment due to loads causing appreciable sway. Mu = faqored moment at section. M] == smaller factored end moment on a compression member, positive if member is bent in single curvature, negative if bent in double curvature. Min. = factored end moment on a compression member at the end at which MJ acts, due to loads that cause no appreciable sidesway, calculated using a first order elastic frame analysis. M J• = factored end moment on compression members at the end at which M J acts, due to loads that cause appreciable sidesway, calculated using a first-order elastic frame analysis. M2 larger factored end moment on compression member, always positive. M 2,min = minimum value ofM 2 . M 2n• = factored end moment on compression member at the end at which M2 acts, due to loads that cause no appreciable sidesway, calculated using a first order elastic frame analysis. M 2• factored end moment on compression member at the end at which M2 acts, due to loads that cause appreciable sidesway, calculated using a first-order elastic frame analysis. Pb nominal axial load strength at balanced strain conditions. See Section 410.4.2. Pe critical load. See Equation (410- J I). Pl'I = nominal axial load strength at given eccentricity. Po nominal axial load strength at zero eccentricity, Pu = factored axial load at given eccentricity

r s

~

¢>P".

stability index for a story, See Section 410.12.4. radius of gyration of cross section of a compression member. = maximum center-to-center. spacing of flexural tension reinforcement neare.st •.'to the extreme tension face, mm (where thei~ only one bar or wire nearest to the extremetensionface, s is the maximum width ofthe extreme tension face.) factored horizontal shear in a story.

is

Vu


FLEXURE AND AXIAL LOADS

z

/3J

Pd

,10

8ns

t>: Bt

p

Po

Ps

¢> ¢> k

= quantity

limiting distribution of flexural reinforcement. See Section 410.7. = factor defined in Section 410.3 .7.3. = (a) for non~sway frames, Pd is the ratio of the maximum factored axial sustained load to the maximum factored axial load associated with the same load combination; = (b) for sway frames, except as required in Item (c) of this definition, Pd is the ratio of the maximum factored sustained shear within a story to the maximum factored shear in that story; = (c) for stability checks of sway frames carried out in accordance with Section 410.14.6, Pd is the ratio of the maximum factored sustained axial load to the maximum factored axial load. relative lateral deflection between the top and bottom of a story due to Vu, computed using a first~ order elastic frame analysis and stiffness values satisfying Section 410.12.1. morqent magnification factor for frames braced agaitst sidesway to reflect effects of member curvature between ends of compression members. moment magnification factor for frames not braced against sidesway to reflect lateral drift resulting from lateral and gravity loads. net tensile strain in extreme tension steel at nominal strength. = ratio·ofnonprestressed tension reinforcement. = Af{lbd = reinforcement ratio producing balanced strain conditions. See Section 410.4.2. ratio of volume of spiral reinforcement to total volume of core (out~to~ut of spirals) of a spirally reinforced compression member. = strength~reduetion factor. See Section 409.4. = stiffness reduction factor

410.2 SCOPE Provisions of Section 410 shall apply for design of members subject to flexure or axial loads or to combined flexure and axial loads.

410.3 DESIGN ASSUMPTIONS 410.3.1 Strength design of members for flexure and axial loads shall be based on assumptions given in Sections 410.3.2 through 410.3.7 and on satisfaction of applicable conditions of equilibrium and compatibility of strains. 410.3.2 Strain ih reinforcement and concrete shall be assumed directly proportional to the distance from the neutral axis, except, for deep flexural members with overall

depth-t~clear-span ratios greater than two fifths for continuous spans and four fifths for simple spans, a nonlinear distribution of strain shall be considered. See Section 410.8.

410.3.3 Maximum usable strain at extreme concrete compression fiber shall be assumed equal to 0.003. 410.3.4 Stress in reinforcement below specified yield strength.!;, for grade of reinforcement used shall be taken as Es times steel strain. For strains greater than that corresponding to .!;., stress in reinforcement shall be considered independent of strain and equal to./y. 410.3.5 Tensile strength of concrete shall be neglected in axial and flexural calculations of reinforced concrete, except where meeting requirements of Section 418.5. 410.3.6 Relationship between concrete compressive stress distribution and concrete strain shall be assumed to be rectangular, trapezoidal, parabolic or any other shape that results in prediction of strength in substantial agreement with results of comprehensive tests. 410.3.7 Requirements of Section 410.3.6 may be considered satisfied by an equivalent rectangular concrete stress distribution defined by the following: 410.3.7.1 Concrete stress of 0.85f'c shall be assumed uniformly distributed over an equivalent compression zone bounded by edges of the cross section and a straight line located parallel to the neutral axis at a distance a = Pi C from the fiber of maximum compressive strain. 410.3.7.2 Distance c from fiber of maximum strain to the neutral axis shall be measured in a direction perpendicular to the axis. 410.3.7.3 Factor Pi shall be taken as 0.85 for concrete strengths f'c up to and including 30 MPa. For strengths above 30 MPa, Pl shall be reduced continuously at a rate of 0.05 for each 7 MPa of strength in excess of 30 MPa, but /3J shall not be taken less than 0.65.

410.4 GENERAL PRINCIPLES AND REQUIREMENTS 410.4.1 Design~f cross section subject to flexure or axial loads or to combined flexure and axial loads shall be based on stress and strain compatibility using assumptions in Section 410.3. 410.4.2 Balanced strain conditions exist at a cross section when tension reinforcement reaches the strain corresponding to its specified yield strength./y just as


4-35

CONCRETE

CO:lcrete in compression reaches its assumed ultimate strl;lin of 0.003.

410.6 MlNlMUM RElNFORCEM~ENT OF FLEXURAL MEMBERS

410.4.3 For flexural members, and for members subject to combined flexure and compressive axial load when the design axial load strength rjJPn is less than the smaller of 0.10 f'c Ag or rjJPb, the ratio of reinforcement p provided shall not exceed 0.75 of the ratio Ph that would produce balanced strain conditions for the section under flexure without axial load. For members with compression reinforcement, the portion of Ph equalized by compression reinforcement need not be reduced by the 0.75 factor.

410.6.1 . At every section of a flexural member where tensile reinforcement is required by analysis, except as provided in Sections 410.6.2,410.6.3 and 410.6.4, the area As provided shall not be less than that given by:

As,min

410.6.2 For a statically determinate T-section with flange in tension, the area A•. min shall be equal to or greater than the smaller value given either by:

if

As,min = - - b",d

410.4.5 Design axial load strength rjJPn of compression members shall not be taken greater than the following:

2/,·

(410-4)

or Equation (410-3) with b", set equal to the width of the flange.

410.4.5.1 For nonprestressed members with spiral reinforcement confonning to Section 407.1 L 4 or composite members conforming to Section 410.17:

with

(410-3)

and not less than 1.4 bw d if;,

410.4.4 Use of compression reinforcement shall be permitted in conjunction with additional tension reinforcement to increase the strength of flexural members.

410.4.5.2 For nonprestressed members reinforcement conforming to Section 407.11.5:

Jf'c bwd 4 Iv

410.6.3 The requirements of Sections 410.6.1 and 410.6.2 need not be applied if at every section the area of tensile reinforcement provided is at least one-third greater than that required by analysis.

tie 410.6.4 For structural slabs and footings of uniform thickness, the minimum area of tensile reinforcement in the direction of span shall be the same as that required by Section 407. 13. Maximum spacing of this reinforcement shall not exceed the lesser of three times the thickness and 450mm.

410.4.5.3 For prestressed members, design axial load strength ¢lP" shall not be taken greater than 0.85 (for members with spiral reinforcement) or 0.80 (for members with tie reinforcement) of the design axial load strength at zero eccentricity rjJ PQ.

410.7 DISTRIBUTION OF FLEXURAL REINFORCEMENT IN BEAMS AND ONE WAY SLABS

410.4.6 Members subject to compressive axial load shall be designed for the maximum moment that can accompany the axial load. The factored axial load Pu ' at given eccentricity shall not exceed that given in Section 410.4.5. The maximum factored moment Mu shall be magnified for slenderness effects in accordance with Section 410.11.

410.7.1 This section prescribes rules for distribution of flexural reinforcement to control flexural cracking in beams and in one-way slabs (slabs reinforced to resist flexural stresses in only one direction). 410.7.2 Distribution of flexural reinforcement in two-way slabs shall be as required by Section 413.4.

410.5 DISTANCE BETWEEN LATERAL SUPPORTS OF FLEXURAL MEMBERS

410.7.3 Flexural tension reinforcement shall be well distributed within maximum flexural tension zones of a member cross section as required by Section 410.7.4.

410.5.1 Spacing of lateral supports for a beam shall not exceed SO times the least width b of compression flange or face.

410.7.4 The spacing s of reinforcement closest to a surface in tension shall not exceed that given by

410.5.2 Effects of lateral eccentricity of load shall be taken into account in detennining spacing of lateral supports.


s

of

95,OOQ _ 2.5c


j~

c

(410-5)


4-36

but not greater than (75,0001fs) Calculated stress in reinforcement Is (in MFa) shall be computed as the unfactored moment divided by the product of steel area and internal moment arm. It shall be permitted to takelsas 60 percent of specified yield strength h. 410.7.5 Provisions of Section 410.7.4 may not be sufficient for structures subject to very aggressive exposure or designed to be watertight. For such structures, special investigations and precautions are required. 410.7.6 Where flanges of T-beam construction are in tension, part of the flexural tension reinforcement shall be distributed over an effective flange width as defined in Section 408.11, or a width equal to one tenth the span, whichever is smaller. If the effective flange width exceeds one tenth the span, some longitudinal reinforcement shall be provided in the outer portions ofthe flange. 410.7.7 If the effective depth d of a beam or joist exceeds 900 mm, longitudinal skin reinforcement shall be uniformly distributed along both side faces of the member for a distance dl2 nearest the flexural tension reinforcement. The ar~a of skin reinforcement Ask per mm of height on each side face shall be at least equal to 1.0(d - 750). The maximum spacing of the skin reinforcement shall not exceed the lesser of d/6 and 300 mm. It shall be permitted to include such reinforcement in strength computations if a strain compatibility analysis is made to determine stresses in the individual bars or wires. The total area of longitudinal skin reinforcement in both faces need not exceed one half of the required flexural tensile reinforcement.

410.8 DEEP FLEXURAL MEMBERS 410.8.1 Flexural members with overall depth-to-clear span ratios greater than 0.4 for continuous spans, or 0.8 for simple spans, shall be designed as deep flexural members, taking into account nonlinear distribution of strain and lateral buckling. (See also Section 412.11.6)

410.9 DESIGN DIMENSIONS FOR COMPRESSION MEMBERS 410.9.1 Isolated Compression Member With Multiple Spirals. Outer limits of the effectivJ: cross section of a compression member with two or more interlocking spirals shall be taken at a distance outside the extreme limits of the spirals equal to the minimum concrete cover required by Section 407.8. 410.9.2 Compression Member Built Monolitbically With Wall. Outer limits of the effective cross section of a spirally reinforced or tied reinforced compression member built monolithically with a concrete wall or pier shall be taken not greater than 40 mm outside the spiral or tie reinforcement. 410.9.3 Equivalent Circular Compressiou Member. As an alternate to using the full gross area for design of a compressive member with a square, octagonal or other shaped cross section, it shall be permitted to use a circular section with a diameter equal to the least lateral dimension of the actual shape. Gross area considered, required percentage of reinforcement, and design strength shall be based on that circular section 410.9.4 Limits of Section. For a compression member with a cross section larger than required by considerations of loading, it shall be permitted to base the minimum reinforcement and design strength on a reduced effective not less than one half the total area. This provision area shall not apply in Seismic Zone 4.

Ag

410.10 LIMITS FOR REINPORCE~fENT OF' COMPRESSION MEMBERS 410.10.1 Area of longitudinal reinf'·ff'.ement f;)r noncomposite compression members shall not be less than 0.01 or more than 0.08 times gross areaA g of section

410.8.2 Shear strength of deep flexural members shall be in accordance with Section 411.9.

410.10.2 Minimum number of longitudinal bars in compression members shall be four (4) for bars within rectangular or circular ties, three (3) for bars within triangular ties, and six (6) for bars enclosed by spirals conforming to Section 410. 10.3.

410.8.3 Minimum flexural tension reinforcement shall conform to Section 410.6.

410.10.3 Ratio of spiral reinforcement P. shall not be less than the value given by

410.8.4 Minimum horizontal and vertical reinforcement in the side faces of deep flexural members shall be the greater ofthe requirements of Sections 411.9.8,411.9.9 and 411.9.10 or Sections 414.4.2 and 414.4.3.

P.

= 0.45 (Ag

Ac

1) i'e i

(410-6)

y

where h is the specified yield strength of spiral reinforcement but not more than 415 MFa.


CONCRETE

4-37

410.11 SLENDERNESS EFFECTS IN COMPRESSION MEMBERS

permitted to compute the radius of gyration for the gross concrete section.

410.11.1 Except as allowed in Section 410.11.2, the design of compression members, restraining beams and other supporting members shall be based on the factored forces and moments from a second order analysis considering materials nonlinearity and cracking, as well as the effects of member curvature and lateral drift, duration of loads, shrinkage and creep, and interaction with the supporting foundation. The dimensions of each member cross section used in the analysis shall be within 10 percent of the dimensions of the members shown on the design drawings and the analysis shall be repeated. The analysis procedure shall have been shown to result in prediction of strength in substantial agreement with the results of comprehensive tests of columns in statically indeterminate reinforced concrete structures.

410.12.3 Unsupported Length Of Compression

Members

410.11.2 As an alternate of the procedure prescribed in Section 41 0.11. 1, it shall be permitted to base the design of compression members, restraining beams, and other supporting members on axial forces and moments from the analyses described in Section 410.12.

410.12 MAGNIFIED MOMENTS - GENERAL 410.12.1 The factored axial forces, P u , the factored moments, MJ and M 2, at the ends of the column and, where required, the relative lateral story deflections, .do, shall be computed using an elastic first-order frame analysis with the section properties determined taking into account the influence of axial loads, the presence of cracked regions along the length of the member and effects of duration of loads. Alternatively, it shall be permitted to use the following properties for the members in the structure: 1. 2.

Modulus of elasticity .... ... from Section 408.6.1. Moment of inertia: Beams .......... ........... ........... ........ ... 0.351g Columns ....................................... 0.70Ig Walls - Uncracked .............. 0.701" - Cracked ........... ....... 0.35Ig

Flat plates and flat slabs .. ............ 0.25Ig

3. Area .............................................. 1.0 Ag The moments of inertia shall be divided by (1 +h) 1. when sustained lateral loads act, or 2. for stability checks made in accordance with Section 410.14.6.

410.12.2 It shall be permitted to take the radius of gyration, r, equal to 0.30 times the overalliimension of the direction stability is being considered for rectangular compression members and 0.25 times ihe dIameter for circular compression members. For other simpes. it shall be

-410.12.3.1 The unsupported length lu of a compression member shall be taken as the clear distance between floor slabs, beams or other members capable of providing lateral support in the direction being considered. 410.12.3.2 Where column capitals or haunches are present, the unsupported length shall be measured to the lower extremity of the capital or haunch in the plane considered. 410.12.4 Columns and stories in structures shall be designated as nonsway or sway columns or stories. The design of .columns in nonsway frames or stories shall be based on Section 410.13. The design of columns in sway frames or stories shall be based on Section 410.14. 410.12.4.1 It shall be permitted to assume a column in a structure is non-sway if the increase in column end moments due to second-order effects does not exceed 5 percent of the first-order end moments. 410.12.4.2 It also shall be permitted to assume a story within a structure is nonsway if: (410-7)

,

is less than or equal to 0.05, where 'EPu and Vu are the total vertical load and the story shear, respectively, in the story in question and .10 is the first-order relative deflection between the top and bottom ofthat story due to Vu. 410.12.5 Where an individual compression member in the frame has a slenderness, kl,/r, of more than 100, Section 410.11.1 shall be used to compute the forces and moments in the frame. 410.12.6 For compression members subject to bending about both principal axes, the moment about each axis shall be magnified separately based on the conditions of restraint corresponding to that axis.

410.13 MAGNIFIED MOMENTS - NONSWAY FRAMES 410.13.1 For compression members in nonsway frames, the effective length factor k shall be taken as 1.0, unless analysis shows that a lower value is justified. The calculation of k shall be based on the E and J values used in Section 410,12.1.



4-38

410.13.2 In non-sway frames, shall be permitted to ignore slenderness effect for compression members which satisfy:

k:u ~

34

12(~J

(410-8)

where the term [34-12MJIM21 shall not be taken greater than 40. The term MiM2 is positive if the member is bent in single curvature, and negative if the member is bent in double curvature. 410.13.3 Compression members shall be designed for the factored axial load, Pu, and the moment amplified for the effects of member curvature, Me, as follows:

410.14 MAGNIFIED MOMENTS - SWAY FRAMES For compression members not braced against sidesway, the effective length factor k shall be determined using E and I values in accordance with Section 410.12.1 and shall be greater than 1.0. 410.14.1

For compression members not braced against sidesway, effects of slenderness may be neglected when kllr is less than 22,

410.14.2

410.14.3 The moments M J and M2 at the ends of an individual compression member shall be taken as '

(410-9)

Where:

M J "" M Jns + 0 sMJ.

(410-16)

M 2ns + OsM2s

(410-17)

M2 ~

1.0

(410-10)

0.75 Pc

=

where 0. MJs and 0. M2s shall be computed according to Section 410.14.4. 410.14.4 Calculation of 4,M..

(410-11)

AI shall be taken as

El

(0.2EJg +E,lJ

(410-12)

1+ Pd

The magnified sway moments & Ms shall be taken as the column end moments calculated using a second-order elastic analysis based on the member stiffnesses given in Section 410.12,1.

410.14.4.1

Alternatively, it shall be permitted to calculate 0.M.. as

410.14.4.2

or

El

(410-13) 1

For members without transverse loads between supports, shall be taken as

410.13.3.1

em

(410-14)

where MJIM2 is positive if the column is bent in single curvature. For members with transverse loads between supports, Cm shall be taken as 1.0. The factored moment M2 in Equation (410 410.13.3.2 9) shall not be taken less than M 2.J".in = P u (15 + 0.03h) (410-15) about each axis separately, where 15 and h are in millimeters. For members for which M 2•min exceeds M 2, the value ofC", in Equation (410-14) shall either be taken equal to 1,0, or shall be based on the ratio of the computed end moments MJ and M 2 ,

Q

~

(410-18)

Ms

If 0. calculated in this way exceeds 1.5, li', A{, shall be calculated using Section 410, 14.4.1 or 410.14.4.3. 410.14.4.3 Alternatively, it shall be perl1litted to calculate the magnified sway moment lisM, as 11,1,

0" M s = - - - ' - - - -IF" ----,

(410-19)

0.75IPc where EPII is the summation for all the vertical loads in a story and E Pc is the summation for all sway resisting columns in a story, Pc is calculated using Equation (410-11) using k from Section 410.13,1 and EI from Equation (410 12) or (410-13). 410.14.5

If an individual compression member has r

>

35


(410-20)

CONCRETE

be designed for the factored axial load, PlI , and the Me. calculated using Section 410.13.3 in which MJ 2 are computed in accordance with Section 410.14.3, as defined for 'd combination under consideration k as defined in ~t.y'10n 410,13,1. l'410.14.6In addition to load cases involving lateral loads, ." the strength and stability of the structure as a whole under factored gravity loads shall be considered.

1.

2.

3.

a.M,

When is computed from Section 410.14.4.1, the ratio of second-order lateral deflections to first-order lateral deflections for 1.4 dead load and 1.7 live load plus lateral load applied to the structure shall not exceed 2.5,

a.

When Ms is computed according to Section 410.14.4.2, the value ofQ computed using SPu for 1. 4, dead load plus 1. 7 live load shall not exceed 0.60.

a.

a.M.

When is computed from Section 410.14.4.3, computed using SPu and SPc corresponding to the factored dead and live loads shall be positive and shall not exceed 2.5.

In cases 1, 2 and 3 above, fJd shall be taken as the ratio of the maximum factored sustained axial load to the total factored axial load. 410.14.7 In sway frames, flexural members shall be designed for the total magnified end moments of the compression members at the joint.

410.15 AXIALLY LOADED MEMBERS

SUPPORTING SLAB SYSTEM

Axially loaded members supporting slab system included within the scope of Section 413.2 shall be designed as provided in Section 410 and in accordance with the additional requirements of Section 413.

410.16 TRANSMISSION OF COLUMN

LOADS THROUGH FLOOR SYSTEM

When the specified compressive strength of concrete in a column is greater than 1.4 times that specified for a floor system, transmission of load through the floor system shall be provided by. Section 410.16.1, 410.16.2, or 410.16.3: 410.16.1 Concrete of strength specified for the column shall be placed in the floor at the column location. Top surface of the column concrete shall extend 600 mm into the slab from face of column. Column concrete shall be

4-39

well integrated with floor concrete, and shall be placed in accordance with Sections 406.4.5 and 406.4.6. 410.16.2 Strength of a column through a floor system shall be based on the lower value of concrete strength with vertical dowels and spirals as required. 410.16.3 For columns laterally supported on four sides by beams of approximately equal depth or by slabs, strength of the column may be based on an assumed concrete strength in the column joint equal to 75 percent of column concrete strength plus 35 percent of floor concrete strength.

410.17 COMPOSITE COMPRESSION MEMBERS 410.17.1 Composite compression members shall include all such members reinforced longitudinally with structural steel shapes, pipe or tubing with or without longitudinal bars. 410.17.2 Strength of a composite member shall be computed for the same limiting conditions applicable to ordinary reinforced concrete members. 410.17.3 Any axial load strength assigned to concrete ofa composite member shall be transferred to the concrete by members or brackets in direct bearing on the composite member concrete. 410.17.4 All axial load strength not assignen *') concrete of a composite member shall be develop. )y ditect connection to the structural steel shape, pipe or tube. 410.17.5 For evaluation of slenderness effects, radius of gyration of a composite section shall not be greater than the value given by: (410-21)

and, as an alternative to a more accurate calculation, El in Equation (410-11) shall be taken either as Equation (410 12) or (410-22)

410.17.6

Structural steel-encased concrete core

410.17.6.1 For a composite member with concrete core encased by structural steel, thickness of the steel encasement shall not be less than



for each face of width b nor for circular sections of diameter h

410.17.6.2 Longitudinal bars located within the encased concrete core shall be permitted to be used in computing At and It. 410.17.7 Spiral reinforcement around structural steel core. A composite member with spirally reinforced concrete around a structural steel core shall conform to Sections 410.17.7.1 through 410.17.7.5.

410.17.8.5 Vertical spacing of lateral ties shall not exceed 16 longitudinal bar diameters, 48 tie bar diameters, or one half times the least side dimension of the composite member. 410.17.8.6 Longitudinal bars located within the ties shall not be less than 0.01 or more than 0.08 times net area of concrete section. 410.17.8.7 A longitudinal bar shall be located at every corner of a rectangular cross section, with other longitudinal bars spaced not farther apart than one half the least side dimension of the composite member. 410.17.8.8 Longitudinal bars located within the ties shall be permitted to be used in computing AI for strength but not in computing It for evaluation of slenderness effects.

410.17.7.1 Specified compressive strength of concrete f'c shall not be less than 17 MFa.

410.18 BEARING STRENGTH 410.17.7.2 Design yield strength of structural steel core shall be the specified minimum yield strength for grade of structural steel used but not to exceed 345 MFa.

,

410.17.7.3 Spiral reinforcement shall conform to Section 410. 10.3.

Iq

410.17.7.4 Longitudinal bars located within the spiral shall not be less than 0.01 or more than 0.08 times net area of concrete section.

410.18.1 Design bearing strength on concrete shall not exceed If? (0.85f'c AI), except when the supporting surface is wider on all sides than the loaded area, design bearing strength on the loaded area shall be permitted to be mUltiplied by "A 2 1AI, but not more than 2. 410.18.2 Section 410.18 does not apply to post-tensioning anchorage.

410.17.7.5 Longitudinal bars located within the spiral shall be permitted to be used in computing At and It.

".

410.17.8 Tie reinforcement around structural steel core. A composite member with laterally tied concrete around a structural steel core shall conform to Sections 410.17.8.1 through 410.17.8.8:

":

",

'""

410.17.8.1 Specified compressive strength of concrete f'c shall not be less than 17 MFa. 410.17.8.2 Design yield strength of structural steel core shall be the specified minimum yield strength for grade of structural steel used but not to exceed 345 MFa. 410.17.8.3 Lateral ties shall extend completely around the structural steel core. 410.17.8.4 Lateral ties shall have a diameter not less than 0.02 times the greatest side dimension of composite member, except that ties shall not be smaller than 10 mm diameter and are not required to be larger than 16 mm diameter. Welded wire fabric of equivalent area shall be permitted.


CONCRETE

SECTION 411 - SHEAR AND TORSION 411.1 NOTATIONS Ac = area of coricrete section resisting shear transfer, 2 mm • are~ enclosed by outside perimeter of concrete cross section, mm2. See Section 411. 7.1. area of reinforcement in bracket or corbel resisting 2 factored moment [V"a + N.w(h - d)], mm . gross area of section, mml. area of shear reinforcement parallel to flexural tension reinforcement, mml. total area of longitudinal reinforcement to resist torsion, mm2 area of reinfurcement in bracket or corbel resisting tensile force N.,e, mml. gross area enclosed by shear flow, mm2 area enclosed by centerline of the outermost closed transverse torsional reinforcement, mml. area of prestressed reinforcement in tension zone, Aps

mml. A,

a

area of non-prestressed tension reinforcement,

mm2.

area of one leg of a closed stirrup resisting torsion within a distance s, mm2. area of shear reinforcement within a distance s, or area of shear reinforcement perpendicular to flexural tension reinforcement within a distance S for deep flexural members, mm2 . area of shear-friction reinforcement, mm2 area of shear reinforcement parallel to flexural tension reinforcement within a distance S2, mm2 . shear span, distance between concentrated load and face of supports, mm. width of compression face of member, mm. perimeter of critical section for slabs and footings, mm. width of that part of cross section containing the closed stirrups resisting torsion. web width, or diameter of circular section, mm. width of the critical section defined in Section 411.13.6.1 measured in the direction of the span for which moments are determined, mm. width of the critical section defined in Section 411.13.6.1 measured in the direction perpendicular to h j , mm. size of rectangular or equivalent rectangular column, capital or bracket measured in the direction of the span for which moments are being determined, mm. size of rectangular or equivalent rectangular column, capital or bracket measured transverse to

4....1

the direction of the span for which moments are being determinee, mm. d distance from extreme compression fiber to centroid of longitudinal tension reinforcement, but need not be less than O.SOh for prestressed members, millimeters. (For circular sections, d need not be less than the distance from extreme compression fiber to centroid of tension reinforcement in opposite half of member), mm. Pe specified compressive strength of concrete, :MPa. = square root of specified compressive strength of concrete, :MPa. fet average splitting tensile strength of lightweight aggregate concrete, :MPa. h stress due to unfactored dead load, at extreme fiber of section where tensile stress is caused by externally applied loads, :MPa. fpc compressive stress in concrete (after allowance for all prestress losses) at centroid of cross secti6n resisting externally applied loads or at junction of web and flange when the centroid lies within the flange, MFa. (In a composite member, fpc is resultant compressive stress at centroid of composite section, or at junction of web and flange when the centroid lies within the flange, due to both prestress and moments resisted by precast member acting alone.) fpe compressive stress in concrete due to effective prestress forces only (after allowance for all prestress losses) at extreme fiber of section where tensile stress is caused by externally applied loads, :MPa. /p" specified tensile strength of prestressing tendons,. MFa. 1;. specified yield strength of non-prestressed reinforcement, MFa. hi yield strength of longitudinal torsional reinforcement, MFa. .h'V yield strength of closed transverse torsional reinforcement, MFa. h overall thickness of member, mm. h" total depth of shearhead cross section, mm. hw total height ofwall from base to top, mm. I moment of inertia of section resisting externally applied factored loads, mm4. In clear span measured face to face of supports. Iv length of shearhead arm from centroid of concentrated load or reaction, mm. lw horizontal length of wall, mm. Mer moment causing flexural cracking at section due to externally applied loads. See Section 411.5.2.1. Mm = modified moment. Mmar= maximum factored moment at section due to externally applied loads. Mp = required plastic moment strength of shearhead cross section.

ff:


4 4-42

N"

Pcp

Ph

s

"oj,

y, a

a, a ,.

SHEAR AND Tm'IC111')N

factored moment at section.

moment resistance contributed by shearhead

reinforcement.

factored axial load normal to cross section

occurring simultaneously with Vu; to be taken as positive for compression, negative for tension, and to include effects of tension due to creep and shrinkage. factored tensile force applied at top of bracket or corbel acting simultaneously with Vii to be laken as positive for tension. outside perimeter of the concrete cross section, mrn. perimeter of centerline of outermost closed transverse torsional reinforcement, mrn. spacing of shear or torsion reinforcement in direction parallel to longitudinal reinforcement, mm. spacing of vertical reinforcement in wall, mm. spacing of shear or torsion reinforcement in direction . perpendicular to longitudinal reinforcement-or spacing of horizontal reinforcement in wall, mm. nominal torsional moment strength. factored torsional moment at section. thickness of a wall of a hollow section, mm. nominal shear strength provided by concrete. nominal shear strength provided by concrete when diagonal cracking results from combined shear and moment. nominal shear strength provided by concrete when diagonal cracking results from excessive principal tensile stress in web. shear force at section due to unfactored dead load. factored shear force at section due to externally

applied loads occurring simultaneously with Mmax.

nominal shear strength.

vertical component of effective prestress force at

section.

nominal shear strength provided by shear

reinforcement.

factored shear force at section.

nominal shear stress, MPa. See Section 411.13.6.2.

distance from centroidal axis of gross section. neglecting reinforcement, to extreme fiber in tension. angle between included stirrups and longitudinal axis of member. angle between shear-friction reinforcement and shear plane. constant used to compute Vc in slabs and footings. ratio of stiffness of shearhead arm to surrounding composite slab section. See Section 411.13.4.5. ratio of long side to short side of concentrated load or reaction area. constant used to compute f~ in prestressed slabs.

rf

fraction of unbalanced moment transferred by flexure at slab-column connection. See Section

r"

fraction of unbalanced moment tr~sferred by

eccentricity of shear at slab-column connections.

See Section 411.13.6.1.

",

number of identical arms of shearhead.

coefficient of friction. See Section 411.8.4.3.

correction factor related to unit weight ofconcrete.

ratio of non-prestressed tension reinforcement.

A/bd ratio of horizontal shear reinforcement area t'O gross

concrete area of vertical section.

ratio of vertical shear reinforcement area to gross

concrete area of horizontal section.

A/b"d. angle of compression diagonals in truss analogy for

torsion.

strength reduction factor. See Section 409.4.

413.6.3.2.

1f.1.

A p Ph

Pn

Pw () '"

411.2

rf

SHEAR STRENGTH

411.2.1 Design of cross sections subject to shear shall be based on (411-1)

where V;, is factored shear force at section considered and Vn is nominal shear strength computed by (411-2)

where Vc is nominal shear strength provided by concrete in accordance with Section 411.4 or Section 411.5, and 1/~ is nominal shear strength provided by shear reinforcement in accordance with Section 411.6.6. 411.2.1.1 In determining shear strength Vn , the effect of any openings in members shall be considered. 411.2.1.2 In determining shear strength Vel whenever applicable. effects of axial tension due to creep and shrinkage in restrained members shall be considered and effects of inclined flexural compression in variable-depth members shall be permitted to be included. 411.2.2 The values of -.Jf'e used in Section 411 shall not exceed 0.7 MPa. EXCEPTION: Values of lie greater than 0.7 MPa is allowed ill computing V", V ci and Vel\' for reinforced or prestressed concrete beams and concrete jOist cOllstruction having

I

l

L


CONCRETE

web reinforcement equal to f'/35 times, but not than three times the amounts required by Sections

through 411.4.1.3 unless a more detailed calculation is made in accordance with Section 411.4.2.

.. 6.5.3, 411.6.5.4 and 411. 7.5.2.

Computations of maximum factored shear force supports in accordance with Section 411.2.3. 1 or .3.2 shall be permitted when both of the following two .ndltlOllS are satisfied: Support reaction, in direction of applied shear, introduces compression into the end regions of member, and No concentrated load occurs between face of support and location of critical section defined in Sections 411.2.3.1 and 411.2.3.2.

1.2.3.1 For non-prestressed members, sections . . located less than a distance d from face of support shall be permitted to be designed for the same shear v~ as that computed at a distance d 411.2.3.2 For prestressed members, sections located less than a distance hl2 from face of support shall be permitted to be designed for the same shear V" as that computed at a distance h12. 411.2.4 For deep flexural members, brackets and corbels, walls and slabs and footings, the special provisions of Sections 411.9 through 411.13 shall apply.

411.3

LIGHTWEIGHT CONCRETE

411.3.1 Provisions for shear strength Ve apply to normal weight concrete. When lightweight aggregate concrete is used, one of the following modifications shall apply: 411.3.1.1 When let is specified and concrete is proportioned in accordance with Section 405.3, provisions for Ve shall be modified by substituting 1.8fet for ...J/,,,, but the value of 1.8/ct shall not exceed ...J/'e.

411.4.1.1 only,

For members subject to shear and flexure

V=!Ff"bd a 6 "Ii' a w

411.4.1.2

(411-3)

For members subject to axial compression,

Va

=

1(l+~)

Ff" b d 14Ag "Ii' c w

6

(411-4)

Quantity N"IAg shall be expressed in MFa.

411.4.1.3 For members subject to significant axial tension, shear reinforcement shall be designed to carry total shear, unless a more detailed analysis is made using Section 411.4.2.3. . 411.4.2 Detailed calculation for Vc- Shear strength Vc shall be permitted to be computed by the more detailed calculation of Sections 411.4.2.1 through 411.4 .2.3. 411.4.2.1 only,

For members subject to shear and flexure

Va

1(

dJ b,. d

r;;- + 120 Pw _u_ V -l"lif'c 7

M.

(411-5)

but not greater than 0.3...J f~ bw d. Quantity Vu 1M" shall not be taken greater than 1.0 in computing Vc by Equation (411-5), where M" is factored moment occurring • simultaneously with V" at section considered.

411.4.2.2 For members subject to axial compression, it shall be permitted to compute Vc using Equation (411-5) with Mm substituted for M" and V.,dIM" not then limited to 1.0, where M",

M -N (4h-dl •

U

(411-6)

8)

However, Vc shall not be taken greater than

411.3.1.2 When fet is not specified, all values of...J /,c affecting Ve, Tc and Mer shall be multiplied by 0.75 for all lightweight concrete and 0.85 for sand-lightweight concrete. Linear interpolation shall be permitted when partial sand replacement is used.

411.4 SHEAR STRENGTH PROVIDED BY CONCRETE FOR NONPRESTRESSED MEMBERS

;: " 0.3 (

(411-7)

Quantity N.,IA g shall be expressed in MFa. When Mm as computed by Equation (411-6) is negative, Vc shall be computed by Equation (411-7).

411.4.2.3 tension,

For members subject to significant axial

Va

411.4.1 Simplified calculation for Vc- Shear strength Vc shall be computed by provisions of Sections 411.4.1.1

JI + o.~~. )~1', b.d

~(1 + O.~~u )~f'c b

w

d

(411-8)

but not less than zero, where N" is negative for tension. Quantity NulAg shall be expressed in MPa.


SHEAR AND TORSION

411.4.3 Circular members. For circular members, the area used to compute V" shall be taken as the product of the diameter and effective depth of the concrete section. It shall be permitted to take the effective depth as 0.8 times the diameter of the concrete section.

principal tensile stress shall be computed using the cross section that resists live load.

411.5 SHEAR STRENGTH PROVIDED BY CONCRETE FOR PRESTRESSED· MEMBERS

411.5.3 In a pretensioned member in which the section at a distance hl2 from face of support is closer to end of member than the transfer length of the prestressing tendons, the reduced prestress shall be considered when computing Vow. This value of V"w shall also be taken as the maximum limit for Equation (411-9). Prestress force may be assumed to vary linearly from zero at end of tendon to a maximum at a distance from end of tendon equal to the transfer lengt~ assumed to be 50 diameters for strand and 100 diameters for single wire.

411.5.1 For members with effective prestress force not less than 40 percent of the tensile strength of flexural reinforcement, unless more detailed calculation is made in accordance with Section 411.5.2.

V = .c

(J,f'c; 20

+5 VudJb d Mu'"

(411-9)

but Vc need not be taken less than (1/6)"1'" bw d nor shall V" be taken greater than 0.4" fe bw d nor the value given in Section 411.5.3 or 411.5.4. The quantity V,.dIM" f shall not be taken greater than 1.0, where M" is factored moment occurring simultaneously with V" at section considered. When applying Equation (411-9), d in the term V,.dIM" shall be the distance from extreme compression fiber to centroid of prestressed reinforcement.

""""

411.5.2 Shear strength v;, shall be permitted to be computed in accordance with Sections 411.5.2.1 and 411.5.2.2 where Vc shall be the lesser of Vet or VCWo

"

411.6 SHEAR STRENGTH PROVIDED BY SHEAR REINFORCEMENT

~fc b 20

411.6.1

w

.: ::~~:

d + V + V;Mcr d M max

(411-10)

but Vet need not be taken less than (1/7) "fe. where (411-11)

and values of Mmax and V; shall be computed from the load combination causing maximum moment to occur at the section. 411.5.2.2

411.5.4 In a pretensioned member where bonding of some tendons does not extend to end of member, a reduced prestress shall be considered when computing Vc in accordance with Section 411.5.1 or 411.5.2. Value of V"w calculated using the reduced prestress shall also be taken as the maximum limit for Equation (411-9). Prestress force due to tendons for which bonding does not extend to end of member may be assumed to vary linearly from zero at the point at which bonding commences to a maximum at a distance from this point equal to the transfer length, assumed to be 50 diameters for strand and 100 diameters for single wire.

Shear strength Vet shall be computed by

~'''''

411.5.2.1

411.5.2.3 In Equations (411-10) and (411-12), d shall be the distance from extreme compression fiber to centroid of prestressed reinforcement or 0.8h, whichever is greater.

Shear strength Vow shall be computed by (411-12)

Alternatively, Vcw may be computed as the shear force corresponding to dead load plus live load that results in a principal tensile stress of (113) "fe at the centroidal axis of member, or at intersection of flange and web when centroidal axis is in the flange. In composite members,

Types of shear reinforcement.

411.6.1.1 Shear reinforcement consisting of the following

shall be permitted:

L Stirrups pefpendicular to axis of member.

2. Welded wire fabric with wires located perpendicular to axis of member. 3. Spirals, circular ties, or hoops. 411.6.1.2 For non-prestressed . members, reinforcement shall be permitted to also consist of: 1. Stirrups making an angle of 45 degrees or more with longitudinal tension reinforcement. 2. Longitudinal reinforcement with bent portion making an angle of 30 degrees or more with the longitudinal tension reinforcement. Combination of stirrups and bent 3. reinforcement.


CONCRETE

411.6.2 Design yield strength of shear reinforcement shall not exceed 415 MPa, except that the design yield strength ofwelded deformed wire fabric shall not exceed 550 MPa.

411.6.5.4) and non-prestressed members shall be computed by: b"s

Stirrups and other bars or wires used as shear reinforcement shall extend to a distance d from extreme compression fiber and shall be anchor~ at both ends according, to Section 412.14 to develop the design yield strength ofreinforcement.

411.6.4

Spacing Limits for Shear Reinforcement

Spacing of shear reinforcement pl~ perpendicular to axis of member shall not exceed dI2 in non-prestressed members and (3/4)h in prestressed members or 600 rom.

. 411.6.4.2

Inclined stirrups and bent longitudinal . reinforcement shall be so spaced that every 45-degree line, extending toward the reaction from mid-depth of member dI2 to longitudinal tension reinforcement, shall be crossed . , by at least one line of shear reinforcement. 1

411.6.4.3 When Vs exceeds (1/3)" Pc b" d , maximum spacing given in Sections 411.6.4,1 and 411.6.4.2 shall be reduced by one half 411.6.5

Minimum shear reinforcement

(411-13)

A" '" 3/ y

411.6.3

where bw and s are in millimeters.

411.6.5.4 For prestressed members with effective prestress force not less than 40 percent of the tensile strength of flexural reinforcement, the area of shear reinforcement shall not be less than the smaller A", computed by Equation (411-13) or (411-14). (411-14)

411.6.6

Design of Shear Reinforcement

411.6.6.1 Where factored shear force Vu exceeds shear strength ;Vc> shear reinforcement shall be provided to satisfy Equations (411-1) and (411-2), where shear strength Vs sha:ll be computed in accordance with Sections 411.6.6.2 through 411.6.6.8. 411.6.6.2

When shear reinforcement perpendicular to axis of member is used, (411-15)

411.6.5.1

A minimum area of shear reinforcement shall be provided in all reinforced concrete flexural members (prestressed and non-prestressed) where factored shear force Vu exceeds one half the shear strength provided by concrete; Vc, except: 1. 2. 3.

Slabs and footings, Concrete joist construction defined by Section 408,12. Beams with total depth not greater than 250 rom, two and one half times thickness of flange or one half the width ofweb, whichever is greater.

where Av is the area of shear reinforcement within a distance s.

411.6.6.3 When circular .ties, hoops, or spirals are used as shear reinforcement, shall be computed using equation (411-15) where d shall be taken as the effective depth defined in Section 411.4.3. Av shall be taken as two times the area ofthe bar in a circular tie, hoop, or spiral at a spacing s, and /yh is the specified yield strength of circular tie, hoop or spiral reinforcement.

v..

411.6.6.4 411.6.5.2 Minimum shear reinforcement requirements of Section 411.6.5.l shall be waived if shown by test that required nominal flexural and shear strengths can be developed when shear reinforcement is omitted. Such tests shall simulate effects of differential settlement, creep, shrinkage and temperature change, based on a realistic assessment of such effects occurring in service.

When inclined stirrups are used as shear

reinforcement,

v. = A.,/vs d (sino. + coso. )

(411-16)

411.6.6.5 When shear reinforcement consists of a single bar or a single group of parallel bars, all bent up at the same distance from the support,

411.6.5.3

Where shear reinforcement is required by Section 411.6.5.1 or for strength and· where Section 411.7.l allows torsion to be neglected, the minimum area of shear reinforcement for prestressed (except as provided in Section

(411-17) but not greater than (1/4) "Pc hwd

SHEAR AND TORSION

411.6.6.6 When shear reinforcement consists of a series of parallel bent-up bars or groups of parallel bent-up bars at different distances from the support, shear strength v~ shall be computed by Equation (411-16). 411.6.6.7 Dnly the center three fourths of the inclined portion of any longitudinal bent bar shall be considered effective for shear reinforcement

1.

for non-prestressed members, described in Section 411.7.2.4:

411.7 DESIGN FOR TORSION 411.7.1 It shall be permitted to neglect torsion effects when the factored torsional moment T" is less than: 1.

for non-prestressed members:

;[.1'; [A!) 12

2.

; [.1'; [A! J' Pcp

1+

3fpc

~j'c

For members cast monolithically with a slab, the overhanging flange width used in computing Acp and Pcp shall conform to Section 413.3.4.

411.7.2

sections

3 2.

Pcp

for prestressed members, at the sections described in Section 411.7.2.5:

;r.r: [A!Pcp ]1 3

3

+ fpc ~j'c

In such a case, the correspondingly redistributed bending moments and shears in the adjoining members shall be used in the design ofthose members.

411.7.2.3 Unless determined by a more exact analysis, it shall be permitted to take the torsional loading from a slab as uniformly distributed along the member. 411.7.2.4 In non-prestressed members" sections located less than a distance d from the face of a support shall be designed for not less than the torsion Tu computed at a distance d. If a concentrated torque occurs within this distance, the critical section for design shall be at the face of the support.

Pcp

for prestressed members:

12

the

;[.1'; [A!]

411.6.6.8 Where more than one type of shear reinforcement is used to reinforce the same portion of a member, shear strength Vs shall be computed as the sum of the Vs values computed for the various types. 411.6.6.9 Shear strength Vs shall not be taken greater than (2/3) ..jf'c bwd

at

Calculation of Factored Torsional Moment

Tl1.' 411.7.2.1 If the factored torsional moment Tu in a member is required to maintain equilibrium and exceeds the minimum value given in Section 411.7.1, the member shall be designed to carry that torsional moment in accordance with Sections 411.7.3 through 411.7.6. 411.7.2.2 In a statically indeterminate structure where reduction of the torsional moment in a member can occur due to redistribution of internal forces upon cracking, the maximum factored torsional moment 1;, shall be permitted to be reduced to

411.7.2.5 In prestressed members, sections located less than a distance hl2 from the face of a support shall be designed for not less than the torsion Tu computed at a distance h12. If a concentrated torque occurs within this distance, the critical section for design shall be at the face of the support. 411.7.3

Torsional Moment Strength

411.7.3.1 The cross-sectional dimensions shall be such that: 1. for solid sections:

(~)2 'l/(~)2 + 1.7 A~ b", d

<

[~+ 2[.1';J 3

- ; bw d

(411-18) 2. for hollow sections: :<;

;[~+ 2~j'c J b",d 3 (411-19)

411.7.3.2 If the wall thickness varies around the perimeter of a holloyv section, Equation (411-19) shall be evaluated at the Idcation where the left-hand side of Equation (411-19) is a maximum.


447

CONCRETE

If the wall thickness is less than Aoh Ph, the term in Equation (41 1-19) shall be taken as:

411.7.3.10 1.

The total longitudinal reinforcement including tendons at each section shall resist the factored bending moment at that section plus an additional concentric longitudinal tensile force equal to A/;:I, based on the factored torsion at that section, and

2.

The spacing of the longitudinal reinforcement including tendons shall satisfy the requirements in Section 411.7.6.2.

(1.7~Oh t) t .is the thickness of the wall of the hollow section at location where the stresses are being checked.

Design yield strength of non-prestressed 411.7.3.4 t6rSion reinforcement shall not exceed 415 MPa.

lIt 7.3.5

The reinforcement required for torsion shall be;determined from: (411-20)

T"

411.7.3.6 The transverse reinforcement for torsion shall be designed using: _-=-..:.::...;c.:...

cotO

s

(411-21)

where Ao shall be determined by analysis except that it shall be permitted to take Ao equal to 0.85Aoh; 0 shall not be taken smaller than 30 degrees nor larger than 60 degrees. It shall be permitted to take 0 equal to: 1.

45 degrees for non-prestressed members or members with less prestress than in Item 2 below,

z.

37.5 degrees for prestressed members with an effective prestress force not less than 40 percent of the tensile strength of the longitudinal reinforcement.

411.7.3.7 The additional longitudinal reinforcement required for torsion shall not be less than: At Ivv t2f) p,,-_·-co

(411-22)

S fyl \-~·here 0 shall be the same value used in Equation (411-21) and AI is shall be taken as the amount computed from Equation (411-21) not modified in accordance with Section 411.7.5.20r411.7.5.3.

411.7.3.8 Reinforcement required for torsion shall be added to that required for the shear, moment and axial force that act in combination with the torsion. The most restrictive requirements for reinforcement spacing and placement must be met. 411.7.3.9 It shall be permitted to reduce the area of longitudinal torsion reinforcement in the flexural compression zone by an amount equal to M" 1(0.9dJ;,), where M" is the factored moment acting at the section in combination with Til, except that the reinforcement provided shall not be less than that required by Section 4 t!. 7.5.3 or 4117.6.2.

In Prestressed Beams:

411.7.3.11 In prestressed beams, it shall be permitted to reduce the area oflongitudinal torsional reinforcement on the side of the member in compression due to flexure below that required by Section 4117.3.10 in accordance with Section 411.7.3.9. 411.7.4

Details of torsional reinforcement

411.7.4.1 Torsion reinforcement shall consist of longitudinal bars or tendons and one or more of the following: L Closed stirrups or closed ties, perpendicular to the

axis of the member, or

2. A closed cage of welded wire fabric with transverse wires perpendicular to the axis ofthe member, or 3. In non-prestressed beams, spiral reinforcement.

411.7.4.2 Transverse torsional reinforcement shall be anchored by one of the following: 1 A 135-degree standard hook around a longitudinal • bar, or 2. According to Section 412.14.2.1, 412.14.2.2 or 412.14.2.3 in regions where the concrete surrounding the anchorage is restrained against spaUing by a flange or slab or similar member.

411.7.4.3 Longitudinal torsion reinforcement shall be developed at both ends. 411.7.4.4 For hollow sections in torsion, the distance measured from the centerline of the transverse torsional reinforcement to the inside face of the wall of a hollow section shall not be less than O.SAohlph 411.7.5

Minimum Torsion Reinforcement

411.7.5.1 A minimum area of torsion reinforcement shall be provided in all regions where the factored torsional moment Til exceeds the values specified in Section 411.7.1.


SHEAR AND TORSION

411.7.5.2 Where torsional reinforcement is required by Section 411.7.5.1, the minimum area of transverse closed stirrups shall be computed by: (411-23)

411.7.5.3 Where torsional reinforcement is required by Section 411.7.5.1, the minimum total area of longitudinal torsional reinforcement shall be computed by:

~min ,

==

5ffc A.,p (At '1 Iyv Ph I21yl s ) Iyl

(411-24)

where A/s shall not be taken less than (I/6)b'/fyv.

411.7.6

Spacing of Torsion Reinforcement.

411.7.6.1 The spacing of transverse torsion reinforcement shall not exceed the smaller of p"I8 or 300 mm. 411.7.6.2 The longitudinal reinforcement required for torsion shall be distributed around the perimeter of the dosed stirrups with a maximum spacing of 300 mm. The longitudinal bars or tendons shall be inside the stirrups. There shall be at least one longitudinal bar or tendon in each comer of the stirrups. Bars shall have a diameter at leas! 1/24 of the stirrup spacing but not less than a 10 mm diameter bar. 411.7.6.3 Torsion reinforcement shall be provided for a distance of at least (b l + d) beyond the point theore-tically required.

411.8

SHEAR - FRICTION

411.8.1 The following provisions shall be applied where it is appropriate to consider shear transfer across a given plane, such as an existing or potential crack, an interface between dissimilar materials, or an interface between two concretes cast at different times. 411.8.2 Design of cross sections subject to shear transfer as described in Section 411.8 shall be based on Equation (411-1) where Vn is calculated in accordance with provisions of Section 411.8.3 or 411.8.4. 411.8.3 A crack shall be assumed to occur along the shear plane considered. Required area of shear-friction reinforcement Avf across the shear plane may be designed using either Section 411.8.4 or any other shear transfer design methods that result in prediction of strength in substantial agreement with results of comprehensive tests.

411.8.3.1 Provisions of Sections 411.8.5 through 411.8.1 0 shall apply for all calculations of shear transfer strength. 411.8.4

Shear-Friction .{)esign Methods

411.8.4.1 When shear-friction reinforcement 1S perpendicular to shear plane, shear strength Vn shall be computed by Vn

=

Avf/yP

(411-25)

where p is coefficient of friction in accordance with Section 411.8.4.3.

411.8.4.2 When shear-friction reinforcement is inclined to shear plane such that the shear force produces tension in shear-friction reinforcement, shear strength Vn shall be computed by (411-26) where af is angle between shear-friction reinforcement and shear plane.

411.8.4.3 Coefficient of friction p in Equation (411 25) and Equation (411-26) shaIl be Concrete placed monolithically.................. 1.4A

Concrete placed against hardened

concrete with surface intentionally

roughened as specified in Section

411.8.9 ............................................... LOA Concrete placed against hardened concrete not intentionally roughened ........................................... 0.6A Concrete anchored to as-roIled structural steel by headed studs or by reinforcing bars (see Section 411.8.10) ....................................... O.H where .A = 1.0 for normal-weight concrete, 0.85 fOI saIl'! lightweight concrete and 0.75 for all-lightweight concrete Linear interpolation shall be permitted when partial sand replacement is used.

411.8.5 Shear strength Vn shall not be taken greater than O.2f'aAc or 55 Ac in newlons, where Ac is area of concrete section resisting shear transfer. 411.8.6 Design yield strength of reinforcement shall not exceed 415 MPa.

shear-friction

411.8.7 Net tension across shear plane shall be resisted by . additional reinforcement. Permanent net compression across shear plane shaIl be permitted to be taken as additive to the force in the shear-friction reinforcement Avfh' when calculating required A,of:


CONCRETE

reinforcement shall be placed along the shear plane and shall be develop the specified yield strength on both em!bedlm~~nt, hooks or welding to special devices. For the purpose of Section 411.8, when concrete against previously hardened concrete, the interface transfer shall be clean and free of laitance. If p is ll""'~"'~-' to LOA, interface shall be roughened to a full of approximately 6 mm. When shear is transferred between as-rolled concrete using headed studs or welded reinforcing steel shall be clean and free of paint

SPECIAL PROVISIONS FOR DEEP MEMBERS 1 provisions of this section shall apply for members t;,ld less than 5 that are loaded on one face and on the opposite face so that the compression can develop between the loads and the supports. See also Section 412.11.6.

.9.2 The design of simple supported deep flexural ;.; mlemlbers for shear shall be based on Equations (411-1) and (41 V2), where shear strength Vc shall be in accordance with S~iion 411.9.6 or 411.9.7, and shear strength V. shall be in a,,60rdance with Section 411.9.8. 411.9.3 The design of continuous deep flexural members for shear shall be based on Sections 411.2 through 411.6 'with Section 411.9.5 substituted for Section 411.23, or on methods satisfying equilibrium and strength requirements. In either case, the design shall also satisfy Sections 41 1.9.4, 411.9.9 and 411.9,10. 411.9.4 Shear strength Vn for deep flexural members shall not be taken greater than (2/3) Pe bw d when lid is less than 2. When I,/d is between 2 and 5,

v

n

:=

1(1O+~) TF'

18

d

1JJ

c

bd '"

(411-27)

411.9.S Critical section for shear measured from face of support shall be taken at a distance O. I5ln for uniformly loaded beams and 0.50a for beams with concentrated loads, but not greater than d 411.9.6 Unless a more detailed calculation is made in accordance with Section 411.9.7. (411-28)

411.9.7 Shear strength l'c shall be permitted to be computed by

M\(IF: + 120 p", -'"Vd) b

f>::-1 ( 3.5 -2.5-:;:-,,--j 7 fud

w

Mu

d

(411-29)

except that the tenn shall not exceed 2.5, and Ve shall not be taken greater than (1/2) "Pc b,p. MIl is factored moment occutring simul taneously with Vu at the critical section defined in Section 411.9.5. 411.9.8 Where factored shear force Vu exceeds shear strength ¢lc~, shear reinforcement shall be provided to satisfy Equations (411- 1) and (411-2), where shear strength V. shall be computed by

vs

[

l+~-l

~ _d_ + s 12

r

AVh S2

[1l._!'!d_..lJ] f

d

__

12

}' (411-30)

where Av is area of shear reinforcement perpendicular to flexural tension reinforcem~nt within a distance s, and Avh is area of shear reinforcement parallel to flexural reinforcement within a distance S2. 411.9.9 Area of shear reinforcement Av shall not be than 0.0015 b,.s, and s shall not exceed diS or 450 mm.

k~i

411.9.10 Area of horizontal shear reinforcement AVh shall not be less than 0.0025 b"s2, and S2 shall not exceed d/3 or 450 mm. 411.9.11 Shear reinforcement required at the critical section defined in Section 411.9.5 shall be used throughout the span.

411.10 SPECIAL PROVISIONS FOR BRACKETS AND CORBELS 411.10.1 The following provisions apply to brackets and corbels with a shear span-to-depth ratio aid not greater than unity, and subject to a horizontal tensile force Nuc not larger than Vu. Distance d shall be measured at face of support. 411.10.2 Depth at outside edge of bearing area shall not be less than 0.5d 411.10.3 Section at face of support shall be designed to resist simultaneously a shear I:" a moment [Vua + N"e (h d)], and a horizontal tensile force N;,c'

National Structural Code of the Philippines, Volume 1 -, ~"_,,,_,_--"""TIlii'_"iIIl7IrrrI1Inltl~tll"

4-50

SHEAR AND TORSION

411.10.3.1 In all design calculations in accordance with Section 411.9, strength-reduction factor (J shall be taken equal to 0.85. 411.10.3.2 Design of shear-friction reinforcement Alifto resist shear Vu shall be in accordance with Section 411.8. 411.10.3.2.1 For normal-weight concrete, shear strength Vn shall not be taken greater .than 0.2 j'eb" d nor 5.5 bw d in newtons. 411.10.3.2.2 For all lightweight or sand-lightweight concrete, shear strength Vn shall not be taken greater than (0.2 - 0.07 a/d)!eb,.d nor (5.5 - 1.9 aid) b,p in newtons. 411.10.3.3 Reinforcement AI to resist moment [V,,a + Nue (h-d)] shall be computed in accordance with Sections 410.3 and 410.4. 411.10.3.4 Reinforcement An to resist tensile force Nile shall be determined from Nue < (JA,/y. Tensile force N,1t: shall not be taken less than O.2Vu unless special provisions are made to avoid tensile forces. Tensile force Nue shall be 'regarded as a live load even when tension results from creep, shrinkage or temperature change. .

,.

.,

II

411.10.3.5 Area of primary tension reinforcement As shall be made equal to the greater of (Af + An) or (2A'f/3 + An). 411.10.4 Closed stirrups or ties parallel to As, with a total area Ah not less than O.S(As - An), shall be uniformly distributed within two thirds of the effective depth adjacent toA,.

411.10.5 Ratio p=A/bdshall not be less than 0.04 (j'e!fv).

h'

.' ~,

'I

411.11

SPECIAL PROVISIONS FOR WALLS

411.11.1 Design for shear forces perpendicular to face of wall shall be in accordance with provisions for slabs in Section 411.13. Design for horizontal shear forces in plane of wall shall be in accordance with Section 411.11.2 through 411.11.8. 411.11.2 Design of horizontal section for shear in plane of wall shall be based on Equations (411-1) and (411-2), where shear strength Ve shall be in accordance with Section 411.11.5 or 411.1 1.6 and shear strength Vs shall be in accordance with Section 41 L 11.9. 411.11.3 Shear strength Vn at any horizontal section for shear in plane of wall shall not be taken greater than (S/6) ...Jj'c hd 411.11.4 For design for horizontal shear forces in plane of wall, d shall be taken equal to 0.8Iw . A larger value of d, equal to the distance from extreme compression fiber to center of force of all reinforcement in tension shall be permitted to be used when determined by a strain compatibility analysis. 411.11.5 Unless a more detailed calculation is made in accordance with Section 411.1 1.6, shear strength ~~ shall not be taken greater than (1/6) ...Jl' c h d for walls subject to N" in compression, or ~.~ shall not be taken greater than the value given in Section 411.4.23 for walls subject to N" in tension. 411.11.6 Shear strength Ve shall be permitted to be computed by Equations (411-31) and (411-32), where Vc shall be the lesser of Equation (411-31) or (411-32).

V =

411.10.6 At front face of bracket or corbel, primary tension reinforcement As shall be anchored by one of the following:

c

~~f'c 4

hd + N"d 41w

(411-31)

or

'\ "

2 3

by a structural weld to a transverse bar of at least equal size; weld to be designed to develop specified yield strength/y of As bars; by bending primary tension bars As back to form a horizontal loop; or by some other means of positive anchorage.

411.10.7 Bearing area of load on bracket or corbel shall not project beyond straight portion of primary tension bar As, or project beyond interior face of transverse anchor bar (if one is provided).

vc (411-32) where N" is negative for tension. When (M,,/v,, negative, Equation (411-32) shall not apply.

1)2) is

411.11.7 Sections located closer to wall base than a distance /,./2 or one half the wall height, whichever is less, shall be permitted to be designed for the same T'c as that computed at a distance 1,/2 or one half the height


CONCRETE

411.11.8 When factored shear force VII is less than ¢ vJ2, "reinforcement shall be provided in accordance with Section 411.11. 9 or in accordance with Section 414. When VI( exceeds ¢ Vc 12, wall reinforcement for resisting shear shall be provided in accordance with Section 411.11.9. 411.11.~

4--51

depth not less than that of the deepest connection of framing elements to the columns. See also Section 407.10.

411.13 SPECIAL PROVISIONS FOR SLABS AND FOOTINGS

Design of Shear Reinforcement for Walls

411.11.9.1 Where factored shear force VI( exceeds shear strength ¢ Vc, horizontal shear reinforcement shall be provided to satisfy Equations (411-1) and (411-2), where shear strength V. shall be computed by (411-33) where Av is area of horizontal shear reinforcement within a distance S2 and distance d is in accordance with Section 411.11.4. Vertical shear reinforcement shall be provided in accordance with Section 411.11.9.4.

411.13.1 The shear strength of slabs and footings in the vicinity of columns, concentrated loads or reactions is governed by the more severe of two conditions: 411.13.1.1 Beam action where each critical section to be investigated extends in a plane across the entire width. For beam action the slab or footing shall be designed in accordance with Sections 411.2 through 411.6.

S2

411.11.9.3 Spacing of horizontal shear reinforcement shall not exceed 1... 15, 3h or 450 mm.

411.13.1.2 Two-way action where each of the critical sections to be investigated shall be located so that its perimeter, bo. is a minimum, but need not approach closer than d/2 to: 1. Edges or comers of columns, concentrated loads or reaction areas, or 2. Changes in slab thickness such as edges of capitals or drop panels. For two-way action, the slab of footing shall be designed in accordance with Sections 411.13.2 through 411.13.6.

411.11.9.4 Ratio Pn of vertical shear reinforcement area to gross concrete area of horizontal section shall not be less than

411.13.1.3 For square or rectangular columns, concentrated loads or reactions areas, the critical sections with four straight sides shall be permitted.

411.11.9.2 Ratio Ph of horizontal shear reinforcement area to gross concrete area of vertical section shall not be less than 0.0025.

r - h': PI! = 0.0025 + 0.5l2.5

J (Ph

0.0025)

(411-34) nor 0.0025, but need not be greater than the required horizontal shear reinforcement.

411.11.9.5 Spacing of vertical shear reinforcement shall not exceed 1".13, 3h or 450 mm.

Sl

411.12 TRANSFER OF MOMENTS TO COLUMNS 411.12.1 When gravity load, wind, earthquake or other lateral forces cause transfer of moment at connections of framing elements to columns, the shear resulting from moment transfer shall be considered in the design of lateral reinforcement in the columns. 411.12.2 Except for connections not part of a primary seismic load-resisting system that are restrained on four sides by beams or slabs of approximateiy equal depth, connections shall have lateral reinforcement not less than that required by Equation (411-13) within the column for a

411.13.2 The design of a slab or footing for two-'WaY action is based on Equations (411-1) and (411-2). Vc shall be computed in accordance with Section 411.13.2.1, Vs shall be computed in 411.13.2.2 or 411.13.3.1. accordance with Section 411.12.3. For slabs with shear heads, Vn shall be in accordance with Section 411.13.4. When moment is transferred between a slab and a column, Section 411.13.6 shall apply. 411.13.2.1 For non-prestressed slabs and footings, Vc shall be the smallest of: 1.

Vc

.!..(1+~J~f'c bod 6 Pc

(411-35)

where Pc is the ratio of long side to short side of the column, concentrated load or reaction area 2.

1l' asd + 2J IF: b d b(}

12

c

0

(411-36)

where a~ is 40 for interior columns, 30 for edge columns and 20 for comer columns, and

National S1ructural Code of the Philippines. Volume 1

SHEAR AND TORSION

4-52

(411-37)

3.

411.13.2.2 At columns of two-way prestressed slabs and footings that meet the requirements of Section 418.9.3:

411.13.4.3 . The ends of each shearhead arm shall be permitted to be cut at angles not less tran 30 degrees with the horizontal, provided the plastic moment strength of the remaining tapered section is adequate to resist the shear force attributed to the arm ofthe shearhead. 411.13.4.4 All compression flanges of steel shapes shall be located within O.3d of compression surface of slab.

where Pp is the smaller of 0.3 or (asdlbo + 1.5)/12, as is 40 for interior columns, 30 for edge columns and 20 for comer columns, bo is perimeter of critical section defined in Section 41 1.1 3.1.2, fpc is the average value of fpc for the two directions, and v;, is the vertical component of all effective prestress forces crossing the critical section. Vc shall be permitted to be computed by Equation (411-38) if the following are satisfied; otherwise, Section 411.13 .2.1 shall apply: 1. No portion of the column cross section shall be closer to the discontinuous edge than four times the slab thickness, and 2. f'c in Equation (411-38) shall not be taken greater than 35 MPa), and 3. fpc in each direction shall not be less than 0.9 MPa, or be taken greater than 3.5 MPa.

.. . '

~.

:1

I""

'" .,;.

", 'f~"

". I.~,

,~

..,

:i '" ''""

'". Iii

1'I "

L",.

II,

:~!

411.13.3 Shear reinforcement consisting of bars or wires shall be permitted in slabs and footings in accordance with the following: 411.13.3.1 Vn shall be computed by Equation (411-2), where ~.~ shall not be taken greater than (/6) ..J f'cbdi, and

the required area of shear reinforcement AI' and Vs shall be

calculated in accordance with Section 411.6 and anchored in accordance with Section 412.14. 411.13.3.2 O.s..Jf'cbo d.

Vn shall not be taken greater than

411.13.4 Shear reinforcement conslstmg of steel 1- or channel- shaped sections (shearheads) shall be permitted-in slabs. The provisions of Sections 41 L 13.4. 1 through 411.13.4.9 shall apply where shear due to gravity load is transferred at interior column supports. Where moment is transferred to columns, Section 411.13.6.3 shall apply. 411.13.4.1 Each shearhead shall consist of steel shapes fabricated by welding with a full penetration weld into identical arms at right angles. Shearhead arms shall not 1. be interrupted within the column section. 411.13.4.2 A shearhead shall not be deeper than 70 2 times the web thickness of the steel shape. . 3.

411.13.4.5 The ratio a" between the stiffness of each shearhead arm and that of the surrounding composite cracked slab section of width (C2' + d) shall not be less than 0.15. 411.13.4.6 The plastic moment strength Mp required for each arm of the shearhead shall be computed by

~Mp = ~~[h" + a (I,. - ~ JJ v

(411-39)

where ~ is the strength-reduction factor for flexure, 11 is the number of arms, and I" is the minimum length of each shearhead arm required to comply with requirements of Section 411.13.4.7 and 411.13 .4.8. 411.12.4.7 The critical slab section for shear shall be perpendicular to the plane of the slab and shall cross each shearhead arm at three fourths the distance [Iv - (cJI2)] from the column face to the end of the shearhead arm. The critical section shall be located so that its perimeter bo is a minimum, but need not be closer than the perimeter defined in Section 411.13 .1.2, Item 1.

Vn shall not be taken greater than (1/3) ..Jf'c '.

bod, on the critical section defined in Section 411.13.4.7.

When shearhead reinforcement is provided, Vn shall not be

taken greater than 0.6..J Pc bod , on the critical section defined in Section 411.13.1.2, Item 1.

411.12.4.8

411.13.4.9 The moment resistance "WI' contributed to each slab column strip computed by a shearhead shall not be taken greater than

~a,. ~~, (I _~) 2 11

l. ,.

2

(411-40)

where r/J is the strength-reduction factor for flexure, 11 is the number of arms, and I,. is the length of each shearhead arm actually provided. However, M" shall not be taken larger than the smaller of: Thirty percent of the total factored moment required for each slab column strip, The change in column strip moment over the length I", The value ofMp computed by Equation (411-39).


CONCRETE

When unbalanced moments are consi shearhead must have adequate anchoragt) to transmit Mp to column.

where Vc and VI are defined in Section 41 U.::'.3. If shear reinforcement is provided, the design shall take into account the variation of shear stress around the column.

Opening in slabs. When openings in slabs are . lOcated at a distance less than 10 times the slab thickness from a concentrated load or reaction area, or when openings in flat slabs are located within column strips as defined in Section 413, the critical slab sections for shear defined in Section 411.13.1.2 and Section 411.13.4.7 shall be modified as follows:

411.13.6.3 When shear reinforcement consisting of steel 1- or channel-shaped sections (shearheads) is provided, the sum of the shear stresses due to vertical load acting on the critical section' defined by Section 411.13.4.7 and the shear stresses resulting from moment transferred by eccentricity of shear about the centroid of the critical section defined in Section 411.13.1. 2 shall not exceed q, (1/3)

..J/,c

41i.13.5.1 For slabs without shearheads, that part of the perimeter of the critical section that is enclosed by . straight lines projecting from the centroid of the column, concentrated load or reaction area and tangent to the boundaries of the openings shall be considered ineffective. For slabs with shearheads, the ineffective 411.13.5.2 portion of the perimeter shall be one half of that defined in Section 411.13.5.1 411.13.6 Transfer of Moment in Slab-Column

Connections

411.13.6.1 When gravity load, wind, earthquake or other lateral forces cause transfer of unbalanced moment, M u, between a slab and a column, a fraction rr Mu of the unbalanced moment shall be transferred by flexure in accordance with Section 413.6.3. The remainder of the unbalanced moment given by rv Mu shall be considered to be transferred by eccentricity of shear about the centroid of the critical section defined in Section 411.13. 1.2 where:

rv

= (1 - rr)

(411-41)

411.13.6.2 The shear stress resulting from moment transfer by eccentricity of shear shall be assumed to vary linearly about the centroid of the critical sections defined in Section 411.13.1.2. The maximum shear stress Jue to the factored shear force and moment shall not exceed q, lin: L

For members without shear reinforcement:

;vn

=

q,(:a J

(411-42)

where Vc is as defined in Section 411.13.2.1 and 411.13.2.2. 2.

For members with shear reinforcement other than shearheads: (411-43)


DEVELOPMENT AND SPLICES OF REINFORCEMENT

SECTION 412 - DEVELOPMENT AND SPLICES OF REINFORCEMENT

Mn

412.1

n

Ab As Atr

Av

NOTATIONS area ofan individual bar, mm2.

area of non-prestressed tension reinforcement,

mm2 . total cross-sectional area of all transverse reinforcement which is within the spacing sand which crosses the potential plane of splitting through the reinforcement being developed, mm2 area of shear reinforcement within a distance s, mm-. area of an individual wire to be developed or spliced, mm2 . depth of equivalent rectangular stress block as defined in Section 410.3.7.1, mm. web width, or diameter of circular section, mm. spacing or cover dimension, mm. See Section 412.3.4. distance from extreme compression fiber to centroid oftension reinforcement, mm. nominal diameter of bar, wire or prestressing strand, mm. specified compressive strength ofconcrete, MPa. square root of specified compressive strength of concrete, MPa. average splitting tensile strength of lightweight aggregate concrete, MPa.

stress in prestressed reinforcement at nominal

strength, MPa.

effective stress in prestressed reinforcement (after

allowance for all prestress losses), MPa.

specified yield strength of non-prestressed

reinforcement, lVUPa

specified yield strength of transverse reinforceme~t,

MPa.

overall thickness of member, mm.

transverse reinforcement index.

AtrfytllO.m additional embedment length at support or at point

of inflection, mm.

development length, mm.

Idb multiplied by applicable modification factors.

basic development length, mm.

development length of standard hook in tension,

measured from critical section to outside end of

hook [straight embedment length between critical

section and start of hook (point of tangency) plus

radius of jj~ild and one bar diameter], mm.

Ihb tittles appiicable modification factors.

1

Aw

a bw

c d

'I"

fse

Ihb

N

s Sw

Vu

a

fJ /3b

r A.

412.2

basic development length of standard hook in tension, mm. nominal moment strength at section, Newton meter. AJ;{d - a '2). number of bars in a layer being spliced or developed at a critical section. number of bars or wires being spliced or developed along the plane of splitting. maximum center to center spacing of transverse reinforcement within Jd, mm. spacing ofwire to be developed or spliced, mm.

factored shear force at section.

reinforcement location factor. See Section 412.3.4.

coating factor. See Section 412.3.4.

ratio of area of reinforcement cut off to total area of tension reinforcement at section. reinforcement size factor. See Section 412.3.4. lightweight aggregate concrete factor. See Section 412.3.4.

DEVELOPMENT OF

RE~ORCEMENT-GENERAL

412.2.1 Calculated tension or compression in reinforcement at each section of structural concrete members shall be developed on each side of that section by embedment length, hook or mechanical device, or a combination thereof Hooks shall not be used to develop bars in compression. 412.2.2 The values of exceed 0.7 MPa.

"f'c

used in Section 412 shall not

412.3 DEVELOPMENT OF DEFORMED BARS AND DEFORMED WIRE IN TENSION 412.3.1 Development length, lcJ, in terms of diameter, db, for deformed bars and deformed wire in tension shall be determined from either Section 412.3.2 or 412.3.3, but Id shall not be less than 300 mm. 412.3.2 For deformed bars or deformed wire, J)db shall be as follows:


CONCRETE

20 mm diameter and smaller bars and

c 25 mm diameter

and larger bars

K tr

lei 12/y ap;, db

25~f'c

4-55

lei 3/y ap;, db == 5~f'c

lei

IS/yap;,

lei

9/y ap;,

db

25~/'c

db

lO~f'c

=

spacing or cover dimension, millimeters. Use the smaller of either the distance from the center of the bar to the nearest concrete surface or one-half the center-to-center spacing of the bars being developed. transverse reinforcement index Atr/yt 10sn

where: Atr

/yt s

For deformed bars or deformed wire, Ie/db shall N

(412-1)

total cross-sectional area of all transverse reinforcement which is within the spacing sand which crosses the potential plane of splitting through the reinforcement being developed, square millimeters. of transverse specified yield strength reinforcement, square millimeters. maximum center-to-center spacing of transverse reinforcement within Id, millimeters. number of bars or wires being developed along the plane of splitting.

It shall be permitted to use K tr 0 as a design simplification even if transverse reinforcement is present. in which the term than 2.5

(c + ktr)/db shall not be taken greater

412.3.4 The factors for use in the expressions for development of deformed bars and deformed wires In tension in Sections 412.1 through 412.20 are as follows:

a =

f3

reinforcement location factor 1.3 for horizontal reinforcement so placed that more than 300 mm of fresh concrete is cast in the member below the development length or splice 1.0 for other reinforcement. coating factor 1.5 for epoxy-coated bars or wires with cover less than 3d!>. or clear spacing less than 6db 1.2 All other epoxy-coated bars or wires. ] .0 for uncoated reinforcement.

However, the product

af3 need

not be taken greater than

412.3.5 Excess reinforcement. Reduction in development length shall be permitted where reinforcement in a flexural member is in excess of that required by analysis except where anchorage or development for /y is specifically required or the reinforcement is designed under provisions of Section 421.2.1.4 .... [(A.,r
412.4 DEVELOPMENT OF DEFORMED BARS IN COMPRESSION 412.4.1 Development length ld, in millimeters, for deformed bars in compression shall be computed as the product of the basic development length Idb and applicable modification factors as defined in this section, but Id shall not be less than 200 mm. 412.4.2 Basic development length lab shall be

1.7.

r

;.

reinforcement size factor 0.8 for 20 nun diameter and smaller bars and deformed wires. 1.0 25 nun diameter and larger bars lightweight aggregate concrete factor. 1.3 when lightweight aggregate concrete is used, however, when!ct is specified, A. shall be

1.0

permitted to be ~/'c 11.8/at but not less than 1.0 When normal weight concrete is used.

IJb

=

l7.-

4,,/'.

dh

but not less than 0.04dt/y

412.4.3 Basic development length Idb shall be permitted to be multiplied by applicable factors for: 412.4.3.1

Excess reinforcement.

Reinforcement in excess of that required by anal ysi s (A "required)!(A .,provid~)


DEVELOPMENT AND SPLICES OR REINFORCEMENT

412.4.3.2 Spirals and ties Reinforcement enclosed within spiral reinforcement not less than 10 mm diameter and not more than 100 mm pitch or within 12 mm diameter ties in conformance with Section 407.11.5 and spaced not more than 100 mm on center .. ....... ....... ....... ....... ........ ................................ 0.75

412.5

DEVELOPMENT OF BUNDLED BARS

412.5.1 Development length of individual bars within a bundle, in tension or compression, shall be that for the individual bar, increased 20 percent for 3-bar bundle, and 33 percent for 4-bar bundle. 412.5.2 For determining the appropriate factors in Section 412.3, a unit of bundled bars shall be treated as a single bar ofa diameter derived from the equivalent total area.

412.6 DEVELOPMENT OF STANDARD HOOKS IN TENSION 4J2.6.1 Development length ldh in mm for deformed bars in tension terminating in a standard hook shall be computed as the product of the basic development length ihb of Section 412.6.2 and the applicable modification factor or factors of Section 412.6.3, but ldh shall not be less than 8db or less than 150 mm. 412.6.2 Basic development length with h equal to 415 MPa shall be

lhb

lhb

412.6.3.5 concrete

Lightweight aggregate ......................................................... 1.3

412.6.3.6 Epoxy-coated reinforcement. Hooked bars with epoxy coating .............................. 1.2 412.6.4 For bars being developed by a standard hook at discontinuous ends of members with side cover and top (or bottom) cover over hook less than 65 rnm, hooked bar shall be enclosed within ties or stirrups spaced along the full development length ldh not greater than 3db, where db is diameter of hooked bar. For this case, factor of Section 412.6.3.3 shall not apply. 412.6.5 Hooks shall not be considered effective developing bars in compression.

In

412.7 MECHANICAL ANCHORAGE 412.7.1 Any mechanical device capable of developing the strength of reinforcement without damage to concrete may be used as anchorage.

for a hooked bar

412.7.2 Test results showing adequacy of such mechanical devices shall be presented to the building official.

shall be multiplied

412.7.3 Development of reinforcement shall be permitted to consist of a combination of mechanical anchorage plus additional embedment length of reinforcement between the point of maximum bar stress and the mechanical anchorage.

i = 100 d hh ~J'c b 412.6.3 Basic development length by applicable factor or factors for:

412.6.3.4 Excess reinforcement. Where anchorage or development for h is not specifically required, reinforce-ment in excess of that required by analysis [(As required)/(As provi
412.6.3.1 Bar yield strength.

Bars withh other than 415 MPa .......................... h/415

412.8 DEVELOPMENT OF WELDED DEFORMED WIRE FABRIC IN TENSION

412.6.3.2 Concrete cover.

For 36 mm diameter bar and smaller, side cover (normal to

plane of the hook) not less than 65 mm, and for 90-degree

hook, cover on bar extension beyond hook not less than 50

millimeters ........................................................... 0.7

412.3.1 Development length id, in millimeters, of welded deformed wire fabric measured from the point of critical section to the end of wire shall be computed as the product of the development length ld, from' Section 412.3.2 or 412.3.3 times a wire fabric factor from Section 412.8.2 or 412.8.3. It shall be permitted to reduce the development length in accordance with Section 412.3.5 when applicable, but ld shall not be less than 200 mm except in computation of lap splices by Section 412.19. When using the wire fabric factor from Section 412.8.2, it shall be permitted to use an epoxy-coating factor P of 1.0 for epoxy-coated welded wire fabric in Sections 412.3.2 'and 412.3.3.

412.6.3.3 Ties or stirrups.

For 36 mm diameter bar and smaller, hook enclosed

vertically or horizontally within ties or stirrup ties spaced

along the full development length ldh not greater than 3db,

where db is diameter

of hooked bar .......................................................... 0.8

412.3.2 For welded deformed wire fabric with at least one cross wire within the development length and not less than AsSociation of Structural Engineers of the Philippines

CONCRETE

from the point of the critical section, the factor shall be the greater of:

1......""TPr"

4-57

full design strength under specified factored loads shall be permitted. 412.10.3 Where bonding of a strand does not extend to end of member, and design includes tension at service load in pre-compressed tensile zone as permitted by Section 418.5.2, development length specified in Section 412.10.1 shall be doubled.

not be taken greater than 1. For welded deformed wire fabric with no cross within the development length or with a single cross than 50 millimeters from the point of the critical the wire fabric factor shaH be taken as 1, and the lop1melilt length shall be determined as for deformed

When any plain wires are present in the deformed fabric in the direction of the development length, the . shall be developed in accordance with Section 412.9.

DEVELOPMENT OF WELDED PLAIN FABRIC IN TENSION Yield strength of welded plain wire fabric shall considered developed by embedment of two cross wires the closer cross wire not less than 50 millimeters from the point ofthe critical section. However, the development length [d, in millimeters, measured from the point of the critical section to the outermost cross wire shall not be less . than

412.11 DEVELOPMENT OF FLEXURAL REINFORCEMENT -.GENERAL 412.11.1 Development of tension reinforcement by bending across the web to be anchored or made continuous with reinforcement on the opposite face of member shall be permitted. 412.11.2 Critical sections for development of reinforcement in flexural members are at points of maximum stress and at points within the span where adjacent reinforcement terminates or is bent. Provisions of Section 412.12.3 must be satisfied. 412.11.3 Reinforcement shall extend beyond the point at which it is no longer required to resist flexure for a distance equal to the effective depth of member or 12db, whichever is greater, except at supports of simple spans and at free end of cantilevers. 412.11.4 Continuing reinforcement shall have an embedment length not less than the development length,[d beyond the point where bent or terminated tension reinforcement is no longer required to resist flexure.

except that when reinforcement provided is in excess of that required, this length may be reduced in accordance with Section 412.3.5. ld shall not be less than 150 rom except in computation oflap splices by Section 412.20

412.11.5 Flexural reinforcement shall not be termir1ated in a tension zone unless one of the following conditions is satisfied:

412.10 DEVELOPMENT OF PRESTRESSING STRAND

412.11.5.1 Shear at the cutoff point does not exceed two thirds that permitted, including shear strength of shear reinforcement provided.

412.10.1 Three- or seven-wire pre-tensioning strand shall be bonded beyond the critical section for a development length, in millimeters, not less than

Expression in parentheses used as a constant without units. where db is strand diameter in millimeters, and/p. andlse are expressed in megapascals. 412.10.2 Limiting the investigation to cross sections nearest each end of the member that are required to develop

412.11.5.2 Stirrup area in excess of that required for shear and torsion is provided along each terminated bar or wire over a distance from the termination point equal to three fourths the effective depth of member. Excess stirrup areaAv shall not be less than OAby,si;.). Spacing s shall not exceed dl8Pb where Pb is the ratio of area of reinforcement cut offto total area oftension reinforcement at the section, 412.11.5.3 For Diameter 36 mm bar and smaller, continuing reinforcement provides double the area required for flexure at the cutoff point and shear does not exceed three fourths that permitted.



412.11.6 Adequate anchorage shall be provided for tension reinforcement in flexural members where reinforcement stress is not directly proportional to moment, such as sloped, stepped or tapered footings, brackets, deep flexural members, or members in which tension reinforcement is not parallel to compression face. See Sections 412.12.4 and 412.13.4 for deep flexural members.

412.12 DEVELOPMENT OF POSITIVE MOMENT REINFORCEMENT

412.12.2 When a flexural member is part of a primary lateral-load-resisting system, positive moment reinforce ment required to be extended into the support. by Section 412.12.1 shall be anchored to develop the specified yield strength/y in tension at the face of support. 412.12.3 At simple supports and at points of inflection, positive moment tension reinforcement shall be limited to a diameter such that ld computed for by Section 412.3 satisfies Equation (412-2), except Equation (412-2) need not be satisfied for reinforcement terminating beyond center line of simple supports by a standard hook or a mechanical anchorage at least equivalent to a standard hook.

t,

(412-2)

where: la at a support shall be the embedment length beyond

!iIIl

Mn

V"

412.13.1 Negative moment reinforcement in a continuous, restrained or cantilever member, or in any member of a rigid frame, shall be anchored in or through the supporting member by embedment length, hooks or mechanical anchorage. 412.13.2 Negative moment reinforcement shall have an embedment length into the span as required by Sections 412.2 and 412.11, Item 3.

412.12.1 At least one third the positive moment reinforcement in simple members and one fourth the positive moment reinforcement in continuous members shall extend along the same face of member into the support. In beams, such reinforcement shall extend into the support at least 150 mm.

I"

412.13 DEVELOPMENT OF NEGATIVE MOMENT REINFORCEMENT

center of support. at a point of inflection shall be limited to the effective depth of member or 12d", whichever is greater. nominal strength assuming all reinforcement at the section to be stressed to the specified yield strengthJ;. factored shear force at the section.

An increase of 30 percent in the value of M,/V" shall be permitted when the ends of reinforcement are confined by a compressive reaction. 412.12.4 At simple supports of deep flexural members, positive moment tension reinforcement shall be anchored to develop the specified yield strength /y in tension at the face of support. At interior supports of deep flexural members, positive moment tension reinforcement shall be continuous or be spliced with that ofthe adjacent spans.

412.13.3 At least one third the total tension reinforcement provided for negative moment at a support shall have an embedment length beyond the point of inflection not less than effective depth of member, 12db, or 1/l6 the clear span, whichever is greater. 412.13.4 At interior supports of deep flexural members, negative moment tension reinforcement shall be continuous with that of the adjacent spans.

412.14 DEVELOPMENT OF WEB REINFORCEMENT 412.14.1 Web reinforcement shall be carried as close to compression and tension surfaces of member as cover requirements and proximity of other reinforcement will permit. 412.14.2 Ends of single leg, simple U- or multiple U stirrups shall be anchored by one ofthe following means: 412.14.2.1 For 16 mm diameter bar and D31 wire, and smaller, and for 20 and 25 mm diameter bars witht. of 275 MPa or less, a standard stirrup hook around longitudinal reinforcement. For 20 and 25 mm diameter stirrups with,(. 412.14.2.2 greater than 275 MFa, a standard stirrup hook around a longitudinal bar plus an embedment betweenmidheight of the member and the outside end of the hook equal to or greater than 0.1 d,J;.! fc 412.14.2.3 For each leg of welded smooth wire fabric forming simple U-stirrups, either: 1. 2.

Two longitudinal wires spaced at a 50 mm spacing' along the member at the top ofthe U. One longitudinal wire located not more than d/4 from the compression face and a second wire closer to the compression face and spaced not less than 50 millimeters from the first wire. The second wire shall be permitted to be located on the stirrup leg beyond a


CONCRETE

bend, or on a bend with an inside diameter of bend not less than 8db. For each end of a single-leg stirrup of plain or deformed wire fabric, two longitudinal at a minimum spacing of 50 millimeters and with the wire at least the greater of d'4 or 50 millimeters from of member d·?. Outer longitudinal wire at face shall not be farther from the face than the of primary flexural reinforcement closest to the

4.2.5 In joist construction as defined in Section for 12 mm diameter bar and D20 wire and smaller, ~.",.rI'''rri hook.

; Between anchored ends, each bend in the lntl.nW)US portion of a simple U-stirrup or multiple U shall enclose a longitudinal bar. Longitudinal bars bent to act as shear 'reilnt()rc(ID}€mt, if extended into a region of tension, shall be ':c
SPLICES OF REINFORCEMENT Splices of reinforcement shall be made only as required or permitted on design drawings or in specifications, or as authorized by the engineer. 412.15.2

Lap splices

Lap splices shall not be used for bars 412.15.2.1 larger than 36 mm diameter, except as provided in Sections 412.17.2 and 415.9.2.3. Lap splices of bars· in a bundle shall be 412.15.2.2 based on the 'Iap splice length required for individual bars within the bundle, increased in accordance with Section 412.5. Individual bar splices within a bundle shall not overlap. Entire bundles shall not be lap spliced. 412.15.2.3 Bars spliced by non-contact lap splices in flexural members shall not be spaced transversely farther

4-59

apart than one fifth the required lap splice length, or 150 mm. 412.15.3

Welded splices and mechanical connections

412.15.3.1 Welded splices and other mechanical connections may be used. 412.15.3.2 Except as provided in this chapter, all welding shall conform to "Structural Welding Code Reinforcing Steel" (ANSIIAWS D1.4).

A full-welded splice shall develop at least 412.15.3.3 125 percent of specified yield strength,J;" of the bar. 412.15.3.4 A full mechamcal connection shall develop in tension or compression, as required, at least 125 percent of specified yield strength J;. of the bar. 412.15.3.5 Welded splices and mechanical connections not meeting requirements of Section 412.15.3.3 or 412.15.3.4 are allowed only for 16 mm diameter bars and smaller and in accordance with Section 412.16.4.

Welded splices and mechanical 412.15.3.6 connections shall maintain the clearance and coverage requirements of Sections 407.7 and 407.8.

412.16 SPLICES OF DEFORMED BARS AND DEFORMED WIRE IN TENSION 412.16.1 Mimmum length of lap for tension lap spliees shall be as required for Class A or B splice, but not less than 300 mm, where: Class A splice .................................. 1.01d Class B splice ........................ ........... 1.31d where ld is the tensile development length for the specified yield strength./y in accordance with Section 412.3 without the modification factor of Section 412.3.5. 412.16.2 Lap splices of deformed bars and deformed wire in tension shall be Class B splices except that Class A splices may be used when: 1. the area of reinforcement provided is at least twice that required by analysis over the entire length of the splice, and 2. one half or less of the total reinforcement is spliced within the required lap length. 412.16.3 Welded splices or mechamcal connections used where area of reinforcement provided is less than twice that required by analysis shall meet requirements of Section 412.15.3.3 and 412.15.3.4.


4-60


412.16.4 Welded splices or mechanical connections not meeting the requirements of Section 412.15.3.3 or 412.15.3.4 are allowed for 16 mm diameter bars and smaller when the area of reinforcement provided is at least twice that required by analysis, and the following requirements are met: 412.16.4.1 Splices shall be staggered at least 600 mm and in such manner as to develop at every section at least twice the calculated tensile force at that section but not less than 140 MPa for total area of reinforcement provided. 412.16.4.2 In computing tensile forces developed at each section, rate the spliced reinforcement at the specified splice strength. Unspliced reinforcement shall be rated at that fraction of jy defined by the ratio of the shorter actual development length to ld required to develop the specified yield strengthjy. 412.16.4.3 Mechanical connections need not be staggered as required by Section 412.16.4.1 or 412.16.5 provided the clearance and coverage requirements of Sections 407.7 and 407.8 are maintained and, at 90 percent of the yield stress, the strain measured over the full length of the connector does not exceed 50 percent ofthe strain of an unspliced bar when the maximum computed design load stress does not exceed 50 percent ofthe yield stress. 412.16.5 Splices in "tension tie members" shall be made with a full-welded splice or full mechanical connection in accordance with Section 412.15.3.3 and 412.15.3.4, and splices in adjacent bar shall be staggered at least 750 mm. :I~.·

.pl'l

ends held in concentric contact by a suitable device shall be permitted. 412.17.4.2 Bar ends shall terminate in flat surfaces within 1-112 degrees of a right angle to the axis of the bars and shall be fitted within 3 degrees of full bearing after assembly. 412.17.4.3 End-bearing splices shall be used only in members containing closed ties, closed stirrups or spirals.

412.18 SPECIAL SPLICE REQUIREMENTS FOR COLUMNS 412.18.1 Lap splices, butt welded splices, mechanical connections or end-bearing splices shall be used with the limitations of Sections 412.18.2 through 412.18.4. A splice shall satisfY requirements for all load combinations for the column. 412.18.2 Lap Splices in Colnmns 412.18.2.1 Where the bar stress due to factored loads is compressive, lap splices shall conform to Sections 412.17.1 and 412.17.2, and where applicable, to Section 412.18.2.4 or 412.18.2.5. 412.18.2.2 Where the bar stress due to factored load'.> is tensile and does not exceed 0.5};. in tension, lap splices shall be Class B tension lap splices if more than one half of the bars are spliced at any section, or Class A tension lap splices if one half or fewer of the bars are spliced at any section and alternate lap splices are staggered by

'd.

412.17 SPLICES OF DEFORMED BARS IN COMPRESSION 412.17.1 Compression lap splice length shall be 0.07f;db for jy of 415 MPa or less, or (0.13 .t;. - 24) db for.1; greater than 415 MPa, but not less than 300 mm. For f~ less than 20. MPa, length of lap shall be increased by one third. 412.17.2 When bars of different size are lap spliced in compression, splice length shall be the larger of: development length oflarger bar, or splice length of smaller bar. Lap splices of 45 and 60 mm diameter bars to 36 mm diameter and smaller bars shall be permitted. 412.17.3 Welded splices or mechanical connections used in compression shall meet requirements of Sections 412.15.3.3 and 412.15.3.4. 412.17.4 End-Bearing Splices 412.17.4.1 In bars required for compression only, transmission of compressive stress by bearing of square cut

412.18.2.3 Where the bar stress due to factored loads is greater than 0.5 };. in tension, lap splices shall be Class B tension lap splices. 412.18.2.4 In tied reinforced compression members, where ties throughout the lap splice length have an effective area not less than O.OOIsh 05, lap splice length shall be permitted to be multiplied by 0.83, but lap lefibrth shall not be less than 300 mm. Tie legs perpendicular to dimension h shall be used in determining effective area. In spirally reinforced compression 412.18.2.5 members, lap splice length of bars within a spiral shall be permitted to be multiplied by 07<;, but lap length shall not be less than 300 mm. 412.18.3 Welded splices or mechanical connectors in, columns. Welded splices or mechanical connectors in, columns shall meet the requirements of Section 412.15.3. or412.15.3.4.


CONCRETE

splices in columns. End-bearing with Section 412.17.4 shall be permitted to be bars stressed in compression provided the C>t"{1(7~'rM or additional bars are provided at splice continuing bars in each face of the column shall strength, based on the specified yield strength /y, O.2/y times the area of the vertical reinforcement in

4-61

SECTION 413 - TWO-WAY SLAB SYSTEMS 413.1 NOTATION bi

=

width of the critical section defined in Section 411.13 .1.2 measured in the direction of the span for

b2

=

Splices of Welded Deformed Wire Fabric C Minimum length of lap for lap splices of welded wire fabric measured between the ends of each fabric not be less than 1.31d or 200 rom, and the overlap between outermost cross wires of each fabric sheet be less than 50 millimeters, Id shall be the development for the specified yield strength h. in accordance with 12.8.

Lap splices of welded deformed wire fabric, with no within the lap splice length, shall be determined as

CI

C2

When any plain wires are present in the deformed wire in the direction of the lap splice or when deformed wire . lap spliced to plain wire fabric, the fabric shall be lap in accordance with Section 412.20.

Splices of Welded Plain Wire Fabric in

Ecb Ecs h

h Is

""'Millimum length of lap for lap splices of welded smooth wire shall be in accordance with the following:

·!'!'i'l'~12.20.1 When area of reinforcement provided is less than . ,.;..~ce that required by analysis at splice location, length of "';':ovedap measured between outermost cross wires of each fabric ':~:Sheet shall not be less than one spacing of cross wires plus 50 '*[~;millimeters, or less than 1.5 ld, or 150 rom, ld shall be the !'!~evelopment length for the specified yield strength /y in accordance with Section 412.9.

Kr

In 11

12

which moments are determined, mm width of the critical section defined in Section 411.13.1.2 measured in the direction perpendicular to bI, mm cross-sectional constant to define torsional properties

The constant C for T - or L-sections shall be permitted to be evaluated by dividing the section into separate rectangular parts and summing the values of C for each part = size of rectangular or equivalent rectangular column, capital, or bracket measured in the direction of the span for which moments are being determined, mm = size of rectangular or equivalent rectangular column, capital or bracket measured transverse to the direction of the span for which moments are being determined, mm = modulus of elasticity of beam concrete = modulus of elasticity of slab concrete = overall thickness of member, mm moment of inertia about centroidal axis of gross section ofbeam as defined in Section 413.4 • = moment of inertia about centroidal axis of gross section of slab h3/12 times width of slab defined in notations a. and f:Jr torsional stiffness of torsional member; moment per unit rotation = length of clear span in direction that moments are being determined, measured face to face of supports length of span in direction that moments are being determined, measured center to center of supports = length of span transverse to i J, measured center to center of supports. See also Sections 413.7.2.3 and 413.7.2.4

When area of reinforcement provided is at least twice .tthat required by analysis at splice location, length of overlap . measured between outermost cross wires of each fabric sheet "shall not be less than 1.5 ld, or 50 millimeters, ld shall be the '~development length for the specified yield strength h· in accordance with Section 412.9. 412.20.2

Mo

= total factored static moment

Mu Vc

factored moment at section nominal shear strength provided by concrete. See Section 411.13.2.1 factored shear force at section = factored dead load per unit area = factored live load per unit area = factored load per unit area = shorter overall dimension of rectangular part of cross section, mm

VII Wd

WI

Wu

x

=

=:


TWO-WAY SLAB SYSTEMS

4-62

y

a

= longer overall dimension of rectangular part of cross

section, mm ratio of flexural stiffness of beam section to flexural stiffness of a width of slab bounded laterally by center lines of adjacent panels (if any) on each side of the beam = F E ,.,Is

a in direction of II = in direction of 12 = ratio of torsional stiffness of edge beam section to flexural stiffness of a width of slab equal to span length of beam, center to center of supports = EdJC

2E,'S!,

y"

P

Ph

"" fraction ofunbalanced moment transferred by flexure at slab-column connections. See Section 413.6.3.2 fraction of unbalanced moment transferred by eccentricity of shear at slab-column connections = 1 - Yf ratio of nonprestressed tension reinforcement reinforcement ratio producing balanced strain conditions

strength reduction factor

-',

.'"

413.3.3 A panel is bounded by column, beam or wall lines on all sides. 413.3.4 For monolithic or fully composite construction, a includes that portion of slab on each side of the beam a distance equal to the projection of the beam above or below slab, whichever is greater, but not greater than four times slab thickness.

413.4 SLAB REINFORCEMENT 413.4.1 Area of reinforcement in each direction for two-way systems shall be determined from moments at critical but shall not be less than required by Section 407.13. 413.4.2 Spacing of reinforcement at critical sections shall exceed two times the slab thickness, except for portions of area of cellular or ribbed construction. In the slab over spaces, reinforcement shall be provided as required by 407.13. 413.4.3 Positive moment reinforcement perpendicular discontinuous edge shall extend to the edge of slab and embedment, straight or hooked, at least 150 mm in beams, columns or walls.

413.2 SCOPE f!I.i

413.3.2 Middle strip is a design strip bounded by two strips.

413.2.1 The provisions of this Section shall apply for design of slab systems reinforced for flexure in more than one direction, with or without beams between supports. 413.2.2 For a slab system supported by columns or walls, the dimensions Cj and c:! and the clear span In shall be based on an effective support area defined by the intersection of the bottom surface of the slab, or of the drop panel if there is one, with the largest right circular cone, right pyramid, or tapered wedge whose surfaces are located within the column and capital or bracket and are oriented no greater than 45 degrees to the axis of the column.

'"

413.2.3 Solid slabs and slabs with recesses or pockets made by permanent or removable fillers between ribs or joists in two directions are included within the scope of this Section.

413.4.4 Negative moment reinforcement perpendicular to discontinu.ous edge shall be bent, hooked or otherwise in spandrel beams, columns or walls, to be developed at tac~ support according to provisions of Section 412. 413.4.5 Where a slab is not supported by a spandrel wall at a discontinuous edge or where a slab cantilevers the support, anchorage of reinforcement shall be within the slab. 413.4.6 In slabs with beams between supports with a a greater than I. 0, special top and bottom slab r",i,nf'nrf'.pm shall be provided at exterior comers in accordance with following: .

413.3 DEFINITIONS

413.4.6.1 The special reinforcement in both top and slab shall be sufficient to resist a moment equal to the positive moment (per meter of width) in the slab. 413.4.6.2 The moment shall be assumed to be about an· perpendicular to the diagonal from the comer in the top slab and about an axis parallel to the diagonal from the the bottom ofthe slab.

413.3.1 Column strip is a design strip with a width on each side of a column centerline equal to 0.2512 or 0.2511, whichever is less. Column strip includes beams, if any.

413.4.6.3 The special reinforcement shall be provided distance in each direction from the corner equal to one-fifth longer span.

413.2.4 Minimum thickness of slabs designed in accordance with this Section shall be as required by Section 409.6.3.


CONCRETE

The special reinforcement shall be placed in a band the diagonal in the top of the slab and a band to the diagonal in the bottom of the slab. the special reinforcement shall be placed in two to the sides of the slab in both the top and bottom

4-63

and be continuous or spliced with a Class A splice. At exterior columns, the reinforcement shall be anchored at the shearhead or lifting collar.

413.5 OPENINGS IN SLAB SYSTEMS Where a drop panel is used to reduce amount of negative .. reinforcement over the column of a flat slab, size of shall be in accordance with the following: 7.1 Drop panel shall extend in each direction from of support a distance not less than one-sixth the span measured from center-to-center of supports in that

7.2 Projection of drop panel below the slab shall be at one-fourth the slab thickness beyond the drop. 7.3 In computing required slab reinforcement, thickness of below the slab shall not be assumed greater than one the distance from edge of drop panel to edge of column or capital.

dtOl,.t)~Ltlel

Details or Reinforcement In Slabs Without Beams

In addition to the other requirements of Section 413.4, in slabs without beams shall have minimum !I.~ensions as prescribed in Figure 413-1.

413.5.1 Openings of any size shall be permitted in slab systems if shown by analysis that the design strength is at least equal to the strength considering Sections 409.3 and 409.4, and that all serviceability conditions, including the specified linlits on deflections, are met. 413.5.2 As an alternate to special analysis as required by Section 413.5.1, openings shall be permitted in slab systems without beams only in accordance with the following: 413.5.2.1 Openings of any size shall be permitted in the area common to intersecting middle strips, provided total amount of reinforcement required for the panel without the opening is maintained. 413.5.2.2 In the area common to intersecting column strips, not more than one-eighth the width of column strip in either span shall be interrupted by openings. An amount of reinforcement equivalent to that interrupted by an opening shall be added on the sides ofthe opening .

..1.01....0 • .1.

~13.4.8.2 Where adjacent spans are unequal, extension of 1m'~tive moment reinforcement beyond the face of support as preStnbed in Figure 413-1 shall be based on requirements of longer span.

413.5.2.3 In the area common to one column strip and one middle strip, not more than one-fourth the reinforcement in either strip shall be interrupted by openings. An amount of reinforcement equivalent to that interrupted by an opening shall be added on the sides of the opening. 413.5.2.4 Shear requirements of Section 411.13.5 shall be satisfied.

413.4.8.3 Bent bars shall be permitted only when depth-span

. ratio permits use of bends 45 degrees or less.

:~t3~4.8.4

In frames where two-way slabs act as primary 1fi~tllbers resisting lateral loads, lengths of reinforcement shall be di:{cimined by analysis but shall not be less than those prescnbed in Figure 413 -1. '(~r":"

,

413.4.8.5 All bottom bars or wires within the column strip, in each direction, shall be continuous or spliced with Class A splices located as shown in Figure 413-1. At least two of the column strip bottom bars or wires in each direction shall pass . '... the column core and shall be anchored at exterior

413.6 DESIGN PROCEDURES 413.6.1 A slab system shall be designed by any procedure satisfying conditions of equilibrium and geometric compatibility, if shown that the design strength at every section is at least equal to the required strength set forth in Sections 409.3 and 409.4 and that all serviceability conditions, including limits on deflections, are met. 413.6.1.1 Design ofa slab system for gravity loads including the slab and beams (if any) between supports and supporting columns or walls forming orthogonal frames, by either the Direct Design Method pf Section 413.7 or the Equivalent Frame Method of Section 413.8, shall be permitted.

413.4.8.6 In slabs with shearheads and in lift-slab construction 2Y;~ere it is not practical to pass the bottom bars required by

~,~on 413.4.8.5 through the column, at least two bonded :6Ottom bars or wires in each direction shall pass through the .shearbead or lifting collar as dose to the column as practicable

413.6.1.2 For lateral loads, analysis of frames shall take into account effects of cracking and reinforcement on stiffiJ.ess of frame members.


TWO-WAY SLAB SYSTEMS

4-64

413.6.1.3 Combining the results of the gravity load analysis with the results of the lateral load analysis shall be permitted.

413.7.1.1 There shall be a minimum of three continuo,;s each direction.

413.6.2 The slab and beams (if any) between supports shall be proportioned for factored moments prevailing at every section.

413.7.1.2 Panels shall be rectangular, with a ratio of shorter span center-to-center supports within a panel not than 2.

413.6.3 When gravity load, wind, earthquake or other lateral forces cause transfer of moment between slab and column, a fraction of the unbalanced moment shall be transferred by flexure in accordance with Sections 413.6.3.2 and 413.6.3.3.

413.7.1.3 Successive span lengths center-to-center Cl1T,,.,,,rt< each direction shall not differ by more than one-third the span.

413.6.3.1 Fraction of unbalanced moment not transferred by flexure shall be transferred by eccentricity of shear in accordance with Section 411.13.6.

413.7.1.4 Offset of columns by a maximum of 10 percent of span (in direction of offset) from either axis between center of successive columns shall be permitted.

413.6.3.2 A fraction of the unbalanced moment given

413.7.1.5 All loads shall be due to gravity only and distributed over an entire panel Live load shall not exceed times dead load.

by Yf

A1" shall be considered to be transferred by flexure within an effective slab width between lines that are one and one-half slab or drop panel thickness (1.5h) outside opposite faces of the column or capital where M., is the moment to be transferred and (413-1)

r.r

-" "'h, ,~

'j,

"'"

413.7.1.6 For a panel with beams between supports on aU the relative stiffness of beams in two perpendicular

413.6.3.3 For unbalanced moments about an axis parallel to the edge at exterior supports, the value ofYrby Equation (413-1) shall be permitted to be increased up to 1.0 provided that v" at an edge support does not exceed 0.75¢Vc or at a comer support does not exceed O.ScpVc. For unbalanced moments at interior supports, and for unbalanced moments about an axis transverse to the edge at exterior supports, the value of y! in Equation (413-1) shall be permitted to be increased by up to 25 percent provided that Jt~! at the support does not exceed O.4cpVc. The reinforcement ratio p, within the effective slab width defined in Section 413.6.3.2, shall not exceed 0.375pb. No adjustments to Y.r shall be permitted for prestressed slab systems. 413.6.3.4 Concentration of reinforcement over the column by closer spacing or additional reinforcement shall be used to resist moment on the effective slab width defined in Section 413.6.3.2. 413.6.4 Design for transfer of load from slab to supporting columns or walls through shear and torsion shall be in accordance with Section 411.

shall not be less than 0.2 nor greater than 5.0. 413.7.1.7 Moment redistribution as permitted by Section shall not be applied for slab systems designed by the Design Method. See Section 413.7.7. 413.7.1.8 Variations from the limitations of Section 413.7.1 be permitted if demonstrated by analysis as long as ,,,,,-,,uu,,,w of Section 413 .6.1 are satisfied.

413.7.2 Total Factored Static Moment For A Span 413.7.2.1 Total factored static moment for a span determined in a strip bounded laterally by centerline of each side of centerline of supports. 413.7.2.2 Absolute sum of positive and average factored moments in each direction shall not be less than:

M

= o

413.7 DIRECT DESIGN METHOD 413.7.1 Limitations

Design of slab systems within the following limitations by the direct design method shall be permitted:

will 112 n 8

413.7.2.3 Where the transverse span of panels on either the centerline of supports varies, /2 in Equation (413-3) taken as the average of adjacent transverse spans. 413.7.2.4 When the span adjacent and parallel to an being considered, the distance from edge to panel shall be substituted for 12 in Equation (413-3).

Association of Structural E!'1!:.'ineers of the Philippines

CONCRETE

4h;z,,2~5 Cl~ar span

In shall extend from face ~o face. of

'YulllnS, capitals, brackets or walls. Value of In used m Equation

!~i~)§hall not be less than 0.6511. Circular or regular p~lygon

4-65

413.7.4.2 Column strips shall be proportioned to resist the following percentage of exterior negative factored moments:

;~~~' supports shall be treated as square supports With the js.~l!illIea.

4tj.7.3 Negative And Positive Factored Moments

:~;:~.il Negative factored moments shall be located at face of ';~tangular

supports. Circular or regular polygon-shaped supports shall be treated as square supports with the same area.

Linear interpolations shall be made between values shown.

413..7.3.2 In an interior span, total static moment Mo shall be ~diStributed as follows:

413.7.4.3 Where supports consist of columns or walls extending for a distance equal to or greater than three fourths the span length 12 used to compute M,,, negative moments shall be considered to be uniformly distributed across 12 .

Negative factored moment ....................... 0.65

Positive factored moment ................. '" .... 0.35

413.7.4.4 Column strips shall be proportioned to resist the following percentage of positive factored moments:

,413.7.3.3 In an end span, total factored static moment Mo shall ;be.distributed as follows: (1)

(3)

(2) Slabs with

Beam.

(4)

Slab WIthout Beams between Interior Supports

:J5ll Exterior

Edge Fully Restrained

_en

Wilhout

WiIh

All

Edge Seams

Edge Beams

0.70

0.70

0.70

0.65

0.57

0.52

0.50

0.35

0.30

0.65

Su

Its

413.7.3.4 Negative moment sections shall be designed to resist "thelarger of the two interior negative factored moments determined for spans framing into a common support unless an analysis is made to distribute the unbalanced moment in accordance with stiffness of adjoining elements. 413.7.3.5 Edge beams or edges of slab shall be proportioned to resist in torsion their share of exterior negative factored moments. 413.7.3.6 The gravity load moment to be transferred between slab and edge column in accordance with Section 413.6.3.1 shall beO. 3Mo.

413.7.4 Factored Moments In Column Strips 413.7.4.1 Column strips shall be proportioned to resist the following percentage of interior negative factored moments'

Linear interpolations shall be made between values shown: 413.7.4.5 For slabs with beams between supports, the slab portion of column strips shall be proportioned to resist that portion of column strip moments not resisted by beams.

413.7.5 Factored Moments In Beams 413.7.5.1 Beams between supports shaH be propurtioned tQ) resist 85 percent of column strip moments if fa,!],,/!) is equal to or greater than LO. 413.7.5.2 For values of fa/,//,) between LO and zero, proportion of column strip moments resisted by beams. shall be obtained by linear interpolation between 85 and zero percent. 413.7.5.3 In addition to moments calculated for uniform loads according to Sections 413.7.22, 413.7.51 and 4137.5.2, beams shall be proportioned to resist all moments caused by concentrated or linear loads applied directly to beams, including weight of projecting beam stem ahove or below the slab.

413.7.6 Factored Moment'i In I\'fiddle Strips 413.7.6.1 That iJortion of negative and positi ve factored moments not resisted by column strips shall be proportionately assigned to corresponding half middle stlips.

Linear interpolations shall be made between values shown.

413.7.6.2 Each middle strip shali be proportioned to resist the sum of the 1110ments assigned to ib nvu half f11i~ld!e "trips


TWO.JNAY SLAB SYSTEMS

4-66

413.7.6.3 A middle strip adjacent to and parallel with an edge supported by a wall shall be proportioned to resist twice the moment assigned to the half middle strip corresponding to the first row of interior supports.

413.8 EQUIVALENT FRAME METHOD 413.8.1 Design of slab systems by the equivalent frame method shall be based on assumptions given in Sections 413.8.2 through 413.8.6, and all sections of slabs and supporting members shall. be proportioned for moments and shears thus obtained.

413.7.7 Modification Of Factored Moments

Modification of negative and positive factored moments by 10 percent shall be permitted provided the total static moment for a panel in the direction considered is not less than that required by Equation (413-3).

413.8.1.1 Where metal column capitals are used, it shall be permitted to take account of their contributions to stiffuess and resistance to moment and to shear. 413.8.1.2 Neglecting the change in length of columns and slabs due to direct stress, and deflections due to shear, shall be permitted.

413.7.8 Factored Shear In Slab Systems Witb Beams 413.7.8.1 Beams with ai211j equal to or greater than 1.0 shall be proportioned to resist shear caused by factored loads on tributary areas bounded by 45-degree lines drawn from the corners of the panels and the center lines of the adjacent panels parallel to the long sides. 413.7.8.2 In proportioning of beams with ai211Jless than 1.0 to resist. shear, linear interpolation, assuming beams carry no load at aj = 0, shall be permitted. 413.7.8.3 In addition to shears calculated according to Sections 413.7.8.1 and 413.7.8.2, beams shall be proportioned to resist shears caused by factored loads applied directly on beams. 413.7.8.4 Computations of slab shear strength on the assumption that load is distributed to supporting beams in accordance with Section 413.7.8.1 or 413.7.8.2 shall be permitted. Resistance to total shear occurring on a panel shall be provided. 413.7.8.5 Shear strength shall satisfy requirements of Section 411.

413.7.9 Factored Moments In Colnmns And WaDs 413.7.9.1 Columns and walls built integrally with a slab system shall resist moments caused by factored loads on the slab system. 413.7.9.2 At an interior support, supporting elements above and below the slab shal( resist the moment specified by Equation (413-4) in direct/proportion to their stiffnesses unless a general analysis is made.

(413-4) where W

'd,

I '2 and I 'n refer to shorter span.

413.8.2 Equivalent Frame 413.8.2.1 The structure shall be considered to be made up of equivalent frames on column lines taken longitudinally and transversely through the building. 413.8.2.2 Each frame shall consist of a row of columns or supports and slab-beam strips, bounded laterally by the centerline of panel on each side of the centerline of columns or supports. 413.8.2.3 Columns or supports shall be assumed to be attached to slab-beam strips by torsional members (Section 413.8.5) transverse to the direction of the span for which moments are being determined and extending to bounding lateral panel center lines on each side of a column. 413.8.2.4 Frames adjacent and parallel to an edge shall be bounded by that edge and the centerline ofadj acent panel. 413.8.2.5 Analysis of each equivalent frame in its entirety shall be permitted. Alternatively, for gravity loading, a separate analysis of each floor or roof with far ends of columns considered fixed shall be permitted. 413.8.2.6 Where slab-beams are analyzed separately, determination of moment at a given support assuming that the slab-beam is fixed at any support two panels distant therefrom, shall be permitted, provided the slab continues beyond that point.

413.8.3 Slab-Beams 413.8.3.1 Determination of the moment of inertia of slab-beams at any cross section outside ofjoints or column capitals using the gross area of concrete shall be permitted. 413.8.3.2 Variation in moment of inertia along axis of slab beams shall be taken into account.


CONCRETE

4-67

413.8.3.3 Moment of inertia of slab-beams from center of column to face of column, bracket or capital shall be assumed equal to the moment of inertia of the slab-beam at face of column, bracket or capital divided by the quantity (1 C:ll2)2 where C2 and 12 are measured trans-verse to the direction of the span for which moments are being determined.

positive factored moment near midspan of a panel occurs with three-fourths of the full factored live load on the panel and on alternate panels; and it shall be permitted to assume that maximum negative factored moment in the slab at a support occurs with three-fourths of the full live load on adjacent panels only.

413.8.4 Columns

413.8.6.4 Factored moments shall not be taken less than those occurring with full factored live load on all panels.

413.8.4.1 Determination of the moment of inertia of columns at any cro!!s section outside of joints or column capitals using the gross area of concrete shall be permitted.

413.8.7 Factored Moments

413.8.4.2 Variation in moment of inertia along axis of columns shall be taken into account.

413.8.7.1 At interior supports, critical section for negative factored moment (in both column and middle strips) shall be taken at face of rectilinear supports, but not greater than 0.1751} from center of a column.

413.8.4.3 Moment of inertia of columns from top to bottom of the slab-beam at a joint shall be assumed infinite.

413.8.5 Torsional Members 413.8.5.1 Torsional members (see Section 413.8.2.3) shall be assumed to have a constant cross section throughout their length consisting ofthe largest of: 1.

A portion of slab having a width equal to that of the column, bracket or capital in the direction of the span for which moments are being determined, or

2.

For monolithic or fully composite construction, the portion of slab specified in (1) above plus that part of the transverse beam above and below the slab, and

3.

The transverse beam as defined in Section 413.3.4.

413.8.5.2 Where beams frame into columns in the direction of the span for which moments are being determined, the torsional stiffness shall be multiplied by the ratio of moment of inertia of slab with such beam to moment of inertia of slab without such beam.

413.8.7.2 At exterior supports provided with brackets or capitals, critical section for negative factored moment in the span perpendicUlar to an edge shall be taken at a distance from face of supporting element not greater than one-half the projection of bracket or capital beyond face of supporting element. 413.8.7.3 Circular or regular polygon-shaped supports shall be treated as square supports with the same area for location of critical section for negative design moment. 413.8.7.4 When slab systems within limitations of Section 413.7.1 are analyzed by the Equivalent Frame Method, it shall be permitted to reduce the resulting computed moments in such proportion ·that the absolute sum of the positive and average negative moments used in the design need not exceed the value obtained from Equation (413-3). 413.8.7.5 Distribution of moments at critical sections across the slab-beam strip of each frame to column strips, beams and middle strips as provided in Sections 413.7.4, 413.7.5 and 413.7.6 shall be permitted if the requirement of Section 413.7.1.6 is satisfied.

413.8.6 Arrangement Of Live Load 413.8.6.1 When loading pattern is known, the equivalent frame shall be analyzed for that load. 413.8.6.2 When live load is variable but does not exceed three fourths of the dead load, or the nature of live load is such that all panels will be loaded simultaneously, it shall be permitted to assume that maximum factored moments occur at all sections with full factored live load on entire slab system. 413.8.6.3 For loading conditions other than those defined in Section 413.8.6.2, it shall be permitted to assume that maximum


Or the Philippines, Volume 1

WALLS

414.2 SCOPE

SECTION 414 - WALLS

414.2.1 Provisions of Section 414 shall apply for design of walls subjected to axial load, with or without flexure.

414.1 NOTATION · mm2 = gross area 0 f sectIOn, = area of longitudinal tension

c

d

n

reinforcement in wall segment, mm2 area of effective longitudinal tension reinforce~ment in wall segment, mm2 as calculated by Equation 414-8 = distance from extreme compression fiber to neutral axis, mm = distance of extreme compression fiber to centroid of longitudinal tension r~inforcement, mm = modulus of elastiCity of concrete, MPa specified compressive strength of concrete, MPa specified yield strength of non-prestressed reinforcement, MPa = overall thickness of member, mm = moment of inertia of cracked section transformed to concrete, mm4 effective moment of inertia for computation of deflection, mm4 '= effective length factor = vertical distance between supports, mm = horizontal length of wall, m m = maximum unfactored moment due to service loads, including P A effects maximum moment in member at stage deflection is computed = moment causing flexural cracking due to applied lateral and vertical loads = nominal moment strength at section = maximum unfactored applied moment due to service loads, not including PA effects factored moment at section including PA effects = moment at the midheight section of the wall due to factored lateral and eccentric vertical loads = modular ratio of elasticity, but not less than 6

=E/Ec

Pnw = nominal axial load strength of wall designed by Section 414.5. unfactored axial load at the design (midheight) section including effects of self-weight = factored axial load = maximum deflection at or near mid height due to service loads, mm deflection at midheight of wall due to factored loads, mm strength-reduction factor. See Section 409.4. = ratio of tension reinforcement = A/(lvtl) reinforcement ratio producing balanced strain conditions

414.2.2 Cantilever retaining walls are designed according to flexural design provisions of Section 410 with minimum horizontal reinforcement according to Section 414.4.3.

414.3 GENERAL 414.3.1 Walls shall be designed for eccentric loads and any lateral or other loads to which they are SUbjected. 414.3.2 Walls subject to axial loads shall be designed in accordance with Sections 414.3,414.4 and either Section 414.5, 414.6 or 414.9. 414.3.3 Design for shear shall be in accordance with Section 411.11. 414.3.4 Unless demonstrated by a detailed analysis, horizontal length of wall to be considered as effective for each concentrated load shall not exceed center-to-center distance between loads, nor width of bearing plus four times the wall thickness. 414.3.5 Compression members built integrally with walls shall conform to Section 410.9.2. 414.3.6 Walls shall be anchored to intersecting elements such as floors or roofs; or to columns, pilasters, buttresses, and intersecting walls; and to footings. 414.3.7 Quantity of reinforcement and limits of thickness required by Sections 414.4 and 414.6 shall be permitted to be waived where structural analysis shows adequate strength and stability. 414.3.8 Transfer of force to footing at base of wall shall be in accordance with Section 415.9.

414.4 MINIMUM REINFORCEMENT 414.4.1 Minimum vertical and horizontal reinforcement shall be in accordance with Sections 414.4.2 and 414.4.3 unless a greater amount is required for shear by Sections 411.11.8 and 411.11.9. 414.4.2 Minimum ratio of vertical reinforcement area to gross concrete area shall be: 1. 2.

0.0012 for deformed bars not larger than 16 mm diameter with a specified yield strength not less than 420 MPa, or 0.0015 for other deformed bars, or

Association of Structural Engineers ·of the Philippines

CONCRETE

4-69

0.0012 for welded wire fabric (plain or deformed) not larger than W31 or D31.

middle third of the overall thickness of wall and all limits of Sections 414.3, 414.4 and 414.6 are satisfied.

414.4.3 Minimum ratio of horizontal reinforcement area to gross concrete area shall be:

414.6.2 Design axial load strength P"". of a wall satisfying limitations of Section 414.6.1 shall be computed by Equation (414-1) unless designed in accordance with Section 414.5:

3.

L

2. 3.

0.0020 for deformed bars not larger than 16 mm diameter with a specified yield strength not less than 420 MPa, or 0.0025 for other deformed bars, or 0.0020 for welded wire fabric (plain or deformed) not larger than W31 or D3 1.

414.4.4 Walls more than 250 rom thick, except basement walls, shall have reinforcement for each direction placed in two layers parallel with faces ofwall in accordance with the following: 1.

2,

One layer consisting of not less than one half and not more than Jwo-thirds of total reinforcement required for each direction shall be placed not less than 50 mm or more than one-third the thickness of wall from exterior surface. The other layer, consisting of the balance of required reinforcement in that direction, shall be placed not less than 20 rom or more than one-third the thickness of wall from interior surface.

414.4.5 Vertical and horizontal reinforcement shall not be spaced farther apart than three times the wall thickness, nor farther apart than 500 mm. 414.4.6 Vertical reinforcement need not be enclosed by lateral ties if vertical reinforcement area is not greater than 0,01 times gross concrete area, or where vertical reinforce-ment is not required as compression reinforcement. 414.4.7 In addition to the minimum reinforcement required by Section 414.4.1, not less than two 16 mm diameter bars shall be provided around all window and door openings. Such bars shall be extended to develop the bar beyond the corners of the openings but not less than 600 mm.

414.5 WALLS MEMBERS

DESIGNED

AS

COMPRESSION

Except as provided in Section 414.6, walls subject to axial load or combined flexure and axial load shall be designed as compression members in accordance with provisions of Sections 410.3, 410.4, 410.1i, 410.12, 410.13, 410.14, 410.15, 410.18, 414.3 and 414.4.

414.6 EMPIRICAL DESIGN METHOD 414.6.1 Walls of solid rectangular cross section shall be permitted to be designed by the empirical provisions of Section 414.6 if resultant of all factored loads is located within the

(4i4-1)

where

=

0.70 and effective length factor k shall be:

For walls braced top and bottom against lateral translation and

2.

Restrained against rotation at one or both ends (top, bottom, or both) ., ......... 0.8 Unrestrained against rotation at both ends ... 1,0

For walls not braced against lateral translation ..... 2.0

414.6.3 Minimum Thickness Empirical Design Method

Of Walls

Designed

By

414.6.3.1 Thickness of bearing walls shall not be less than 1/25 the supported height or length, whichever is shorter, nor less thap. 100 mm. 414.6.3.2 Thickness of exterior basement walls and foundation walls shall not be less than 190 mm.

414.7 NON-BEARING WALLS 414.7.1 Thickness of nonbearing walls shall not be less than 100 mm, or not less than 1/30 the least distance between members that provide lateral support,

414.8 WALLS AS GRADE BEAMS 414.8.1 Walls designed as grade beams shall have top and bottom reinforcement as required for moment in accordance with provisions of Sections 410.3 through 410,8. Design for shear shall be in accordance with provisions of Section 411. 414.8.2 Portions of grade beam walls exposed above grade shall also meet requirements of Section 414.4.

414.9 ALTERNATE DESIGN OF SLENDER WALLS 414.9.1 When flexural tension controls the design of a wall, the requirements of Section 414.9 are considered to satisfy Section 410.11.


WALLS

4-70

414.9.2 Walls designed by the provisions of Section 414.9 shall satisfy Sections 414.9.2.1 through 414.9.2.6. 414.9.2.1 The wall panel shall be designed as a simply supported, axially loaded member subjected to an out-of-plane uniform lateral load, with maximum moments and deflections occurring at midspan.

(414-6)

Mil

where: 2

lwe'

== nAse ( d - c ) + -3

414.9.2.2 The cross section shall be constant over the height of the panel.

(414-7)

and 414.9.2.3 The reinforcement ratio p shall not exceed 0.6p". (414-8)

414.9.2.4 Reinforcement shall provide a design strength: (414-2) where Mer shall be obtained using the modulus of rupture given by Equation 409-9. 414.9.2.5 Concentrated gravity loads applied to the wall above the design flexural section shall be assumed to be distributed over a width: (a)

".,

Equal to the bearing width, plus a width on each side that increases at a slope of2 vertical to 1 horizontal down to the design section; but

414.9.4 The maximum deflection Lls• due to service loads, including P Ll effects, shall not exceed IJJ50. The mid height deflection Lls shall be determined by: A

(5M)I/ 48EJ,

(414-9)

Ms.

(414-10)

= -'--':""";'-

s

M =

5P1 2

1 _ -S- " 48£).

.....

1~II'h~

,~,

(b)

Not greater than the spacing of the concentrated loai:ls; and

(c)

Does not extend beyond the edges of the wall paneL

Ie shall be calculated using the procedure of Section 409.6.2.3, substituting M for Ma . lor shall be evaluated using Equation 414-7.

,;::,

414.9.2.6 Vertical stresses P,,/Ag at the midheight section shall not exceed 0.061'0' 414.9.3 The design moment strength ¢A1n for combined flexure and axial loads at the mid-height cross section shall be: (414-3)

where: (414-4)

M,f.{J is the moment at the midheight section of the wall due to factored loads, and Ll" is: 5MJc~

(414-5)

t/J48EJcr

Mu shall be obtained by iteration of deflections, or by direct calculation using Equation 414-6:


CONCRETE

g:~~TION 415 - FOOTINGS

4-71

415.5.2 Maximum factored moment for an isolated footing shall be computed as prescribed in Section 415.5.1 at critical sections

located as follows:

,iii;.. NOTATlON l

d; ""

It :::

gross area of section, mm 2 diameter of pile at footing base, mm

ratio oflong side to short side offooting

415.2SCOPE

1.

At face of column, pedestal, or wall, for footings supporting a concrete column, pedestal, or wall;

2.

Halfway between middle and edge of wall, for footings supporting a masonry wall;

3.

Halfway between face of column and edge of steel base plate, for footings supporting a column with steel base plate.

4{5.2.1 Provisions of Section 415 shall apply for design of isolated footings and, where applicable, to combined footings alld mats.

415.5.3 In one-way footings and two-way square footings,

415.2.2 Additional requirements for design of combined footings mats are given in Section 415.11.

415.5.4 In two-way rectangular footings, reinforcement shall be

ana

reinforcement shall be distributed uniformly across entire width of footing.

distributed as follows: 415.5.4.1 Reinforcement in long direction shall be distributed

415.3 LOADS AND REACTIONS

uniformly across entire width of footing.

415.3.1 Footings shall be proportioned to resist the factored

loads and induced reactions, in accordance with the appropriate design requirements of this code and as provided in this section. 415.3.2 Base area of footing or number and arrangement of piles

shall be determined from unfactored forces and moments transmitted by footing to soil or piles and permissible soil pressure or permissible pile capacity selected through principles ofsoil mechanics. 415.3.3 For footings on piles, computations for moments and

shears may be based on the assumption that the reaction from . any pile is concentrated at pile center.

415.4 FOOTINGS SUPPORTING CIRCULAR OR

415.5.4.2 For reinforcement in short direction, a portion of the total reinforcement given by Equation (415-1) shall be distributed uniformly over a band width (centered on centerline of column or pedestal) equal to the length of short side of footing. Remainder of reinforcement required in short direction shall be distributed uniformly outside center band width of footing.

Reinforcement in bandwidth Total Reinforcement in short direction

(415-1) •

(fJ+1)

415.6 SHEAR IN FOOTINGS

REGULAR POLYGON-SHAPED COLUMNS OR PEDESTALS

415.6.1 Shear strength in footings shall be in accordance with Section 411.13.

For location of critical sections for moment, shear and development of reinforcement in footings, it shall be permitted to treat circular or regular polygon-shaped concrete columns or pedestals as square members with the same area.

415.6.2 Location of critical section for shear in accordance with Section 411 shall be measured from face of column, pedestal or

wall, for footings supporting a column, pedestal or wall. For footings supporting a column or pedestal with steel base plates, the critical section shall be measured from location defined in Section 415.5.2, Item 3.

415.5 MOMENT IN FOOTINGS 415.6.3 Computation of shear on any section through a footing 415.5.1 External moment on any section of a footing shall be

determined by passing a vertical plane through the footing and computing the moment of the forces acting over the entire area of footing on one side of that vertical plane.

supported on piles shall be in accordance with the following: 415.6.3.1 Entire reaction from any pile whose center is located dJ2 or more outside the section shaH be considered as producing shear on that section.


FOOTINGS

4-72

415.6.3.2 Reaction from any pile whose center is located dJ2 or more inside the section shall be considered as producing no shear in that section. 415.6.3.3 For intermediate positions of pile center, the portion of the pile reaction to be considered as producing shear on the section shall be based on straight-line interpolation between full value at dp/2 outside the section and zero value at dJ2 inside the section.

415.7 DEVELOPMENT OF REINFORCEMENT IN FOOTINGS 415.7.1 Development of reinforcement in footings shall be in accordance with Section 412. 415.7.2 Calculated tension or compression in reinforcement at each section shall be developed on each side of that section by embedment length, hook (tension only) or mechanical device, or combinations thereof 415.7.3 Critical sections for development of reinforcement shall be as!\llmed at the same locations as defined in Section 415.5.2 for maximum factored moment, and at all other vertical planes where changes of section or reinforcement occur. See also Section 412.11.6.

415.8 MINIMUM FOOTING DEPTH Depth of footing above bottom reinforcement shall not be less than 150 mm for footings on soil, or not less than 300 mm for footings on piles.

415.9 TRANSFER OF FORCE AT BASE OF COLUMN, WALL OR REINFORCED PEDESTAL 415.9.1 Forces and moments at base of column. wall. or pedestal shall be transferred to supporting pedestal or footing by bearing on concrete and by reinfurcement. dowels, and mechanical connectors. 415.9.1.1 Bearing on concrete at contact surface between supported and supporting member shall not exceed concrete bearing strength for either surface as given by Section 410.18. 415.9.1.2 Reinforcement, dowels, or mechanical connectors between supported and supporting members shall be adequate to transfer: 1.

All compressive force that exceeds concrete bearing strength ofeither member;

2.

Any computed tensile force across interface.

In addition, reinforcement, dowels or mechanical shall satisfy Section 415.9.2 or 415.9.3.

415.9.1.3 If calculated moments are transferred to .,..,.'UV1<11I

pedestal or footing, reinforcement, dowels or

connectors shall be adequate to satisfy Section 412.18.

415.9.1.4 Lateral forces shall be transferred to

pedestal or footing in accordance with shear-friction nrrn""l1","

of Section 411.8 or by other appropriate means.

415.9.2 In cast-in-place construction, reinforcement required

satisfy Section 415.9.1 shaH be provided either by ext:en
longitudinal bars into supporting pedestal or footing, or<

dowels.

415.9.2.1 For cast-in-place columns and pedestals, area

reinforcement across interface shall not be less than 0.005

gross area of supported member.

415.9.2.2 For cast-in-place walls, area of reinforcement across

interface shall not be less than minimum vertical .."'inF"..."" .... '~ntC";jn

given in Section 414.4,2.

415.9.2.3 At footings, 45 mm and 55 mm diameter longitudinal

bars, in compression only, may be lap spliced with dowels

provide reinforcement required to satisfy Section 415,9, 1.

Dowels shall not be larger than 32 rnm diameter bar and

extend into supported member a distance not less than the

development length of 45 mm or 55 rnm diameter bars or the

splice length of the dowels, whichever is greater, and into the

footing a distance not less than the development length of

dowels.

415.9.2.4 If a pinned or rocker connection is provided in cast-in

place construction, connection shall conform to Sections 415.9.1

and 415.9.3,

415.9.3 In precast construction, reinforcement required to

Section 415.9.1 may be provided by anchor bolts or suitable

mechanical connectors.

415.9.3.1 Connection between precast columns or pedestals and supporting members shall meet the requirements of Section 416.6.1.3, Item 1. 415.9.3.2 Connection between precast walls and supporting members shall meet the requirements of Section 416,6.1.3, Items 2 and 3. EXCEPTION: In tilt-up constroction, this connection may be to an adjacent floor slab. In no case sha" the connection prOVided be less than that required by Section 411.


CONCRETE

415.9.3.3 Anchor bolts and mechanical connectors shall be designed to reach their design strength prior to anchorage failure or failure of surrounding concrete.

4·73

SECTION 416 - PRECAST CONCRETE 416.1 NOTATION

415.10 SLOPED OR STEPPED FOOTINGS

Ag

415.10.1 In sloped or stepped footings, angle of slope or depth and location of steps shall be such that design requirements are satisfied at every section. 415.10.2 Sloped or stepped footings designed as a unit shall be constructed to ensure action as a unit.

I

gross area of column, mm2 clear span, mm.

416.2 SCOPE 416.2.1 All provisions of this code not specifically excluded and riot in conflict with the provisions of Section 416, shall apply to structures incorporating precast concrete structural members.

415.11 COMBINED FOOTINGS AND MATS 415.11.1 Footings supporting more than one column, pedestal, or wall (combined footings or mats) shall be proportioned to resist the factored loads and induced reactions, in accordance with appropriate design requirements of this code. 415.11.2 The Direct Design Method of Section 413 shall not be used for design of combined footings and mats. 415.113 Distribution of soil pressure under combined footings and mats shall be consistent with properties of the soil and the structure and with established principles of soil mechanics.

415.12 PLAIN CONCRETE FOOTINGS. See Section 422.

PEDESTALS

AND

416.3 GENERAL 416.3.1 Design of precast members and connections shall include loading and restraint conditions from initial fabrication to end use in the structure, including form removal, storage, transportation and erection. 416.3.2 When precast members are incorporated into a structural system, the forces and deformations occurring in and adjacent to connections shall be included in the design. 416.3.3 Tolerances for botb precast members and interfacing members shall be specified. Design of precast members and connections shall include the effects of these tolerances.

•

416.3.4 In addition to the standard requirements for drawings and specifications, the following shall be included in either the contract documents or shop drawings: 1.

Details of reinforcement, inserts and lifting devices required to resist temporary loads from handling, storage, transportation and erection;

2.

Required concrete strength at stated ages or stages of construction.

416.4 DISTRIBUTION MEMBERS

OF

FORCES

AMONG

416.4.1 Distribution of forces that are perpendicular to tbe plane of members shall be established by analysis or by test. 416.4.2 Where tbe system behavior requires in-plane forces to be transferred betweel1 the members of a precast floor or wall system, tbe following shall apply: 416.4.2.1 In-plane force paths shall be continuous through both connections and members.

National Structural Code of the Philippines, Volume 1 - $

$)"

d

1£11;-

.'~

PRECAST CONCRETE

4·74

416.4.2.2 Where tension forces occur, a continuous path of steel or steel reinforcement shall be provided.

relTltor'c~n:

416.6.1.4 Connection details that rely solely on friction by gravity loads shall not be used.

416.5 MEMBER DESIGN 416.5.1 In one-way precast floor and roof slabs and in one-way precast, prestressed wall panels, all not wider than 4 m, and where members are not mechanically connected to cause restraint in the transverse direction, the shrinkage and temperature reinforcement requirements of Section 407.13 in the direction normal to the flexural reinforcement shall be permitted to be waived. This waiver shall not apply to members which require reinforcement to resist transverse flexural stresses. 416.5.2 For precas~ nonprestressed walls the reinforcement shall be designed in accordance with the provisions of Section 410 or 414, except that the area of horizontal and vertical reinforcement shall each be not less than 0.001 times the gross cross-sectional area of the wall panel. Spacing of reinforcement shall not exceed five times the wall thickness or 800 mm for interior walls or 500 mm for exterior walls.

416.6 STRUCTURAL INTEGRITY 416.6.1 Except where the provisions of Section 416.6.2 govern, the following minimum provisions for structural integrity shall apply to all precast concrete structures: 416.6.1.1 Longitudinal and transverse ties required by Section 407.14.3 shall connect members to a lateral load resisting system. 416.6.1.2 Where precast elements form floor or roof diaphragms, the connections between diaphragm and those members being laterally supported shall have a nominal tensile strength capable of resisting not less than 45 kN/m. 416.6.1.3 Vertical tension tie requirements of Section 407.}4.3 shall apply to all vertical structural members, except cladding., and shall be achieved by providing connections at horizontal joints in accordance with the following:

I.

permitted to be anchored into an appropriately concrete floor slab on grade,

Precast columns shall have a nominal strength in tension not less than I.SAg in kN. For columns with a larger cross section than required by consideration of loading, a reduced effective area Ag , based on cross section required but not less than one-half the total area, shall be pennitted;

416.6.2 For precast concrete bearing wall structures three

more stories in height, the following minimum provisions

apply:

416.6.2.1 Longitudinal and transverse ties shall be provided floor and roof systems to provide a nominal strength of 20 kN/m of width or length. Ties shall be provided over interior wall supports and between members and exterior walls. Ties shall be positioned in or within 0,6 m of the plane of the floor or roOf, ~~.

~ /~

416.6.2.2 Longitudinal ties parallel to floor or roof slab spaJ shall be spaced not more than 3.0 m on centers, Provisions shall be made to transfer forces around openings. 416.6.2.3 Transverse ties perpendicular to floor or roof spans shall be spaced not greater than the bearing wall spacing;, 416.6.2.4 Ties around the perimeter of each floor and within 1.2 m of the edge, shall provide a nominal <:tr'>nath tension not less than 70 kN. 416.6.2.5 Vertical tension ties shall be provided in all walls shall be continuous over the height of the building. They provide a nominal tensile strength not less than 40 kN horizontal meter of waIL Not less than two ties shall be for each precast panel.

416.7 CONNECTION AND BEARING DESIGN 416.7.1 Forces shall be permitted to be transferred between members by grouted joints, shear keys, mechanical cormec~tol reinforcing steel connections, reinforced topping or combination ofthese means. 416.7.1.1 The adequacy of connections to transfer between members shall be determined by analysis or by Where shear is the primary result of imposed loading, it shall permitted to use the provisions of Section 411 ,8 as applicable. 416.7.1.2 When designing a connection using materials different structural properties, their relative stiffhesses, and ductilities shall be considered.

2.

Precast wall panels shall have a minimum of two ties per panel, with a nominal tensile strength not less than 45 kN per tie~

416.7.2 Bearing for precast floor and roof members on supports shall satisfy the following:

3.

When design forces result in no tension at the base,' the ties required by Section 416.6.1.3, Item 2, shall be

.416.7.2.1 The allowable bearing stress at the contact between supported and supporting members and between


CONCRETE

intermediate bearing elements shall not exceed the bearing strength for both surface and the bearing element. Concrete bearing strength shall be as given in Section 410.18. 416.7.2.2 Unless shown by test or analysis that performance will not be impaired, the following minimum requirements shall be met:

1.

Each member and its supporting system shall have design dimensions selected so that, after consideration of tolerances, the distance from the edge of the support to the end of the precast member in the direction of the span is at least 11180 of the clear span, I, but not less than:

For solid or hollow-core slabs... ... .. ...... . . .. 50 mm For beams or stemmed members... ...... . . . . . . . .. 75 mm

2.

Bearing pads at unarmored edges shall be set back a minimum of 15 mm from the face of the support, or at least the chamfer dimension at chamfered edges.

416.7.2.3 The requirements of Section 412.12.1 shall not apply . to the positive bending moment reinforcement for statically determinate precast members, but at least one-third of such reinforcement shall extend to the center of the bearing length.

416.8 ITEMS EMBEDDED AFTER CONCRETE PLACEMEl"n' 416.8.1 When approved by the engineer, embedded items (such as dowels or inserts) that either protrude from the concrete or remain exposed for inspection shall be permitted to be embedded while the concrete is in a plastic state provided that:

4-75

416.10 HANDLING 416.10.1 Member design shall consider forces and distortions during curing, stripping, storage, transportation and erection so that precast members are not overstressed or otherwise damaged. 416.10.2 During erection, precast members and structures shall be adequately supported and braced to ensure proper alignment and structural integrity until permanent connections are completed.

416.11 STRENGTH EVALUATION OF PRECAST CONSTRUCTION 416.11.1 A precast element to be made composite with cast-in place concrete shall be permitted to be tested in flexure as a precast element alone in accordance with the following: 416.11.1.1 Test loads shall be applied only when calculations indicate the i.solated precast element will not be critical in compression or buckling. 416.11.1.2 The test load shall be that load which, when applied to the precast member alone, induces the same total force in the tension reinforcement as would be induced by loading the composite member with the test load required by Section 420.4.2. 416.11.2 The provisions of Section 420.6 shall be the basis for acceptance or rejection of the precast element.

416.8.1.1 Embedded items are not required to be hooked or tied to reinforcement within the concrete. ~16.8.1.2 Embedded items are maintained in the correct position while the concrete remains plastic.

416.8.1.3 The concrete is properly con'solidated around the embedded item.

0116.9 MARKING AND IDENTIFICATION 416.9.1 Each precast member shall be marked to indicate its location and orientation in the structure and date of manufacture.

416•.9.2 Identification marks shall correspond to placing drawings.


COMPOSITE CONCRETE FLEXURAL MEMBERS

4·76

SECTION 417 - COlVIPOSITE CONCRETE FLEXURAL MEMBERS

417.3.5 All elements shall be designed to support all loads introduced prior to full development of design strength of composite members.

417.1 NOTATION

417.3.6 Reinforcement shall be provided as required to control cracking and to prevent separation of individual elements of composite members.

Ac AI' h"

d h s ~ 'ryh

VII

A PI'

area of contact surface being investigated for horizontal shear, mm 2 2 = area ofti"es within a distance s, mm width of cross section at contact surface being investigated for horizontal shear, mm = distance from extreme compression fiber to centroid of tension reinforcement for entire composite section, mm overall thickness of composite members, mm = spacing of ties measured along the longitudinal axis of the member, mm nominal horizontal shear strength = factored shear force at section = correction factor related to unit weight of concrete. ratio of tie reinforcement area to area of contact surface. =

h,.s strength-reduction factor. See Section 409.4

417.3.7 Composite members shall meet requirements for control of deflections in accordance with Section 409.6.5.

417.4 SHORING When used, shoring shall not be removed until suppor.ted elements have developed design properties required to suPPort all loads and limit deflections and cracking at time of shoring removal.

417.5 VERTICAL SHEAR STRENGTH 417.5.1 When an entire composite member is assumed to resist vertical shear, design shall be in accordance with requirements of Section 411 as for a monolithically cast member of the same cross-sectional shape.

417.2 SCOPE 417.2.1 Provisions of Section 417 shall apply for design of composite concrete flexural members defined as precast or cast in-place concrete elements or both constructed in separate placements but so interconnected that all elements respond to load., as a unit. 417.2.2 A.ll provi<;ions of this code shall apply to composite concrete flexural members, except as specifically modified in thi.., Section.

417.5.2 Shear reinforcement shall be fully anchored into interconnected elements in accordance with Section 412.14. 4 t 7.5.3 Extended and anchored shear reinforcement shall be permitted to be included as ties for horizontal shear.

417.6 HORIZONTAL SHEAR STRENGTH 417 .6.1 In a composite member, full transfer of horizontal shear forces shall be assured at contact surfaces of interconnected elements.

417.3 GENERAL 4 P .3.1 The use of an entire composite member or portions thereof for resisting shear and moment shall be permitted.

4l".6.1.1 Full transfer of horizontal shear force may be assumed when all of the following are satisfied: 1.

417.3.2 Individual ciements shall be investigated for all critical stages of loading. 2.

417.3.3 If the specified stren!:,rth, unit weight or other properties :)f ~!Je 'various elements are different, properties of the individual ciements or the most critical values shall be used in design.

3. 4.

417.3.4 In strength computations of composite members, no distinction shaH be made between shored and unshored members

Contact surfaces are clean, free of laitance, and intentionally roughened to a full amplitude of· approximately 6 mm. Minimum ties are provided in accordance with Section 417.7. Web members are designed to resist total vertical shear, and All shear reinforcement is fully anchored into
417.6.1.2 If all the requirements of Section 4l7.6.1.1 are not satisfied, horizontal shear shall be investigated in accordance with Section 4l7.6.2 or 417.6.3.


CONCRETE

4-77

417.7 TIES FOR HORIZONTAL SHEAR 417.6.2 Unless calculated in accordance with Section 417.6.3, design of cross sections subject to horizontal shear shall be based on: (417-1)

417.7.1 When ties are provided to transfer horizontal shear, tie area shall not be less than that required by Section 41 1.6.5.3 and tie spacing shall not exceed four times the least dimension of supported element, or 600 mm.

where Vu is factored shear force at section considered and Vnh is nominal horizontal shear strength in accordance with the following:

417.7.2 Ties for horizontal shear shall consist of single bars or wire, multiple leg stirrups, or vertical legs of welded wire fabric (plain or deformed).

417.6.2.1 When contact surfaces are clear, free of laitance and intentionally roughened, shear strength Vnh shall not be taken greater than O.6b,.d, in newtons.

417.7.3 All ties shall be fully anchored into interconnected elements in accordance with Section 412.14.

417.6.2.2 When minimum ties are provided in accordance with Section 417.7 and contact surfaces are clean and free of laitance, but not intentionally roughened, shear strength Vnh shall not be taken greater than O.6b,d, in newtons. 417.6.2.3 When minimum ties are provided in accordance with Section 417.7 and contact surfaces are clean, free of laitance, and intentionally roughened to a full amplitude of approximately 5 mm, shear strength Vnh shall be taken equal to (1.8 + O.6pJ;.)Ab vdin newtons, but not greater than 3.5bvd, in newtons. Values for A in Section 411.8.4.3 shall apply. 417.6.2.4 When factored shear force Vu at section considered exceeds

PRESTRESSED CONCRETE

SECTION 418 - PRESTRESSED CONCRETE

a

418.1 NOTATIONS A

Aps As

As' b D d d'

= area

of that part of cross section between flexural 2 tension face and center of gravity of gross section, mm = larger gross cross-sectional area of the slab-beam strips of the two orthogonal equivalent frames intersecting at 2 a column of a two-way slab, mm 2 = area of prestressed reinforcement in tension zone mm = area of nonprestressed tension reinforcement ~2 2 ' = area of compression reinforcement, mm = width of compression face of member, mm = dead loads or related internal moments and forces = distance from extreme compression fiber to centroid of nonprestressed tension reinforcement, mm = distance from extreme compression fiber to centroid of compression reinforcement, mm = distance from extreme compression fiber to centroid of prestressed reinforcement, mm f = base ofNapierian logarithms = specified compressive strength of concrete, MPa =

!,c; fpc

!;,S fpu fpy

J,. fse

h h

K

Ix L n Nc p. Px

P:ru

p'

co co'

total angular change of prestressing tendon profile radians from tendon jacking end to any point x

= factor defined in Section 410.3.7.3.

= factor for type of prestressing tendon.

= 0.55 forfd!;,. not less than 0.80

= 0.40 forfdfpu not less than 0.85

= 0.28 forfdfpu not less than 0.90

= correction factor related to unit weight of concrete

Section 411.8.4.3)

= curvature friction coefficient

= ratio of nonprestressed tension reinforcement

= A'!(bd) = ratio of compression reinforcement = A,'/(bd) = ratio of prestressed reinforcement = Ap'!(bllp) = strength-reduction factor. See Section 409.4 = phI'c

=

= p'fj!,c

= pp.h>sfc

coP"" co' w = reinforcement indices for flanged sections computed as for OJ, COp. and oJ' except that b shall be the web width, and reinforcement area shall be that required to develop compressive strength of web only

square root of specified compressive strength of

concrete, MPa compressive strength of concrete at time of initial prestress, MPa = average compressive stress in concrete due to effective prestress force only (after allowance for all prestress losses), MPa = stress in prestressed reinforcement at nominal strength, MPa = specified tensile strength of prestressing tendons, MPa = specified yield strength of prestressing tendons, MPa = modulus of rupture of concrete, MPa = effective stress in prestressed reinforcement (after allowance for all prestress losses), MPa = specified yield strength of nonprestressed reinforcement, MPa = overall dimension of member in direction of action considered, mm = wobble friction coefficient per mm of prestressing tendon = length of prestressing tendon element from jacking end to any point x, m. See Equations 418-1 and 418-2 = live loads or related internal moments and forces = number of monostrand anchorage devices in a group = tensile force in concrete due to unfactored dead load plus live load (D + L) = prestressing tendon force at jacking end = prestressing tendon force at any point x = factored post-tensioned tendon force at the anchorage device =

11 p

4-78

418.2 SCOPE 418.2.1 Provisions of this Section shall apply to members prestressed with wire, strands or bars conforming to provisions for prestressing tendons in Section 403.6.5. 418.2.2 All provisions of this code not specifically excluded, and not in conflict with provisions of this Section, shall apply to prestressed concrete. 418.2.3 The following provisions of this code shall not apply to prestressed concrete, except as specifically noted: Sections 407.7.5, 408.5, 408.11.2 through 408.11.4, 408.12, 410.4.2 and 410.4.3,410.6,410.7,410.10.1,410.10.2,413,414.4,414.6 and 414.7.

418.3 GENERAL 418.3.1 Prestressed members shall requirements specified in this code.

meet

the

strength

418.3.2 Design of prestressed members shall be based on strength and on behavior at service conditions at all stages that may be critical during the life of the structure from the time prestress is first applied. 418.3.3 Stress concentrations due to prestressing shall be considered in design.


CONCRETE

4-79

418.3.4 Provisions shall be made for effects on adjoining construction of elastic and plastic deformations, deflections, changes in length and rotations due to prestressing. Effects of temperature and shrinkage shall also be included.

2.

Extreme fiber stress in compression due to prestress plus total load ...... .. . .............. O.60f'c

3.

Extreme fiber stress in tension in precompressed tensile zone. . . . . . . . . . . . . . . . . . . . . . .. 0.50Jj,'

418.3.5 Possibility of buckling in a member between points where concrete and prestressing tendons are in contact and of buckling in thin webs and flanges shall be considered.

4.

Extreme fiber stress in tension in precompressed tensile zone of members (except two-way slab systems), where analysis based on transformed cracked sections and on bilinear moment-deflection relationships show that immediate and long-time deflections comply with requirements of Section 409.6.4, and where cover requirements comply with Section 407.8.3.2 ......... .

418.3.6 In computing seGtion properties prior to bonding of prestressing tendons, effect of loss of area due to open ducts shall be considered.

........... 1.0[1;

418.4 DESIGN ASSUMPTIONS 418.4.1 Str~gth design of prestressed members for flexure and axial loads shall be based on assumptions given in Section 410.3, except that Section 410.3.4 shall apply only to reinforcement conforming to Section 403.6.3. 418.4.2 For investigation of stresses at transfer of prestress, at service loads, and at cracking loads, straight-line theory shall be used with the following assumptions: 418.4.2.1 Strains vary linearly with depth through entire load range.

418.5.3 Permissible stresses in concrete of Sections 418.5.1 and 418.5.2 may be exceeded if shown by test or analysis that performance will not be impaired.

418.6 PERMISSmLE STRESS IN PRESTRESSING TENDONS 418.6.1 Tensile stress in prestressing tendons shall not exceed the following:

1.

0.94fpy

but not greater than the lesser of 0.80./pu and the maximum value recommended by manufacturer of prestressing tendons or anchorage devices.

418.4.2.2 At cracked sections, concrete resists no tension.

418.5 PERMISSmLE STRESSES IN CONCRETE FLEXURAL MEMBERS

Due to tendon jacking force. .. ........

2.

Immediately after prestress transfer ....... 0.82J;y

but not greater than 0.74 j pu'

418.5.1 Stresses in concrete immediately after prestress transfer (before time-dependent prestress losses) shall not exceed the following:

1.

Extreme fiber stress in compression ........ . 0.60f'cI

2.

Extreme fiber stress in tension except as permitted in 3. .. ....................... 0.25g

3.

Extreme fiber stress in tension at ends of simply supported members .................... , 0.50g

Where computed tensile stresses exceed these values, bonded additional reinforcement (nonprestressed or prestressed) shall be provided in the tensile zone to resist the total tensile force in COncrete computed with the assumption of an uncracked section. 418.5.2 Stresses in concrete at service loads (after allowance for aU prestress losses) shall not exceed the following:

1.

3.

Post-tensioning tendons, at anchorage devices and couplers, immediately after force transfer .. 0.70jpu

418.7 LOSS OF PRESTRESS 418.7.1 To determine effective prestress 1_ allowance for the following sources ofloss of prestress shall be considered:

1.

Tendon seating at transfer;

2.

Elastic shortening of concrete;

3.

Creep of concrete;

4.

Shrinkage of concrete;

5.

Relaxation oftendon stress;

6.

Friction loss due to intended or unintended curvature in post-tensioning tendons.

Extreme fiber stress in compression due to prestress plus sustained loads ................... 0.45f'c



418.7.2 FRICTION TENDONS

LOSS

IN

but Ips in Equation (418-4) shall /PJ'> nor greater than (f.e+ 420).

POST·TENSIONING

418.7.2.1 Effect of friction loss in post-tensioning tendons shall be computed by:

4-80

3.

not be taken greater

For members with unbonded prestressing tendons with a span-to-depth ratio greater than 35: f'e

fs< + 7 0 + 30 Opp

(418-1)

but/ps in Equation (418-5) shall not be taken greater

When (Klx + pa) is not greater than 0.3, effect of friction loss shall be permitted to be computed by:

Ps

Px ( 1 + Klx + pa)

(418-2)

418.7.2.2 Friction loss shall be based on experimentally determined wobble K and curvature p friction coefficients and shall be verified during tendon stressing operations. 418.7.2.3 Values of wobble and curvature friction coefficients used in design shall be shown on design drawings. 418.7.3 Where loss of prestress in member may occur due to connection of member to adjoining construction, such loss of prestress shall be allowed for in design.

,

418.8 FLEXURAL STRENGTH 418.8.1 Design moment strength of flexural members shall be computed by the strength design methods of this chapter. For prestressing tendons, Ips shall be substituted for 1; in streng1" computations. 418.8.2 As an alternative to a more accurate determination of/ps based on strain compatibility, the following approximate values of/p. shall be used if/.e is not less than 0.5/p".

J.

For members with bonded prestressing tendons: (418-3)

If any compression reinforcement is taken into account when calculating/ps by Equation (418-3), the term:

[pp

fe'

~

lU')]

shall be taken not less than 0.17 and d' shall be no greater than 0.15 dp

2.

For members with unbonded prestressing tendons and with a span-to-depth ratio of35 or less: (418-4)

/py, nor greater than (f.e + 200). 418.8.3 Non-prestressed reinforcement conforming to ije;ctlcm 403.6.3, if used with prestressing tendons, shall be permitted be considered to contribute to the tensile force and to included in moment strength computations at a stress equal the specified yield strength /y. Other reinforcement shall be permitted to be included in "t""ncrl"h" computations only if a strain compatibility analysis is made determine stresses in such reinforcement.

418.9 LIMITS FOR REINFORCEMENT OF FLEXURAL MEMBERS 418.9.1 Ratio of prestressed and nonprestressed reiJrlforce-m,mf used for computation of moment strength of a member, except as provided in this section shall be such that wp' [ ~ (dlllp)(w - w')], or [lDpw + (dlllp)(w,., - w'w)] is not greater than , 36ftl. 418.9.2 When a reinforcement ratio in excess of that specified' Section 418.9.1 is provided, design moment strength shall not exceed the moment strength based on the compression portion the moment couple. 418.9.3 Total amount of prestressed and reinforcement shall be adequate to develop a factored load least 1.2 times the cracking load computed on the basis of modulus of rupture f, specified in Section 409.6.2.3. provision shall be permitted to be waived for: 1.

Two-way, unbonded post-tensioned slabs;

2.

Flexural members with shear and flexural strength at least twice that required by Section 409.3.

418.10 MINIMUM BONDED REINFORCEMENT 418.10.1 A minimum area of bonded reinforcement shall provided in all flexural members with unbonded nri>dri'·.,.,itUI tendons as required by Sections 418.10.2 and 418.10.3. 418.10.2 Except as provided in Section 418.10.3, minimum area ofbonded reinforcement shall be computed by:

Association of Structural Engineers of the PhiliDDines

CONCRETE

{~A£?

A,=O.004A

(418-6)

"ffL.::,;,

"'418.10.2.1 Bonded reinforcement required by Equation (418-6) §hall be uniformly distributed over precompressed tensile zone a~ close as practicable to extreme tension fiber. At;{

418.10.2.2 Bonded reinforcement shall be required regardless of service load stress conditions.

One-way, unbonded, post-tensioned slabs and beams plus 25 .percent of the unreduced superimposed live load by some •method other. than the primary unbonded post-tensioned reinforcement. Design shall be based on the strength method of design with a load factor and capacity reduction factor of one. ;All reinforcement other than the primary unbonded . reinfurcement provided to meet other requirements of this section may be used in the design. 418.10.2.3 Maximum spacing limitations of Sections 407.7.1 and 408.11.5.2, for bonded reinforcement in slabs are not 'lipplicable to spacing of bonded reinforcement in members with Urtbonded tendons. 418.10.3 For two-way flat plates, defined as solid slabs of uniform thickness, minimum area and distribution of bonded reinforcement shall be as follows: 418.10.3.1 Bonded reinforcement shall not be required in positive moment areas where computed tensile stress in concrete at service load (after allowance for prestress losses) does not

exceed 0.17

Jl;

418.10.3.2 In positive moment areas where computed tensile r· stress in concrete at service load exceeds 0.17 J.t: minimum area

of bonded reinforcement shall be computed by:

A,

(418-7)

~ 0.5

f,

where design yield strength';;. shall not exceed 420 MPa. Bonded reinforcement shall be uniformly distributed over precompressed tensile zone as close as practicable to extreme tension fiber.

418.10.4.1 In positive moment areas, minimum length of bonded reinforcement shall be one-third the clear span length and centered in positive moment area. 418.10.4.2 In negative moment areas, bonded reinforce-ment shall extend one-sixth the clear span on each side of support. 418.10.4.3 Where bonded reinforcement is provided for design moment strength in accordance with Section 418.8.3, or for tensile stress conditions in accordance with Section 418.10.3.2, minimum length also shall conform to provisions of Section 412 .

418.11 STATICALLY STRUCTURES

INDETERMINATE

418.11.1 Frames and continuous constf!.!¢tion of prestressed concrete shall be designed for satisfactory performance at service load conditions and for adequate strength. 418.11.2 Performance at service load conditions shall be determined by elastic analysis, considering reactions, moments, shears, and axial forces produced by prestressing, creep, shrinkage, temperature change, axial deformation, restraint of attached structural elements and foundation settlement. 418.11.3 Moments used to compute required strength shall be the sum of the moments due to reactions induced by prestressing (with a load factor of 1.0) and the moments due to factored loads. Adjustment of the sum of these moments shall be permitted as allowed in Section 418.11.4. 418.11.4 Redistribution Of Negative Moments In Continuous Prestressed Flexural Members 418.11.4.1 Where bonded reinforcement is provided at supports in accordance with Section 418.10, negative moments calculated by elastic theory for any assumed loading arrangement shall be permitted to be increased or decreased by not more than:

percent 418.10.3.3 In negative moment areas at column supports, minimum area of bonded reinforcement As in the top of the slab in each direction shall be computed by: As . 000075Ac{

(418-8)

Bonded reinforcement required by Equation (418-8) shall be distributed between lines that are 1.5h outside opposite faces of the column support. At least four bars or wires shall be provided in each direction. Spacing of bonded reinforcement shall not e\ceed JOO mm.

418.11.4.2 The modified negative moments shall be used for calculating moments at sections within spans for the same loading arrangement. 418.11.4.3 Redistribution of negative moments shall be made only when the section at which moment is reduced is so designed that 0Jp, [mp + «(lIdp)(m m')], or [lk./pw + «(Vtlp)(mw m'w)], whichever is applicable, is not greater than 0.2413,.

418.10.4 Mini mum length of bonded reinforcement required by Sections :!18.10.:2 and 4\8.10.3 shall be as follows


CONCRETE

418.12 COMPRESSION MEMBERS - COMBINED FLEXURE AND AXIAL LOADS

prestressed slabs at columns shall be at least equal to required strength considering Sections 409.3, 409.4, 41 411.13.2 and 411.13.6.2.

418.12.1 Prestressed concrete members subject to combined flexure and axial load, with or without nonprestressed reinforcement, shall be proportioned by the strength design methods of this chapter. Effects of prestress, creep, shrinkage and temperature change shall be included.

418.13.3 At service load conditions, all limitations, including specified limits on deflections, shall met, with appropriate consideration of the factors listed Section 418.11.2.

418.12.2 Limits for Reinforcement of Prestressed Compression Members 418.12.2.1 Members with average prestress/pc less than 1.5 MPa shall have minimum reinforcement in accordance with Sections 407.11,410.10.1 and 410.10.2 for columns, or Section 414.4 for walls. 418.12.2.2 Except for walls, members with average prestress/pc equal to or greater than 1.5 MPa shall have all prestressing tendons enclosed by spirals or lateral ties in accordance with the following: 1.

,, .

4-82

f

418.13.5 In slabs with unbonded prestressing tendons, bonded reinforcement shall be provided in accordance with Sections' 418.10.3 and 418.10.4.

Spirals shall conform to Section 407.11.4;

2.

Lateral ties shall be at least 10 mm diameter in size or welded wire fabric of equivalent area, and spaced vertically not to exceed 48 tie bar or wire diameters or least dimension of compression member;

3.

Ties shall be located vertically not more than half a tie spacing above top of footing or slab in any story, and shall be spaced as provided herein to not more than half a tie spacing below lowest horizontal reinforcement in members supported above;

4.

418.13.4 For normal live loads and load uniformly distributed,' spacing of prestressing tendons or groups of tendons in one: direction shall not exceed eight times the slab thickness, nor LSi m. Spacing of tendons also shall provide a minimum averagey prestress (after allowance for all prestress losses) of 0.9 MPa on'~ the slab section tributary to the tendon or tendon group. k.~ minimum of two tendons shall be provided in each directionJ through the critical shear section over columns. SpeciaL consideration of tendon spacing shall be provided for slabs with: concentrated loads.

Where beams or brackets frame into all sides of a column, it shall be permitted to terminate ties not more than 75 mm below lowest reinforcement in such beams or brackets.

418.12.2.3 For walls with average prestress fpc equal to or greater than 1.5 MPa, minimum reinforcement required by Section 414.4 may be waived where structural analysis shows adequate strength and stability.

418.13.6 In lift slabs, bonded bottom reinforcement shall bet detailed in accordance with the last paragraph of Section 413.4.8.6.

418.14 POST-TENSIONED TENDON ANCHORAGE ZONES 418.14.1 Anchorage Zone The anchorage zone shall be considered as composed of two zones: 1.

2.

The local zone is the rectangular prism (or equivalent rectangular prism for circular or oval anchorages) of concrete immediately surrounding the anchorage device and any confining reinforcement; The general zone is the anchorage zone as defined in Section 402 and includes the local zone.

418.14.2 Local Zone

418.13 SLAB SYSTEMS 418.13.1 Factored moments and shears in prestressed slab systems reinforced for flexure in more than one direction shall be determined in accordance with provisions of Section 413.8, (excluding Sections 413.8.7.4 and 413.8.7.5), or by more detailed design procedures. 418.13.2 Moment strength of prestressed slabs at every section shall be at least equal to the required strength considering Sections 409.3,409.4,418.11.3 and 418.11.4. Shear strength of

418.14.2.1 Design of local zones shall be based upon the factored tendon force, p.u , and the requirements of Sections 409.3.8 and 409.4.2.5 418.14.2.2 Local-zone reinforcement shall be provided where required for proper functioning of the anchorage device. 418.14.2.3 Local-zone requirements of Section 418.14.2.2 are satisfied by Section 418.15.1 or 418.16.1 and 418.16.2.



4-33

418.14.3 General Zone cc'~i

;418.14.3.1 Design of general zones shall be based upon the factored tendon force, P,"" and the requirements of Sections 409.3.8 and 409.4.2.5 ;:418.14.3.2 General-zone reinforcement shall be provided where :~equired to resist bursting, spalling, and longitudinal edge tension forces induced by anchorage devices. Effects of abrupt change in section shall be considered. 418.14.3.3 The general-zone requirements of Section 418.14.3.2 are satisfied by Sections 418.14.4, 418.14.5, 418.14.6 and $,~hichever one of Section 418.15.2 or 418.15.3 or 418.16.3 is Applicable.

418.14.4 Nominal Material Strengths 418.14.4.1 Nominal tensile strength of bonded reinforce-ment is 'limited to /y for nonprestressed reinforcement and to /py for §prestressed reinforcement. Nominal tensile stress of unbonded 'prestressed reinforcement for resisting tensile forces in the anchorage zone shall be limited to

Ips =Ise + 10,000.

418.14.4.2 Except for concrete confined within spirals or hoops providing confinement equivalent to that corresponding to Equation (410-6), nominal compressive strength of concrete in the general zone shall be limited to 0.7 Al'd. 418.14.4.3 Compressive strength of concrete at time of post tensioning shall be specified on the design drawings. Unless oversize anchorage devices sized to compensate for the lower compressive strength are used or the tendons are stressed to no more than 50 percent of the final tendon force, tendons shall not be stressed until f'cb as indicated by tests consistent with the .curing of the member, is at least 28 MFa for multi strand tendons or at least 17 MFa for single-strand or bar tendons.

418.14.5.2 Simplified equations shall not be used where member cross sections are nonrectangular, where discontinuities in or near the general zone cause deviations in the force flow path, where minimum edge distance is less than 1.5 times the anchorage device lateral dimension in that direction, or where multiple anchorage devices are used in other than one closely spaced group. 418.14.5.3 The stressing sequence shall be specified on the design drawings and considered in the design. 418.14.5.4 Three-dimensional effects shall be considered in design and analyzed using three-dimensional procedures or approximated by considering the summation of effects for two orthogonal planes. 418.14.5.5 For intermediate anchorage devices, bonded reinforcement shall be provided to transfer at least 0.35 Pm into the concrete section behind the anchor. Such reinforcement shall be placed symmetrically around the anchorage devices and shall be fully developed both behind and ahead of the anchorage devices. 418.14.5.6 Where curved tendons are used in the general zone, except for monostrand tendons in slabs or where analysis shows reinforcement is not required, bonded reinforcement shall be provided to resist radial and splitting forces. 418.14.5.7 Except for mono-strand tendons in slabs on where analysis shows reinforcement is not required, minimum reinforcement with a nominal tensile strength equal to 2 percent of each factored tendon force shall be provided in orthogonal directions parallel to the back face of all anchorage zones to limit spalling. 418.14.5.8 Tensile strength of concrete shall be neglected in calculations of reinforcement requirements.

418.14.6 Detailing Requirements 418.14.5 Design Methods 418.13.5.1 The following methods shall be permitted for the design of general zones provided that the specific procedures used result in prediction of strength in substantial agreement with results of comprehensive tests:

1.

Equilibrium models);

2.

Linear stress analysis (including finite element analysis or equivalent); or

3.

Simplified equations where applicable.

based

plasticity

models

Selection of reinforcement sizes, spacings, cover, and other details for anchorage zones shall make allowances for tolerances on the bending, fabrication, and placement of reinforcement, for the size of aggregate, and for adequate placement and consolidation ofthe concrete.

(strut-and-tie


CONCRETE

418.15 DESIGN OF ANCHORAGE ZONES FOR MONO-STRAND OR SINGLE 16 MM DIAMETER BAR TENDONS 41S.1S.1 Local Zone Design Mono-strand or single 16 mm or smaller diameter bar anchorage devices and local zone reinforcement shall meet the requirements of the Post-Tensioning Institute's "Specification for Unbonded Single Strand Tendons" or the special anchorage device requirements of Section 418.16.1.

41S.1S.2 General Zone Design For Slab Tendons 41S.1S.2.1 F9r anchorage devices for 12 mm or smaller diameter strands in n
""'''

'''Itt"

41SUS.2.2 Two horizontal bars at least 12 mm diameter in size shall be provided parallel to the slab edge. They shall be permitted to be in contact with the front face of the anchorage device and shall be within a distance of ~ h ahead of each device. Those bars shall extend at least 150 rom either side ofthe outer edges of each device. 41S.1S.2.3 If the center-to-center spacing of anchorage devices is 300 rom or less, the anchorage devices shall be considered as a group. For each group of six or more anchorage devices, n + 1 hairpin bars or closed stirrups at least 10 mm diameter in size shall be provided, where n is the number of anchorage devices. One hairpin bar or stirrup shall be placed between each anchorage device and one on each side of the group. The hairpin bars or stirrups shall be placed with the legs extending into the slab perpendicular to the edge. The center portion of the hairpin bars or stirrups shall be placed perpendicular to the plane of the slab from 3h18 to hl2 ahead of the anchorage devices.

'IIm.

41S.1S.2.4 For anchorage devices not conforming to Section 418.15.2.1, minimum reinforcement shall be based upon a detailed analysis satisfying Section 418.14.5.

418.15.3 General one Design for Groups of Mono-strand Tendons in Bearns and Girders Design of general zones for groups of mono strand tendons in beams and girders shaH meet the requirements of Sections 418.14.3 through 418.14.5.

4-84

418.16 DESIGN OF ANCHORAGE ZONES FOR MULTI-STRAND TENDONS 418.16.1 Local Zone Design Basic multi-strand anchorage devices and local zo reinforcement shall meet the requirements of AASHT. "Standard Specifications for Highway Bridges," Division I Articles 9.21.7.2.2 through 9.21.7.2.4. Special anchorage devices shall satisfy the tests required i' AASHTO "Standard Specifications for Highway Bridges, Division I, Article 9.21.7.3 and described in AASHT "Standard Specifications for Highway Bridges," Division Article 10.3.2.3. 418.16.2 Use Of Special Anchorage Devices Where special anchorage devices are to be used, supplemen skin reinforcement shall be furnished in the correspoO(lm~\I regions of the anchorage zone, in addition to the confinin reinforcement specified for the anchorage device. Thi supplemental reinforcement shall be similar in configuration at least equivalent in volumetric ratio to any supplementary s reinforcement used in the qualifying acceptance tests of th anchorage device. 418.16.3 General Zone Design Design for general zones for multi strand tendons shall meet requirements of Sections 418.14.3 through 418.14.5.

418.17 CORROSION PROTECTION FOR UNBONDED PRESTRESSING TENDONS 418.17.1 Unbonded tendons shall be encased with Sh€~attltn~:.~ The tendons shall be completely coated and the sheathing the tendon filled with suitable material to inhibit corrosion. 418.17.2 Sheathing shall be watertight and continuous entire length to be unbonded. 418.17.3 For applications in corrosive environments, sheathing shall be connected'to all stressing, intermediate fixed anchorages in a watertight fashion. 418.17.4 Unbonded single strand tendons shall be protected against corrosion in accordance with the Post-Tensioning Institute's "Specifications for Unbonded Single Strand Tendons."



ill8.18

POST-TENSIONING DUCTS

c~HtI8.1

Ducts for grouted tendons shall be mortar-tight and nonreactive with concrete, tendons, grout, and corrosion JIDibitor.

418.18.2 Ducts for grouted single wire, single strand, or single b~ tendons shall have an inside diameter at least 6 mm larger tendon diameter.

4-85

418.19.3.3 Water content shall be minimum necessary for proper pumping of grout; however, water-cement ratio shall not exceed 0.45 by' weight. 418.19.3.4 Water shall not be added to increase grout flowability that has been decreased by delayed use of the grout.

than

418.19.4 Mixing and pumping grout

418.18.3 Ducts for grouted multiple wire, multiple strand, or multiple bar tendons shall have an inside cross-sectional area at least two times the cross-sectional area of tendons.

418.19.4.1 Grout shall be mixed in equipment capable of continuous mechanical mixing and agitation that will produce uniform distribution of materials, passed through screens, and pumped in a manner that will completely fill tendon ducts.

418.18.4 Ducts shall be maintained free of ponded water if members to be grouted are exposed to temperatures below freezing prior to grouting.

418.19 GROUT FOR BONDED PRESTRESSING TENDONS

418.19.4.2 Temperature of members at time of grouting shall be above 2 °c and shall be maintained above 2 °c until field-cured 50 mm cubes of grout reach a minimum compressive strength of 5,5 MPa. 418.19.4.3 Grout temperatures shall not be above 32 degrees C during mixing and pumping.

418.19.1 Grout shall consist of portland cement and water; or portland cement, sand, and water. 418.19.2 Materials for grout shall conform to 418.19.2.1 through 418.19.2.4.

Sections

418.19.2.1 Portland cement shall conform to Section 403.3. 418.19.2.2 Water shall conform to Section 403.5.

418.20 PROTECTION FOR PRESTRESSING TENDONS Burning or welding operations in the vicinity of prestressing tendons shall not be performed so that tendons are not subject to excessive temperatures, welding sparks, or ground currents.

•

,">{

418.19.2.3 Sand, if used, shall conform to "Standard Specification for Aggregate for Masonry Mortar" (ASTM C 144) except that gradation shall be permitted to be modified as necessary to obtain satisfactory workability. 418.19.2.4 Admixtures conforming to Section 403.7 and known to have no injurious effects on grout, steel, or concrete shall be permitted. Calcium chloride shall not be used.

418.19.3 Selection of grout proportions 418.19.3.1 Proportions of materials for grout shall be based on either of the following: 1

Results of tests on fresh and hardened grout prior to beginning grouting operations; or

2.

Prior documented experience with similar materials and equipment and under comparable field conditions.

418.19.3.2 Cement used in the work shall correspond to that on which selection of grout proportions was based.

418.21 APPLICATION AND MEASUREMENT OF PRESTRESSING FORCE 418.21.1 Prestressing force shall be determined by both of the following methods:

1.

Measurement of tendon elongation. Required elongation shall be determined from average load elongation curves for the prestressing tendons used;

2.

Observation of jacking force on a calibrated gage or load cell or by use of a calibrated dynamometer.

Cause of any difference in force detennination between methods 1 and 2 that exceeds 5 percent for pretensioned elements or 7 percent for post-tensioned construction shall be ascertained and corrected. 418.21.2 Where the transfer of force from the bulkheads of pretensioning bed to the concrete is accomplished by flame cutting prestressing tendons, cutting points and cutting sequence shall be predetermined to avoid undesired temporary stresses.


CONCRETE

418.21.3 Long lengths of exposed pretensioned strand shall be cut near the member to minimize shock to concrete. 418.21.4 Total loss of prestress due to umeplaced broken tendons shall not exceed 2 percent of total prestress.

SECTION 419 - SHELLS AND FOLDED PLATE MEMBERS 419.1 NOTATION modulus of elasticity of concrete, MPa, See 408.6.1 = specified compressive strength of concrete, MPa = square root of specified compressive strength =

418.22 POST-TENSIONING ANCHORAGES AND COUPLERS. 418.22.1 Anchorages and couplers for bonded and unbonded prestressing tendons shall develop at least 95 percent of the specified breaking strength of the tendons, when tested in an unbonded condition, without exceeding anticipated set. For bonded tendons, anchorages and couplers shall be located so that 100 percent of the specified breaking strength of the tendons shall be developed at critical sections after tendons are bonded in the member. 418.22.2 Couplers shall be placed in areas approved by the engineer and enclosed in housing long enough to permit necessary movements.

,

418.22.3 In unbonded construction subject to repetitive loads, special attention shall be given to the possibility of fatigue in anchorages and couplers.

..

4-86

concrete, MPa

1;, = specified yield strength of nonprestressed reinforcemen h

Id ¢J

MPa thickness of shell or folded plate, mm = development length, mm = strength-reduction factor. See Section 409.4

419.2 SCOPE AND DEFINITIONS 419.2.1 Provisions of Section 419 shall apply to thin-shell folded-plate concrete structures, including ribs and ed members. 419.2.2 All provisions of this Code not specifically exclude and not in conflict with provisions of Section 419, shall apply t thin-shell structures.' .

418.22.4 Anchorages, couplers, and end fittings shall be permanently protected against corrosion.

AUXILIARY MEMBERS - Ribs or edge beams that serve t strengthen, stiffen, or support the shell; usually, auxili members act jointly with the shell.

418.23 EXTERNAL POST-TENSIONING

ELASTIC ANALYSIS - An analysis of deformations a internal forces based on equilibrium, compatibility of strai and assumed elastic behavior, and representing to a suita approximation the three-dimensional action of the shell toget with its auxiliary members,

418.23.1 Post-tensioning tendons shall be permitted to be external to any concrete section of a member. The strength serviceability design methods of this code shall be used in evaluating the effects of external tendon forces on the concrete structure. 418.23.2 External tendons shall be considered as unbonded tendons when computing flexural strength unless provisions are made to effectively bond the external tendons to the concrete section along its entire length. 418.23.3 External tendons shall be attached to the concrete member in a manner that maintains the desired eccentricity between the tendons and the concrete centroid throughout the full range of anticipateo member deflection. 418.23.4 External tendons and tendon anchorage regions shall be protected against corrosion, and the details of the protection method shall be indicated on the drawings or in the project specifications.

EXPERIMENTAL ANALYSIS - An analysis procedure base on the measurement of deformations and/or strains of structure or its model; experimental analysis may be based 0 either elastic or inelastic behavior. FOLDED PLATES - A special class of shell structure form by joining flat, thin slabs along their edges to create a thr dimensional spatial structure. INELASTIC ANALYSIS - An analysis of deformations a internal forces based on equilibrium, nonlinear stress-st relations for concrete and reinforcement, consi-deration cracking and time-dependent effects and compatibility of stra The analysis shall represent a suitable approximation of t three-dimensional action of the shell together with its auxili members,


SHELLS AND FOLDED PLATE MEMBERS

4-87

l I

IUBBED SHELLS - Spatial structures with material placed primarily along certain preferred rib lines, with the area between the ribs filled with thin slabs or left open.

such portions of the shell, the reinforcement perpendicular to the auxiliary member shall be at least equal to that required for the flange of aT-beam by Section 408.11.5.

THIN SHELLS - Three-dimensional spatial structures made up of one or more curved slabs or folded plates whose thicknesses

419.3.10 Strength design of shell slabs for membrane and bending forces shall be based on the distribution of stresses and strains as determined from either an elastic or an inelastic analysis.

are small compared to their other dimensions. Thin shells are characterized by their three-dimensional load-carrying behavior which is determined by the geometry of their forms, by the manner in which they are supported and by the nature of the applied load.

419.3.11 In a region where membrane cracking is predicted, the nominal compressive strength parallel to the cracks shall be taken as O.4/'c.

419.3 ANALYSIS AND DESIGN 419.4 DESIGN STRENGTH OF MATERIALS 419.3.1 Elastic behavior shall be an accepted basis for determining internal forces and displacements of thin shells. This behavior shall be permitted to be established by computations based on an analysis of the uncracked concrete structure in which the material is assumed linearly elastic, homogeneous and isotropic. Poisson's ratio of concrete shall be permitted to be taken equal to zero. . 419.3.2 Inelastic analysis shall be permitted to be used where it can be shown that such methods provide a safe basis for design. 419.3.3 Equilibrium checks of internal resistances and external loads shall be made to ensure consistency of results. 419.3.4 Experimental or numerical analysis procedures shall be permitted where it can be shown that such procedures provide a safe basis for design. 419.3.5 Approximate methods of analysis shall be permitted where it can be shown that such methods provide a safe basis for design. 419.3.6 In prestressed shells, the analysis shaH also consider behavior under loads induced during prestressing, at cracking load and at factored load. Where prestressing tendons are draped within a shell, design shall take into account force components on the shell resulting from the tendon profile not lying in one plane. 419.3.7 The thickness of a shell and its reinforcement shall be proportioned for the required strength and serviceability, using either the strength design method of Section 408.2.1 or the . alternate design method of Section 408.2.2. 419.3.8 Shell instability shall be investigated and shown by

design to be precluded.

419.3.9 Auxiliary members shall be designed according to the applicable provisions of this code. It shall be permitted to assume that a portion of the shell equal to the flange width, as specified in Section 408.11, acts with the auxiliary member. In

419.4.1 Specified compressive strength of concrete fc at 28 days shall not be less than 21 MPa. 419.4.2 Specified yield strength of nonprestressed reinforcement

1;, shall not exceed 420 MPa. 419.5 SHELL REINFORCEMENT 419.5.1 Shell reinforcement shall be provided to resist tensile stresses from internal membrane forces, to resist tension from bending and twisting moments, to control shrinkage and temperature cracking and as special reinforcement as shell boundaries, load attachments and shell openings. 419.5.2 Tensile reinforcement shall be provided in two or more directions and shall be proportioned such that its resistaJIce in any direction equals or exceeds the component of internal forces in that direction.

Alternatively, reinforcement for the membrane forces in the slab shall be calculated as the reinforcement required to resist axial tensile forces plus the tensile force due to shear- friction required to transfer shear across any cross section of the membrane. The assumed coefficient of friction shall not exceed LOA where A = 1.0 for normal-weight concrete, 0.85 for sand-lightweight concrete, and 0.75 for all lightweight concrete. Linear interpolation shall be permitted when partial sand replacement is used. 419.5.3 The area of shell reinforcement at any section as measured in two orthogonal directions shall not be less than the slab shrinkage or temperature reinforcement required by Section 407.13. 419.5.4 Reinforcement for shear and bending moments about axes in the plane of the shell slab shall be calculated in accordance with Sections 410, 411 and 413.

National Struct-"ral Code of the Philippines, Volume 1

CONCRETE

419.5.5 The area of shell tension reinforcement shall be limited so that the reinforcement will yield before either crushing of roncrete in compression or shell buckling can take place. 419.5.6 In regions of high tension, membrane reinforcement shall, if practica~ be placed in the general directions of the principal tensile membrane forces. Where this is not practical, it shall be permitted to place membrane reinforcement in two or more component directions. 419.5.7 If the direction of reinforcement varies more than 10 degrees from the direction of principal tensile membrane force, the amount of reinforcement shall be reviewed in relation to cracking at service loads. 419.5.8 Where the magnitude of the principal tensile membrane stress within the shell varies greatly over the area of the shell surface, reinforcement resisting the total tension may be concentrated in the regions of largest tensile stress where it can be shown that this provides a safe basis for design. However, the ratio of shell reinforcement in any portion of the tensile zone shall not be less than 0.0035 based on the overall thickness of the shell. 419.5.~

Reinforcement required to resist shell bending moments shall be proportioned with due regard to the simultaneous action of membrane axial forces at the same location. Where shell reinfurcement is required in only one face to resist bending moments, equal amounts shall be placed near both surfaces of the shell even though a reversal of bending moments is not indicated by the analysis. 419.5.10 Shell reinforcement in any direction shall not be spaced farther apart than 500 mm, or five times the shell thickness. Where the principal membrane tensile stress on the gross concrete area due to factored loads exceeds 0.331/1.[1:

419.6 CONSTRUCTION 419.6.1 When removal of formwork is based on a modulus of elasticity of concrete because of stability deflection considerations, the value of the modulus of Ee shall be determined -from flexural tests of field-cured specimens. The number of test specimens, the dimensions test beam specimens and test procedures shall be specified. 419.6.2 The tolerances for the shape of the shell shall specified. If construction results in deviations from the greater than the specified tolerances, an analysis of the effect the deviations shall be made and any required remedial shall be taken to ensure safe behavior.

SECTION 420 - STRENGTH EVALUATION OF EXISTING STRUCTURES 420.1 NOTATION D

Fc h L

It

reinforcement shall not be spaced farther apart than three times the shell thickness.

Amax 419.5.11 Shell reinforcement at the junction of the shell and supporting members or edge members shall 'be anchored in or extended through such members in accordance with the requirements of Section 412, except that the minimum development length shall be 1.214 but not less than 500 mm. 419.5.12 Splice development lengths of shell reinforcement shall . be governed by the provisions of Section 412, except that the minimum splice length of tension bars shall be 1.2 times the value required by Section 412 but not less than 500 mm. The number of splices in principal tensile reinforcement shall be kept to a practical minimum. Where splices are necessary, they shall be staggered at least 14 with not more than one-third of the reinforcement spliced at any section.

Ar max A/max

dead loads or related internal moments and forces specified compressive strength concrete, MPa. = overall thickness of member in the direction of action considered, mm = live loads or related internal moments and forces = span of member under load test, mm. (The shorter span for two-way slab systems.) Span is the smaller of (1) distance between centers of supports and clear distance between supports plus thickness h of member. In Equation (420-1), span for a cantilever shall be taken as twice the distance from support to cantilever end = measured maximum deflection, mm. See Equation (420-1) = measured residual deflection, mm. See Equations (420-2) and (420-3) maximum deflection measured during the second test relative to the position of the structure at the beginning of the second test, mm. See Equation (420- . 3)

420.2 STRENGTH EVALUATION-GENERAL 420.2.1 If there is a doubt that a part or all of a structure meets the safetyrequirements5)f this code, a strength evaluation shall be carried out as required by the engineer or building officiaL 420.2.2 Ifthe effect of the strength deficiency is well understood and if it is feasible to measure the dimensions and materials


STRENGTH EVALUATION OF EXISTING STRUCTURES

4-89

properties required for analysis, analytical evaluations of strength based on those measurements shall suffice. Required data shall be determined in accordance with Section 420.3.

420.4 LOAD TEST PROCEDURE

420.2.3 If the effect of the~-'Strength deficiency is not well understood or if it is not feasible to establish the required dimensions and material properties by measurement, a load test shall be required if the structure is to remain HLservl~

The number and arrangement of spans or panels loaded shall be selected to maximize the deflection and stresses in the critical regions of the structural elements of which strength is in doubt. More than one test load arrangement shall be used if a single arrangement will not simultaneously result in maximum values of the effects (such as deflection, rotation or stress) necessary to demonstrate the adequacy of the structure.

420.2.4 If the doubt about safety of a part or all of a structure involves deterioration and if the observed response during the .load test satisfies the acceptance criteria, the structure or part of the structure shall be permitted to remain in service for a specified time period. If deemed necessary by the engineer, periodic re-evaluations shall be conducted.

420.3 DETERMINATION OF REQUIRED DIMEl'N'SIONS AND MATERIAL PROPERTIES .420.3.1 Dimensions of the structural elements shall be established at critical sections. 420.3.2 Locations and sizes of the reinforcing bars, welded wire fabric or tendons shall be determined by measurement. It shall be permitted to base reinforcement locations on available drawings if spot checks are made confirming the information on the drawings. 420.3.3 If required, concrete strength shall be based on results of cylinder tests or tests of cores removed from the part of the structure where the strength is in doubt. Concrete strength shall be determined as specified in Section 405.7.3. 420.3.4 If required, reinforcement or tendon strength shall be based on tensile tests of representative samples of the material in the structure in question. 420.3.5 If the required dimensions and material properties are determined through measurements and testing, and if calculations can be made in accordance with Section 420.2.2, it . shall be permitted to increase the strength-reduction factor in Section 409.4, but the strength-reduction factor shall not be more than:

Flexure without axial load ..... . . . . . . . .. .. .......

1. 0

Axial tension and axial tension with flexure.... . . . . . .. 1.0 Axial compression and axial compression with flexure: Members with spiral reinforcement conforming to 0.9

Section410.10.3 ...................... Other members . . . . . . . . . . . . . . . . . . . . . . . .

420.4.1 Load arrangement

420.4.2 Load intensity

The total test load (including dead load already in place) shall not be less than 0.S5(1.4D + 1.71-). It shall be permitted to reduce I- in accordance with the requirements of this code. 420.4.3 A load test shall not be made until that portion of 'the structure to be subject to load is at least 56 days old. If the o~r of the structure, the contractor, and all involved parties agree, it shall be permitted to make the test at an earlier age.

420.5 LOADING CRITERIA 420.5.1 The initial value for all applicable response measurements (such as deflection, rotation, strain, slip, crack widths) shall be obtained not more than one hour before application of the first load increment. Measurements shall be made at locations where maximum response is expected. • Additional measurements shall be made ifrequired. 420.5.2 Test load shall be applled in not less than four approximately equal increments. 420.5.3 Uniform test load shall be applied in a manner to ensure uniform distribution of the load transmitted to the structure or portion of the structure being tested. Arching of the applied load shall be avoided. 420.5.4 A set of response measurements shall be made after each load increment is applied and after the total load has been applied on the structure for at least 24 hours. 420.5.5 Total test load shall be removed immediately after all response measurements defined in Section 420.5.4 are made. 420.5.6 A set of final response measurements shall be made 24 hours after the test load is removed.

420.6 ACCEPTANCE CRITERIA

0.85

Shear and/or torsion... ........................ 0.9

. Bearing on concrete. . ..... . ................... 0.85

420.6.1 The portion of the structure tested shall show no evidence of failure. Spalling and crushing of compressed concrete shall be considered an indication offailure.


1

CONCRETE

420.6.2 Measured maximum deflections shall satisfy one of the following conditions:

4-90

SECTION 421- SPECIAL PROVISIONS FOR SEISMIC DESIGN

e

~max ~ 20 ,~OOh

(420-1)

~rmax ~ 4

(420-2)

421.1 NOTATION

= cross-sectional area of a structural member

If the measured maximum and residual deflections do not satisfy Equation (420-1) or (420-2), it shall be permitted to repeat the load test. The repeated test shall be conducted not earlier than 72 hours after removal of the first test load. The portion of the structure tested in the repeat test shall be considered acceptable if deflection recovery satisfied the condition: ~

rmax

~

5

(420-3)

where AI max is the maximum deflection measured during the second test relative to the position of the structure at the beginning of the second test. 420.6.3 Structural members tested shall not have cracks indicating the imminence of shear failure. 420.6.4 In regions of structural members without transverse reinforcement, appearance of structural cracks inclined to the longitudinal axis and having a horizontal projection longer than the depth of the member at mid-point of the crack shall be evaluated. 420.6.5 In regions of anchorage and lap splices, the appearance along the line of reinforcement of a series of short inclined cracks or horizontal cracks shall be evaluated.

420.7 PROVISIONS FOR LOWER LOAD RATING If the structure under investigation does not satisfy conditions or criteria of Section 420.2.2,420.6.2 or 420.6.3, the structure may be permitted for use at a lower load rating based on the results of the load test or analysis, if approved by the building official.

b

out-to-out oftransverse reinforcement, mm2 area of concrete section, resisting shear, individual pier or horizontal wall segment, mm2 = gross area of concrete section bounded by thickness and length of section in the direction of force considered, mm2 gross area of section, mm2 effective cross-sectional area within a joint (see CI<;;',U"-'R.1!jJ 421.6.3.1) in a plane parallel to flane of generating shear in the joint, mm . The joint depth be the overall depth of the column. Where a frames into a support of larger width, the "'t+,~Ml'" width of the joint shall not exceed the smaller of 1. beam width plus the joint depth 2. twice the smaller perpendicular distance from the longitudinal axis of the beam to the column' side. See Section 421.6.3.1. = total cross-sectional area of transverse rel:n-icJroement (including crossties) within spacing, s, perpendicular to dimension, he, mm 2 total area of reinforcement in each group of """!5V""'" bars in a diagonally reinforced coupling beam, = effective compressive flange width of a member, mm = web width, or diameter ofcircular section, mm = distance from the extreme compression fiber to neutral axis, see Section 410.3.7, calculated for the factored axial force and nominal moment strength, consistent with the design displacement 0;" resulting in the largest neutral axis depth, mm = effective depth of section, mm = bar diameter, mm = load effects of earthquake, or related internal moments and forces specified compressive strength of concrete, .MFa square root of specified compressive strength of = =

420.8 SAFETY 420.8.1 Load tests shall be cond~cted in such a manner as to provide for safety of life and structure during the test.

= =

420.8.2 No safety measures shall interfere with load test procedures or affect results.

concrete, .MFa specified yield strength of reinforcement, MPa specified yield strength of transverse reinforcement, MPa cross-sectional dimension of column core measured center-to-center ofconfining reinforcement, mm height of entire wall or of the segment of wall considered, mm maximum horizontal spacing of hoop or crosstie legs on all faces of the column, mm development length for a straight bar


SPECIAL PROVISIONS FOR SEISMIC DESIGN

'.'M.g

Mpr

Ms

M" s

"" development length for a bar with a standard hook as defined in Equation (421-6), mm clear span measured face-to-face of supports, mm == minimum length, measured from joint face along axis of structural member, over which transverse reinforcement must be provided, mm "" length of entire wall or of segment of wall considered in direction of shear force, mm moment at the face of the joint, corresponding to the nominal flexural strength of the column framing into that joint, calculated for the factored axial force, consistent with the direction of the lateral forces considered, resulting in the lowest flexural strength, see Section 421.5.2.2 "" moment at the face of the joint, corresponding to the nominal flexural strength of the girder including slab where in tension, framing into that joint, see Section 421.5.2.2 probable flexural strength of members, with or without axial load, determined using the properties of the member at the joint faces assuming a tensile strength in the longitudinal bars of at least 1.25./y and a strength reduction factor tP of 1.0 = portion of slab moment balanced by support moment factored moment at section = spacing of transverse reinforcement measured along the longitudinal axis ofthe structural member, mm

Se CONNECTION moment, shear or axial force at connection cross section other than the nonlinear action location corresponding to probable strength at the nonlinear action location, taking gravity load effects into consideration, per Section 421.3.7.3

Sn COf..WECTION

vc

re

Vn Vu

a

p

nominal strength of connection cross section in flexural, shear or axial action, per Section 421.3.7.3 = maximum spacing of transverse reinforcement, mm = longitudinal spacing of transverse reinforcement within the length 10 , mm = nominal shear strength provided by concrete design shear force determined from Section 421.4.4.1 or421.5.5.1 = nominal shear strength factored shear force at section angle between the diagonal reinforcement and the longitudinal axis of a diagonally reinforced coupling beam coefficient defining the relative contribution of concrete strength to wall strength, See Equation 421-7 = design displacement, mm ratio of nonprestressed tension reinforcement = A,(hd) ratio o(total reinforcement area to cross-sectional area of column

Pn

P.

Pv

tP Llm Lls

tp

4-91

ratio of area of distributed reinforcement parallel to the plane of Acv to gross concrete area perpendicular to that reinforcement = ratio of volume of spiral reinforcement to the core volume confined by the spiral reinforcement (measured out-to-out) = ratio of area of distributed reinforcement perpendicular to the plane of Acv to gross concrete area Acv = strength-reduction factor R",Ll•. = Design Level Response Displacement, which is the total drift or total story drift that occurs when the structure is subjected to the design seismic forces. =Dynamic Amplification Factor from Sections 421.3.7.3 and 421.3.7.4.

=

421.2 DEFINITIONS BASE OF STRUCTURE - Level at which earthquake motions are assumed to be imparted to a building. This level does not necessarily coincide with the ground level. BOUNDARY ELEMENTS - Portions along structural wall and structural diaphragm edges strengthened by longitudinal and transverse reinforcement. Boundary elements do not necessarily require an increase in the thickness of the wall or diaphragm. Edges of openings within walls and diaphragms shall be provided with boundary elements as required by Sections 421.7.6 and 421.8.5.3. COLLECTOR ELEMENTS - Elements that serve to transmit the inertial forces within structural diaphragms to me~bers of the lateral-force-resisting systems.

CONFINED CORE - the area within the core defined by he CONNECTION - an element that joins two precast members or a precast member and a cast-in-place member. COUPLING BEAM - a horizontal element in plane with and connecting two shear walls. CROSSTIE - A continuous reinforcing bar having a seismic hook at one end and a hook of not less than 90 degrees with at least six-diameter extension at the other end. The hooks shall engage peripheral longitudinal bars. The 90-degree hooks of two successive crossties engaging the same longitudinal bars shall be alternated end for end. DESIGN DISPLACEMENT - Total lateral displacement expected for the design-basis earthquake, as required by the governing code for earthquake-resistant design. DESIGN LOAD COMBINATIONS - Combinations of factored loads and forces specified in Section 409.3. DEVELOPMENT LENGTH FOR A BAR WITH A STANDARD BOOK - The shortest distance between the


CONCRETE

critical section (where the strength of the bar is to be developed) and a tangent to the outer edge of the 9O-degree hook.

shear force prescribed by the governing code for ..",.,rhf11!1",lr: resistant design.

DRY CONNECTION - a connection used between precast members which does not qualify as a wet connection.

STRONG CONNECTION - a connection that remains while the designated nonlinear action regions undergo . response under the Design Basis Ground Motion.

FACTORED LOADS AND FORCES - Loads and forces modified by the factors in Section 409.3. HOOP - A closed tie or continuously wound tie. A closed tie can be made up of several reinforcing elements, each having seismic hooks at both ends. A continuously wound tie shall have a seismic hook at both ends. JOINT - the geometric volume common to intersecting members. LATERAL FORCE RESISTING SYSTEM - That portion of the structure composed of members proportioned to resist forces related to earthquake effects. LIGHTWEIGHT-AGGREGATE CONCRETE All lightweight or sand-lightweight aggregate concrete made with lightweight aggregates conforming to Section 403.4. MOMENT FRAME - Space frames in which members and joints • resist forces through flexure, shear, and, axial force. Moment frames shall be categorized as follows:

Intermediate moment frame - A frame complying with the requirements of Sections 421.3.2.3 and 421. 11 in addition to the requirements for ordinary moment frames. Ordinary moment frame - A frame complying with the requirements of Sections 401 through 418. Special moment frame - A frame complying with the requirements of Sections 421.3 through 421.6 in addition to the requirements for ordinary moment frames. NONLINEAR ACTION LOCATION - the center of the region of yielding in flexure, shear or axial action. NONLINEAR ACTION REGION - the member length over which nonlinear action takes place. It shall be taken as extending a distance of no less than hJ2 on either side of the nonlinear action location. SEISMIC HOOK - A hook on a stirrup, hoop or crosstie having a bend not less than 135 degrees, except that circular hoops shall have a bend not less than 90 degrees. Hooks shall have a six-diameter [but not less than 75 mm], extension "that engages the longitudinal reinforcement and projects into the interior of the stirrup or hoop. SHELL CONCRETE - concrete outside the transverse reinforcement confining the concrete. SPECIAL BOUNDARY ELEMENTS - Boundary elements required by Section 421. 7.6.2 or 421.7.6.3. SPECIFIED LATERAL FORCES Lateral forces corresponding to the appropriate distribution of the design bast'

STRUCTURAL DIAPHRAGMS - Structural members, as floor and roof slabs, that transmit inertial forces to force resisting members. STRUCTURAL TRUSSES - Assemblages of concrete members subjected primarily to axial forces. STRUCTURAL WALLS - Walls proportioned to combinations of shears: moment, and axial forces induced earthquake motions. A shear wall is a structural wall. "'-t,.,,,I"I1,,>' walls shall be categorized as follows:

Ordinary reinforced concrete structural walls complying with the requirements of Sections 401 through 418. Ordinary structural plain concrete wall with the requirements of Section 422.

A wall

",.,llllJlV ....

Special reinforced coIicrete structural wall complying with the requirements of Sections 421.3 and 421.7 addition to the requirements for ordinary reinforced structural walls. STRUT - An element of a structural diaphragm used to continuity around an opening in the diaphragm. TIE ELEMENTS - Elements that serve to transmit forces and prevent separation of building components such footings and walls. WALL PIER - a wall segment with a horizontal lengrll-tO thickness ratio between 2.5 and 6, and whose clear height is least two times its horizontal length. WET CONNECTION - uses any of the splicing methods, Section 421.3.6.1 or 421.4.2.3, to connect precast members uses cast-in-place concrete or grout to fill the splicing closure.

421.3 GENERAL REQUIREMENTS 421.3.1 Scope 421.3.1.1 Section 421 contains special requirements for and construction of reinforced concrete members of a for which the design forces, related to earthquake motions, been determined on the basis of energy dissipation in nonlinear range of response. 421.3.1.2 The provisions of Sections 401 through 418 apply except as modified by the provisions of Section 421 Where the design seismic loads are computed using for intermediate or special concrete systems, the requirements



s~ion 421 for intermediate or special systems, as applicable, shaH be satisfied.

421;3.1.3 In Seismic Zone 2, reinforced concrete frames resisting forces induced by earthquake motions shall be intermediate moment-resisting frames proportioned to satisfy onlY Section 421.11 in addition to the requirements of Sections 401 through 418. In Seismic Zone 2, frame members which are not designated to be part of the lateral-force-resisting system shall conform to Section 421.1 O. 421.3.1.4 In Seismic Zone 4, all reinforced concrete structural members that are part of the lateral-foree-resisting system shall satisfy the requirements of Sections 421.3 through 421.10, in addition to the requirements of Sections 401 through 417. 4~1..3.1.5 A reinforced concrete structural system not satisfying it~~ . requirements of this Section shall be permitted if it is

demonstrated by experimental evidence and analysis that the proposed system will have strength and toughness equal to or exceeding those provided by a comparable monolithic reinforced concrete structure satisfying this Section. 421.3.1.6 Precast lateral-foree-resisting systems shall satisfy either ofthe following criteria: L

Emulate the behavior of monolithic reinforced concrete construction and satisfy Section 421.3.2.5, or

2.

Rely on the unique properties of a structural system composed of interconnected precast elements and conform to Section 208.4.6.6.

421.3.1.7 In structures having precast gravity systems, the lateral-foree-resisting system shall be one of the systems listed in Table 208-11 and shall be well distributed using one of the following methods:

1.

The lateral-foree-resisting systems shall be spaced such that the span of the diaphragm or diaphragm segment between lateral-foree-resisting systems shall be no more than three times the width of the diaphragm or diaphragm segment. Where the lateral-force-resisting system consists of moment-resisting frames, at least [(Nof4) + I} of the bays (rounded up to the nearest integer) along any frame line at any story shall be part of the lateral-foree-resisting system, where No is the total number of bays along that line at that story. This requirement applies to only the lower two thirds of the stories of buildings three stories or taller.

2.

4-93

Connection design force. The connection shall be designed to develop strength M. M is the moment developed at the connection when the frame is displaced by 11s assuming fixity at the connection and a beam flexural stiffuess of no more than one-half of the gross section stiffuess. M shall be sustained through a deformation of Lim. Connection cbaracteristics. The connection shall be permitted to resist moment in one direction only, positive or negative. The connection at the opposite end of the member shall resist moment with same positive or negative sign. The connection shall be permitted to have zero flexural stiffuess up to a frame displacement of Lis. In addition, complete calculations for the deformation compatibility of the gravity load carrying system sha1l be made in accordance with Section 208.8.2.3 using cracked section stiffuesses in the lateral-foree-resisting system and the diaphragm.

Where gravity columns are not provided with lateral support on all sides, a positive connection shall be provided along each unsupported direction parallel to a principal plan axis of the structure. The connection shall be designed for a horizontal force equal to 4 percent of the axial load strength (Po) ofthe column. The bearing length shall be 50 mm more than that required for bearing strength. 421.3.2 Analysis and proportioning of structural members 421.3.2.1 The interaction of all structural and nonstructural members which materially affect the linear and nonlinear response of the structure to earthquake motions shall be considered in the analysis. 421.3.2.2 Rigid members assumed not to be a part of the lateral force resisting system shall be permitted, provided their effect on the response of the system is considered and accommodated in the structural design. Consequences of failure of structural and nonstructural members, which are not a part of the lateral-force resisting system, shall also be considered. 421.3.2.3 Structural members below base of structure that are required to transmit to the foundation forces resulting from earthquake effects shall also comply with the requirements of Section 421. 421.3.2.4 All structural members assumed not to be part of the lateral-force resisting system shall conform to Section 421.10.

All beam-to-column connections that are not part of the lateral-force-resisting system shall be designed in accordance with the following:


CONCRETE

421.3.2.5 Precast structural systems using frames and emulating the behavior of monolithic reinforced concrete construction shall satisfy either Section 421.3.2.6 or 421.3.2.7. 421.3.2.6 Precast structural systems, utilizing wet connections, shall comply with all the applicable requirements of monolithic concrete construction for resisting seismic forces. 421.3.2.7 Precast structural systems not meeting Section 421.3.2.6 shall utilize strong connections resulting in nonlinear response away from connections. Design shall satisfy the requirements of Section 421.3.7 in addition to all the applicable requirements of monolithic concrete construction for resisting seismic forces, except that provisions of Section 421.4.1.2 shall apply to the segments between nonlinear action locations. 421.3.3 S(rength-reduction factors

2.

The ratio of the actual ultimate tensile strength to actual tensile yield strength is not less than 1.25.

421.3.5.3 The average prestress fpc, calculated for an area to the member's shortest cross-sectional dimension multiplied the perpendicular dimension, shall be the lesser of 2.4 MPa 1')12 at locations of nonlinear action, where tendons are used in members of frames. 421.3.5.4 For members in which prestressing tendons are together with mild reinforcement to resist forces, prestressing tendons shall not provide more than quarter of the strength for both positive and negative moments the joint face and shall extend through exterior joints and anchored at the exterior face of the joint or beyond. 421.3.5.5 Shear strength provided by prestressing tendons shall

not be considered in design.

Strength reduction factors shall be as given in Section 409.4.4. 421.3.4 .Concrete in members resisting earthquake-induced forces.

EXCEPTION:

421.3.6.1 Reinforcement resisting earthquake-induced or axial forces in frame members or in wall boundary shall be permitted to be spliced using welded splices mechanical connectors conforming to Section 412.15.3.3 412.15.3.4.

Footings of buildings three stories or less may have concrete with f 'c ofnot less than 17 MPa.

Splice locations in frame members shall conform to 421.3.6.1.1 or 421.3.6.1.2.

421.3.4.2 Compressive strength of lightweight aggregate concrete used in design shall not exceed 28 MPa. Lightweight aggregate concrete with higher design compressive strength shall be permitted if demonstrated by experimental evidence that structural members made with that lightweight aggregate concrete provide strength and toughness equal to or exceeding those of comparable members made with normal weight aggregate concrete of the same strength. In no case shall the compressive strength of lightweight concrete used in design exceed 41 MPa.

421.3.6.1.1 Welded splices. In Seismic Zones 2 and 4, welded splices on billet steel A615 or low allow A 706 reinforcement shall not be used within an anticipated plastic hinge region nor within a distance of one beam depth on either side of the I"~"W~>" hinge region or within a joint.

421.3.4.1 Compressive strength MPa~

.. ,

~I. ~ I

421.3.6 Welded splices and mechanically connected

reinforcement

Fe

shall be not less than 21

421.3.5 Reinforcement in members resisting earth-quake induced forces 421.3.5.1 Reinforcement resisting earthquake-induced flexural and axial forces in' frame members and in wall boundary elements shall comply with ASTM A 706M. 421.3.5.2 ASTM A615M Grades 275 and 420 reinforcement shall be permitted in these. members if: 1.

The actual yield strength based on mill tests does not exceed the specified yield strength by more than 120 MFa (retests shall not exceed this value by more than an additional 20 MFa), and

~e<~lOllifll

421.3.6.1.2 Mechanical connection splices. Splices

mechanical connections shall be classified according to C1tr,>nath

capacity as follows:

Type 1 splice. Mechanical connections meeting

requirements of Sections 412.15.3.4 and 412.15.3.5.

Type 2 splice. Mechanical connections that develop in tension the lesser of 95 percent of the ultimate tensile strength or 160 per cent of specified yield strength,J;., ofthe bar. Mechanical connection splices shall be permitted to be located as follows: Type I splice. In Seismic Zones 2 and 4, a Type 1 splice shall not be used within an anticipated plastic hinge region or within a distance of one beam depth on either side of the plastic hinge region or within a joint. Type 2 splice. A Type 2 splice shall be permitted in any location

within a member.



:421.3.6.2 Welding of stirrups, ties, inserts or other similar elements to longitudinal reinforcement required by design shall not be permitted.

tension or compression, as required, at least 140 percent of specified yield strength,f", ofthe bar.

;lit.3.7 Emulation of monolithic construction using strong connections. Members resisting earthquake-induced forces in precast frames using strong connections shall satisfy the following:

421.4 FLEXURAL MEMBERS OF FRAMES

421.3.7.1 Location. Nonlinear action location shall be selected sO that there is a strong column/weak beam deformation mechanism under seismic effects. The nonlinear action location shall be no closer to the near face of strong connection than hl2. For column-to-footing connections, where nonlinear action may bcCur at the column base to complete the mechanism, the nonlinear action location shall be no closer to the near face of the connection than hl2. 421.3.7.2 Anchorage and splices. Reinforcement in the cfioruinear action region shall be fully developed outside both the strong connection region and the nonlinear action region. N"9ncontinuous anchorage reinforcement of strong connection 'shan be fully developed between the connection and the beginning of nonlinear action region. Lap splices are prohibited within connections adjacent to a joint. .~Jl.3.7.3

Design forces. Design strength of strong connections

421.4.1 Scope

Requirements of Section 421.4 apply to special moment frame members (1) resisting earthquake-induced forces and (2) proportioned primarily to resist flexure. These frame members shall also satisfy the following conditions: 421.4.1.1 Factored axial compressive force on the member shall not exceed (Agf/10). 421.4.1.2 Clear span for the members shall not be less than four times its effective depth. 421.4.1.3 The width-to-depth ratio shall not be less than 0.3. 421.4.1.4 The width shall not be (1) less than 250 mm, and (2) more than the width of the supporting member (measured on a plane perpendicular to the longitudinal axis of the flexural member) plus distances on each side of the supporting member not exceeding three-fourths ofthe depth of the flexural member. 421.4.2 Longitudinal reinforcement

~~all be based on: ·"c,:",'·

\If Se CONNECTION

(421-1)

Dynamic amplification factor \If shall be taken as 1.0. 421.3.7.4 Column-to-column connection. The strength of such connections shall comply with Section 421.3.7.3 with \If taken as 1.4. Where column-to-column connections occur, the columns (!hall be provided with transverse reinforcement as specified in Sections 421.5.4.1 through 421.5.4.3 over their full height if the factored axial compressive force in these members, including seismic effects, exceeds AJ"/10.

EXCEPTION: r,Wl!ere column-to-column connection is located within the {Iljidd/e third of the column clear height, the follOWing shall fffpply: (1) The design moment strength ¢ivf" of the connection #shall not be less than 0.4 times the maximum Mpr for the column . the story height, and (2) the design shear strength ;V" oj C01:mel-:ticln shall lIot be less than that determined per Section

Column-face connection. Any strong connection outside the middle half of a beam span shall be a wet unless a dry connection can be substantiated by cyclic test results. Any mechanical connector located such a column-face strong connection shall develop in

421.4.2.1 At any section of a flexural member, except as provided in Section 410.6.3, for top as well as for bottom reinforcement, the amount of reinforcement shall not be less than that given by Equation (420-3) but not less than 1.4pwc/IJ;., and the reinforcement ratio, p, shall not exceed 0.025. At least two bars shall be provided continuously both top and bottom. 421.4.2.2 Positive-moment strength at joint face shall not be less than one half of the negative-moment strength provided at that face of the joint. Neither the negative nor the positive-moment strength at any section along member length shall be less than one fourth the maximum moment strength provided at face of either joint. 421.4.2.3 Lap splices of flexural reinforcement shall be permitted only if hoop or spiral reinforcement is provided over the lap length. Maximum spacing of the transverse reinforcement enclosing the lapped bars shall not exceed dl4 or 100 mm. Lap splices shall not be used (1) within the joints, (2) within a distance of twice the member depth from the face of the joint, and (3) at locations where analysis indicates flexural yielding caused by inelastic lateral displacements of the frame. 421.4.2.4 Welded splices and mechanical connections shall conform to Section 421.3.6.1.

National ~ral Code of the Philippines, Volume 1

CONCRETE

421.4.3 Transverse reinforcement 421.4.3.1 Hoops shall be provided in the following regions of frame members: 1.

Over a length equal to twice the member depth measured from the face of the supporting member toward midspan, at both ends of the flexural member;

2.

Over lengths equal to twice the member depth on both sides. of a section where flexural yielding is likely to occur in connection with inelastic lateral displacements of the frame.

421.4.3.2 The first hoop shall be located not more than 50 mm from the face of a supporting member. Maximum spacing of the 'hoops shall not exceed (1) d/4, (2) eight times the diameter of the smallest longitudinal bars, (3) 24 times the diameter of the hoop bars, and (4) 300 mm. 421.4.3.3 Where hoops are required, longitudinal bars on the perimeter shall have lateral support conforming to Section 407.11.5.3. 421.4:3.4 Where hoops are not required, stirrups with seismic hooks at both ends shall be spaced at a distance not more than dl2 throughout the length ofthe member. 421.4.3.5 Stirrups or ties required to resist shear shall be hoops over lengths of members as specified in Sections 421.4.3, 4215.4 and 421.6.2. 421.4.3.6 Hoops in flexural members shall be permitted to be made up of two pieces of reinforcement: a stirrup having seismic hooks at both ends and closed by a crosstie. Consecutive crossties engaging the same longitudinal bar shall have their 90 degree hooks at opposite sides of the flexural member. If the longitudinal reinforcing bars secured by the crossties are confined by a slab on only one side of the flexural frame member, the 90-degree hooks of the crossties shall all be placed on that side. 421.4.4 Shear strength requirements

The earthquake-induced shear force calculated in with Section 421.4.4.1 represents one-half or more maximum required shear strength within those lengths; The factored axial compressive force including effects is less than Ag{'cl20.

414.5 SPECIAL MOMENT FRAME MEMBERS SUBJECTED TO BENDING AND AXIAL LOAD 421.5.1 Scope The requirements of Section 421.5 apply to special frame members (1) resisting earthquake-induced forces and having a factored axial force exceeding Ag{'clIO. These members shall also satisfy the following conditions: 421.5.1.1 The shortest cross-sectional dimension, measured on straight line passing through the geometric centroid, shall not less than 300 mm. 421.5.1.2 The ratio of the shortest cross-sectional dimension the perpendicular dimension shall not be less than 0.4. 421.5.2 Minimum flexural strength of columns 421.5.2.1 Flexural strength of any column proportioned to resist a factored axial compressive force exceeding AI'clIO shall satisfy Section 421.5.2.2 or 421.5.2.3. Lateral strength and stiffhess of columns not satisfying Section 421.5.2.2 shall be ignored in determining the calculated strength and stiffhess of the structure, but such column shall conform to Section 421. 10. 421.4.2.2 The flexural strengths of the columns shall satisfy Equation (421-2):

EMe

2:

(6/5)EMg

(421-2)

where:

rue =

421.4.4.1 Design forces The design shear forces Ve shall be determined from consideration of the static forces on the portion of the member between faces of the joint. It shall be assumed that moments of opposite sign corresponding to probable flexural strength Mpr act at the joint faces and that the member is loaded with the tributary gravity load along its span. 421.4.4.2 Transverse reinforcement Transverse reinforcement over the lengths identified in Section 421.4.3.1 shall be proportioned to resist shear assuming Vc = 0 when both of the following conditions occur:

sum of moments at the faces of the joint corresponding to the nominal flexural strength of the columns framing into that joint. Column flexural strength shall be calculated for the factored axial force, consistent with the direction of the lateral forces considered, resulting in the lowest flexural strength.

rug

= sum of moments at the faces of the joint corresponding to the nominal flexural strengths of the girders framing into that joint. In T-beam construction, where the slab is in tension under moments at the face of the joint, slab reinforcement within an effective slab width defined in Section 408.11 shall be assumed to contribute to flexural strength if the slab reinforcement is developed at the critical section for flexure.



I

Flexural strengths shall be summed such that the column moments oppose the beam moments. Equation (421~2) shall be satisfied for beam moments acting in both directions in the vertical plane ofthe frame considered. 421.5.2.3 If Section 42l.5.2.2 is not satisfied at a joint, columns SUpporting reactions from that joint shall be provided with tranSVerse reinforcement as specified in Sections 421.5.4.1 through 421.5.4.3 over their full height.

4-97

5.

If the thickness of the concrete outside the transverse reinforcement exceeds 100 mm, transverse reinforcement shall be provided at not exceeding 300 mm. Concrete cover on the reinforcement shall not exceed 100 mm.

6.

Where the calculated point of contraflexure is not within the middle half of the member clear height, provide transverse reinforcement as specified in Sections 421.5.4.1, Items 1 through 3, over the full height of the member.

confining additional a spacing additional

421.5.3 Longitudinal reinforcement 421.5.4.2 Transverse reinforcemt:nt shall be spaced at a distu...lce

not exceeding (1) one-fourth of the minimum member

dimension, (2) six times the diameter of the longitudinal

reinforcement, and (3) Sx. as defined by Equation (421-6):

421.5.3.1 The reinforcement ratio Pg shall not be less than 0.01 and shall not exceed 0.06. 421.5.3.2 Mechanical splices shall conform to Section 421.3.6.1.2 and welded splices shall conform to Section 421.3.6.1.1. Lap splices shall be permitted only within the center half of the member length, shall be designed as CONCRETE ten~ sion lap splices, and shall be enclosed within transverse reinforcement conforming to Sections 421.5.4.2 and 421.5.4.3.

(421-6)

The value of Sx shall not exceed 150 mm and need not be taken ~

less than 100 mm. Anchor bolts set in the top of a column shall

be enclosed with ties as specified in Section 421.5.4.8.

421.5.4 Transverse reinforcement 421.5.4.3 Crossties or legs of overlapping hoops shall not be spaced more than 350 mm on center in the direction perpendicular to the longitudinal axis ofthe structural member.

421.5.4.1 Transverse reinforcement as required below shall be provided unless a larger amount is required by Section 421.5.3.1 or 421.5.5.

1.

421.5.4.4 Transverse reinforcement in amount specified in Sections 421.5.4.1 through 421.5.4.3 shall be provided over a length 10 from each joint face and on both sides of any section where flexural yielding is likely to occur as a result of i~lastic lateral displacements of the frame. The length to shall not be less than (1) the depth of the member at the joint face or at the section where flexural yielding is likely to occur, (2) one~sixth of the clear span of the member, and (3) 450 mm.

The volumetric ratio of spiral or circular hoop reinforcement p$ shall not be less than that required by Equation (421~3): (421~3)

and shall not be less than that required by Equation (41O~6).

2.

The total cross~sectional area of rectangular hoop. reinforcement shall not be less than that required by Equations (421~) and (421~5):

Ash

0.3 (shcfc4,h)(AIAch) -1]

A$h = 0.09(shcfc4,h)

421.5.4.5 Columns supporting reactions from discontinued stiff members, such as walls, shall be provided with transverse reinforcement as specified in Sections 421. 5.4.1 through 421.5.4.3 over their full height beneath the level at which the discontinuity occurs if the factored axial compressive force in these members, related to earthquake effect, exceeds At!'cliO. Transverse reinforcement as required in Sections 421.5.4.1 through 421.5.4.3 shall extend into the discontinued member for at least the development length of the largest longitudinal reinfurcement in the column in accordance with Section 421.6.4. If the lower end of the column terminates on a wall, transverse reinforcement as required in Sections 421.5.4.1 through 421.5.4.3 shall extend into the wall for at least the development length of the largest longitudinal bar in the column at the point of terminatIon. If the column terminates on a footing or mat, transverse reinforcement as required in Sections 421.5.4.1 through 421.5.4.3 shall extend at least 300 mm into the footing or mat.

(421-4) (421~5)

3.

Transverse reinforcement shall be provided by either single or overlapping hoops. Crossties of the same bar size and spacing as the hoops shall be permitted. Each end of the crosstie shall engage a peripheral longitudinal reinforcing bar. Consecutive crossties shall be alternated end for end along the longitudinal reinforcement.

4.

If the design strength of member core satisfies the requirement of the design loading combinations including earthquake effect, Equations (421~4) and (410-1) need not be satisfied.


of


CONCERETE

421.5.4.6 Where transverse reinforcement, as specified in Sections 421.5.4.1 through 421.5.4.3, is not provided throughout the full length of the column, the remainder of the column length shall contain spiral or hoop reinforcement with center-to-center spacing not exceeding the smaller of six times the diameter of the longitudinal column bars or 150 mm. 421.5.4.7 At any section where the design strength, ¢lPn, of the column is less than the sum of the shears Ve computed in accordance with Sections 421.4.4.1 and 421.5.5.1 for all the beams framing into the column above the level under consideration, transverse reinforcement as specified in Sections 421.5.4.1 through 421.5.4.3 shall be provided. For beams framing into opposite sides of the column, the moment components may be assumed to be of opposite sign. For the determination of the design strength, 4>Pn, of the column, these moments may be assumed to result from the deformation of the frame in anyone principal axis. 421.5.4.8 Ties at anchor bolts. Anchor bolts which are set in the top of a column shall be provided with ties which enclose at least four vertical column bars. Such ties shall be in accordance withSection 407.2.3, Item 3, shall be within 125 mm of the top of the folumn, and shall consist of at least two 12 mm diameter bars or three 10 rom diameter bars.

421.5.5.1 Design forces The design shear force V" shall be determined from consideration of the maximum forces that can be generated at the faces of the joints at each end of the member. These joint forces shall be determined using the maximum probable moment strengths Mpr of the member associated with the range of factored axial loads on the member. The member shear need not exceed those determined from joint strengths based on the probable moment strength Mpr of the transverse members framing in the joint. In no case shall V" be less than the factored shear determined by analysis of the structure. 421.5.5.2 Transverse reinforcement over the lengths 10 , identified in Section 421.5.4.4, shall be proportioned to resist shear assuming Vc 0 when both ofthe following conditions occur:

2.

421.6.1 General requirements

421.6.1.1 Forces in longitudinal beam reinforcement at the

face shall be determine.
flexural tensile reinforcement is 1.25/y.

421.6.1.2 Strength of joint shall be governed by the !>nn,rnnri"f,

strength reduction factors specified in Section 409.4.

421.6.1.3 Beam longitudinal reinforcement terminated column shall be extended to the far face of the confined

core and anchored in tension according to Section 421.6.4,

in compression according to Section 412.

421.6.1.4 Where longitudinal beam reinforcement

through a beam-column joint, the column dimension parallel

the .beam reinforcement shall not be less than 20 times

diameter of the largest longitudinal bar for normal concrete. For lightweight concrete, the dimension shall not

less than 26 times the bar diameter.

421.6.2 Transverse reinforcement

421.6.2.1 Transverse hoop reinforcement as specified in

421.5.4 shall be provided within the joint, unless the joint

confined by structural members as specified in 421.6.2.2.

421.5.5 Shear strength requirements

1.

421.6 JOINTS OF SPECIAL MOMENT FRAMES

The earthquake-induced shear force, calculated in accordance with Section 421.5.5.1, represents one-half or more of the maximum required shear strength within those lengths; The factored axial compressive force earthquake effects is less than AJ"flO.

421.6.2.2 Within the depth of the shallowest framing mernoer"

transverse reinforcement equal to at least one half the
frame into all four sides of the joint and where each member

width is at least three- fourths the column width. At these

locations, the spacing required in Section 421.5.4.2(2) shall be

permitted to be increased to 150 rom.

421.6.2.3 Transverse reinforcement as required 421.5.4 shall be provided through the joint confinement for longitudinal beam reinforcement column core if such confinement is not provided framing into the joint.

by Section

to provide

outside the

by a beam

421.6.3 Shear strength

421.6.3.1 The nominal shear strength of the joint shall not be

taken greater than the forces specified below for normal weight

aggregate concrete.

including For joints confined on all four faces. . . . . ..

1.7 .fl:.AJ

For joints confined on three faces or on two opposite faces

1.25.fl:.Aj

Forothers ......................... . LO.fl:.Aj



4·99

;A member that frames into a face is considered to provide ·c~nfinement to the joint if at least three-fourths of the face of the joint is covered by the framing member. A joint is considered to be confined if such confining members frame into all faces of thejoint.

421.7.2 Reinforcement

421.6.3.2 For lightweight aggregate concrete, the nominal shear strength of the joint shall not exceed three- fourths of the limits for normal-weight aggregate concrete given in Section 421.6.3.1.

reinforcement for structural walls shall be permitted to be reduced to that required in Section 414.3. Reinforcement spacing each way in structural walls shall not exceed 450 mm. Reinforcement provided for shear strength shall be continuous and shall be distributed across the shear plane.

421.6.4 Development length for bars in tension 421.6.4.1 The development length I.u. for a bar with a standard 90-degree hook in normal weight lif~gregate concrete shall not be less than the largest of 8d", 150 mll':, and the length required by Equation G421-7): (421-7) fur bar sizes 10 mm through 36 rom diameter. For lightweight aggregate concrete, the development length for a bar with a standard 90-degree hook shall not be less than the largest of 10d", 190 rom, and 1.25 t:mes that required by Equation (421-7). The 90-degree hook shall be located within the c('nfined core of a column or of a boundary member.

421.7.2.1 The distributed web reinforcement ratios, PI' and PIl' for structural walls shall not be less than 0.0025, except if the design shear force does not exceed (l112)A",.f1:" the minimum

421.7.2.2 At least two curtains of reinforcement shall be used in a wall if the in-plane factored shear force assigned to the wall exceeds (I/6)Acv.[1;.

When Vu in the plane of the all exceeds 0.08A""f1:" horizontal reinforcement terminating at the edges of shear walls shall have a standard hook engaging the edge reinforcement, or the edge reinforcement shall be enclosed in "U" stirrups having the same size and spacing as, and spliced to, the horizontal reinforcement. 421.7.2.3 All continuous reinforcement in structural walls shall be anchored or spliced in accordance with the provisions for reinforcement in tension in Section 421.6.4. 421.7.3 Design forces

421.6.4.2 For bar sizes 10 rom through 38 mm diameter, the deVelopment length Id for a straight bar shall not be less than (1) 2.5 times the length required by Section 421.6.4.1 if the depth of the concrete cast in one lift beneath the baf does not exceed 300 mm, and (2) 3.5 times the length required by'Section 421.6.4.1 if the depth of the concrete cast in one lift beneath the bar exceeds 300 rom. 421.6.4.3 Straight bars terminated at a joint shall pass through the confined core of a column or of a boundary member. Any portion of the straight embedment length not within the confined core shall be increased by a factor of 1.6. 421.6.4.4 If epoxy-coated reinforcement is used, the development lengths in Sections 421.6.4.1 through Section 421.6.4.3 shall be multiplied by the applicable factor specified in Section 412.3.4 or 412.6.3.6.

421.7 SPECIAL REINFORCED CONCRETE STRUCTURAL WALLS AND COUPLING BEAMS 421.7.1 Scope The requirements of Section 421.7 apply to special reinforced concrete structural walls and coupling beams serving as part of the earthquake force resisting system.

The design shear force Vu shall be obtained from the lateral load analysis in accordance with the factored load combinations specified in Section 409.3 and as modified in Section 203.3.1. ~

421.7.4 Shear strength 421.7.4.1 Nominal shear strength exceed

v,. of structural walls shall not

v,. = A"I'[ acfll12) ff + P,J;· ]

(421-8)

where the coefficient a" is 3.0 for h..I1". S; 1.5, is 2.0 for h,.ll,.. ~ 2.0, and varies linearly between 3.0 and 2.0 for 11."11,,, between 1.5 and 2.0. 421.7.4.2 In Section 421. 7.4.1, the value of ratio h..lI,.. used for determining Va for segments of a wall shall be the larger of the ratios for the entire wall and the segment ofwall considered. 421.7.4.3 Walls shall have distributed shear reinforcement providing resistance in two orthogonal directions in the plane of the wall. If the ratio h"lI,.. does not exceed 2.0, reinforcement ratio p. shall not be less than reinforcement ratio p". 421.7.4.4 Nominal shear strength of all wall piers sharing a common lateral force shall not be assumed to exceed


CONCRETE

(2/3)Acv J7':, where Acv is the total cross-sectional area, and the nominal shear strength of anyone of the individual wall piers shall not be assumed to exceed (5/6)Aq>J7':, where Aq> is the cross-sectional area of the pier considered. 421.7.4.5 Nominal shear strength of horiwntal wall segments and coupling beams shall be assumed not to exceed (5/6)Aq>J7':, where Aq> is the cross-sectional area of a horizontal wall segment or coupling beam. 421.7.5 Design for flexural and axial loads 421.7.5.1 Structural walls and portions of such walls subject to combined flexural and axial loads shall be designed in accordance with Sections 410.3 and 410.4 except that Section 410.4.6 and the nonlinear strain requirements of Section 410.3.2 shall not apply. Concrete and developed longitudinal rein forcement within effective flange widths, boundary elements, and the wall web shall be considered effective. The effects of openings shall be considered. 421.7.5.2

Unless a more detailed analysis is performed,

effectiv~ flange widths of flanged sections shall extend from the

42.1.7.6.3 Structural walls not designed to the provisions Section 421.7.6.2 shall have special boundary elements boundaries and edges around openings of structural walls the maximum extreme fiber compressive stress, COIreSDOIldin to factored forces including earthquake effect, exceeds The special boundary element shall be permitted to be tinued where the calculated compressive stress is less O.15.fc' Stresses shall be calculated for the factored forces a linearly elastic model and gross section properties. For with flanges, an effective flange width as defined 421.7.5.2 shall be used. 421.7.6.4 Where special boundary elements are required Section 421.7.6.2 or 421. 7.6.3, the following shall be satisfied: 1.

The boundary element shall extend horizontally from extreme compression fiber a distance not less than larger of c - O. II.. and ell;

2.

In flanged sections, the boundary element shall . the effective flange width in compression and shall at least 300 mm into the web;

3.

Special boundary element transverse reinforcement satisfy the requirements of Sections 421.5.4.1 421.5.4.3, except Equation (421-4) need not be satisfied;

face of the web a distance equal to the smaller of one-half the distance to an adjacent wall web and 25 percent of the total wall height.

Special boundary element transverse reinforcement at wall base shall extend into the support at least development length of the largest longitudinal ment in the special boundary element unless the boundary element terminates on a footing or mat, special boundary element transverse reinforcement extend at least 300 mm into the footing or mat;

421.7.6 Boundary elements ofspecial reinforced concrete structural walls 421.7.6.1 The need for special boundary elements at the edges of structural walls shall be evaluated in accordance with Section 421.7.6.2 or 421.7.6.3. The requirements of Sections 421.7.6.4 and 421.7.6.5 also shall be satisfied. 421.7.6.2 This section applies to walls or wall piers that are effectively continuous from the base of structure to top of wall and designed to have a single critical section for flexure and axial loads. Walls not satisfying these requirements shall be designed by Section 421. 7.6.3. 1.

Compression zones shall be reinforced with special boundary elements where:

c 2: The quantity than 0.007. 2.

~

l w

600 (0. I h.,.)

Ihw

5.

Horizontal reinforcement in the wall web shall anchored to develop the specified yield strength h. the confined core of the boundary element;

6.

Mechanical splices of longitudinal reinforcement boundary elements shall conform to Section 421.3.6.1. Welded splices of longitudinal reinforcement of UUI.U1\.IIU J elements shall conform to Section 421.3.6.1.1.

421.7.6.5 Where special boundary elements are not required Section 421.7.6.2 or 421. 7.6.3, the following shall be satisfied: 1.

If the longitudinal reinforcement ratio at the boundary is greater than 2.81.1;. boundary tr"'n~'l,..r""f reinforcement shall satisfy Sections 421.5.4.1(3 421.5.4.3, and 421.7.6.4(1). The maximum 10n:gituldinaJ: spacing of transverse reinforcement in the boundary not exceed 200 mm;

2.

Except when V" in the plane of the wall is less (1I12}AcvJ7':, horizontal reinforcement terminating

(421-9)

:n Equation (421-9) shall not be taken less

Where special boundary elements are required by Section 421.7.6.2(1), the special boundary element reinforcement shall extend vertically from the critical section a distance not less than the larger of lw or M,,/(4V,J.

the edges of structural walls without boundary



shall have a standard hook engaging the edge reinforcement or the edge reinforcement shall be enclosed in U-stirrups having the same size and spacing as, and spliced to, the horizontal reinforcement.

4·101

displacements. Design strength of coupling beams assumed to be part of the seismic force resisting system shall not be reduced below the values otherwise required

3.

Each group of diagonally placed bars shall be enclosed in transverse reinforcement satisfying Sections 421.5.4.1 through 421.5.4.3. For the purpose of computing Ag for use in Equations (410-6) and (421-4), the minimum concrete cover as required in Section 407.8 shall be assumed on all four sides of each group of diagonally placed reinforcing bars;

:421.7.6.6 Mechanical and welded splices of longitudinal rehlforcement of boundary elements shall conform to Sections 421.3.6.

421.7.7 Coupling beams 421.7.7.1 Coupling beams with aspect ratio I" Id~.4, shall satisfy the requirements of Section 421.4. The provisions of Sections 421.4.1.3 and 421.4.1.4(1) shall not be required if it can be shown by analysis that the beam has adequate lateral stability.

4.

The diagonally placed bars shall be developed for tension in the wall;

5.

421.7.7.2 Coupling beams with aspect ratio, 1"ld < 4, shall be permitted to be reinforced with two intersecting groups of diagonally placed bars symmetrical about the midspan.

The diagonally placed bars shall be considered to contribute to nominal flexural strength of the coupling beam;

6.

Reinforcement parallel and transverse to the longitudinal axis shall be provided and, as a minimum, shall conform to Sections 412.8.9 and 412.8.10.

421.7.7.3 Coupling beams with aspect ratio, 1"ld < 2, and with factored shear force V,.. exceeding (1/3)Jl': b..d shall be reinforced with two intersecting groups of diagonally placed bars symmetrical about the midspan, unless it can be shown that loss of stiffuess and strength of the coupling beams will not impair the vertical load carrying capacity of the structure, or the egress from the structure, or the integrity of non structural com ponents and their connections to the structure. 421.7.7.4 Coupling beams reinforced with two intersecting groups of diagonally placed bars symmetrical about the midspan shall satisfy the following:

1.

2.

Each group of diagonally placed bars shall consist of a minimum of four bars assembled in a core having sides measured to the outside of transverse reinforcement no smaller than bw 12 perpendiCUlar to the plane of the beam and b... 15 in the plane of the beam and perpendicular to the diagonal bars; The nominal shear strength, V" • shall be determined

by Vn

=

1Avd./v sin a $ (5/6)

ff b,.d

(421-10)

421.7.8 Construction joints All construction joints in structural walls shall conform to Section 406.4 and contact surfaces shall be roughened as in Section 411.8.9. 421.7.9 Discontinuous walls Columns supporting discontinuous structural walls shall be reinforced in accordance with Section 421.5.4.5. '

421.8 STRUCTURAL DIAPHRAGMS AND TRUSSES 421.8.1 Scope Floor and roof slabs acting as structural diaphragms to transmit design actions induced by earthquake ground motions shall be designed in accordance with this Section 421.8. This Section also applies to struts, ties, chords, and collector elements that transmit forces induced by earthquakes, as well as trusses serving as parts of the earthquake force-resisting systems. 421.8.2

Cast-in-place composite topping slab diaphragms

EXCEPTION: The design of coupling beams need not comply with the requirements for diagonal reinforcement if it can be shown that fail of the coupling beams will not impair the vertical load carrying capacity of the structure, the egress from the structure, or the integrity of nons/ructural components and connections. The analysis shall take into account the effects if the failure of the coupling beams (]fI foundation rota/iou and overall system

A composite-topping slab cast in place on a precast floor or roof shall be permitted to be used as a structural diaphragm provided the topping slab is reinforced and its connections are proportioned and detailed to provide for a complete transfer of forces to chords, collector elements, and the lateral-force resisting system. The surface of the previously hardened concrete on which the topping slab is placed shall be clean, free oflaitance, and intentionally roughened.


CONCRETE

421.8.3 Cast-in-place topping slab diaphragms

A cast-in-place noncomposite topping on a precast floor or roof shall be permitted to serve as a structural diaphragm, provided the cast-in-place topping acting alone is proportioned and detailed to resist the design forces. 421.8.4 Minimum tbickness of diaphragms

Concrete slabs and composite topping slabs serving as structural diaphragms used to transmit earthquake forces shall not be less than 50 mm thick. Topping slabs placed over precast floor or roof elements, acting as structural diaphragms and not relying on composite action with the precast elements to resist the design seismic forces, shall have thickness not less than 65 mm.

4-102

The seismic design forces for structural diaphragms shall be obtained from the lateral load analysis in accordance with the design load combinations. 421.8.7 Shear strength 421.8.7.1 Nominal shear diaphragms shall not exceed:

Vn

of

(421-11) 421.8.7.2 Nominal shear strength Vn of cast-in-place compositetopping slab diaphragms and cast-in-place noncomposite . slab diaphragms on a precast floor or roof shall not exceed shear force

421.8.5 Reinforcement

(421-12)

The minimum reinforcement ratio for structural 421.8.5.1 diaphragms shall be in conformance with Section 407.13. Reinforcement spacing each way in nonposttensioned floor or roof systems shall not exceed 450 mm. Where welded wire fabric is used as the distributed reinforcement to resist shear in topping slabs placed over precast floor and roof elements, the wires parallel to the span of the precast elements shall be spaced not less than 250 mm on center. Reinforcement provided for shear strength shall be continuous and shall be distributed uniformly across the shear plane. 421.8.5.2 Bonded prestressing tendons used as primary reinforcement in diaphragm chords or collectors shall be proportioned such that the stress due to design seismic forces does not exceed 420 :MFa. Pre-compression from unbonded tendons shall be permitted to resist diaphragm design forces if a complete load path is provided. 421.8.5.3 Structural truss elements, struts, ties, diaphragm chords, and collector elements with compressive stresses exceeding 0.2f" at any section shall have transverse reinforcement, as in Sections 421.5.4.1 through 421.5.4.3, over the length of the element. The special transverse reinforcement is allowed to be discontinued at a section where the calculated compressive strength is less than 0.15f". Stresses shall be calculated for the factored forces using a linearly elastic model and gross-section properties ofthe elements considered. 421.8.5.4 All continuous reinforcement in diaphragms, trusses, struts, ties, chords, and collector elements shall be anchored or spliced in accordance with the provisions for reinforcement tension as specified in Section 421.6.4. 421.8.5.5 Type 2 splices are required where mechanical splices are used to transfer forces between the diaphragm and the vertical components of the lateral-force-resisting system. 421.8.6 Design forces

strength

where A"" is based on the thickness of the topping slab. The, required web reinforcement shall be distributed uniformly in both directions. 421.8.7.3 Nominal shear strength shall not exceed (213)A""Jl': where A"" is the gross cross-sectional area of the

diaphragm. 421.8.8 Boundary elements of structural diaphragms 421.8.8.1 Boundary elements of structural diaphragms shall be proportioned to resist the sum of the factored axial forces acting in the plane of the diaphragm and the force obtained from dividing the factored moment at the section by the distance between the boundary elements of the diaphragm at that section. 421.8.8.2 Splices of tensile reinforcement in the chords and . collector elements of diaphragms shall develop the yield strength of the reinforcement. Mechanical and welded splices shall conform to Sections 421.3.6. 421.8.8.3 Reinforcement for chords and collectors at splices and anchorage zones shall have either:

1.

A minimum spacing of three longitudinal bar diameters, but not less than 40 mm, and a minimum concrete cover of two and one-half longitudinal bar diameters, but not less than 50 mm; or

2.

Transverse reinforcement as required by Section 411.6.5.3, except as required in Section 421.8.5.3.

421.8.9 Construction joints

All construction joints in diaphragms shall conform to Section 406.4 and contact surfaces shall be roughened as in Section 411.8.9.



4~1.9

FOUNDATIONS

421.9.1 Scope

Foundations resisting earthquake~induced forces or transferring earthquake-induced forces between structure and gtbund shall comply with Section 421.9 and other applicable code provisions.

'4Z1.9.1.1

421.9.1.2 The provisions in Section 421.9 for piles, drilled piers, caissons, and slabs on grade shall supplement other applicable code design and construction criteria. See Section& 401.2.5 and 401.2.6. 421.9.2 Footings, foundation mats, and pile caps 421.9.2.1 Longitudinal reinforcement of columns and structural walls resisting forces induced by earthquake effects shall extend into the footing, mat, or pile cap, and shall be fully developed for tension at the interface.

.4.21.9.2.2 Columns designed assuming fixed-end conditions at thefoundation shall comply with Section 421.9.2.1 and, ifhooks are required, longitudinal reinforcement resisting flexure shall have 90-degree hooks near the bottom of the foundation with the free end of the bars oriented towards the center ofthe column. 421.9.2.3 Columns or boundary elements of special reinforced concrete structural walls that have an edge within one-half the footing depth from an edge of the' footing shall have transverse reinforcement in accordance with Section 421.5.4 provided below the top of the footing. This reinforcement shall extend into the footing a distance no less than the smaller of the depth of the footing, mat, or pile cap, or the development length in tension of the longitudinal reinforcement. 421.9.2.4 Where earthquake effects create uplift forces in boundary elements of special reinforced concrete structural walls or columns, flexural reinforcement shall be provided in the top of the footing, mat or pile cap to resist the design load combinations, and shall not be less than required by Section 410.6. 421.9.2.5 See Section 422. I 1 for use of plain concrete footings and basement walls.

4-103

smallest cross-sectional dimension shall be equal to or greater than the clear spacing between connected columns divided by 20, but need not be greater than 450 mrn. Closed ties shall be provided at a spacing not to exceed the lesser of one-half the smallest orthogonal cross-sectional dimension or 300 mm 421.9.3.3 Grade beams and beams that are part of a mat foundation subjected to flexure from columns that are part of the lateral-force-resisting system shall conform to Section 421.4. 421.9.3.4 Slabs on grade that resist seismic forces from walls or columns that are part of the lateral-force-resisting system shall be designed as structural diaphragms in accordance with Section 421.8. The design drawings shall clearly state that the slab on grade is a structural diaphragm and part of the lateral-force resisting system. 421.9.4 Piles, piers, and caissons 421.9.4.1 Provisions of Section 421,9.4 shall apply to concrete piles, piers, and caissons supporting structures designed for earthquake resistance . 421.9.4.2 Piles, piers, or caissons resisting tension loads shall have continuous longitudinal reinforcement over the length resisting design tension forces, The longitudinal reinforcement shall be detailed to transfer tension forces within the pile cap to supported structural members, 421.9.4.3 Where tension forces induced by earthquake effects are transferred between pile cap or mat foundation and precast pile by reinforcing bars grouted or post-installed in the top of the pile, the grouting system shall have been demonstrated bytest to develop at least 125 percent of the specified yield strength of the bar, 421.9.4.4 Piles, piers, or caissons shall have transverse reinforcement in accordance with Section 421.5,4 at the following locations:

1.

At the top of the member for at least 5 times the member cross-sectional dimension. but not less than 2 m below the bottom ofthe pile cap;

2.

For the portion of piles in soil that is not capable of providing lateral support, or in air and water, along the entire unsupported length plus the length required in Section 421.9.4.4(1),

In

421.9.3 Grade beams and slabs on grade

Grade beams designed to act as horizontal ties 421.9.3.1 between pile caps or footings shall have continuous longitudinal reinforcement that shall be developed within or beyond the supported column or anchored within the pile cap or footing at all discontinuities, 421.9.3.2 Grade beams designed to act as horizontal ties between pile caps or footings shall be proportioned such that the

421.9.4.5 For precast concrete driven piles, the length of transverse reinforcement provided shall be sufficient to account for potential variations in the elevation in pile tips. 421.9.4.6 Concrete piles, piers, or caissons in foundations supporting one- and two-story stud bearing wall construction are exempt from the transverse reinforcement requirements of


CONCRETE

Sections 421.9.4.4 and 421.9.4.5. 421.9.4.7 Pile caps incorporating batter piles shall be designed to resist the full compressive strength of the batter piles acting as short columns. The slenderness effects of batter piles shall be considered for the portion of the piles in soil that is not capable of providing lateral support, or in air or water.

421.10 FRAME MEMBERS NOT PROPORTIONED TO RESIST FORCES INDUCED BY EARTHQUAKE MOTIONS 421.10.1 Frame members assumed not to contribute to lateral resistance shall be detailed according to Section 421.10.2 or 421.10.3 depending on the magnitude of moments induced in those members if subjected to the design displacement, AM. If effects of design displacements are not explicitly checked, it shall be permitted to apply the requirements of Section 421.10.3. 421.10.2 When the induced moments and shears under design displacements of Section 421.1 0.1 combined with the factored gravity moments and shears do not exceed the design moment and shear strength of the frame member, the conditions of Sections 421.10.2.1, 421.10.2.2, and 421.10.2.3 shall be satisfied. For this purpose, the load combinations (lAD + 1.4L) and O.9D shall be used. 421.10.2.1 Members with factored gravity axial forces not . exceedingA./'tflO shall satisfy Section 421.4.2.1. Stirrups shall be spaced not more than d/2 throughout the length of the member. 421.10.2.2 Members with factored gravity axial forces exceeding A./'c 110, but not exceeding O.3P0> shall satisfy Sections 421.5.3, 421.5.4.1(3), and 421.5.5. Design shear strength shall not be less than the shear associated with the development of nominal moment strengths of the member at each end of the clear span. The maximum longitudinal spacing ofties shall be So for the full column height. The spacing So shall not be more than (I) six diameters of the smallest longitudinal bar enclosed, (2) 16 tie-bar diameters, (3) one-half the least cross-sectional dimension of the column, and (4) 150 mm, whichever is smaller.

421.10.3.1 Materials shall satisfy Sections 421.3.4 and 421.3. Mechanical splices shall satisfy Section 421.3 .6.1.2 and splices shall satisfy Section 421.3.6. 1. 1. 421.10.3.2 Members with factored gravity axial forces exceeding A./'.110 shall satisfy Sections 421.4.2.1 and 421 Stirrups shall be spaced at not more than d/2 throughout length of the member. 421.10.3.3 Members with factored gravity axial exceeding A./'.110 shall satisfy Sections 421.5.4, 421.5.5, 421.6.2.1. 421.10.4 Ties at anchor bolts. Anchor bolts set in the top of a column shall be enclosed with ties as specified in Section 421.5.4.8.

421.11 REQUIREMENTS FOR INTERMEDIATE MOMENT FRAMES, SEISMIC ZONE 2. 421.11.1 The requirements of Section 421.11 apply to

intermediate moment frames in addition to those of Sections 401

through 418.

421.11.2 Reinforcement details in a frame member shall satisfy

Section 421.11.4 if the factored compressive axial load for the member does not exceed A./'.110. If the factored compressive

axi~ load is larger, frame reinforcement details shall satisfy

Sectlon 421.11.5 unless the member has spiral reinforcement

according to Equation (410-6). Ifa two-way slab system

be.ams is treated as part of a frame resisting earthquake effect,

reinforcement details in any span resisting moments caused by

lateral force shall satisfy Section 421.11.6.

421.11.3 Design shear strength of beams, columns. And two

way slabs, resisting earthquake effect shall not be less than either:

1.

The sum of the shear associated with development of nominal moment strengths of the member at each retrained end of the clear span and the shear calculated fur factored gravity loads;

2.

The maximum shear obtained from design load

combinations that include earthquake effect E, with E assumed to be twice that prescribed in Section 208.

421.10.2.3 Members with factored gravity axial forces exceeding 0.35Po shall satisfy Section 421.10.2.2 and the amount oftransverse reinforcement provided shall be one-half of that required by Section 421.5.4.1 but shall not exceed a spacing So for the full height ofthe column.

421.11.4 Beams

421.10.3 If the induced moment or shear under design displacements of Section 421.10.1 exceeds the design moment or shear strength of the frame member, or if induced moments are not calculated, the conditions of Sections 421.10.3.1, 421.10.3.2, and 421.10.3.3 shall be satisfied.

421.11.4.1 The positive moment strength at the face of the joint shall be not less than one-third the negative' moment strength provided at that face of the joint. Neither the negative nor the positive moment strength at any section along the length of the member shall be less than one-fifth the maximum moment



4-105

strength provided at the face of either joint.

in Section 413.3.1.

~ii11.4.2 At both ends of the member, stirrups shall be provided over lengths equal to twice the member depth measured from the face of the supporting member toward fnjdspan. The first stirrup shall be located at not more than 50 rdtri from the face of the supporting member. Maximum stirrup spacing shall not exceed:

421.11.6.2 The fraction, defined by Equation (413-1), of moment M$ shall be resisted by reinforcement placed within the effective width in Section 413.6.3.2.

1. 2. 3.

4.

d/4;

Eight times the diameter of the smallest longitudinal bar enclosed; Twenty four times the diameter ofthe stirrup bar; and 300mm.

421.11.4.3 Stirrups shall be placed at not more than d/2 throughout the length of the member. 421.11.5 Columns 421.11.5.1 Maximum tie spacing shall not exceed So over a length 10 measured from the joint face. Spacing So shall not exceed the smallest of 1.

2. 3. 4.

421.11.6.3 Not less than one-half of the reinforcement in the column strip at support shall be placed within the effective slab width specified in Section 413.6.3.2.

Eight times the diameter of the smallest longitudinal bar enclosed; 24 times the diameter ofthe tie bar; One-half of the smallest cross sectional dimension of the frame member; and 300 mm

421.11.6.4 Not less than one-fourth of the top reinforcement at the support in the column strip shall be continuous throughout the span. 421.11.6.5 Continuous bottom reinforcement in the column strip shall be not less than one-third of the top reinforcement at the support in the column strip. 421.11.6.6 Not less than one-half of all bottom reinforcement at midspan shall be continuous and shall develop its yield strength at face of support as defined in Section 413.7.2.5. 421.11.6.7 At discontinuous edges of the slab all top and bottom reinforcement at support shall be developed at the face of support as defined in Section 413.7.2.5.

Length 10 shall not be less than the largest of: LOne-sixth of the clear span of the member; 2. Maximum cross-sectional dimension of the member; and 3. 450mm. 421.11.5.2 The first tie shall be located at not more than st/2 from the joint face. 421.11.5.3 Joint reinforcement shall conform to 411.12.2.

Section

421.11.5.4 Tie spacing shall not exceed twice the spacing

So.

421.11.5.5 Column lateral ties shall be as specified in Section 107.2.3. Anchor bolts set in the top of a column shall be enclosed with ties as specified in Section 421.5.4.8. 421.11.6 Two-way slabs without beams 421.11.6.1 Factored slab moment at support related to earthquake effect shall be determined for load combinations defined by Equations (409-2) and (409-3). All reinforcement provided to resist M s, the portion of slab moment balanced by support moment shall be placed within the column strip defined


CONCRETE

SECTION 422 - STRUCTURAL PLAIN CONCRETE

422.2.1.2 Design and construction of soil-supported slabs, as sidewalks and slabs on grade, shall not be governed by code unless they transmit vertical loads from other parts of structure to the soil.

422.1 NOTATION Ag Al

A2

b bo

B"

Pc:

Ffc

= gross area of section, mm 2 2

loaded area, mm = the area of the lower base of the largest frustum of a pyramid, cone, or tapered wedge contained wholly within the support and having for its upper base the loaded area, arid having side slopes of I vertical to 2 horizontal, mm2 = width of member, mm = perimeter ofcritical section for shear in footings, nun = nominal bearing load specified compressive strength of concrete, MPa. See Section 405. = square root of specified compressive strength of =

concrete, MPa splitting tensile strength of lightweight aggregate concrete, MPa. See Sections 405.2.4 and 405.2.5. f = overall thickness of member, mm vertical distance between supports, mm = nominal moment strength at section = factored moment at section = nominal strength of cross section subject to compression nominal axial load strength of wall designed by Section 422.7.5 = factored axial load at given eccentricity = elastic section modulus of section = nominal shear strength at section = shear stress due to factored shear force at section. factored shear force at section ratio of long side to short side of concentrated load or reaction area = strength reduction factor. See Section 409.4.5 = average

h

'< AI" Mil

1'" P nw

1'" S

r:, I'"

l'lI

Be Q>

422.2.2 For special structures, such as arches, utility structures, gravity walls, and shielding walls, ofthis section shall govern where applicable.

nrrnnc""

422.3 LIMITATIONS 422.3.1 Provisions of Section 422 shall apply for design structural plain concrete members defined as either um:eiljlfol'CC or containing less reinforcement than the minimum specified in this code for reinforced concrete. See Section 402: 422.3.2 Use of structural plain concrete shall be limited to:

1.

Members that are continuously supported by soil supported by other structural members capable providing continuous vertical support;

2.

Members for which arch action provides under all conditions of loading; or

3.

Walls and pedestals. See Sections 422.7 and 422.9. use of structural plain concrete columns shall permitted.

~~,~~'""'''.';r

422.3.3 Section 422 shall not govern design and installation cast-in-place concrete piles and piers embedded in ground. 422.3.4 Minimum strength. Specified compressive strength plain concrete to be used for structural purposes shall be not than 17 MPa. 422.3.5 Seismic Zones 2 and 4. Plain concrete shall not be in Seismic Zone 2 or 4 except where specifically permitted Section 422.11.3.

422.2 SCOPE 422.4 JOINTS 422.2.1 Section 422 provides minimum requirements for design and construction of structural plain concrete members (cast-in place or precast) except as specified in Sections 422.2.1.1 and 422.2.1.2.

EXCEPTION: The design is not required nhen the minimum foundation for stud walls is in accordance with I.able 305-1. 422.2.1.1 Structural plain concrete basement walls shall be exempted from the requirements for special exposure conditions of Section 404.3.1.

422.4.1 Contraction or isolation joints shall be provided divide structural plain concrete members into t1 discontinuous elements. The size of each element shall limit control excessive buildup of internal stresses caused by to movements from creep. shrinkage and temperature effects. 422.4.2 In determining the number and location of contraction isolation joints, consideration shall be given to: influence climatic conditions; selection and proportioning of m~ttel[1al mixing, placing and curing of concrete; degree of restraint movement; stresses due to loads to which an element is subj and construction techniques.


STRUCTURAL PLAIN CONCRETE

~~~.5 DESIGN MEmOD

4-107

where P" is fact.ored load and Pn is nominal compression strength computed by:

~22;5.1

Structural plain concrete members shall be designed for strength in accordance with the code, using load . f~ors and design strength. ~dequate

422.5.2 Factored loads and forces shall be in combinations as in Section 409.3. 422.5.3 Where required strength exceeds design strength, reinforcement shall be provided and the member designed as a reinforced concrete member in accordance with appropriate design requirements of the code.

(422-4)

where Al is the loaded area. 422.6.3 Members subject to combined flexure and axial load in compression shall be proportioned such that on the compression face:

(422-5)

422.5.4 Strength design of structural plain concrete members for flexure and axial loads shall be based on a linear stress-strain r'eIationship in both tension and compression.

and on the tension face:

(422-6)

422.5.5 Tensile strength of concrete shall be permitted to be considered in design of plain concrete members when provisions ofSection 422.4 have been followed.

422.6.4 Design of rectangular cross sections subject to shear shall be based on:

422.5.6 No strength shall be assigned to steel reinforcement that

(422-7)

may be present.

422.5.7 Tension shall not be transmitted through outside edges, construction joints, contraction joints, or isolation joints of an iildividual plain concrete element No flexural continuity due to (ension shall be assumed between adjacent structural plain Concrete elements.

where Vu is factored shear and Vn is nominal shear strength computed by:

(422-8) for beam action and by:

422.5.8 When computing strength in flexure, combined flexure and axial load, and shear, the entire cross section of a member shall be considered in design, except for concrete cast against Soil where overall thickness h shall be taken as 50 mm less than actual thickness.

(422-9)

for two-way action but not greater than 2/9 ..[l'; bJr.

422.6 STRENGTH DESIGN 422.6.1 Design of cross sections subject to flexure shall be

based on:

(422-1) where Mil is factored moment and Mn is nominal moment ~ength computed by: Mn

= (51I2).[J': s

(422-2)

S is the elastic section modulus ofthe cross section.

(422-3)

422.6.5 Design of bearing areas subject to compression shall be based on (422-10) where P u is factored bearing load and Bn is the nominal bearing strength ofloaded area Al computed by: En = 0.8:if'cA] (422-11) except when the supporting surface is wider on all sides than the loaded area, design bearing strength on the loaded area shall be multiplied by ~ Az I A1 but not more than 2.

. 422.6.6 Lightweight concrete Equations for nominal flexural and shear strengths apply for normal weight concrete; for lightweight aggregate concrete, one ofthe following modifications shall apply:


----

-------,-

-~~- ~--...,...,-.-

~-~ ~- ~~ --~--

-

-~~---~~-~~

CONCRETE

L

When 1<1 is specified and concrete is proportioned in accordance with Section 405.3,1<1/6.7 shall be substi tuted for (I112)..[1': but the value of 1<1/6.7 shall not exceed (l1l2)..[1': ;

2.

When 1<1 is not specified, the value of (1/12)..[1': shall be multiplied by 0.75 for all-lightweight concrete and by 0.85 for sand-lightweight concrete. Linear interpolation shall be permitted when partial sand replacement is used.

422.6.6.1 Provisions of Section 422.6 apply to normal weight concrete. When lightweight aggregate concrete is used, one of the following modifications shall apply: 1.

When 1<1 is specified and concrete is proportioned in accordance with Section 405.3, equations that include (1112)..[1': shall be modified by substituting 1.,/6.7 for (1/12)..[1': wherever it appears in Section 422., but the

422.7.5.1 Structural plain concrete walls of solid rec1tan~~la cross section shall be permitted to be designed by .....'l'... 'O
~t)ITlm'PQ'''t"\~

where Pu is the factored axial load and P"",is nominal axial strength computed by

422.7.6 Limitations

When 1<1 is not specified, all values of (1112)..[1': in

422.7.6.1 Unless demonstrated by a detailed analysis, horizoltltal length of wall to be considered effective for each concentrated load shall not exceed center-to-center between loads, nor width of bearing plus four times the thickness.

Section 422.6 shall be multiplied by 0.75 for all lightweight concrete, and 0.85 for sand-lightweight concrete. Linear interpolation shall be permitted when partial sand replacement is used.

422.7.6.2 Except as provided for in Section 422. 7.6.3, thl(~kflieSSl of bearing walls shall not be less than 1124 the uns:UPI)of1ted" height or length, whichever is shorter, nor less than 140 mm.

value oflctl6.7 shall not exceed (1112)..[1':; 2.

422.7.5 Empirical design method

422.7.6.3 Thickness of exterior basement walls and walls shall be not less than 190 mm.

422.7 WALLS 422.7.1 Structural plain concrete walls shall be continuously supported by soil, footings, foundation walls, grade beams or other structUral members capable of providing continuous vertical support. 422.7.2 Structural plain concrete walls shall be designed for vertical, lateral and other loads to which they are subjected. 422.7.3 Structural plain concrete walls shall be designed for an eccentricity corresponding to the maximum moment that can accompany the axial load but not less than O.10h. lfthe resultant of all factored loads is located within the middle- third of the overall wall thickness, the design shall be in accordance with Section 422.6.3 or 422.7.5. Otherwise, walls shall be designed in accordance with Section 422.6.3. 422.7.4 Design for shear shall be in accordance with Section 422.6.4.

tOlmdati!)n'~11

422.7.6.4 Walls shall be braced against lateral translation. See Sections 422.4 and 422.5.7. 422.7.6.5 Not less than two 16 mm diameter bars shall be provided around all window and door openings. Such bars shall extend at least 600 mm beyond the corners of openings.

·422.8 FOOTINGS 422.8.1 Structural plain concrete footings shall be designed for factored loads and induced reactions in accordance with appropriate design requirements of this Chapter and as provided in Sections 422.8.2 through 422.8.8. 422.8.2 Base area of footing shall be determined from unfactored forces and moments transmitted by footing to soil . and permissible soil pressure selected through principles of soil mechanics.


STRUCTURAL PLAIN CONCRETE

422.8.3 Plain concrete shall not be used for footings on piles. 422.8.4 Thickness of structural plain concrete footings shall be not less than 200 nun. See Section 422.5.8. 422.8.5 Maximum factored moment shall be computed at critical sections located as follows: 1.

At the face of the column, pedestal or wall, for footing supporting a concrete column. pedestal or wall;

2.

Halfway between center and face of the wall, for footing supporting a masonry wall;

3.

Halfway between face of column and edge of steel base plate, for footing supporting a column with steel base plate.

422.8.6 Shear in plain concrete footing 422.8.6.1 Maximum factored shear shall be computed in accordance with Section 422.8.6.2, with location of critical section measured at face of column, pedestal or wall for footing supporting a column, pedestal or wall. For footing supporting a column with steel base plates, the critical section shall be measured at location defined in Section 422.8.5 (3). 422.8.6.2 Shear strength of structural plain concrete footings in the vicinity of concentrated loads or reactions shall be governed by the more severe of two conditions:

1.

2.

Beam action for footing, with a critical section extending in a plane across the entire footing width and located at a distance h from face ofconcentrated load or reaction area. For this condition, the footing shall be designed in accordance with Equation (422-8). ' Two-way action for footing, with a critical section perpendicular to plane of footing and located so that its perimeter 110 is a minimum, but need not approach closer than hl2 to perimeter of concentrated load or reaction area. For this condition. the footing shall be designed in accordance with Equation (422-9).

·422.8.7 Circular or regular polygon shaped· concrete columns or pedestals shall be permitted to be treated as square members with the same area for location of critical sections for moment and shear. 422.8.8 Factored bearing load on concrete at contact surface between supporting. and supported member shall not exceed design bearing strength for either surface as given in Section 422.6.5.

422.9.2 Ratio of unsupported height to average least lateral dimension of plain concrete pedestals shall not exceed 3. 422.9.3 Maximum factored axial load applied to plain concrete pedestals shall not exceed design bearing strength given in Section 422.6.5.

422.10 PRECAST MEMBERS 422.10.1 Design of precast plain concrete members shall consider all loading conditions from initial fabrication to completion of the structure, including form removal, storage. transportation and erection. 422.10.2 Limitations of Section 422.3 apply to precast members of plain concrete not only to the final condition but also during fabrication, transportation and erection. 422.10.3 Precast members shall be connected securely to transfer all lateral forces into a structural system capabTe of resisting such forces. 422.10.4 Precast members shall be adequately braced and supported during erection to ensure proper alignment and structural integrity until permanent connections are completed.

422.11 PLAIN CONCRETE IN EARTHQUAKE RESISTING STRUCTURES 422.11.1 General. The design and construction of plain cQncrete components that resist seismic forces shall conform to the requirements of Section 422, except as modified by this section. 422.11.2 Seismic Zones 2 and 4. Structural plain concrete members are not permitted in buildings located in Seismic Zones 2 and 4. EXCEPTIONS: (1) Footings for buildings of Group R, Division 3 or Group U, Division 1 Occupa11C)l constrocted in accordance with Table 305-1. (2) Non-structural slabs supported directly on the ground or by approved structural systems.

422.11.3 Structures designed for earthquake induced forces in regions of high seismic risk or assigned to high seismic performance or design categories shall not have foundation elements of structural plain concrete, except as follows: 1.

422.9 PEDESTALS 422.9.1 Plain concrete pedestals shall be designed for vertical, lateral and other loads to which they are SUbjected.

4-109

For detached one- and two-family dwellings three stories or less in height and constructed with stud bearing walls, plain concrete footings without longitudinal reinforcements supporting walls and isolated plain


.,,

CONCRETE

concrete footings supporting columns or pedestals are

permitted;

2.

For all other structures, plain concrete footings supporting walls are permitted provided the· footings are reinforced longitudinally with not less than two continuous reinforcing bars. Bars shall not be smaller than 12 mm diameter and shall have a total area of not less than 0.002 times the gross cross-sectional area of the footing. Continuity of reinforcement shall be provided at corners and intersections;

SECTION 423 - ANCHORAGE TO CONCRETE 423.1 SERVICE LOAD DESIGN Bolts and headed stud anchors shall be solidly cast in concrete and the service load shear and tension shall not exceed values set forth in Table 423-1. For combined tension and shear:

3.

For detached one- and two-family dwellings three stories or less in height and constructed with stud bearing walls" plain concrete foundations or basement walls are permitted provided the wall is not less than 190 mm thick and retains no more than 1.2 mofunbalanced fill.

(423-1)

Where: p. = applied service tension load PI = Table 423-1 service tension load Vs = applied service shear load Vr = Table 423-1 service shear load

423.2 STRENGTH DESIGN The factored loads on embedded anchor bolts and headed ~+>"ci.,<,~. shall not exceed the design strengths determined by ':>V\,L1U'lU~a 423.3. In addition to the load factors in Section 409.3, a multiplier of2 shall be used if special inspection is not provided, or of 1.3 if it is provided. When anchors are embedded in the tension zone a member, the load factors in Section 409.3 shall have multiplier of3 if special inspection is not provided, or of2 if it is provided.

423.3 STRENGTH OF ANCHORS 423.3.1 General The strength of headed bolts and headed studs solidly cast in concrete shall be taken as the average of 10 tests approved by the building official for each concrete strength and anchor size. Alternatively, the strength of the anchor shall be calculated in accordance with Sections 423.3.2 through 423.3.4. The bearing area of headed anchors shall be at least one and one-half times the shank area. 423.3.2 Design strength in tension The design strength of anchors in tension shall be the minimum of Pu or ; Pc where: (423-2)


ANCHORAGE TO CONCRETE

and for an anchor group where the distance between anchors is less than twice th~ir embedment length or for a single anchor or anchor group where the distance between anchors is equal to or greater than twice their embedment length: (423-3) where: area of anchor. Must be used with the corresponding steel properties to determine the weakest part of the assembly in tension, mm2 . • = the effective area (in mm2 ) of the projection of an assumed concrete failure surface upon the surface from which the anchor protrudes. For a single anchor or for an anchor group where the distance between anchors is equal to or greater than twice their embedment length, the surface is assumed to be that of a truncated cone radiating at a 45-degree slope from the bearing edge of the anchor toward the surface from which the anchor protrudes. The effective area is the projection of the cone on this surface. For an anchor which is perpendicular to the surface from which it protrudes, the effective area is a circle.

.~

For an anchor group where the distance between anchors is less than twice their embedment length, the failure surface is assumed to be that of a truncated pyramid radiating at a 45-degree slope from the bearing edge of the anchor group toward the surface from which the anchors protrudes. The effective area is the projection of this truncated pyramid on this surface. In addition, for thin sections with anchor groups, the failure surface shall be assumed to follow the extension of this slope through to the far side rather than be truncated, and the failure mode resulting in the lower value of ¢ Pc shall control. = anchor shank diameter specified compression strength of concrete, which shall not be taken as greater than 42 MPa for design. = minimum specified tensile strength of the anchor, MPa. May be assumed to be 420 MPa for AJ07 bolts or A108 studs. = design tensile strength = required tensile strength from factored loads design shear strength = required shear strength from factored loads = 1.0 for normal weight concrete, 0.75 for "all lightweight" concrete, and 0.85 for "sand-lightweight" concrete. strength reduction factor 0.65

4--111

EXCEPI10N: When the anchor is attached to or hooked around reinforcing steel or otherwise terminated to effectively transfer forces to the reinforcing steel that is designed to distribute forces and avert sudden local failure, ¢ may be taken as 0.85. Where edge distance is less than embedment length, reduce ;Pc proportionately. For multiple edge distances less than embedment length, use multiple reductions.

423.3.3 Design strength in shear The design strength of anchors in shear shall be the minilllum of Vss or ;Vc where: (423-4) and where loaded toward an edge greater than 10 diameters away, (423-5) or where loaded toward an edge equal to or less than 10 diameters away, (423-6) where tie equals the edge distance from the anchor axis to the free edge. For groups of anchors, the concrete design shear strength shall be taken as the smallest of: 1.

2.

3.

The design strength of the weakest anchor times the number of anchors; The design strength of the row of anchors nearest the free edge in the direction of shear times the number of rows; or The design strength of the row farthest from the free edge in the direction of shear.

For shear loading toward an edge equal to or less than 10 diameters away, or tension or shear not toward an edge less than five diameters away, reinforcing sufficient to carry the load shall be provided to prevent failure of the concrete in tension. In no case shall the edge distance be less than four diamet:tn.

National Structural Code of the Philippines, Vokme 1

CONCRETE

423.3.4 Combined tension and shear

s

spacing of shear reinforcement in direction longitudinal reinforcement, mm When tension and shear act simultaneously, all of the following v = design shear stress shall be met: Vc = permissible shear stress carried by concrete, MFa VII = permissible horizontal shear stress, MPa V = design shear force at section (423-7) -1 - <1 a = angle between inclined stirrups and longitudinal axis tP V, member Pc = ratio of long side to short side of concentrated load pV ~l reaction area ( Pss Vss Pw = ratio of tension reinforcement =

(Vu)

)2 +(Vu)2

=A/b,.d {I

=

strength reduction factor. See Section 424.3.1

424.2 SCOPE

SECTION 424 - AL TERNA TE DESIGN METHOD 424.1 NOTATION Some notation definitions are modified from those in the main body of the code for specific use in the application of Section 424. = gross area of section, mm

Is

h M n

N

424.2.2 For design of members not covered by Section appropriate provisions ofthis code shall apply. 424.2.3 All applicable provisions of this code for n01mrt~str'essed concrete, except Section 408.5, shall apply to members Uv:)1~II"U by the Alternate Design Method.

2

area of shear reinforcement within a

distance s, mm2 = loaded area 424.2.4 Flexural members shall meet requirements = maximum area of the portion of the supporting surface deflection control in Section 409.6, and requirements ofSe<:tiolns that is geometrically similar to and concentric with the 410.5 through 410.8 ofthis code. loaded area = perimeter of critical section for slabs and footings, mm = web width, or diameter of circular section, rnm 424.3 GENERAL = distance from extreme compression fiber to centroid of tension reinforcement, mm 424.3.1 Load factors and strength reduction factors {I shall = modulus of elasticity of concrete, MPa. See Section taken as unity for members designed by the Alternate 408.6.1 Method. = modulus of elasticity of reinforcement, MFa. See Section 408.6.2 424.3.2 It shall be permitted to proportion members for 75 = specified compressive strength of concrete, MFa. See of capacities required by other parts of Section 424 percent Section 405.

when considering wind or earthquake forces combined = square root of specified compressive strength of

other loads, provided the resulting section is not less than concrete, MPa required for the combination of dead and live load. = average splitting tensile strength of lightweight aggregate concrete, MPa. See 405.2.4 424.3.3 When dead load reduces effects of other loads, members = permissible tensile stress in reinforcement, MFa shall be designed for 85 percent of dead load in combination = specified yield strength of reinforcement, MFa. with the other loads. See Section 403.6.3. == design moment = modular ratio of elasticity 424.4 PERMISSmLE SERVICE LOAD STRESSES =

E.

424.2.1 Non-prestressed reinforced concrete members shall permitted to be designed using service loads (without factors) and permissible service load stresses in accordance provisions of Section 424.

=

E.lEc

=

design axial load normal to cross section occurring simultaneously with V; to be taken as positive for compression, negative for tension, and to include effects of tension due to creep and shrinkage

424.4.1 Stresses in concrete shall not exceed the following: 1.

Flexure Extreme fiber stress in compression............ .0,45j'a

Association of Structural Engineers of the Philippines·

ALTERNA.TE DESIGN METHOD

'., hear*

stressed to the permissible tensile stress/. . and V" shall be taken as unfactored shear force at the section.

~5]S

~~,).Beams

~,

and one-way slabs and footings: Shear carried by concrete, Vc . ...•.•.....

4--113

.

0.09ff

Maximum shear carried by concrete plus shear reinforcement .............. vc + 0.38

ff

424.6

FLEXURE

For investigation of stresses at service loads, straight-line theory (for flexure) shall be used with the following assumptions. Joists:* Shear carried by concrete,

Vc' . . . . . . . . .

Two-way slabs and footings: Shear carried by concrete,

Vc

t .....

1.2ff

{l+21PJ f f

Bearing on loaded areat . . . . . . . . . . . .. ...

O.3fc

. ,,424.4.2 Tensile stress in reinforcementls shall not exceed the following: Grade 275 or Grade 350 reinforcement. . . . . . . . . . . . . . . . . . . . .. 140 MPa

2.

3.

Grade 420 reinforcement or greater

and welded wire fabric (plain

or deformed) . . .. .................

424.6.1 Strains vary linearly as the distance from the neutral axis, except for deep flexural members with overall depth-span ratios greater than 2/5 for continuous spans and 4/5 for simple spans, a nonlinear distribution of strain shall be considered. See Section 410.8 of this Chapter. 424.6.2 Stress-strain relationship of concrete is a straight line under service loads within permissible service load stresses . 424.6.3 In reinforced concrete members, concrete resists no tension. 424.6.4 It shall be permitted to take the modular ratio, n EslE", as the nearest whole number (but not less than 6). Except in calculations for deflections, value of n for lightweight concrete shall be assumed to be the same as for normal weight concrete ofthe same strength.

170 MPa

For flexural reinforcement, 10 mm or less in diameter, in one-way slabs of not more than 4 m span. . . . . . . . . . . .. 0.50/y but not greater than 200 MPa

A24.5 DEVELOPMENT AND SPLICES OF REINFORCEMENT 424.5.1 Development and splices of reinforcement shall be as

required in Section 412 ofthis Chapter.

424.5.2 In satisfYing requirements of Section 412.12.3, Mn shan be taken as computed moment capacity assuming all ;positive moment tension reinforcement at the section to be • For more detailed calculation of the shear stress carried by concrete Vc 8lld shear values for lightweight aggregate concrete, see Section 424.8.4. v'Designed in accord8llce \-'1ith Section 408.12 of this code. 'tlfshear reinforcement is provided, see Sections 424,8.7.4 and 424.8,7.5 tWben the supporting surface is wider on all sides than the loaded area, pemrlssible bearing stress on the loaded area shall be pennitted to be multiplied by ~A,.I Al but not more than 2. When the supporting surface is sloped or

424.65 In doubly reinforced flexural members, an effective modular ratio of 2E/Ec shall be used to transform compression reinforcement for stress computations. Compressive stress in such reinforcement shall not exceed permissible tensile stress.

424.7 Compression members with or without tlexure 424.7.1 Combined flexure and axial load capacity of compression members shall be taken as 40 percent of that computed in accordance with provisions in Section 410 of this Chapter. 424.7 2 Slenderness effects shall be included according to requirements of Sections 410.10 through 410.13. In Equations (41O-lO) and (410-19) the term P" shall be replaced by 2.5 times the design axial load, and the factor 0.75 shall be taken equal to 1.0. 424.7.3 Walls shall be designed in accordance with Section 414 of this Chapter with flexure and axial load capacities taken as 40 percent ofthat computed using Section 414. In Equation (414-1), ; shall be taken equal to 1.0.

stepped, A2 shall be pennitted to be taken as the area of the lower base of the largest 1iustum of a right pyramid or cone contained wholly within the support and having for its upper base the loaded area, and having side slopes of I vertical to 2 horizontal.

National Structural Code of the Philippines,

CONCRETE

424.8 Shear and torsion 424.8.1 Design shear stress V=

l'

shall be computed by

VI(b..d)

Quantity NIA,l shall be expressed in MPa. 424.8.4.6 Shear stresses carried by concrete 1'" apply to weight concrete. When lightweight aggregate concrete is used, one ofthe following modifications shall apply:

(424-1)

1.

When fet is specified and concrete is proportioned accordance with Section 405.3,fc/6.7 shall be for ..Jl': but the value offc/6. 7 shall not exceed ..Jl':.

2.

When fet is not specified, the value of

where V is design shear force at section considered.

424.8.2 When the reaction, in direction of applied shear, introduces compression into the end regions of a member, sections located less than a distance d from face of support shall be permitted to be designed for the same shear l' as that computed at a distance d. 424.8.3 Whenever applicable, effects of torsion, in accordance with provisions of Section 411 of this Chapter, shall be added. Shear and torsional moment strengths provided by concrete and limiting maximum strengths for torsion shall be taken as 55 percent ofthe values given in Section 411.

ffc

shall

multiplied by 0.75 for "all-lightweight" concrete and 0.85 for "sand-lightweight" concrete. Linear intt~rp()latiion; shall be permitted when partial sand replacement is

424.8.4.7 In determining shear stress carried by concrete whenever applicable, eff¢ets of axial tension due to creep s!rrinkage in restrained members shall be included and it shall permitted to include e:tIects of inclined flexural compression variable-depth members.

424.8.4 Shear stress carried hy concrete 424.8.5 424.8.4.1 For members subject to shear and flexure only, shear stres~ carried by concrete Ve shall not exceed 1.1..Jl': unless a more detailed calculation is made in accordance with Section 424.8.4.4.

Shear stress earried by shear reinforcement

424.8.5.1 Types of shear reinforcement Shear reinforcement shall consist of one ofthe following:

1.

Stirrups perpendicular to axis of member;

2.

Welded wire fabric with wires located perpendicular axis of member making an angle of 45 degrees or with longitudinal tension reinforcement;

3.

Longitudinal reinforcement with bent portion making angle of 30 degrees or more with longitudinal tensloll'lt reinforcement;

4.

where N is negative for tension. Quantity NIA,l shall be expressed in MPa.

Combinations of stirrups and bent longitudinal forcement;

5.

Spirals.

424.8.4.4 For members subject to shear and flexure only, it shall be permitted to compute Ve by

424.8.5.2 Design yield strength of shear reinforcement shall exceed 420 MPa.

424.8.4.2 . For members subject to axial compression, shear stress carried by concrete 1'e, shall not exceed 1.1..Jl': unless a more detailed calculation is made in accordance with 424.8.4.5.

424.8.4.3 For members subject to significant axial tension, shear reinforcement shall be designed to carry total shear, unless a more detailed calculation is made using: (424-2)

Ve

but

Ve

0.085..Jl': + 9p,.,Vd/M

(424-3)

shall not exceed 0.14~f'c . Quantity Vd/M shall not be

taken greater than 1.0, where M is design moment occurring simultaneously wi~h Vat section considered.

424.8.4.5 For members subject to axial compression, it shall be permitted to compute l'e by l'e

= 0.09(1 + 0.09NIA,)~f'c

424.8.5.3 Stirrups and other bars or wires used as reinforcement shall extend to a distance d from compression fiber and shall be anchored at both ends acc:or
424.8.5.4 Spacing limits for shear reinforcement 424.8.5.4.1 Spacing of shear reinforcement placed pet"Petldl(~la to axis of member shall not exceed d/l, nor 600 mm.

(4244)


ALTERNATE DESIGN METHOD

424.8.5.4.2

Inclined stirrups and bent longitudinal shall be so spaced that every 45-degree line, i Jxtending toward the reaction from mid-depth of member (d/l) to longitudinal tension reinforcement, shall be crossed by at least line of shear reinforcement. ~einforcement

4-115

424.8.5.6.4 When shear reinforcement consists of a single bar or

a single group of parallel bars, all bent up at the same distance

from the support,

one

~24.8.5.4.3 When (v-vJ exceeds

2.JJ':,

maximum spacing

8iven in Sections 424.8.5.4.1 and 424.8.5.4.2 shall be reduced by one-half

~j4.8.5.5 Minimum shear reinforcement '424.8.5.5.1 A minimum area of shear reinforcement shall be ;provided in all reinforced concrete flexural members where design shear stress v is greater than one-half the permissible shear stress v" carried by concrete, except: Slabs and footings; 2.

3.

(424-8)

Concrete joist construction defined by Section 408.12 of this Chapter; Beam with total depth not greater than 250mm, 2.5 times thickness of flange, or one-half the width of web, whichever is greatest.

424.8 5.5.2 Minimum shear reinforcement requirements of "'Section 424.8.5.5.1 shall be permitted to be waived if shown by test that required ultimate flexural and shear strength can be developed when shear reinforcement is omitted.

where (v - vJ shall not exceed (1/8)

ff..

424.8.5.6.5 When shear reinforcement consists of a series of parallel bent-up bars or groups of parallel bent-up bars at different distances from the support, required area shall be computed by Equation (424-7). 424.8.5.6.6 Only the center three-quarters of the inclined portion of any longitudinal bent bar shall be considered effective for shear reinforcement. 424.8.5.6.7 When more than one type of shear rein-forcement is used to reinforce the same portion of a member, required area shall be computed as the sum of the various types separately. In such computations, Ve shall be included only once. 424.8.5.6.8 Value of (v - vJ shall not exceed (3/8)

ff..

424.8.6 Shear friction

where b w and s are in mm.

Where it is appropriate to consider shear transfer across a given plane, such as. an existing or potential crack, an interface between dissimilar materials, or an interface between two concretes cast at different times, shear-friction provisions of Section 411.8 of this Chapter shall be permitted to be applied, with limiting maximum stress for shear taken as 55 percent of that given in Section 411.8.5. Permissible stress in shear-friction reinforcement shall be that given in Section 424.4.2.

424.8.5.6 Design of shear reinforcement

424.8.7 Special provisions for slabs and footings

424.8.5.5.3 Where shear reinforcement is required by Section 424.8.5.5.1 or by analysis, minimum area of shear reinforcement shall be computed by (424-5)

A. = b..,s/3J;,

424.8.5.6.1 Where design shear stress v exceeds shear stress carried by concrete ve • shear reinforcement shall be provided in 'accordance with Sections 424.8.5.6.2 through 424.8.5.6.8 .

424.8.7.1 Shear capacity of slabs and footings in the vicinity of concentrated loads or reactions is governed by the more severe oftwo conditions:

. 424.8.5.6.2 When shear reinforcement perpendicular to axis of 'member is used:

424.8.7.1.1 Beam action for slab or footing, with a critical section extending in a plane across the entire width and located at a distance d from face of concentrated load or reaction area. For this condition, the slab or footing shall be designed in accordance with Sections 424.8.1 through 424.8.5.

Av = (v-vJb..,s1J;,

(424-6)

424.8.5.6.3 When inclined stirrups are used as shear reinforcement,

(424-7)

f.(sin a + cosa)

424.8.7.1.2 Two-way action for slab or footing, with a critical section perpendicular to plane of slab and located so that its perimeter is a minimum, but need not approach closer than d/l to perimeter of concentrated load or reaction area. For this


CONCRETE

condition, the slab or footing shall be designed in accordance with Sections 424.8.7.2 and 424.8.7.3.

424.8.7.2 Design shear stress v shall be computed by

v= VI(bot/)

(424-9)

where V and b o , shall be taken at the critical section defined in Section 424.8.7.1.2.

424.8.7.3 Design shear stress v shall not exceed v" given by Equation (424-10) unless shear reinforcement is provided (424-10)

but

Vc

shall not exceed

(1I6).[r;' Pc

is the ratio oflong side to

short side of concentrated load or reaction area. When lightweight aggregate concrete is used, the modifications of Section 424.8.4.6 shall apply.

424.8.7.4 If shear reinforcement consisting of bars or wires is provi4ed in accordance with Section 411.13.3 of this Chapter, v" shall not exceed (1/12) and v shall not exceed 0.25

ff.,

ff..

424.8.7.5 If shear reinforcement consisting of steel 1- or channel-shaped sections (shearheads) is provided in accordance with Section 411.13.4 of this Chapter, l' on the critical section and v on defined in Section 424.8.7.1.2 shall not exceed 0.3

ff.,

the critical section defined in Section 41 1.1 3.4.7 shall not exceed In Equations (411-39) and (411-40), design shear

(1I6).[r;,

force V shall be multiplied by 2 and substituted for Vu'

424.8.8 Special provisions for other members For design of deep flexural members, brackets and corbels, and walls, the special provisions of Section 411 of this Chapter shall be used, with shear strengths provided by concrete and limiting maximum strengths for shear taken as 55 percent of the values given in Section 411. In Section 411.11.6, the design axial load shall be multiplied by 1.2 if compression and 2.0 if tension, and substituted for Nil'

424.8.9 Composite concrete flexural memhers For design of composite concrete flexural members, permissible horizontal shear stress Vh shall not exceed 55 percent of the horizontal shear strengths given in Section 417.6.2 ofthis Chapter.

SECTION 425 - UNIFIED DESIGN PROVISIONS FOR REINFORCED PRESTRESSED CONCRETE FLEXURAL AND COMPRESSION MEMBERS 425.1 SCOPE Design for flexure and axial load by provisions of Section shall be pennitted. When Section 425 is used in d~sign, provisions of this Section shall be used in place of corresponding provisions in Sections 408,409,410 and 418. instance, Section 425.408.4 is substituted for Section Section 425.418.10.4 is substituted for Section 418.1J.1·.If section in Section 425 is used, all sections in Section 425 be substituted for the corresponding sections in the body of code, and all other sections in the body of the code shall applicable.

425.408.5 Redistribution of negative moments in continuous flexural members 425.408.5.1 Except where approximate values for moments used, it shall be permitted to increase or decrease moments calculated by elastic theory at supports of COfltmu4 flexural members for any assumed loading arrangement by more than 1000e, percent, with a maximum of20 percent. 425.408.5.2 The modified negative moments shall be used calculating moments at sections within the spans. 425.408.5.3 Redistribution of negative moments shall be only when e, is equal to or greater than 0.0075 at the section which moment is reduced.

425.409.4 Design Strength 425.409.4.1 Design strength provided by a member, connections to other members, and its cross sections, in flexure, axial load, shear, and torsion, shall be taken as nominal strength calculated in accordance with requirements assumptions of this code, multiplied by a strength factor ;. 425.409.4.2 Strength reduction factor; shall be as follows: 425.409.4.2.1 Tension-controlled sections. . . . . . 425.409.4.2.2 Compression-controlled sections: 1.

Members with spiral reinforcement


0.90

UNIFIED DESIGN PROVISIONS FOR REINFORCED AND PRESTRESSED CONCRETE FLEXURAL AND COMPRESSION MEMBERS

Conforming to Section 410.9.3 ...... ... Other reinforced members ..............

0.75 0.70

sections in which the net tensile strain in the extreme tension at nominal strength is between the limits for compression COll,UUJll"'-' and tension-controlled sections, ; shall be linearly ';"'I'.-",aSp.C1 from that for compression-controlled sections to 0.90 as the net tensile strain in the extreme tension steel at nominal strength increases from the compression-controlled strain limit to 0.005. Alternatively, it shall be permitted to take; as that for compression- controlled sections. '425.409.4.2.3 Shear and torsion

0.85

4-117

425.418.9.2 Total amount of prestressed and nonprestressed reinforcement shall be adequate to develop a factored load at least 1.2 times the cracking load computed on the basis of the modulus ofrupturef,. specified in Section 409.6.2.3, except for flexural members with shear and flexural strength at least twice that required by Section 409.3. 425.418.9.3 Part or all of the bonded reinforcement consisting of bars or tendons shall be provided as close as practicable to the extreme tension fiber in all prestressed flexural members, except that in members prestressed with unbonded tendons, the minimum bonded reinforcement consisting of bars or tendons shall be as required by Section 418.10.

425.409.4.2.4 Bearing on concrete. .. See also Section 418.13 , ........... 0.70

425.418.11.4 Redistribution ofnegative moments in continuous prestressed flexural members

425.410.4.2 Balanced strain conditions exist at a cross section when tension reinforcement reaches the strain corresponding to its specified yield strength /, just as concrete in compression . reaches its assumed strain limit of 0.003.

425.418.11.4.1 Where bonded reinforcement is provided at supports in accordance with Section 418.10.2, it shall be permitted to increase or decrease negative moments calculated by-elastic theory for any assumed loading, in accordance with Section 425.408.5.

The compression-controlled strain limit is the net tensile strain in the reinforcement at balanced strain conditions. For prestressed sections, it shall be permitted to use the same compression controlled strain limit as that for reinforcement with a design yield strength/, of 420 MPa.

425.418.11.4.2 The modified negative moments shall be used for calculating moments at sections within spans for the same loading arrangement.

425.410.4 3 Sections are compression-controlled when the net tensile strain in the extreme tension steel is equal to or less than the compression-controlled strairi limit at the time the concrete in compression reaches its assumed strain limit of 0.003. Sections are tension-controlled when the net tensile strain in the extreme tension steel is equal to or greater than 0.005 just as the concrete in compression reaches its assumed strain limit of 0.003. Sections with net tensile strain in the extreme tension steel between the compression-controlled strain limit and 0.005 constitute a transition region between compression-controlled and tension- controlled sections, 425.418.2.3 The following provisions of this code shall not apply to prestressed concrete, except as specifically noted: Sections 407.7.5, 408.11.2, 408.11.3, 408.11.4,408.12,410.6, 410.7,410.10.1 and 410.10.2; Section 413; and Sections 414.4, 414.6 and 414.7.

425.418.9 Limits for reinforcement of flexural

members

425.418.9.rPresuessed concrete sections shaH be classified as tension-controlled and compression-controlled sections in accordance with Section 425.410.4.3. The appropriate9I- fa(:tors from Section 425.409.4.2 shall apply.


CONCRETE

SECTION 426 - ALTERNATIVE LOAD AND STRENGTH REDUCTION FACTORS

the load factors of Section 409.2.8 and ;- factors of 409.4.2.5.

426.1 GENERAL 426.1.1 It shall be permitted to proportion the concrete members of a building structure using the load factor combinations in ASCE 7-95 in conjunction with the following strength reduction factors, .if the structural framing includes primary members of other materials proportioned to satisfy the load factor combinations in Section 2.3 of ASCE 7-95. 426.1.1.1 Flexure, without axial load . . . . . . . . . . . .

0.80

426.1.1.2 Axial tension and axial tension with flexure. . . . . . . . . . . . . . . . . . . . . . . .

0.80

426.1.1.3 flexure: 1.

2.

Axial compression and axial compression with

Members with spiral reinforcement

~nforming to Section 410.10.3 ...

0.70

Other reinforced members. . . . . . . . . . . . . . . .. 0.65

except that for low values of axial compression, it shall be permitted to increase ;towards the value for flexure, 0.80, using the linear interpolation provided in either Section 409.4.2.2 or 425.409.3.2.2.

426.1.1.4 Shear and torsion. . . . . . . . . . . . . . . . . . .

0.75

Except in structures that rely on special moment resisting frames or special reinforced concrete structural walls to resist earthquake effects:

L

Shear in any member that is designed to resist earthquake effects if its nominal shear strength is less than the shear corresponding to the development of the nominal flexural strength ofthe member......... 0.55

2.

Shear in. diaphragms shall not exceed the nurumum strength reduction factor for shear used for the vertical components ofthe primary lateral-force resisting system

3.

Shear in joints and diagonally reinforced coupling beams 0.80

426.1.1.5 Bearing. . . . . . . . . . . . . . . . . . . . . . . . .

0.65

426.1.1.6 Plain concrete. . . . . . . . . . . . . . . . . . . .

0.55

426.1.2 The design of post-tensioned anchorage zones shall use

1"I.::II::tUClatlon or ~:,,:ructural

Engineers

of

the Philippines

1 i

CHAPTERS STRUCTURAL STEEL

TABLE OF CONTENTS

SECTION 501 - GENERAL PROVISIONS .......................................................................... 5-1

Scope ..................................................... 5-1

Limits ofApplicability ............. ........ ...... 5-1 Materials ....................................... ......... 5-2 Loads and Forces ................................. 5-4

501-5 501-6 501-7

Design Basis .......................................... 5-5

Referenced Codes and Standards ........... 5-5

Design Documents ................................. 5-6

SECTION 502 - DESIGN REQUIREMENTS ....................................................................... 5-7

Scope .................................................... 5-7 5-7 5-7 5-7 5-S Local Buckling... . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5-8

Gross Area .. ..... ... .... .. ................. ........... Net Area ............. ............. ..................... Effective Net Area................................... Stability...................................................

Rotational Restraint at Points of

Support ............. ................. ............... 502.S Limiting Slenderness Ratios .............. 502.9 Simple Spans ....................................... 502.10 End Restraint . ............ ............. ............ 502.11 Proportions of Beams and Girders ....... 502.12 Proportioning of Crane Girders 502.7

5-12

5-12

5-12

5-12

5-12

5-13

SECTION 503 - FRAMES AND OTHER STRUCTURES ........................................... 5-14

503.1 503.2

Scope ......................................... ,......... 5.14 General ................................................ 5-14

503.2

Frame Stability ...................................

5-14

'SECTION 504 - TENSION MEMBERS .................•.........•................................................. 5-14

504.1 504.2

Scope ................................................... 5-14 Allowable Stress ................................ 5-14

504.3 504.4

Built-Up Members ............................. 5-14

Pin-Connected Members .................... 5~15

SECTION 505 - COLUMNS AND OTHER COMPRESSION MEMBERS ............. 5-16

505.1 Scope ................................................... 5·16 505.2 Effective Length and Slenderness Ratio ................................................ 5·16 505.3 Allowable Stress ................................ : 5-16 505.4 Flexural-Torsional Buckling .............. 5-16

505.5 505.6 505.7

Built-Up Members ............................. 5-16

Pin-Connected Compression

Members .......................................... 5-17

Column Web Shear ............................ 5-17


STRUCTURAL STEEL

SECTION 506 • BEAM AND OTHER FLEXURAL MEMBERS ............................. 5-18

506,1 506.2

Scope ................................................. 5-18 Allowable Stress: Strong Axis Bending ofI-Shaped Members and Channels ............... ..................... 5-18 Allowable stress: Weak Axis Bending ofT-Shaped Members, Solid Bars and Rectangular Plates -.... 5-19 ,~

506.3

~'"

~

506.4

Allowable Stress: Bending ofBox

Members, Rectangular Tubes and Circular Tubes ...... ........... , ............... 5-20 Allowable Shear Stress ·t···················· 5-20

Transverse Stiffeners ............................ 5-20

Built-Up Members ................ .......... , .. 5-21

Web-Tapered Members . ........ .. .... 5-21

~

506.5 506.6 506.7 506.8

~

~

~

~

'"

~

SECTION 561 - PUTE G'IMERS ....................................................................................... 5-23

507.1 507.2 507.3

Scope ................................................... 5-23 Web-Slenderness Limitations ............ 5-23 Allowable Bending Stress ................. 5-23

507.4 507.5 507.6

Allowable Shear Stress with

Tension Field Action ...................... 5-24

Transverse Stiffeners ............... ........... 5-24

Combined Shear and Tension Stress... 5-25

SECTION 508 - COMBIN'ED STRESSES .......".................................................................. !§...25

508.1 508.2

Scope .... ...... ..... ..... .......... .................... Axial Compression and Bending .......

5-25

508.3

Axial Tension and Bending ...............

5-26

5~25

t

SECTION 509 - COMPOSITE CONSTRUCTION ........................................................_.. .5-27

509.1 509.2 509.3 509.4

Scope .................................................. Definition .......................................... Design Assumptions ................ ........... End Shear ......... .................... ..............

5-27 5-27 5-27 5-27

509.5 509.6 509.7

Shear Connectors ............................... 5-28

Composite Beams or Girders with

Fonned Steel Deck. ........................ 5-29

Special Cases ......... ................ .............. 5-30

SECTION 510 - CONNECTIONS, JOINTS, AND FASTENERS ................................ 5-31

510.1 510.2 510.3 510.4 510.5 510.6

Scope .................................................. .. General Provisions ............................. . Welds................................................... . Bolts, Threaded Parts and Rivets ... .. Allowable Shear Rupture ................... Connecting Elements ........................ ..

5-31 5-31 5-33 5-37 5-41 5-41

510.7 510.8 510.9 510.10

Fillers ................................................. . Splices ................................................. Allowable Bearing Stress ................. . Columns Bases and Bearing on Masonry and Concrete ................... . 510.11 Anchor Bolts ..................................... .

5-42

5-42

5-42

5-42

5-42

'.

SECTION 511 - SPECIAL DESIGN CONSIDERATIONS ............._............................... 5-43

Scope .................................................. 5-43 51Ll 511.2 Webs and Flanges Under Concentrated Forces .................. ...... 5-43

511.3 511.4 511.5

Ponding......... .................. ...................... Torsion ................................................ Fatigue .......................... .......... .............

5-45

5-45

5-45

SECTION 512 - SERVICEABILITY DESIGN CONSIDERATIONS .......................... 5-51

512.1 512.2 512.3

Scope .................................................. 5-51 Camber ........ ........... ............................. 5-51 Expansion and Contraction ................ 5-51

512.4 512.5 512.6

Deflecition.. Vibration and Drift ......... 5-51

Connection Slip ............................... ;.. 5-51

Corrosion ............................................ 5-51


TABLE OF CONTENTS

5-iii

SECTION 513 - FABRICATION, ERECTION AND QUALITY CONTROL ............ 5-52

Shop Drawings ......... ........ ... ..... ....... ... 5-52 Fabrication ........ ................................. 5-52 Shop Painting ................ ...... ..... .... ... ... 5-53

513.4 513.5

Erection ............................................... Quality Control...................................

5-53

5-54

SECTION 514 - P.LASTIC DESIGN ................................................................................... 5-55

514.1 514.2 514.3 514.4

Scope .................................................. . Structural Steel .................................. . Basis for Maximum Strength Determination .................................. . Columns ............................................. .

5-55 5-55 5-55 5-56

514.5 514.6 514.7 514.8 514.9 514.10

Shear .................................................. . Web Crippling ................................... . Minimum Width-Thickness Ratios .... . Connections ........................................ . Lateral Bracing .................................. . Fabrication ........................................ .

5-56

5-56

5-56

5-57

5-57

5-57

SECTION 515 - SEISMIC PROVISIONS FOR STRUCTURAL STEEL

BUILDINGS J:N" SEISMIC ZONE 4 ............................................................................. ,.......... 5-58

515.1 515.2 515.3 515.4 515.5 515.6 515.7

Scope ................................................... General ................................................. Definitions ........... ................................. Materials .......... ..................... ........ ....... Column Requirements ......................... Ordinary Moment Frame Requirements ..................................... Special Moment-Resisting Frame

(SMRF) Requirements .......... ............

5-58 5-58 5-58 5-58 5-59 5-59

515.8 515.9

Requirements for Braced Frames ........ Requirements for Special

Concentrically Braced Frames ........... 515.10 Eccentrically Braced Frame

Requirements .............. ..... ......... ... .... 515.11 Requirements Special Truss Moment

Frames......................... .......................

5-62

5-64

5-66

5-68

5-60

SECTION 516 - SEISMIC PROVISIONS FOR STRUCTURAL STEEL

BUlLDJ:N"G J:N" SEISMIC ZONE 2 ................................................................................................... 5-6'9 516.1 516.2 516.3 516.4

General ................................................. Definitions..................... ....................... Materials ............................................... Ordinary Moment Frame

Requirements .....................................

5-69 5-69 5-69

516.5 516.6

Special Moment Resisting Frame

(SMRF) Requirements ......................... 5-69

Requirements for Braced Frames .......... 5-70

5-59

SECTION 517 -LIGHT FRAMED WALL SySTEMS.............................................................. 5-72

516.1 516.2 516.3

General ................................................. 5-72

Boundary Members and Anchorage ....... 5-72

Wood Structural Panel Sheathing .......... 5-72

SECTION 518 - INSPECTION ...........................................................-......................................... 5-72


1I

GENERAL PROVISIONS


PROVISIONS

561.1 SCOPE 501.1.1 Tbe Specifications for Structural Steel Buildings Allowance Stress Design and Plastic Design is intended as an alternate to the currently approved Load and Resistance Factor Design Specifications for Structural Steel Buildings ofthe American Institute of Steel Construction, Inc. 561.1.2 This Section provides minimum requirements for the design and construction of structural steel building elements of any structure erected under requirements of the National Building Code of the Philippines (NBCP) to which this Section fo~s a part of by reference. 501.1.3 This Section shall govern in all matters pertaining to the design, construction, and material properties of structural steel elements wherever this Section is in conflict with requirements contained in other standards referenced in this Section. 501.1.4 Alternative Design Specification. As an alternative, the design of structural steel buildings using the Load and Resistance Factor Design Specification for Structural Steel Buildings, December 1, 1993, published by the American Institute of Steel Construction, Inc. shall be permitted. 501.1.5 Cold-Formed Steel Strudural Members. The design of cold-formed carbon or low-alloy steel structural members shall be in accordance with the requirements of the Load and Resistance Factor Design Specifications for Cold formed Steel Structural Members, March 16 1991; or the Specifications for Design of Cold-Formed Steel Structural Members, 1986 (with December 1989 Addendum), published by the American Iron and Steel Institute (AlSI). 501.1.6 Special Provisions For Earthquake R.esistance S01.1.6.1 In regions of high seismic risk (seismic zone 4) or moderate (seismic zone 2) provisions of Section 515 shall be satisfied. See Section 515.

501.1 LIMITS OF APPLICABILITY 501.2.1 Structural Steel Dermed 501.2.1.1 As used in this Specification, the term structural steel refers to the steel elements of the structural steel frame essential to the support of the design loads. Such elements are generally enumerated in Section 2.1 of the AlSC Code of

Standard Practice for Steel Buildings and Bridges. For the design of cold-fonned steel structural members, whose profiles contain rounded corners and slender flat elements, the provisions of the American Iron and Steel Institute Specifications for the Design of Cold-formed Steel Structural Members are recommended. 501.2.2 Types of Constmction 501.2.2.1 Three basic types of construction and associated design assumptions are permissible under the respective conditions stated herein, and each will govern in a specific manner the size of members and the types and strength of their connections: Type 1, commonly designated as "rigid-frame" (continuous frame), assumes that beam-column connections have sufficient rigidity to hold virtually unchanged the original angles between intersecting members. Type 2, commonly designated as "simple framing" (unrestrained, free-ended), assumes that, insofar as gravity loading is concerned, ends of beams and girders are connected for shear only and are free to rotate under gravity load. Type 3. commonly designated as "semi-rigid framing" (partially restrained), assumes that the connections of beams and girders possess a dependable and known moment capacity intermediate in degree between the rigidity of Type 1 and the flexibility ofTyj>e 2. 501.2.2.2 The design of all connections shall be consistent with the assumptions as to type of construction called for on the design drawings. 501.2.2.3 Type 1 construction is unconditionally permitted under this Specification. Two different methods of design are recognized. Within the limitations laid down in Section 514.1, members of continuous frames or continuous portions of frames maybe proportioned, on the basis of their maxiII\.um predictable strength, to resist the specified design loads multiplied by the prescribed load factors. Otherwise, Type 1 construction shall be designed, within the limitations of Sections 501 through 513, to resist the stresses produced by the specified design loads, assuming moment distribution in accordance with the elastic theory. 501.2.2'.4 Type 2 construction is permitted under this Specification, subject to the stipulations of the following paragraph, wherever applicable. 501.2.2.5 In buildings designed as Type 2 construction (Le., with beam-to-column connections other than wind connections assumed flexible under gravity loading) the

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STRUCTURAL STEEL

5-2

wind moments may be distributed among selected joints of the frame, provided:

Steel, Sheet and Strip, Carbon, Hot-rolled, Structural Quality, ASTM A570 Grade 275,310 and 345

1.

High-strength, Low-alloy Columbium-Vanadium Steels of Structural Quality, ASTM A572

2. 3.

Connections and connected members have adequate capacity to resist wind moments. Girders are adequate to carry full gravity load as "simple beams." Connections have adequate inelastic rotation capacity to avoid overstress of the fasteners or welds under combined gravity and wind loading.

501.2.2.6 Type 3 (semi-rigid) construction is permitted upon evidence, the connections to be used are capable of furnishing, as a minimum, a predictable proportion of full end restraint. The proportioning of main members joined by such connections shall be predicated upon no greater degree of end restraint than this minimum. 501.2.2.7 Type 2 and 3 construction may necessitate some non elastic, but self-limiting, deformation of a structural steel part.

High-strOength Low-alloy Structural Steel With 345 MPa Minimum Yield Point to 100 mm Thick, ASTM A588 Steel, Sheet and Strip, High-strength, Low-alloy, Hot-rolled and Cold-rolled, With Improved Atmospheric Corrosion Resistance, ASTM A606 Steel, Sheet and Strip, High-Strength, Low-alloy, Columbium or Vanadium, or both Hot-Rolled and Cold Rolled, ASTM A607 Hot-formed Welded and Seamless High-strength Low-alloy Structural Tubing, ASTM A618 Structural Steel for Bridges, ASTM A709 Quenched and Tempered Low-alloy Structural Steel Plate with 483 MPa Minimum Yield Strength to 100 mm thick, ASTM A852

501.3 MATERIAL 501.3.1 Structural Steel

2.

501.3.1.1 ASTM Designations

1.

Material conforming to one of the following standard specifications is approved for use under this Specification:

Structural Steel, ASTM A36 Pipe, Steel, Black and Hot-dipped, Zinc-coated Welded and Seamless Steel Pipe, ASTM A53, Grade B ~" ;~

High-strength Low-alloy Structural Steel, ASTM A242 High-strength Low-alloy Structural Manganese Vanadium Steel, ASTM A441

Certified mill test reports or certified reports of tests made by the fabricator or a testing laboratory in accordance with ASTM A6 or A568, as applicable, and the governing specification shall constitute sufficient evidence of conformity with one of the above ASTM standards. Additionally, the fabricator shall, if requested, provide an affidavit stating the structural steel furnished meets the requirements of the grade specified.

501.3.1.2 Unidentified steel. Unidentified steel, if free from surface imperfections, is permitted for parts of minor importance, or for unimportant details, where the precise physical properties of the steel and its weldability would not affect the strength of the structure. 501.3.1.3 Heavy shapes

Cold-formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes, ASTM A500 Hot-formed Welded and Seamless Carbon Steel Structural Tubing, ASTM A501 High-yield Strength, Quenched and Tempered A1loy-Steel Plate, Suitable for Welding, ASTM A514 Structural Steel with 290 MPa Minimum Yield Point, ASTM A529

For ASTM A6 Groups 4 and 5 rolled shapes to be used as members subject to primary tensile stresses due to tension or flexure, toughness need not be specified if splices are made by bolting. If such members are spliced using full penetration welds, the steel shall be specified in the contract documents to be supplied with Charpy V-Notch testing in accordance with ASTM A6, Supplementary Requirement S5. The impact test shall meet a minimum average value of 27 N-m, absorbed energy at +21.1 °C and shall be conducted in accordance with ASTM A673 with the following exceptions:


GENERAL PROVISIONS

The center longitudinal axis of the specimens shall be located as near as practical to midway between the inner flange surface and the center of the flange thickness at the intersection with the web mid thickness.

501.3.3 Rivets 501.3.3.1 Steel rivets shall conform to the following standard specifications:

Steel Structural Rivets, ASTM AS02 Tests shall be conducted by the producer on material selected from a location representing the top of each ingot or part of an ingot used to produce the product represented by these tests.

501.3.3.2 Manufacturer's certification shall constitute sufficient evidence of conformity with the standard. 501.3.4 Bolts. Washers and Nuts

For plates exceeding 50 mm thick used for built-up members with bolted splices and subject to primary tensile stresses due to tension or flexure, material toughness need not be specified. If such members are spliced using full penetration welds, the steel shall be specified in the contract documents to be supplied with Charpy V-Notch testing in accordance with ASTM A6, Supplementary Requirement S5. The impact test shall be conducted by the producer in accordance with ASTM A673, Frequency P, and shall meet a minimum average value of 27 N-m absorbed energy at +21.1 0c. The above supplementary toughness requirements shall also be considered for welded full-penetration joints other than splices in heavy rolled and built-up members subject to primary tensile stresses. 4.

Additional requirements for joints in heavy rolled and built-up members are given in Sections 510.2.7, 510.2.8,510.3.7,510.3.8 and 513.2.2.

501.3.4.1 Steel bolts shall conform to one of the .following standard specifications:

Carbon Steel Bolts and Studs, 414 MPa Tensile Strength, ASTMA407 High-Strength Bolts for Structural Steel Joints, ASTM A325 Quenched and Tempered Steel Bolts and Studs, ASTM A449 Heat-treated Steel Structural Bolts, 1034 MPa Minimum Tensile Strength, ASTM A490 Carbon and Alloy Steel Nuts, ASTM AS63 Hardened Steel Washers, ASTM F436 501.3.4.2 A449 bolts are pennitted only in connections requiring bolt diameters greater than 38 mm and shall not be used in slip-critical connections. 501.3.4.3 Manufacturer's certification shall constitute sufficient evidence of conformity with the standards.

501.3.2 Steel Casting and Forgings 501.3.5 Anchor Bolts aud Threaded Rods 501.3.2.1 Cast steel shall conform to one of the following standard specifications:

501.3.5.1 Anchor bolt and threaded rod steel shall conform to one ofthe following standard specifications:

Mild-to-medium-strength Carbon-steel Castings for General Applications, ASTM A27, Grade 448-241

Structural Steel ASTM A36

High-Strength Steel Castings for Structural Purposes, ASTM A148, Grade 551-345

Carbon and Alloy Steel Nuts for Bolts for High-Pressure and High-temperature Service, ASTM A194, Grade 48

501.3.2.2 Steel forgings shall conform to the following standard specifications:

Quenched and Tempered Alloy Steel Bolts, Studs and Other Externally Threaded Fasteners, ASTM A354

Steel Forgings Carbon and Alloy for General Industrial Use, ASTMA668

Quenched and Tempered Steel Bolts and Studs, ASTM A449

501.3.2.3 Certified test reports shall constitute sufficient evidence of conformity with the standards.

High-strength Low-alloy Columbium-Vanadium Steels of Structural Quality, ASTM A572

501.3.2.4 Allowable stresses shall be the same as those provided for other steels, where applicable.

High-strength Low-alloy Structural Steel With 345 MPa Minimum Yield Point to 100 mm Thick, ASTM A588

National Structural Code of tile Philippines, Volume 1

STRUCTURAL STEEL

High-strength Non-headed Steel Bolts and Studs, ASTM A681

SOI.3.7.2 Manufacturer's certification shall sufficient evidence of conformity with the code.

S01.3.S.2 Threads on bolts and rods shall conform to Unified Standard Series of latest edition of ANSI BI8.I and shall have Class 2A tolerances.

501.4 LOADS AND FORCES

S01.3.S.3 Steel bolts conforming to other proVIsIons of Section 501.3 are permitted as anchor bolts. A449 material is acceptable for high-strength anchor bolts and threaded rods of any diameter. SOI.3.S.4 Manufacturer's certification shall constitute sufficient evidence of conformity with the standards. S01.3.6 Filler Metal and Flux for Weldiug SOI.3.6.1 Welding electrodes and fluxes shall conform to one of the following specifications of the American Welding Society: * Specifications for Covered Carbon Steel Arc Welding Electrodes, AWS A5.I

Sp~cifications for Low-alloy Steel Covered Arc Welding Electrodes, AWS A5.5 Specifications for Carbon Steel Electrodes and Fluxes for Submerged-Arc Welding, AWS AS.I1 Specifications for Carbon Steel Filler Metals for Gas Shielded Arc Welding, AWS A5.I8 Specifications for Carbon Steel Electrodes for Flux.,.Cored Arc Welding, AWS A5.20 Specifications for Low-Alloy Steel Electrodes and Fluxes for Submerged-Arc Welding, AWS A5.23 Specifications for Low-Alloy Steel Filler Metals for Gas Shielded Arc Welding, AWS A5.28 Specifications for Low-Alloy Steel Electrodes for Flux Cored Arc Welding AWS AS.29 S01.3.6.2 Manufacturer's certification shall constitute sufficient evidence of conformity with the standards. SOI.3.7 Stud Shear Connectors 501.3.7.1 Steel stud shear connectors shall conform to the requirements of Structural Welding Code - Steel, AWS D1.1. • Approval of these welding electrode specifications is given without regard to weld metal notch toughness requirements, which are generally not critical to building construction.

constitute

501.4.1 The nominal loads shall be the minimum design loads stipulated by the applicable code under which the structure is designed or dictated by the conditions involved. In the absence of a code, the loads and load combinations shall be those stipulated in Chapter 2. SOI.4.1.1 Dead Load and Live Load The dead load to be assumed in design shall consist of the weight of steelwork and all material permanently fastened thereto or supported thereby. The live load shall be that stipulated by the applicable code under which the structure is being designed or that dictated by the conditions involved. S01.4.1.2 Impact For structures carrying live loads'" "'which induce impact, the assumed live load shall be increased sufficiently to provide for same. If not otherwise specified, the increase shall be not less than: For supports of elevators ................................... For cab-operated traveling crane support girders and their connections ........ , ... ... ..... For pendant-operated traveling crane support girders and their connections .................... For supports of light machinery, shaft or motor driven.. .......................... For supports of reciprocating machinery or power driven units... . . ... . .. . .. ... .. . . .. .. .... For hangers supporting floors and balconies... .. . . ..... ..........................

100% 25% 10% 20% 50% 33%

501.4.1.3 Crane Runaway Horizontal Forces The lateral force on crane runways to provide for the effect of moving crane trolleys shall be not less than 20% of the sum of weights of the lifted load and of the crane trolley, but exclusive of other parts of the crane. The force shall be assumed to be applied at the top of the rails, acting in either direction normal to the runway rails, and shall be dis~buted with due regard for lateral stiffhess of the structure supporting the rails. The longitudinal tractive force shall be not less than 10010 of the maximum wheel loads of the crane applied at the top of the rail, unless otherwise specified.


GENERAL PROVISIONS

crane runway shall also be designed for crane stop

provision shall be made for stresses caused by wind, during erection and after completion of the building.

501.5~4 Design for Serviceability and Other Considerations

501.5.4.1 The overall structure and the individual members, connectiOns and connectors shall be checked for serviceability in accordance with Section 512.

561.6 REFERENCED CODES AND STANDARDS in localities subject to earthquakes, typhoons and extraordinary conditions shall be designed with due for such conditions.

L.l\. . . . . . . 'w,.,

501.6.1 Where codes and standards are referenced in this Specification, the following standards with to be used as reference are listed: American National Standards Institute

ANSI B1S.1-72

ANSIA5S.1-82

American Society of Testing and Materials

.,v,............. Except as provided in Section 514, all structural membiers, connections and connectors shall be proportioned the stresses due to the working loads do not exceed the afi()w8lble stresses specified in Sections 504 through 511. allowance stresses specified in these Sections do not to peak stresses in regions of connections (see also ~Secticln 502.10), provided requirements of Section 511 are

Specifications for General Requirements for Rolled Steel Plates, Shapes, Sheet Piling and Bars for Structural Use, ASTMA6-S7d Specifications for Steel Castings, Carbon for General Application, ASTM A27-87 . Specifications for Structural Steel, ASTM A36-87

SOI.5.1.2 For provisions pertaining to plastic design, refer to Section 514.

Specifications for Pipe, Steel, Black and Hot-Dipped, Zinc Coated Welded and Seamless, ASTM A53-88

SOl.S.2 Wind and Seismic Stresses

Specifications for Steel Castings, Structural Purposes, ASTM A148-84

SOI.S.2.1 Allowable stresses may be increased 113 above the values otherwise provided when produced by wind or seismic loading, acting alone or in combination with the design dead and live loads, provided the required section computed on this basis is not less than that required for the design dead and live load and impact (if any) computed without the 1/3 stress increase, and further provided that stresses are not otherwise required to be calculated on the basis of reduction factors applied to design loads in combinations. The above stress increase does not apply to allowable stress ranges provided in Section 511.5.

High-Strength,

for

Specifications for High-Strength Low-Alloy Structural Steel, ASTM A142-87 Specifications for Carbon Steel Externally Standard Fasteners, ASTM A307-86a

Threaded

Specifications for High-Strength Bolts for Structural Steel Joints, ASTM A325-86 Specifications for Quenched and Tempered Alloy Steel Bolts, Studs and Other Externally Threaded fasteners, ASTM A354-86 Specifications for High-Strength Low-Alloy Structural Manganese Vanadium Steel, ASTM A441-85

SOl.5.3 Structural Analysis SOl.5.3.1 The stresses in members, connections and connectors shall be determined by structural analysis for the loads defined" in Section 501.4. Selection of the method of analysis is the prerogative ofthe responsible engineer.

Specifications for Quenched and Tempered Steel Bolts and Studs, AStM A449-87 Specifications for Heat-Treated, Steel Structural Bolts 1034 MPa Tensile Strength, ASTM A490-85

•• Live loads on crane support girders shall be taken as the maximum crane wheel/oads.

National structural Code of

the


STRUCTURAL STEEL

Specifications for Cold-Formed Welded and Seamless Carbon Steel Structural Tubings in Rounds and Shapes, ASTM A500-84 Specifications for Hot-Formed Welded and Seamless Carbon Steel Structural Tubing, ASTM A501-84 Specifications for High-Yield Strength, Quenched and Tempered Alloy Steel Plate, Suitable for Welding, ASTM A514-87a

AWS A5.5-81 AWS A5.18-79 AWS A5.23-80 AWS A5.29-80

AWS A5.17-80 AWS A5.20-79 AWS A5.28-79

Research Council on Structural Connections , Specifications for Structural Joints Using ASTM A325 of A490 Bolts, 1985

501.7 DESIGN DOCUMENTS Specifications for Structural Steel with 290 MPa Minimum Yield Point 12 mm Minimum Thickness, ASTM A529-85 Specifications for Carbon and Alloy Steel Nuts, ASTM A563-84 Specifications for Steel, Sheet and Strip, Carbon, Hot Rolled, Structural Quality, ASTM A570-85 Specifications for High-Strength Low-Alloy Columbium Vanadium Steels of Structural Quality, ASTM A572-85

501.7.1 Plans 501.7.1.1 The design plans shall show a complete design with sizes, sections and relative locations of the various members. Floor levels, column centers and offsets shall be ' dimensioned. Drawings shall be drawn to a scale large enough to show the information clearly.

Specifications for High-Strength Low-Alloy Structural Steel "'lith 345 MPa Minimum Yield Point to 100 mm Thick, ASTM A588-87

501.7.1.2 Design documents shall indicate the type or types of construction as defined in Section 501.2.2 and shall include the loads and design requirements necessary for preparation of shop drawings including shears, moments and axial forces to be resisted by all members and their connections.

Specifications for Steel, Sheet and Strip, High-Strength, Low-Alloy, Hot-Rolled and Cold-Rolled, With Improved Atmospheric Corrosion Resistance, ASTM A606-85

501.7.1.3 Where Jomts are to be assembled with high strength bolts, design documents shall indicate the connection type (slip-critical, tension or bearing).

Specifications for Steel, Sheet and Strip, High-Strength, Low-Alloy Columbium or Vanadium, or Both, Hot-Rolled and Cold-Rolled, ASTM A607-85

501.7.1.4 Camber of trusses, beams and girders, if required, shall be called for in the design documents. The requirements for stiffeners and bracing shall be shown on the design documents.

"

""

Ii

Specifications for Hot-Formed Welded and Seamless High Strength Low-Alloy Structural Tubing, ASTM A618-84 Specifications for Steel Forgings, Carbon and Alloy, for General Industrial Use, ASTM A668-85a Specifications for Quenched and Tempered Carbon-Steel and High-Strength Low-Alloy Steel Plates for Structural Applications, ASTM A678-84

501.7.2 Standards Symbols and Nomenclature 501.7.2.1 Welding and inspection symbols used on plans and shop drawings shall preferably be the American Welding Society symbols. Other adequate welding symbols are permitted, provided a complete explanation thereof is shown in the design documents. 501.7.3 Notation for Welding

Specifications for Concrete Aggregates, ASTM C33-86 Specifications for Lightweight Aggregates for Structural Concrete, ASTM C330-87 ASTM F436-86 Specifications for Steel Structural Rivets, ASTM A502-83A ASTM A709-87b ASTM A852-85

501.7.3.1 Notes shall be made in the design documents and on the shop drawings of those joints or groups of joints in which the welding sequence and technique of welding shall be carefully controlled to minimize distortion. 501.7.3.2 Weld lengths called for in the design documents and on the shop drawings shall be the net effective lengths.

American Welding Society AWS D1.l-88 AWS A5.1-81


DESIGN REQUIREMENTS

5-7

502.4 EFFECTIVE NET AREA 502.4.1 When the load is transmitted directly to each of the cross-sectional elements by connectors, the effective net area Ae is equal to the net area An. This Section contains provisions which are common the Specifications as a whole.

502.4.2 When the load is transmitted by bolts or rivets through some but not all of the cross-sectional elements of the member, the effective net areaAe shall be computed as: (502-1)

GROSS AREA where: 1 The gross area of a member at any point shall be detemlll'Ilea by summing the products of the thickness and gross width of each element as measured normai to the ofthe member. For angles, the gross width shall be the sum of the ofthe legs less the thickness.

.;:lV."••,• •

2 An net area ofthe member, mm U = reduction coefficient

502.4.3 When the load is transmitted by welds through some but not all of the cross sectional elements of the member, the effective net area Ae shall be computed as: (502-2) where:

1 The net area A" of a member is the sum of the of the thickness and the net width of each element computed as follows:

Ag

502.4.4 Unless a larger coefficient is justified by tests or other criteria, the following values of U shall be used: 1.

W, M or S shapes with flange widths not less than 2/3 the depth, and structural tees' cut from these shapes, provided the connection is to the flanges. Bolted or riveted connections shall have no fewer than three of fasteners per line in the direction stress. .. . ............................................... U= 0.90

2.

W, M or S shapes not meeting the conditions of

F~V"',·~.,;,

For a chain of holes extending across a part in any diagonal or zigzag line, the net width of the part shall be obtained by deducting from the gross width the sum of the diameters or slot dimensions as provided in Section 510.4.2, of all holes in the chain, and adding, for each gage space in the chain, the quantity

where: longitudinal center-to~center spacing (pitch) of any two consecutive holes, mm transverse center-to-center spacing (gage) between fastener gage lines, mm 502.3.4 For angles, the gage for holes in opposite adjacent legs shall be the sum of the gages from the back of the angles less the thickness.

2

gross area of the member, mm

subparagraph a, structural tees cut from these shapes and all other shapes including built-up cross sections. Bolted or riveted connections shall have no fewer than three fasteners per line in the direction of stress.............................. '" .. . ... . . .. . ..... U = 0.85 3.

All members with bolted or riveted connections having only two fasteners per line in the direction of stress ............................................... U = 0.75

502.3.5 The critical net area An of the part is obtained from that chain which gives the least net width.

502.4.5 When load' is transmitted by transverse welds to some but not all of the cross-sectional elements of W, M or S shapes and structural tees cut from these shapes, A~ shall be taken as the area ofthe directly connected elements.

502.3.6 In determining the net area across plug or slots welds, the weld metal shall not be considered as adding to the net area.

502.4.6 When the' load is transmitted to a plate by longitudinal welds along both edges at the end of the plate, the length ofthe welds shall not be less than the width of the

Nationat Structural Code of.the Philippines, Volume 1

STRUCTURAL STEEL

5-3

plate. The effective net area Ae shall be computed by Equation (502-2).

502.4.7 Unless a larger coefficient can be justified by tests or other criteria, the following values of U shall be used:

2.

3. 4.

l. 2. 3.

When I> 2w . .. .................................. U=1.00

When 2w > I> 1.5w ......... ............... ...... U= 0.81

When 1.5w > I> It' .......................... ... .fJ= 0.15

Where: I = weld length, mm w plate width (distance between welds), mm

502.6.1.3 For stiffened elements, i.e., supported along edges parallel to the direction of the compression force, width shall be taken as follows: L

2.

502.4.8 Bolted and riveted splice and gusset plates and other connection fittings subject to tensile force shall be designed in accordance with the provisions of Section 504.2, where the effective net area shall be taken as the actual net area, except that, for the purpose of design calculations, it shall not be taken as greater than 85% of the gross area.

3.

4.

502.5 STABILITY

,

502.5.1 General stability shall be provided for the structure as a whole and for each compression element. 502.5.2 Consideration shall be given to significant load effects resulting from the deflected shape of the structure or of individual elements of the lateral load resisting system, including effects on beams, columns, bracing, connections and shear walls.

502.6 LOCAL BUCKLING 502.6.1 Classification of Steel Sections 502.6.1.1 Steel sections are classified as compact, non compact and slender element sections. For a section to qualify as compact, its flanges must be continuously connected to the web or webs and the width-thickness ratios of its compression elements must not exceed the applicable limiting width-thickness ratios from Table 502-1. Steel sections that do not qualify as compact are classified as non compact if the width-thickness ratios of the compression elements do not exceed the values shown for non-compact in Table 502-1. If the width-thickness ratios of any compression element exceed the latter applicable value, the section is classified as a slender element section. 502.6.1.2 For unstiffened elements, which are supported along only one edge, parallel to the djrection of the compression force, the width shall ee4aken as follows: 1.

is half the full nominal width. For legs of angles and flanges of channels and the width b is the full nominal dimension. For plates, the width b is the distance from the edge to the frrst row of fasteners of line of welds. For stems of tees, dis taken as the full nominal

For webs of rolled, built-up or formed sections, his clear distance between flanges. For webs of rolled, built-up or formed sections, dis the full nominal depth. For flange or diaphragm plates in built-up sections, the width b is the distance between adjacent lines of fasteners or lines of welds. For flanges of rectangular hollow structural sections, the width b is the clear distance between webs less inside comer radius on each side. Ifthe comer radius is not known, the flat width may be taken as the total section width minus three times the thickness.

502.6.1.4 For tapered flanges of rolled sections, the LHH_"-U."''''' is the nominal value halfway between the free edge and corresponding face of the web. 502.6.2 Slender Compression Elements 502.6.2.1 For the design of flexural and sections with slender compressive elements the IOllOVVlni Section shall apply. 502.6.2.2 Axially loaded members and flexural Ul'-111V"'" containing elements subject to compression which have width-thickness ratio in excess of the applicable compact value shall be proportioned according to Section. 1.

UnstifTened Compression Elements

The allowable stress of unstiffened compression "l"""~'U'., whose width-thickness ratio the applicable value shall be subject to a reduction factor Qs. The value Qs shall be determined by Equations (502-3) (502-8), as applicable, where b is the width of unstiffened element as defined in Section 502.6.1. such elements comprise the compression flange of a member, the maximum allowable bending stress shall exceed 0.60F;Qs nor the applicable value as provided Section 506.2.3. The allowable stress of axially compression members shall be modified by the amlrOlrma:te reduction factor Q, as provided in Section 502.6.2.2 item 3.

For flanges ofl-shaped members and tees, the width b

Association of Structural Engineers of the

P~ilippines

DESIGN REQUIREMENTS

angles:

When 200 I ..{F; -5, bit -5, 407 I ..{F; :

Qs:::; l.340-0.001702(blt)jF;

(502-3)

When bit> 4071 ..jF; :

o : :; _$

106,870 Fy(blti

(502-4)

or plates projecting from columns or other members, and for projecting elements of flanges of beams and girders: When 2491JFy lk c -5,blt-5,512IJFy lk c

Qs =1.293-0.001177(blt)JFy lkc When blt>512IJFy lk c

Q

= 180,640kc

s

Fy(bltf

:

(502-5)

:

(502-6)

stems of tees:

When 3331..jF; -5, bit -5, 462/ ..{F; :

Qs

1.908-0.00272(blt)..{F;

(502-7)

When bl t > 462/..jF;:

Q :::; 137,900 s

~,(blt)2

(502-8)

"" width of unstiffened compression element as defined in Section 502.6.1 =thickness ofunstiffened elements, mm =specified minimum yield stress, MFa

kc ==

4.0~46

(hit) .

if hlt>70, otherwise kc =1.0.

5-9

1,

STRUCTURAL STEEL

5-10

Table 502-1 Members Limiting Width-Thickness Ratios

:nnlnr'~lillnn

j---

Description of Element Flanges ofl-shaped rolled beams and channels in flexure

Compact

Non-compact

a

l701jF;

Flanges ofl-shaped welded beams in flexure

170/ ~r:l'

bit

~--~-~--~-~-~~~-~--~---------~------~-----

Outstanding legs of pairs of angles in continuous contact; I

angles or plates projecting from rolled beams or columns; i stiffeners on . I

Angles or plates projecting from girders, built-up columns or !

other compression members; compression flanges of plate i

b/t

NA

b/t

NA

250/ ----;---~~--

i Stems oftees

333/

NA

1-=-:---:::::--.....-:--;-----:---:,--------::---:------ --,----;--+---

Unstiffened elements simply supported along one edge, such

as legs of single-angle struts, legs of double-angle struts with

separators and cross or star-shaped cross sections

Flanges of square and rectangular box and hollow structural

sections of uniform thickness subject to bending or

c;mpressiond ; flange cover plates and diaphragm plates

between lines of fasteners or welds

Unsupported width of cover plates perforated with a

succession of access holesb All other

-----.--f----.--- - -

200/ ~Fy

500/ ~Fy

625/ ~Fy

NA

stiffened elements, i.e.,

NA

1680/ ~Fy

;-------+----

1995/ ~Fy

Webs in combined flexural and axial compression

For 675

> 0.16

"

'. Circular hollow sections 22,750/ F~

In axial compression Dd

22,750/ Fy

In flexure • For hybrid beams, use the yield the flange 1">1 instead of Fy.

b Assumes net area ofplat« at widest hole.

e For design of slender sections that exceed the non-compact limits see Section 502.6.2.2.

d See also Section 506.4.1.

kc

=

4.05 (h/t)0.46'

jF;

- - ! - -.

NA

bit

dt

............

if h/t>70.othernise kc=l.O.

.

Association of· structural Engineers of the Philippines

---~

DESIGN REQUIREMENTS

Unstiffened elements of tees whose proportions exceed the limits of Section 502.6.1 shall conform to the limits given in Table 502-2. 2.

Stiffened Compression Elements

When the width-thickness ratio of uniformly compressed stiffened elements (except perforated cover plates) exceeds the non-compact limit stipulated in Section 502.6.1, a reduced effective width be shall be used in computing the design properties of the section containing the element, except that the ratio b.jt need not be taken as less than the applicable value permitted in Section 502.6.1. For the flanges of square and rectangular sections of uniform thickness:

j

5-11

For axially loaded circular sections: Members with diameter-to-thickness ratios Dlt greater than 22,750IFy. but having a diameter-to-thickness ratio of less than 89, 63 OIFy , shall not exceed the smaller value determined by Section 505.3 nor

F

4564 +OAF Df t Y

a

(502-11)

where: D

outside diameter, mm

t = wall thickness, mm 3.

Design Properties

Properties of sections shall be determined using the full cross section, except as follows:

\

(502-9)

132.1
For other uniformly compressed elements:

b

6641

e..[j

[1-

116.3 l;f b (b I t)..[j

(502-10)

where:

b = actual width of a stiffened compression element, as

defined in Section 502.6.1, mm be = reduced width, mm t element thickness, mm f = computed compressive stress (axial plus bending stresses in the stiffened elements, based on the design properties as specified in Section 502.6.2.2, MPa. If unstiffened elements are included in the total cross section, f for the stiffened element must be such that the maximum compressive stress in the unstiffened element does not exceed FaUs or FbQ" as applicable.

Limitin

In computing the moment of the inertia and section modulus of flexural members, the effective width of uniformly compressed stiffened elements, as determined in Section 502.6.2.2 item 2 shall be used in determining effective cross-sectional properties. For stiffened elements of the cross section:

effective area actual area

For unstiffened elements of the cross section, Qs is determined from Section 502.6.2.2 item 1 For axially loaded compression members the gross sectional area and the radius of gyration r shall be computed on the basis of the actual cross section. The allowable stress for axially loaded compression members containing unstiffened or stiftened shall not exceed:

Table 502-2

ortioos for Chanoels and Tees

Ratio of full Ratio of flange flange width to thickness to web stem thickness :=---jc-..c....- - - -..

a

~

J

Ql·1----·Fv 2C' 2 •

F =

;f 3.00 ;f 2.00

c

(KI f r)3 - + ..._..... -- - .-- --- 5

3(KI I r)

3

8C'c

(502-13)

8C' c 3

when Klfr is less than C '", where

Built-up te~.!_-l--__~ ._,--,-_.___.._~._._ ..__._;;::_.1.25 Rolled tees I ;;:: 050 ;;:: 1.10

and a. b.

Q

QsQa Cross sections composed entirely of unstiffened elements, Q = Qs i.e. (Q" = 1.0) Cross sections composed entirely of stiffened elements, Q = Q" i.e. (Qs 1.0)

National Structural Code of the Philippines, Volume 1 .. -.----.-.-.~-----

(KI f 1')2

(

-'--._.._.--1------

When the allowable stresses are increased due to wind or seismic loading in accordance with the provisions of Section 501.5.2, the effective width be shan be determined on the basis of 3/4 times the stress caused by wind or seismic loading acting alone or in combination with the design dead and live loading.

(502-12)

STRUCTURAL STEEL

5·12

c.

Cross sections composed of both stiffened and unstiffened elements, Q Qs Qa

When Kllr exceeds C 'c : (502-14)

4.

Combined Axial and Flexural Stress

In applying the provisions of Section 508 to members subject to combined axial and flexural stress and containing stiffened elements whose width-thickness ratio exceeds the applicable non-compact limit given in Section 502.6.1, the stresses Fa, fix; andfiy shall be calculated on the basis ofthe section properties as provided in Section 502.6.2.2 item 3 as applicable. The allowable bending stress Fb for members containing unstiffened elements whose width-thickness ratio exceeds the non-compact limit given in Section 502.6.1 shall be the smaller value, 0.60FyQs or that provided in Section 506.2.3 The termjalO.60Fy in Equations (508-2) and (506-30) shall be replaced by jJO.60FyQ.

502.10 END RESTRAINT 502.10.1 When designed on the assumption of full or partial end restraint due to continuous, semi-continuous or cantilever action, the beams, girders and trusses, as well as the sections of the members to which they connect, shall be designed to carry the shears and moments so introduced as well as all other forces, without exceeding at any point the unit stresses prescribed in Sections 504 through 506, except that some non-elastic but self-limiting deformation of a part of the connection is permitted when this is essential to avoid overstressing of fasteners.

502.11 PROPORTIONS OF BEAMS AND GIRDERS 502.11.1 Rolled or welded shapes, plate girders and cover plated beams shall, in general, be proportioned by the moment of inertia of the gross section. No deduction shall be made for shop or field bolt or rivet holes in either flange provided that:

•

502.7 ROTATIONAL RESTRAINT AT POINTS OF SUPPORT 502.7.1 At points of support, beams, girders and trusses shall be restrained against rotation about their longitudinal axis.

502.8 LIMITING SLENDERNESS RATIOS 502.8.1 For members whose dj;sign is based on compressive force, the slenderness ratio KPr preferably should not exceed 200. If this limit is exceeded, the allowance stress shall not exceed the value obtained from Equation (505-2). 502.8.2 For members whose design is based on tensile force, the slenderness ratio Ur preferably should not exceed 300. The above limitation does not apply to rods in tension. Members which have been designed to perform as tension members in a structural system, but experience some compression loading, need not satisfy the compression slenderness limit.

where Afg is the gross flange area and Afo is the net flange area, calculated in accordance with the provisions 6f Section 502.2 and 502.3. 502.11.2 If

the member flexural properties shall be effective tension flange area Ate

5 FUA Afe - - fil 6

F;,

502.11.3 Hybrid girders may be proportioned by the moment of inertia of their gross section,' subject to the applicable provisions in Section 507.2, provided they are not required to resist an axial force greater than O.15Fy times the area of the gross section, where Fy is the yield stress of the flange material. To qualify as hybrid girders, the flanges at any given section shall have the same cross sectional area and be made of the same grade of steel.

502.9 SIMPLE SPANS 502.9.1 Beams, girders and trusses designed on the basis of simple spans shall have an effective length equal to the distance between centers of gravity of the members to which they deliver their end reactions.

• No limit is placed on the web stresses produced by the applied bending moment for which a hybrid girder is designed; except as provided in Section 511.5.


DESIGN REQUIREMENTS

11.4 Flanges of welded beams or girders may be varied thic:kness or width by splicing a series of plates or by the of cover plates. 11.5 The total cross~sectional area of cover plates of or riveted girders shall not exceed 70% of the total

5·13

502.12 PROPORTIONING OF CRANE GIRDERS 502.12.1 The flanges of plate girders supporting cranes or other moving loads shall be proportioned to resist the horizontal forces produced by such loads.

1.6 High-strength bolts, rivets or welds connecting to web, or cover plate to flange, shall be ·t\nt~rtl,rm~·t1 to resist the total horizontal shear resulting the bending forces on the girder. The longitudinal . of these bolts, rivets or intermittent welds shall n proportion to the intensity of the shear. However, the . spacing shall not exceed the maximum ermllttt~<1 for compression or tension members in Section or 505.5, respectively. Bolts, rivets or welds cormelctirlg flange to web shall also be proportioned to transnlit to the web any loads applied directly to the flange, provision is made to transmit such loads by direct

_,>,.u,,,...... 7

Partial length cover plates shall be extended the theoretical cut-off point and the extended portion and the extended portion shall be attached to the beam or girder by high-strength bolts in a slip-critical connection, rivets or fillet welds adequate, at the applicable stresses allowed in Sections 510.3.5,510.4.4, or 511.5, to develop the cover plate's portion of the flexural stresses in -the beam or girder at the theoretical cutoff point. 502.11.8 In addition, for welded cover plates, the welds connecting the cover plate termination to the beam or girder in the length a', defined below, shall be adequate, at the allowed stresses, to develop the cover plate'S portion of the flexural stresses in the beam or girder at the distance a' from the end of the cover plate. The length a " measured from the end of the cover plate, shall be:

A distance equal to the width of the cover plate when there is a continuous weld equal to or larger than 3/4 of the plate thickness across the end of the plate and continuous welds along both edges of the cover plate in the length a '. A distance equal to l1f2 times the width of the cover plate when there is a continuous weld smaller than 3/4 of the plate thickness across the end of the plate and continuous welds along both edges of the cover plate in the length a'. A distance equal to 2 times the width of the cover plate when there is no weld across the end of the end of the plate, but continuous welds along both edges ofthe cover plate in the length a'.

National ~I Code of the Philippines, Volume 1

STRUCTURAL STEEL

5·14

SECTION 503 - FRAMES AND OTHER STRUCTURES

SECTION 504 - TENSION MEMBERS

503.1 SCOPE

504.1 SCOPE

503.1.1 This Section specifies general requirements to assure stability of the structure as a whole.

503.2 GENERAL 503.2.1 In addition to meeting the requirements of member strength and stiffhess, frames and other continuous structures ~ll be designed to provide the needed deformation capacity and to assure over-all frame stability.

503.3. FRAME STABILITY 503.3.1 Braced Frames In trusses and in those frames where lateral stability is , provided by adequate attachment to diagonal bracing, to shear walls, to an adjacent structure having adequate lateral stability or to floor slabs or roof decks secured horizontally by walls or bracing systems parallel to the plane of the frame, the effective length factor K for the compression members shall be taken as unity, unless analysis shows that a smaller value is permitted. 503.3.2 Unbraced Frames

,..

"'".'

'\

~I

'It.. :

\

In frames where lateral stability is dependent upon the bending stiffiless of rigidly connected beams and columns, the effective length K1 of compression members shall be determined by analysis and shall not be less than the actual unbraced length.

504.1.1 This section applies to prismatic members subject to axial tension caused by forces acting through the centroidal axis. For members subject to combined axial tension and flexure, see Section 508.3. For members subject to fatigue, see Section 511.5. For tapered members, see Section 506.8. For threaded rods see Section 510.4.

504.2 ALLOWABLE STRESS 504.2.1 The allowable stress Fr shall not exceed 0.60Fy on the gross area nor 0.50Fu on the effective net area. In addition, pin-connected members shall meet the requirements of Section 504.4.1 at the pinhole. 504.2.2 Block shear strength shall be checked at end connections oftension members in accordance with Section 510.5. 504.2.3 Eyebars shall meet the requirements of Section 504.4.1.

504.3 BUILT-UP MEMBERS 504.3.1 The longitudinal spacing of connectors between elements in continuous contact consisting of a plate and a shape or two plates shall not exceed: 24 times the thickness of the thinner plate, nor 300 mm for painted members or unpainted members not subject to corrosion. 14 times the thickness of the thinner plate, nor 175 mm for unpainted members of weathering steel subject to atmospheric corrosion. 504.3.2 In a tension member the longitudinal spacing of fasteners and intermittent welds connecting two or more shapes in contact shall not exceed 600 mm. Tension members composed of two or more shapes or plates separated by intermittent fillers shall be connected to one another at these fillers at intervals such that the slenderness ratio of either component between the fasteners does not exceed 300. 504.3.3 Either perforated cover plates or tie plates without lacing are permitted on the open sides of built-up tension members. Tie plates shall have a length not less than 2/3 the distance between the lines of welds or fasteners connecting


TENSION

to the components of the member. The thickness of tie plates shall not be less than 1150 of the distance these lines. The longitudinal spacing of "rn"ittf"nt welds or fasteners at tie plates shall not exceed

The spacing of tie plates shall be such that the ratio of any component in the length between plates should preferably not exceed 300.

"nnf"rne!':>!

MEMBE~S

5-15

504.4.3 Eyebars 504.4.3.1 Eyebars shall be of uniform thickness, without reinforcement at the pinholes, and have circular heads whose periphery is concentric with the pin hole. The radius of the transition between the circular head and the eyebar body shall not be less than the diameter of the head. 504.4.3.2 For calculation purposes, the width of the body of an eyebar shall not exceed 8 times its thickness.

PIN-CONNECTED MEMBERS Allowable Stress The allowable stress on the net area of the pinhole pin-connected members is 0.45Fy . The bearing stress on projected area of the pin shall not exceed the stress ,,,11.,,,,,,.11 in Section 510.9.

;:.,,,'...."7,,-1 . . .

The allowable stress on eyebars meeting the ,,.,..,••ir"m,·nt,, of Section 504.4.3 is 0,60Fy on the body area.

504.4.3.3 The thickness may be less than 12 mm only if external nuts are provided to tighten pin plates into snug contact. For calculation purposes, the distance from the hole edge to plate edge perpendicular to the direction of the applied load shall not be less than 2/3 nor greater than 3/4 times the width of the eyebar body. 504.4.3.4 The pin diameter shall be not less than 7/8 times the eyebar width. 504.4.3.5 The pinhole diameter shall be no more than n 8 mm greater than the pin diameter.

";''''...'1.,,, Pin-connected Plates ;''''•.'1.",.1 The minimum net area beyond the pinhole, to the axis of the member, shaH not be less than 2/3 the net area across the pinhole.

nJlJraliel

504.4.3.6 For steel having a yield stress greater than 483 MPa, the hole diameter shall not exceed 5 times the plate thickness and the width of the eyebar shall be reduced accordingly.

The distance used in calculations, transverse to the axis of pin-connected plates or any individual element of a built-up member, from the edge of the pinhole to the edge ofthe member or element shall not exceed 4 times the thickness at the pinhole. For calculation purposes, the distance from the edge of the pin hole to the edge of the plate or to the edge of a separated element of a built-up member at the pinhole, shall not be assumed to be more than 4/5 times the diameter ofthe pinhole.

h ;:;;>:lU't.''t.'"'.'''

, 504.4.2.3 For pin-connected members in which the pin is expected to provide for relative movement between connected parts while under full load, the diameter of the pinhole shall not be more than 0.8 mm greater than the diameter of the pin. 504.4.2.4 The corners beyond the pin hole may be cut at 45° to the axis of the member, provided the net area beyond the pin hole, on a plane perpendicular to the cut, is not less than that perpendicular to the direction ofthe applied load.


STRUCTURAL STEEL

5-16

SECTION 505 - COLUMNS AND OTHER COMPRESSION MEMBERS

505.1 SCOPE 505.1.1. This section applies to prismatic members with compact and non-compact sections subject to axial compression through the centroidal axis. For members with slender elements, see Section 502.6.2. For members subject to combined axial· compression and flexure, see Section 508. For tapered members, see Section 506.8.

505.2 EFFECTIVE LENGTH AND SLENDER NESS RATIO 595.2.1 The effective-length factor K shall be determined in accordance with Section 503.3.

f

....

"

505.2.2 In determining the slenderness ratio of an axially loaded compression member, the length shall be taken as its effective length Kl and r as the corresponding radius of gyration. For fimiting slenderness ratios, see Section 502.8.

505.3 ALLOWABLE STRESS 505.3.1 On the gross section of axially loaded compression members whose cross sections meet the provisions of Table 502-1, when Kllr, the largest effective slenderness ratio of any unbraced segment is less than Cc , the allowable stress is:

a

\

(505-1)

c

505.4.1 Singly symmetric and unsymmetric columns, such as angles or tee-shaped columns, and doubly symmetric columns such as cruciform or built-up columns with very thin walls, may require consideration of flexural-torsional· and torsional Quckling.

505.5 BUILT-UP MEMBERS 505.5.1 All parts of built-up compression members and the transverse spacing of their lines of fasteners shall meet requirements of Section 502.8. 505.5.2 For spacing and edge distance requirements for weathering steel members, see Section 510.4. 10. 505.5.3 At the ends of built-up compression members bearing on base plates or milled surfaces, all components in' contact with one another shall be connected by rivets bolts spaced longitudinally not more than 4 diameters apart for a distance equal to 1112 times the maximum width of the member, or by continuous welds having a length not less than the maximum width ofthe member. 505.5.4 The longitudinal spacing for intermediate bolts, rivets or intermittent welds in built-up members shall be adequate to provide for the transfer of calculated stress. The maximum longitudinal spacing of bolts, rivets or intermittent welds connecting two rolled shapes in contact shall not exceed 600 mm. In addition, for painted members and unpainted members not subject to corrosion where the outside component consists of a plate, the maximum longitudinal spacing shall not exceed:

JF;

1- (K!/ r)2 )F [ 2C 2 Y

=

F

505,4 FLEXURAL-TORSIONAL BUCKLING

3 Kllr (Kllr)3 +---_._- 3 8 Cc 8e c 3

times the thickness ofthe outside 333 1 plate nor 300 mm when fasteners are not staggered along adjacent gage lines.

5

5001.JF; times the thickness ofthe outside plate nor 450 mm when fasteners are staggered along adjacent gage lines.

where: (505-1a)

505.2.2 On the gross section of axially loaded compression members, when KI/r exceeds Cc the allowable stress is: F =

2

12n E a 23(Kllr)2

(505-2)

505.5.5 Compression members composed of two or more rolled shapes separated by intermittent fillers shall be connected at these fillers at intervals such that the slenderness ratio KFr of either shape, between the fasteners does not exceed 3/4 times the governing slenderness of the built-up member. The least radius of gyration r shaH be used in computing the slenderness ratio of component part. At least two intermediate connectors be used along the length of the built-up member.


COLUMNS AND OTHER COMPRESSION MEMBERS

All connections, including those at the ends, shall welded or shall utilize high-strength bolts tightened to requirements of Table 510-12. 7 Open sides of compression members built-up from or shapes shall be provided with lacing having tie at each end and at intermediate points if the lacing is Tie plates shall be as near the ends as I1"Ll"U'Lll.-. In main members carrying calculated stress, the plates shall have a length of not less than the .<1u,tarlce between the lines of fasteners or welds connecting to the components of the member. Intermediate tie shall have a length not less than 1/2 of this distance. thickness of tie plates shall not be less than 1/50 of the distance between the lines of fasteners or welds connecting them to the components of the member. In bolted and riveted construction, the spacing in the direction of stress in tie plates shall not be more than 6 diameters and the tie shall be connected to each component by at least 3 fasteners. In welded construction, the welding on each line connecting a tie plate shall aggregate not less than 1/3 the of the plate.

5-17

505.6 PIN-CONNECTED COMPRESSION MEMBERS 505.6.1 Pin-connection of pin-connected compression members shall conform to the requirements of Section 504.4.

505.7 COLUMN WEB SHEAR 505.7.1 Column connections must be investigated for concentrated force introduction in accordance with Section 511.2.

505.5.8 Lacing, including flat bars, angles, channels or other shapes employed as lacing, shall be so spaced that the ratio //r of the flange included between their connections . shall not exceed 3/4' times the governing ratio for the member as a whole. Lacing shall be proportioned to resist a shearing stress normal to the axis of the member equal to 2% of the total compressive stress in the member. The ratio fir for lacing bars arranged in single systems shall not exceed 140. For double lacing this ratio shall not exceed 200. Double. 'hicing bars shall be joined at their intersections. For lacing bars in compression the unsupported length of the lacing bar shall be taken as the distance between fasteners or welds connecting it to the component of the built-up member for single lacing, and 70% of that distance for double lacing. The inclination of lacing bars to the axis of the member shall preferably be not than 60° for single lacing and 45° for double lacing. When the distance. between the lines of fasteners or welds in the flanges is more than 380 mm., the lacing preferably shall be double or be made of angles. 505.5.9 The function of tie plates and lacing may be performed by continuous cover plates perforated with access holes. The unsupported width of such plates at access holes, as defined in Section 502.6, is assumed available to resist axial stress, provided that: the width-to thickness ratio conforms to the limitations of Section 502.6; the ratio of length (in direction of stress) to width of holes shall not exceed 2; the clear distance between holes in the direction of stress shall be not less than the transverse distance between nearest lines of connecting fasteners or welds; and the periphery of the holes at all points shall have a minimum radius of38 mm.


1 i

STRUCTURAL STEEL

5-18

SECTION 506 - BEAMS AND OTHER FLEXURAL MEMBERS

506.1 SCOPE 506.1.1 Beams shall be distinguished from plate girders on the basis of the web slenderness ratio hlw. When this value is greater than the 2547 I ~Fy> allowable bending stress is given in Section 507. The allowable shear stresses and stiffener requirements are given in Section 506 unless tension field action is used, then the allowable shear stresses are given in Section 507. 506.1.2 This Section applies to singly or doubly symmetric beams including hybrid beams and girders loaded in the plane of symmetry. It also applies to channels loaded in a plane passing through the shear center parallel to the web or restrained against twisting at load points and points of • support. For members subject to combined flexural and axial force, see Section 508.2.

that, for such members, the maximum positive m(lml~ntj, increased by 1110 of the average negative moments. reduction shall not apply to moments produced by on cantilevers. If the negative moment is resisted column rigidly framed to the beam or girder, the reduction is permitted in proportioning the column for combined axial and bending loading, provided that stress fa due to any concurrent axial load on the does not exceed 0.15Fa. 506.2.2 Members with Non-cGmpact Sections 506.2.2.1 For members meeting the requirements of 506.2.1 except that their flanges are (excluding built-up members and members with points greater than 448 MFa), the allowable stress is:

506.2.2.2 For built-up members meeting the r"'r"'ir"'...... "" of Section 506.2.1 except that their flanges are D0I1-C()ml and their webs are compact or non-compact, hybrid girders and members with yield points greater 448 MPa) the allowable stress is:

506.2 ALLOWABLE STRESS: STRONG AXIS

BENDING OF I-SHAPED MEMBERS AND

CHANNELS

506.2.1 Members with Compact Sections

where:

506.2.1.1 For members with compact sections as defined in Section 502.6.1 (excluding hybrid beams and members with yield points greater than 448 MPa) symmetrical about, and loaded in, the plane of their minor axis the allowable stress IS:

F" =0.66F.v

(506-1 )

provided the flanges are connected continuously to the web or webs and the laterally unsupported length of the compression flange Lh does not exceed the value of Le , as given by the smaller of:

200bf 137,900 - - or-----'- (dIAf)Fy

,JF;

(506-2)

506.2.1.2 Members (including composite members and excluding hybrid members and members with yield points greater than 448 MPa) which meet the requirements for compact sections and are continuous over supports or rigidly framed to columns, may be proportioned for 9/1 0 of the negative moments produced by gravity loading when such moments are maximum at points of support, \provided

k = C

4.05 (hI I.,., )0.46

if h'lw > 70, otherwise ke = 1

506.2.2.3 For members with a non-compact (Section 502.6), but not included above, and through the shear center and braced laterally in the of compression stress at intervals not exc:eeidin

200b f l ~F.p the allowable stress is:

Fb

0.60.z.:v

506.2.3 Members with Compact or Non-compact

Sections with Unbraced Length Greater than L"

506.2.3.1 For flexural members with compact or compact sections as defined in Se.ction 502.6.1, and unbraced lengths greater than I.e as defined in 506,2.1, the allowable bending stress in tension determined from Equation (506-5). 506.2.3.2 For such members with an axis of symmetry and loaded in the plane of their web, the


5-19

BEAMS AND OTHER FLEXURAL MEMBERS

stress in compression is detennined as the larger from Equations (506-6) or (506-7) and (506-8), that Equation (506-8) is applicable only to sections compression flange that is solid and approximately in cross section and that has an area not less tension flange. Higher values of the allowable . stress are permitted if justified by a more analysis. Stresses shall not exceed those pennitted 507, if applicable. For channel bent about their major axis, the compressive stress is determined from Equation

bending) and negative when they are of opposite signs (single curvature bending). When the bending moment at any point within an unbraced length is larger than that at both ends of this length, the value of Cb shall be taken as unity. When computing Fbx to be used in Equation (508-1), Cb may be computed by the equation given above for frames subject to joint translation, and it shall be taken as unity for frames braced against joint translation. Cb may conservatively be taken as unity for cantilever beams." 506.2.3.4 For hybrid plate girders, Fy for Equations (506-6) and (506-7) is the yield stress of the compression flange. Equation (506-8) shall not apply to hybrid girders. Section 506.2.3 does not apply to tee sections if the sections if the stem is in compression anywhere along the unbraced length.

When

(506-6)

When

506.3 ALLOWABLE STRESS: WEAK AXIS BENDING OF I-SHAPED MEMBERS, SOLID BARS AND RECTANGULAR PLATES 506.3.1 Lateral bracing is not required for members loaded through the shear center about their weak axis nor for members of equal strength about both axes.

(506-7)

For any value of llrT: F =~2,740Cb ~0.60F b (ld/ AI) Y

(506-8)

. where: I = distance between cross sections braced against twist or lateral displacements of the compression flange, mm. For cantilevers braced against twist only at the support, I may conservatively be taken as the actual length. radius of gyration of a section comprising the compression flange plus 1/3 of the compression web area, taken about an axis in the plane ofthe web, mm area of the compression flange, mm2 1. 75 + 1.05 (Mr M 2 ) + 0.3 (M1!M2 but not more than 2.3', M J is the smaller andM2 the larger bending moment at the ends of the unbraced length, taken about the strong axis of the member, and where M J.M2 , the ratio of end moments, is positive when M1 and M2 have the same sign (reverse curvature

i,

506.3.1.1 Memhers With Compact Sections 506.3.1.1.1 For doubly symmetrical 1- and H-shape members with compact flanges (Section 502.6) continuously connected to the web and bent about their weak axes (except members with yield points greater than • 448 MFa); solid ,round and square bars; and solid rectangular sections bent about their weaker axes, the allowable stress is: (506-9)

506.3.1.2 Members With Non-compact Sections 506.3.1.2.1' For members not meeting the requirements for compact sections of Section 502.6 and not covered in Section 506.4, bent about their minor axis, the allowable stress is (506-10) 506.3.1.2.2 Doubly symmetrical 1- and H-shape members bent about their weak axes (except members with yield points greater than 448 MFa) with non-compact flanges

----.-----.--~

• It is conservative to take Cb as unity. For values smaller than 2.3, see Table 6 in the Numerical Values Section.

··For the use oflarger Cb values, see Guide to Stability Design Criteria for Metal Structures, 4th Edition, Galambos (1988).

National Structural Code of thePhilippines,Vohme 1

--.-.---~-.----

STRUCTURAL STEEL

5-20

(Section 502.6) continuously connected to the web may be designed on the basis of an allowable stress of: b

Fb=Fy [ 1.075

'\

0.00192~JF;j

506.5 ALLOWABLE SHEAR STRESS 506.5.1 For on hltw::::;998/~F.l" the overall depth the web thickness, the allowable shear stress is:

(506-11)

F..,

506.4 ALLOWABLE STRESS: BENDING OF BOX MEMBERS, RECTANGULAR TUBES AND CIRCULAR TUBES

0.40

r:v

506.5.2 For hltw >998/.[F;~ the allowable stress is on the clear distance between flanges times the thickness is: Fy Fy = --(C,.)::::; 0.40F.. 2.89 .

506.4.1 Members With Compact Sections where: 506.4.1.1 For members bent about their strong or weak axes, members with compact sections as defined in Section 502.6 and flanges continuously connected to the webs, the allowable stress is:

C" =

Fy

except that it need not be less than 8,275(b/Fy), where M J is the smaller and J.12 the larger bending moment at the ends of the unbraced length, taken about the strong axis of the member, and where MiM2, the ratio of end moments, is positive when M J and M2 have the same sign (reverse curvature bending) and negative when they are of opposite signs (single curvature bending).

C· y

IS

less than 0.8

~fk,:-

hit.,.

kv

Fy

=4.00+~when

a/h is less than 1.0

=5.34+~when

a'h is more than l.0

(al h)2

(al h)2

t,. = a (506-13)

when

=500 - - - - w hen ( , v .Ismorethan 0 .8

506.4.1.2 To be classified as a compact section, a box shaped member shall have, in addition to the requirements tin Section 502.6, a depth not greater than 6 times the width, a flange thickness not greater than 2 times the web thickness and a laterall y unsupported length Lb less than or equal to:

M2

2

Fy(hlt ... )

(506-12)

( MI) -b, rom Lc = l13,445 +8,275-

31O,264kv

h =

thickness of web, mm clear distance between transverse stiffeners, rom clear distance between flanges at the section investigation, mm

506.5.3 For shear rupture on coped beam end cormelchC'1\1 see Section 510.5. 506.5.4 Maximum hit", limits are given in Section 507. 506.5.5 An alternative design method for plate utilizing tension field action is given in Section 507.

506.4.2 Members With Non-compact Sections

506.6 TRANSVERSE STIFFENERS

506.4.2.1 For box-type and tubular flexural members that meet the non-compact section requirements of Section 502.6, the allowable stress is:

506.6.1 Intermediate stiffeners are required when the hit", is greater than 260 and the maximum web shear /vis greater than that permitted by Equation (506-16).

(506-14) 506.4.2.2 Lateral bracing is not required for a box section whose depth is less than 6 times its width. Lateral-support requirements for box sections of larger depth-to-width ratios must be determined by special analysis.

506.6.2 The spacing of intermediate stiffeners, required, shall be such that the web shear stress will exceed the value for Fv given by Equation (506-16) (507-4), as applicable, and

a ( 260 ,\2 -::::; - - - ) and 3.0 h (hltw)


5-21

BEAMS AND OTHER FLEXURAL MEMBERS

7 BUILT-UP MEMBERS

When the effective slenderness ratio S is less than Cc :

7.1 Where two or more rolled beams or channels are side-by-side to form a flexural member, they shall be ;onnectea together at intervals of not more than 1.5 meter.

olllzh-,OOlts and separators are permitted, provided that, beams having a depth of 300 mm or more, no fewer than bolts shall be used at each separator location. When

;onceIJttrated loads are carried from one beam to the other, distributed between the beams, diaphragms having

,uu.,,""'" stiffness to distribute the load shall be riveted, bolted or welded between the beams.

(

S2 JFy

1.0

2C c 2

Fay = 5 3S S3 -+---- 3 8C c 8Cc 3

(506-19)

When the effective slenderness ratio S exceeds C Fay

121[2 E

:

(506-20)

23S 2

where: Kilroy for weak axis bending and Kjlrox for strong axis bending WEB-TAPERED MEMBERS K = effective length factor for a prismatic member The design of tapered members meeting theKr = effective length factor for a tapered member as determined by an analysis· requirements of this Section shall be governed by the I = actual unbraced length of member, mm provisions of Section 506. rox strong axis radius of gyration at the smaller end of a tapered member, mm 506.8.2 General Requirements roy = weak axis radius of gyration at the smaller end of tapered ;)U~,.o •.",.1 In order to qualify under this Specification, a member, mm tapered member must meet the following requirements: 506.8.5 Allowable Flexural Stress" It shall' possess at least one axis of symmetry which 506.8.5.1 Tension and compression stresses on extreme shall be perpendicular to the plane of bending if moments are present. fibers of tapered flexural members, in MPa, shall not The flanges shall be of equal and constant area. exceed the following values: The depth shall vary linearly as: S

d

~) doll+Y ~ (

K.

where:

do = depth at smaller end of member, mm dL = depth at larger end of member, mm

'Y (dL _do)/do :::; the smaller of O. 268 (Lido) or 6.0 distance from the smaller end of member, mm

unbraced length of member measured between the

center of gravity of the bracing members, mm

-~[1 0~v IF 3 . 6B IF + F j <060F 2

VI -

(506-18)

"sy

Ffrt

Y

(506-21)

'W'!

=B~Fsy2+F,*/

(506-22)

In the above equations,

F = sy

82,740 hsLdo I AJ

506.8.3.1 The allowable tensile stress of tapered tension members shall be determined in accordance with Section 504.2.

506.8.4.1 On the gross section of axially loaded tapered "nrnnT·"'.....inn members, the allowable compressive stress, in MPa, shall not exceed the following:

Y -.

unless fi,y:::; F/3, in which case

506.8.3 Allowable Tensile Stress

506.8.4 Allowable Compressive Stress

2

(506-23)

(506-24)

where: h, = factor equal to

h". =

factor equal to

1.0+0.0230'Y~Ldo I AJ 1.0+0.00385y~LI r To

radius of gyration of a section at the smaller end, considering only the compression flange. plus 1/3 See Commentary Appendix F7.3 of the M..anual of Steel Construction, Allowable Stress Design. 9th Edition. "See CommentaIy Appendix F7A of the Manual of Steel Construction, Allowable Stress Design. 9th Editi.on.


STRUCTURAL STEEL

5-22

of the compression web area, taken about an axis in the plane of the web, mm area of the compression flange, mm2

Af =

506.8.6.1 The allowlihle shear stress of tapered flexural members shall be in accordance with Section :06 5. 506.8.7 Combined Flexural and Axial Force

and where B is determined as follows: a.

~I

When the maximum moment M2 in three adj'acent segments of approximately equal unbraced length is located withirf'he central segment and M J is the larger moment at one end of the three-segment portion of a member:· B=I+0.37(1+ Ml J+0.50 Y(I+ Ml

-

b.

M2

M2

J~1.0

fb2

c.

fb2

~ 1.0

~ 1.0

1.75 1+0.25.[y

J< LO

(506-29)1

-~-

~~

fa 0.60}~

(506-27)

(506-28)

where Y = (dL - do)/do , calculated for the unbraced length adjacent to the point of zero bending stress.

+ fh Ffry

:0;

fao + fbi Fay F by

:0;

(506-30)~

1.0

where: Fay= axial compressive stress permitted in the absence of bending moment, MPa bending stress permitted in the absence of axial force, MPa Euler stress divided by factor of safety, MPa, equal to:

where lb is the actual unbraced length in the plane of bending and rbo is the corresponding radius of gyration at its smaller end .fao = computed axial stress at the smaller end of the member or unbraced segment thereof, as applicable, MPa fbI = computed bending stress at the larger end of the member or unbraced segment thereof, as applicable, MPa C'm= coefficient applied to bending term In equation =

1+0.1[:~O J+0.3[:~0 J2 e;

506.8.6 Allowable Shear

-~~

1.0

WhenfaJFay:O; 0.15, Equation (506-31) is permitted in lieu ofEquations (506-29) and (506-30),

(506-26)

When the computed bending stress at the smaller end of a tapered member or segment thereof is equal to zero:

B=

J+

and

In the foregoing, Y = (dL - do)/do is calculated for the unbraced length containing the maximum computed bending stress. d.

(~: (;~J (k F' ey

When the largest computed bending stress .fb2 occurs at the smaller end of two adjacent segments of approximately equal unbraced length and fh! is the computed bending stress at the larger end of the two segment portion of a member:'·

B =1+ 0.55(1 + fbi J + 2.2Y(1 + fbi J fb2 fb2

I

(506-25)

When the largest computed bending stress fb2 occurs at the larger end of two adjacent segments of appropriately equal unbraced lengths and fbJ is the computed bending stress at the smaller end of the two-segment portion of a member:' B = 1+0.58(1+ fbI J-0.70 Y(I+ fbi J

506.8.7.1 Tapered members and unbraced ~egments thereof I subjected to both axial compression and bending stresses shall be proportioned to satisfy the following requirement:

(506-33)

<..""1

when the member is subjected to end moments which cause single curvature bending and approximately equal computed bending stresses at the ends

• ,\111112 is considered as negative when producing single CUTyature. In the rare case where M/N!2 is positive, it is recommended it be taken as zero.

'/b1!fi2 is considered as negative when producing single curvature. If a point 9f contrafiell:ure occurs in one of two adjacent unbraced segments, fi,/fi,:! i~ considered as positive. The ratiofi,/fi,:! '" O.

=

l-o.l F') faa 1+ rfaa Y F') I

0 .6

<"'{

Association of Structural EJlQineers of the Philippines

\.

ey

PLATE GIRDERS

the computed bending stress at the smaller end of the length is equal to zero.

Kllr 2: Cc and combined stresses are checked along the length, fao may be replaced by fa, may be replaced by A in Equations (506-29) and

5-23

SECTION 507 - PLATE GIRDERS 507.1 SCOPE

\;U1''''1'''''''1

1).

507.1.1 Plate girders shall be distinguished from beams on the basis of the web slenderness ratio 11 't,... When this value is greater than the 2547/.[i;~ provisions of this Section shall apply for allowable bending stress, otherwise Section 506 is applicable. 507.1.2 For alIowable shear stress and transverse stiffener design see appropriate Articles in Section 506 or this section if tension field action is utilized.

507.2 WEB SLENDERNESS LIMITATIONS 507.2.1 When no transverse stiffeners are provided or when transverse stiffeners are spaced more than 1lh times the distance between flanges:

!!.- <

96,530 t,., - .JFy(Fy + 114)

(507-1)

507.2.2 When transverse stiffeners are provided, spaced not more than llh times the distance between flanges:

h

5,250

(507-2)

<--

tll' -

~F.vf

507.3 ALLOWABLE BENDING STRESS 507.3.1 When the web depth-to-thickness ratio exceeds the 254 7/.[i;~ maximum bending stress in the compression flange shall not exceed: (507-3)

where:

Fb = applicable bending stress given in Section 506,MPa RPG =1 0.0005 A,. (!!.-1996J:S;LO

Af t

JF;

A 12 + --2!..(3a. -0.3)

Re=--........::.----

.0

(non-hybrid girders, Re = 1.0)


STRUCTURAL STEEL

5·24

Aw= area of web at the section under investigation, mm2 Af = area of compression flange, mm2 a = 0.6 FywlFb ~ 1.0

A

l-c,,[a

s(

507.4.1 Except as herein provided, the largest average web shear,!., in MPa, computer for any condition of complete or partial loading, shall not exceed the value given by Equation (506-16). 507.4.2 Alternatively, for girders other than hybrid girders, if intermediate stiffeners are provided and spaced to satisfY the provisions of Section 507.5 and if C" ~ I, the allowable shear including tension field action given by Equation (507 4) is permitted in lieu of the value given by Equation (506 16).

+

I-Cv ) 1.15~1 +(alh)2

AS(

-

--

'~

:

507.5.1 Transverse stiffeners shall meet the requirements of Section 506.6. 507.5.2 In girders designed on the basis of tension field action, the spacing between stiffeners at end panels, at panels containing large holes, and at panels adjacent to panels containing large holes shall be such that Iv does not exceed the value given by Equation (506-16). 507.5.3 Bolts and rivets connecting stiffeners to the girder web shall be spaced not more than 300 mm. on centers. If intermittent fillet welds are used, the clear distance between welds shall not be more than 16 times the web thickness nor more than 250 mm. 507.5.4 The moment of inertia, 1st. of a pair of intermediate stiffeners, or a single intermediate stiffener, with reference to an axis in the plane of the web, shall be limited as follows:

~1+(alh)2

h

YDht

507.5.6 When the greatest shear stress.tv in a panel is than that permitted by Equation (507-4), the reduction this gross area requirements is permitted in like proportion. 507.5.7 Intermediate stiffeners required by Equation 4) shall be connected for a total shear transfer, in N linear millimeter of single stiffener or pair of stiffeners, less than:

j,., where Fy

"",

-

where: C'" a, h, and t are as defined in Section 506.5 Y = ratio of yield stress of web steel to yield stress stiffener steel

D = 1.0 for stiffeners furnished in pairs

1.8 for single angle stiffeners 2.4 for single plate stiffeners

(507-4)*

507.5 TRANSVERSE STIFFENERS

\

=~ ~:[~+(al(i)/;J.YDh)t. 2

507.4 ALWWABLE SHEAR STRESS WITH TENSION FIELD ACTION

(alh)2

=

h

(5:~

J

yield stress ofweb steel, MPa.

507.5.8 This shear. transfer may be reduced in the proportion that the largest computed shear stress j;, in adjacent panels is less than that permitted by JJI.J'L.li1L1Ul (507-4). However, rivets and welds in

stiffeners which are required to transmit to the web

applied concentrated load or reaction shall be nr"nr,.-t;,... for not less than the applied load or reaction.

n",

507.5,9 Intermediate stiffeners may be stopped short of

tension flange, provided bearing is not needed to transmit

concentrated load or reaction. The weld by

intermediate stiffeners are attached to the web shall

terminated not closer than 4 times nor more than 6 times

web thickness from the near toe of the web-to-flange

When single stiffeners are used, they shall be attached

the compression flange, if it consists of rectangu lar plate, .

resist any uplift tendency due to torsion in the plate.

lateral bracing is attached to a stiffener, or a pair

stiffeners, in tum, these shall he connected to

compression flange to transmit 1% of the total flange

unless the flange is composed only ofangles.

(507-5)

507.5.5 The gross area (total area, when stiffeners are furnished in pair), in mm2 , of intermediate stiffeners spaced as required for Equation (507-4) shall be not less than:

• Equation (507-4) recognizes the contribution of tension field action.

Assochltion of structural Engineers of the Philippines

PLATE GIRDERS & COMBINED STRESSES

5·25

SECTION 508 - COMBINED STRESSES Plate girder webs which depend upon tension field as provided in Equation (507-4), shall be so .~~,"'u"""'rl that bending tensile stress, due to moment in plane of the girder web, shall not exceed 0.60Fy . nor ( 0.825 - 0.375 fv \

IFy

508.1 SCOPE 508.1.1 The strength of members subjected to combined stresses shall be determined according to the provisions of this Section.

(507-8)

Fl')

508.1.2 This Section pertains to doubly and singly

computed average web shear stress (total shear divided by web area), MPa allowable web shear stress according to Equation (507-4), l\tIPa

symmetrical members only. See Section 505 for determination of Fa and Section 506 for determination of Fhx and Fby .

The allowable shear stress in the webs of girders flanges and webs with yield point greater than 448 shall not exceed the values given by Equation (506 ifthe flexural stress in the flange./i, exceeds 0.75ft,.

508.2 AXIAL COMPRESSION AND BENDING 508.2.1 Members subjected to both axial compression and bending stresses shall be proportioned to satisfY the following requirements:

(508-1)

(508-2) when fi/Fa ~ 0.15, Equation (508-3) is permitted in lieu of' Equations (508-1) and (508-2):

fa +Ar + iby Fa FO•T Fby

~1.0

(508-3)

508.2.2 In Equations (508..:1), (508-2) and (508-3), the subscripts x and y, combined with subscripts b, m and e,

indicate the axis of bending about which a particular stress or design properly applies, and

= axial compressive stress that would be permitted if . axial force alone existed, MPa Fb = compressive bending stress that would be permitted if bending moment alone existed, MPa Fa

F' e

121t2 E

Euler stress divided by a factor of safety, MPa(In the expression for F'e, I" is the actual unbraced length in the plane of bending and rb is the corresponding radius of gyration. K is the effective length factor in the plane of bending) As in the case of Fa, F" and


of


STRUCTURAL STEEL

5-26

0.60~.,

F'e may be increased 113 in accordance with Section 501.5.2.

fa

computed axial stress, MFa

,in

= computed compressive bending stress at the point

c

under consideration, MFa

Coefficient whose value shall be taken as follows:

a.

For compression members in frames subject to joint

translation (sidesway),

0.85

b.

For rotationally restrained compression members in

frames braced against joint translation and not

subject to transverse loading between their supports

in the plane of bending,

508.3.2 However the computed bending compressive stress arising from an independent load source relative to the axial tension, taken above, shall not exceed the applicable value required in Section 506.

CIII =0.6 0.4(M j /M 2 ) where M r M 2 is the ratio of the smaller to larger

moments at the ends of the portion of the member

unbraced in the plane of bending under

consideration. MI'M2 is positive when the member is

bent in reverse curvature, negative when bent in

single curvature.

c.

em

~

'I

1

\' , " i'l

i.

, ,,

~"

~

For compression members in frames braced against

joint translation in the plane of loading and subjected

to transverse loading between their supports, the

may be determined by an analysis.

value of However, in lieu of such analysis, the following

values are permitted:

:-1

~ -1

11.

For members whose ends are restrained against rotation in the plane of bending, em = 0.85 For members whose ends are unrestrained against

rotation in the plane of bending,

== 1.0

em

508.3 AXIAL TENSION AND BENDING 508.3.1 Members subject to both axial tension and bending

stresses shall be proportioned at all points along their length

to satisfy the following equation:

(508-4)

where Ji> is the computed bending tensile stress, .f~ is the

computed axial tensile stress, Fh is the allowable bending

stress and Ft is the governing aiJowable tensile stress

defined in Section 504.2.


COMPOSITE CONSTRUCTION

.SECTION 509 - COMPOSITE

CONSTRUCTION

509.1 SCOPE 509.1.1 This Section applies to steel beams supporting a reinforced concrete slab so interconnected that the beams and the slab act together to resist bending. Simple and .. continuous composite beams with shear connectors and concrete-encased beams, constructed with or without temporary shores, are included.

509.2 DEFINITION 509.2.1 Two cases of composite members are recognized: Totally encased members which depend upon natural bond for interaction with the concrete and those with shear connectors (mechanical anchorage to the slab) with the steel member not necessarily encased. 509.2.2 A b~am totally encased in concrete cast integrally with the slab may be assumed to be connected to the .concrete by natural bond, without additional anchorage, provided that: 1.

2. 3.

Concrete cover over beam sides and soffit is at least 50mm. The top of the beam is at least 38 mm below the top and 50 mm above bottom of the slab. Concrete encasement contains adequate mesh or other reinforcing steel throughout the whole depth and across the soffit ofthe beam to prevent spalling of the concrete.

509.2.3 Shear connectors must be provided for composite action if the steel member is not totally encased in concrete. The portion of the effective width of the concrete slab on each side ofthe beam centerline shall not exceed:

a. b. c.

One-eighth of the beam span, center-to-center of

supports;

One-half the distance to the centerline of the adjacent beam; or The distance from the beam centerline to the edge of the slab.

509.3 DESIGN ASSUMPTIONS 509.3.1 Encased beams shall be proportioned to support, unassisted, all dead loads applied prior to the hardening of the concrete (unless these loads are supported temporarily

on shoring) and, acting in conjunction with the slab, to support all dead and live loads applied after hardening of the concrete, without exceeding a computed bending stress ofO.66Fy, where F;, is the yield stress of the steel beam. The bending stress produced by loads after the concrete has hardened shall be computed on the basis of the section properties of the composite section. Concrete tension stresses shall be neglected. Alternatively, the steel beam alone may be proportioned to resist, unassisted, the positive moment produced by all loads, live and dead, using a bending stress equal to 0.76Fy, in which case temporary shoring is not required. 509.3.2a When shear connectors are used in accordance with Section 509.5, the composite section shall be proportioned to support all of the loads without exceeding the allowable stress prescribed in Section 506.2.1, even when the steel section is not shored during construction. In positive moment areas, the steel section is exempt from compact flange criteria (Section 502.6) and there is no limit on the unsupported length ofthe compression flange. 509.3.2b Reinforcement parallel to the team within the effective width of the slab, when anchored in accordance with the provisions of the applicable building code, may be included in computing the properties of composite sections, provided shear connectors are furnished in accordance with the requirements of Section 509.5. The section properties of the composite section shall be computed in accordance with the elastic theory. Concrete tension stresses shall be neglected. For stress computations, the compression area of lightweight or normal weight concrete shall be treated as all equivalent area of steel by dividing it by modular ratio n for normal weight concrete of the strength specified when determining the section properties. For deflection calculations, the transformed section properties shall be based on the appropriate modular ratio n for the strength and weight concrete specified, where 11 = E Ec. 509.3.2c In cases where it is not feasible or necessary to provide adequate connectors to satisfy the horizontal shear requirements for full composite action, the effective section modulus shall be determined as, S4J Ss +

~~;~~I (Str

Ss)

(509-1)

where: Vh and V'n are as defined in Section 509.) S, = section modulus ofthe steel beam referred to its bottom flange, mm3 SI1' = section modulus of the transformed composite section referred to its bottom flange, based upon maximum permitted effective width of concrete flange (Section 509.2), mm 3


STRUCTURAL STEEL

5·28

509.3.2d For composite beams constructed without temporary shoring, stresses in the steel section shall not exceed 0.90Py . Stresses shall be computed assuming the steel section alone resists all loads applied before the concrete has reached 75% of its required strength and the effective composite section resists all loads applied after that time. 509.3.2e The actual section modulus of the transformed composite section shall be used in calculating the concrete flexural compression stress and. for construction without temporary shores, this stress shall be based upon loading applied after the concrete has reached 75% of its required strength. The stress in the concrete shall not exceed O.4~f'c.

509.4 END SHEAR 509.4.1 The web and the end connections of the steel beam shall be designed to carry the total reaction.

, 509.5 SHEAR CONNECTORS

I,

509.5.1 Except in the case encased beams, as defined in Section 509.3.1, the entire horizontal shear at the junction of the steel beam and the concrete slab shall be assumed to be transferred by shear connectors welded to the top flange of the beam and embedded in the concrete. For full composite action with concrete subject to flexural compression, the total horizontal shear to be resisted between the point of maximum positive moment and points of zero moment shall be taken as the smaller value using Equations (509-2) and (509-3): (509-2)" and

T.. -

-F" A srl~ /"1

"11- ..v r

(509-4)

where: total area oflongitudinal reintorcing steel at the interior support located within the effective flange width specified in Section 509.2, mm1 specified minimum yield stress of the longitudinal reinforcing steet MPa 509.5.3 For full composite action, the number of connectors resisting the horizontal shear, V" q. where q. the allowable shear load for one connector, is given in Table 509-1 for flat somt concrete slabs made with ASTM C33 aggregates. For flat soffit concrete slabs made with rotary kiln produced aggregates, conforming to ASTM C330 with concrete unit weight not less than 1440 kg/m\ the allowable shear load for one connector is obtained by multiplying the values from Table 509-1 by the coefficient from Table 509·2. 509.5.4 For partial composite action with concrete subject to flexural compression, the horizontal shear V'n to be used in computing S~tTshall be taken as the product of q times the number of connectors furnished between the point of maximum moment and the nearest point of zero moment. 509.5.5 The value of V'n shall not be less than Y4 the smaller value of Equation (509-2), using the maximum permitted effective width of the concrete flange, or Equation (509-3), The effective moment of inertia for deflection computations shall be determined by:

F

Ieff =Is + ,1~(Ilr -Is)

, r II

(509-5)

where: 4 = moment of inertia ofthe steel beam, mm ft,. moment of inertia of the transformed composite 4 section, mm

Is

(509-3) where: 1', specified compression strength of concrete, MPa Ac actual area of effective concrete flange defined Article 509.1, rnm2 2 As area of steel beam, mm

In

509.5.2 In continuous composite beams where longitudinal reinforcing steel is considered to act compositely with the steel beam in the negative moment regions the total horizontal shear to be resisted by shear connectors between an interior support and each adjacent point of contra·flexure shall be taken as: • The term 1I2Fl'.A', shall be added to the right-hand side of Equation (509-2) if longitudinal reinforcing steel with area A 's located within the effective width of the concrete flange is included in the properties of the composite section.

509.5.6 The connectors required each side of the point of maximum moment in an area of positive bending may be uniformly distributed between that point and adjacent points of zero moment, except that N::. the number of shear connectors required between any concentrated load in that area and the nearest point of zero moment, shall be not less than that determined by Equation (509-6).

N2

M(3 1 N( ( ----1) \Mmax (3-1

(509-6)

where: M moment (less than the maximum moment) at a concentrated load point NJ number of connectors required between point of maximum moment and point of zero moment,

Association of Structural Engineers of the Phitippines

COMPOSITE CONSTRUCTION

determined by the relationship VJq or V'hlq, as applicable

Sir f3 == c;-

,) s

TABLE 509-1 Allowable Horizontal Shear Load For One Connector , kN" Specified Compressive Strength of Connectarb 1_______ ~'g!lcre!~__'Lc1J\:1J>a- .

Seff or - - , as applicable

!

Ss

509.5.7 For a continuous beam, connectors required in the region of negative bending may be uniformly distributed between the point of maximum moment and each point of zero moment. 509.5.8 Shear connectors shall have at least 25 mm. of lateral concrete cover, except for connectors installed in the ribs of formed steel decks. Unless located directly over the web, the diameter of studs shall not be greater 2Y2 times the thickness of the flange to which they are welded. The minimum center-to-center spacing of stud connectors shall be 6 diameters along the longitudinal axis of the supporting composite beam and 4 diameters transverse to the longitudinal axis of the supporting composite beam. The maximum center-to-center spacing of stud connectors shall not exceed 8 times the total slab thickness.

509.6.1 Composite construction of concrete slabs on formed steel deck connected to steel beams or girders shall be designed by the applicable portions of Section 509.2 through 509.5, with the following modifications.

_-_

;

24

:

~ 28

26.244

..•

40.923

20mm dia. x 75mm

hooked or headed

59.161

22mm dia. x 90mm

hooked or headed

stud

_1_._.§2}2~_J..-.Z1J?9 [~~9.(j_r.. c

i 0.753w 0.82311'c I 0.8751t,c ChannelC4 x 5.4-10-:-80-5~;c--ri5~875wc, ·0.928;;," x 4.1

i

-Ch~~ei C5 -;;·6.'7·-l0.858-11TTo:928;:;·c·-rO.980J~;:( . :Applicableoniyto conc;ete made wiih ASTrvf C33 aggregates:' The allowable horizontal loads tabulated arc also for studs longer than shown. Ow len or channel, nun

509.6.1.2 Deck Ribs Oriented Perpendicular to Steel Beam or Girder

509.6.1.1 General 1.

21

. 12mm dia. x 50mm hooked or headed stud - - . - .... --_.-.. _. __.. 16mm dia. x 65mm hooked or headed stud

Channel

509.6 COMPOSITE BEAMS OR GIRDERS WITH FORMED STEEL DECK

5-29

Section 509.6 is applicable to decks with nominal rib height not greater than 75 mm. The average width concrete rib or haunch Wr shall be not less than 50 mm, but shall not be taken in calculations as more than the minimum clear width near the top of the steel deck. See Section 509.6.1.3 items 2 and 3, for additional provisions The concrete slab shall be connected to the steel beam or girder with welded stud shear connectors 20 mm or less in diameter (AWS D1.1, Section 7, Part F). Stud shear connectors shall extend not less than 38 mm above the top of the steel deck after installation. The slab thickness above the steel shaH be not less than 50 mm.

1.

2.

3.

Concrete below the top of the steel deck shall be neglected when determining section properties and in calculating Ac for Equation (509-2) The spacing of stud shear connectors along the lenglh of a supporting. beam or girder shall not exceed 900 mm. The aUowable horizontal shear load per stud connector q shall be the value stipulated in Section 509.5.1 (Tables 509-] and 509-2) multiplied by the following reduction factor: 0.85 lr I,(H, ·( --!i l [ii; )\ "r hr


wI'

I

j - ' -1.0 ::S:1.0

J\

)

(509-7)

STRUCTURAL STEEL 5-30

TABLE 509-2

Coefficients for Use with Concrete Made with

C330 A re ates

3

Specified Air Dry Unit Weight of Concrete, kN/m Compressi

i ve Strength

17.3 UU j 18.8 of Concrete

i

where hr and Hs are as defined in Section 509.6.1.2 and Wr

is the average width of concrete rib or haunch (see Section 509.6,1.1 item 2, and Section 509.6.1.3 item3)

509.7 SPECIAL CASES

(f'c)

509.7.1 When composite construction does not confow to the retirements of Section 509.2 through 509.6, the allowable load per shear connector must be established by a suitable test program.

s: 28.MPa

._._._-_...+---;...-

::::34 MPa

Where:

II,. = nominal rib height, mm Us "'" length of stud connector after welding, mm, not to Nr

WI'

4.

exceed the value (h r+75) in computations, although the actual length may be greater = number of stud connectors on a beam in one rib, not to exceed 3 in computations, although more than 3 studs may be installed. = average width of concrete rib, mm (see Section 509.6.1.2) To resist uplift, the steel deck shall be anchored to all compositely designed steel beams or girders at a spacing not to exceed 400 mm. Such anchorage may be provided by stub connectors, a combination of stud connectors and arc spot (puddle) welds, or other devices specified by designer.

509.6.1.3 Deck Ribs Oriented Parallel to Steel Beam or Girder 1.

2.

3.

4.

Concrete below the top of the steel deck may be included when determining section properties and shall be included in calculating Ac for Equation (509-2). Steel deck ribs over supporting beams or girders may be split longitudinally and separated to form a concrete haunch. When the nominal depth of steel deck is 38 mm or greater, the average width Wr of the supported haunch or rib shall be not less than 50 mm for the first stud in the transverse row plus 4 stud diameters for each additional stud. The allowable horizontal shear load per stud connector q shall be the value stipulated in Section 509.5 (Tables 509-1 and 509-2), except when the ratio wrhr is less than 1.5, the allowable load shall be multiplied by the following reduction factor:

(11',. I(H$

)

0.6j - ) --LO ~1.0

(509-8)

\ h,. \ hr


CONNECTIONS, JOINTS AND FASTENERS

CTION 510 - CONNECTIONS, INTS AND FASTENERS

510.1.1 This Section applies to connections consisting of elements (plates, stiffeners, gussets, angles, bralckc~s) and connectors (welds, bolts, rivets).

510.2 GENERAL PROVISIONS 510.2.1 Design Basis

5-31

510.2.5 Connections of Tension and Compression Members in Trusses 510.2.5.1 The connections at ends of tension or compression members in trusses shall develop the force due to the design load, but not less than SO% of the effective ~tr~gth of th~ member, unless a smaller percentage is Justlfiep by engmeering analysis that considers other factors including handling, shipping and erection. 510.2.6 Minimum Connections 510.6.~.1 Connections carrying calculated stresses, except for lacmg, sag bars and girts, shall be designed to support not less than 26.7 kN.

510.2.7 Splices in Heavy Sections

510.2.1.1 Connections shall be proportioned so that the calculated stress is less than the allowable stress determined (1) by structural analysis for loads acting on the structure or (2) as a specified proportion of the strength of the connected members, whichever is appropriate. 510.2.2 Simple Connections 510.2.2.1 Except as otherwise indicated in the design documents, connections of beams, girders or trusses shall be designed as flexible and ordinarily may be proportioned for the reaction shears only. Flexible beam connections shall accommodate end rotations of unrestrained (simple) beams. To accomplish this, inelastic deformation in the connection is permitted.

510.2.7.1 This article applies to ASTM A6 Group 4 and 5 rolled shapes, or shapes built-up by welding plates more than SO mm thick together to form the cross section', and where the cross section is to be spliced and subject to primary tensile stresses due to tension or flexure. 510.2.7.2 When tensile forces in these sections are to be transmitted through splices by full-penetration groove welds, material notch-toughness requirements as given in Sect~on S01.3.1.3, weld access holes details as given in SectIOn SI0.2.8, compatible welding procedures as given in Section Sl 0.3.7, welding preheat requirements as given in Section S10.3.8 and thermal cut surface preparation and inspection requirements as given in Section S13.2.2 apply.

•

510.2.7.3 At tension splices in these sections, weld tabs and backing shall be removed and the surfaces ground smooth.

510.2.3 Moment Connections 510.2.3.1 End connections of restrained beams, girders and trusses shall be designed for the combined effect of forces resulting form moment and shear induced by the rigidity of the connections. 510.2.4 Compression Members with Bearing Joints 510.2.4.1 When column bear on bearing plates or are finished to bear at splices, there shall be sufficient connectors to hold all parts securely in place. 510.2.4.2 When other compression members are finished to bear, the splice material and its connectors shall be arranged to hold all parts in line and shall be proportioned for S(Y}-o of the strength of the member. 510.2.4.3 All compression joints shall be proportioned to . resist any tension developed by the specified lateral loads acting in conjunction with 7S% of the calculated dead-load stress and no live load.

510.2.7.4 When splicing these sections, and where the section is to be used as a primary compression member, all weld access holes required to facilitate groove welding operations shall satisfY the provisions of Section S10.2.8. 510.2.7.5 Alternatively, splicing of such members subject to compression, including members which are subject to tension due to wind or seismic loads, may be accomplished using splice details which do not induce large weld shrinkage strains such as partial-penetration flange groove welds with fillet-welded surface lap plate splices on the web, or with bolted or combination bolted/fillet-welded lap plate splices.

\\'hen the indi\ldual elements of the eros" section are spliccd prior to being joined to form the cross sectilm in accordance \\ itb AWS D1. L Article 3.4,6. the appliCllbk pn.l\j,ion·; of AWS nu applY ill ht'u of the requirements of this 5ectilm. .


STRUCTURAL STEEL

5-32

510.2.8 Beam Copes and Weld Access Holes 510.2.8.1 All weld access holes required to facilitate welding operations shall have a length from the toe of the weld preparation not less than 1V2 times the thickness of the material in which the hole is made. The height of the access hole shall be adequate for deposition of sound of weld metal in the adjacent plates and provide clearance for weld tabs. In hot rolled shapes and built-up shapes, all beam copes and weld access holes shall be shaped free of notches or sharp re-entrant corners except that, when fillet web-to flange welds are used in built-up shapes, access holes are permitted to terminate perpendicular to the tlange. 510.2.8.2 For Group 4 and 5 shapes and built-up shapes of material more than 50 mm thick, the thermally cut surfaces of beam copes and weld access holes shall be ground to bright metal and inspected by either magnetic particle or dye penetrant methods. If the curved transition portion of weld access holes and beam copes are formed by predrilled or sawed holes, that portion of the access or cope need not be ground. Weld access holes and beam copes in other shapes need not be ground nor inspected by dye penetrant • or magnetic particle.

alteration, and the welding need be adequate to carry only the additional stress. 510.2.11 High-Strength Bolts (n Slip-Critical Connections In Combination With Rivets 510.2.11.1 In both new work and alterations, high-strength bolts in slip-critical connections may be considered as sharing the load with rivets. 510.2.12 Limitations on Bolted and Welded Connections 510.2.12.1 Fully-tensioned high-strength bolts (see Table 510.3.7) or welds shall be used for the following connections: Column splices in all tier structures 60 meters or more in height Column splices in tier structures 30 to 60 meters in height, if the least horizontal dimension is less than 40% of the height Column splices in tier structures less than 30 m in height, if the least horizontal dimension is less than 25% of the height

510.2.9 Placement of Welds, Bolts and Rivets 510.2.9.1 Group of welds, bolts or rivets at the ends of any member which transmit axial stress into that member shall be sized so the center of gravity of the member, unless provision is made for the eccentricity. The foregoing provision is not applicable to end connections of statically loaded single-angle, double-angle and similar members. Eccentricity between the gravity axes of such members and the gage lines for their riveted or bolted end connections may be neglected in statically loaded members, but shall be considered in members subject to fatigue loading.

Connections of all beams and girders to columns and of any other beams and girders on which the bracing of columns is dependent, in structures over 38 meters in height. In all structures carrying cranes of over 5-ton capacity: roof splices and connections of trusses to column, column splices, column bracing, knee braces and crane supports Connections for supports of running machinery or of other live loads, which produce impact or reversal of stress Any other connection stipulated on the design plans.

510.2.9.2 See Section 510.4.10 for placement of fasteners in built-up members made of weathering steeL 510.2.10 Bolts in Combination with Welds 510.2.10.1 In new work, A307 bolts or high-strength bolts used in bearing-type connections shall not be considered as sharing the stress in combination with welds. Welds, if used, shall be provided to carry the entire stress in the connection. High-strength bolts proportioned for slip critical connections may be considered as sharing the stress with the welds. 510.2.10.2 In making welded alterations to structures, existing rivets and high-strength bolts tightened to the requirements for slip-critical connections are permitted for carrying stresses resulting from loads present at the time of

510.2.12.2 In aU other cases, connections may be made with high-strength bolts tightened to the snug-tight condition or with A307 bolts. 510.2.12.3 For the purpose of this section, the height of a tier structure shall be taken as the vertical distance from the curb level to the highest point of the roof beams in the case of tlat roofs, or to the mean height of the gable in the case of roofs having a rise of more than 2-2/3 in 12. Where the curb levels has not been established, or where the structure does not adjoin a street, the mean level of the adjoining land shall be used instead of curb level. Penthouses may be excluded in computing the height of the structure.



510.3 WEL.DS 510.3.1 All provisions of the American Welding Society structural Welding Code-Steel, AWS DI.1, except Sections 2.3.2.4, 2.5, 8.13.1, 9, and 10, apply to work performed under this Specification. 510.3.1 Groove Welds 510.3.2.1 Effective Area The effective area a groove welds shall be considered as the effective length of the weld times the effective throat thickness. 2.

The effective length a groove weld shall be the width ofthe part joined.

3.

The effective throat thickness of a complete penetration groove weld shall be the thickness of the thinner part joined,

4.

The effective throat thickness of a partial-penetration groove weld shall be as shown in Table 510-1.

5.

The effective thickness of a partial-penetration groove weld shall be as shown in Table 510-1.

6.

7.

The effective throat thickness of a flare groove weld when flush to the surface of a bar or 90° bend in a formed section shall be as shown in Table 510-2. Random sections of production welds for each welding procedure, or such test sections as may be required by design documents, shall be used to verify that the effective throat is consistently obtained. Larger effective throat thicknesses than those in Table 5 I 0-2 are permitted, provided the fabricator can establish by qualification that he can consistently provide such larger effective throat thicknesses. Qualification shall consist of sectioning the weld normal to its axis, at mid-length and terminal ends, Such sectioning shall be made on a number of combinations of materials sizes representative of the range to be used in the fabrication or as required by the designer.

5·33

ABLE 510-1

Effective Throat Thidmess of Partial

penetration Groove 'Welds

Included Effective Angle at Welding Throat Welding Process Position Root of Thickness Groove Shielded metal arc Submerged arc ) .o((lj~iTlt~ Depth of BevelorV : chamfer Gas metal arc joint .:::: 60° I All

~evel or V i Depth of joint < 60°! chamfer minus but.:::: 45° 3mm

Flux-cored arc

TABLE 510-2

Effective Throat Thickness of Flare Groove Welds

Type of Weld Radius (R) of I Effective Throat Bar or Bend Thickness All i 5/] 6R Flare b e v e l : .....8l'()()ve_. _ _~~~ ____ "~._,_"._.._~_""._."_._ Flare V-s!?ove .L. _ _~L_.~-,... _~_!L21(_~_ . a

Use (3/8)R for Gas Metal Arc Welding (except short circuiting

transfer vrocess) when R.:::: 12 mm.

TABLE 51O~3

Minimum Effective Throat Thickness of Partial

enetration Groove Welds

Minimum Effective Throat Thickness' (mm) 3 5 6

0_,_. _ .._....

Over 38 to 57 Over 57 Over 150 a See Section 510.3.

--.---~-~-.-.-----


,~

~--,- '-~'"'-"'--"---'----'~'

......... . L_ _

510.3.2.2 Limitations. The mlntmum effective throat thickness of a partial-penetration groove weld shall be as shown in Table 510-3. Minimum effective throat thickness is determined by the thicker of the two parts joined, except that the weld siz~ need not exceed the thickness of the thinnest part joined. For this exception, particular care shall be taken to provide sufficient preheat for soundness of the weld.

8 10 12

.. ___.

-----"_ ..

~~ _ _.. _~ ___ ]6~.~ ..... ~~____ _

STRUCTURAL STEEL

5-34

510.3.3 Fillet Welds 510.3.3.1 Effective Area 1.

The effective area of fillet welds shall be taken as the effective length times the effective throat thickness.

2.

The effective length of fillet welds, except fillet welds in holes and slots, shall be the overall length of full-size fillets, including returns.

3.

The effective throat thickness of a fillet weld shall be the shortest distance from the root of the joint to the face of the diagrammatic weld, except that tor fillet welds made by the submerged arc process, the effective throat thickness shall be taken equal to the leg size for 10 mm and smaller fillet welds, and equal to the theoretical throat plus 3 mm for fillet welds larger than 10 mm.

4.

For fillet welds in holes and slots, the effective length shall be the length of the centerline of the weld along the center of the plane through the throat. In the case of overlapping fillets, the effective area shall not exceed the nominal cross-sectional area of the hole slot in the plane of the faying surface.

TABLE 510-4 Minimum Size of Fillet Welds Material Thickness of Minimum Size ofFil!et Thicker Part Joined (mm) \Veld" (mm) To 6 inclusive 3 .---- - 'O~e~6-i-;-i 2---'--'

-1-----'

3.

The minimum etfective length of fillet welds designated on the basis of strenbrth shall be not less than 4 times the nominal size, or else the size of the weld shall be considered not to exceed l/4 of its effective length. If longitudinal fillet welds are used alone in end connections of tlat bar tension members, the length of each tillet '"veld shall be not less than the perpendicular distance between them. The transverse spacing oflongitudinal fillet welds used in end connections of tension members shall not exceed 200 mm, unless the member is designed on the basis of effective net area in accordance with Section 502.4.

4.

The minimum size of fillet welds shall be as shown in Table 510-4. Minimum weld size is dependent upon the thicker of the two parts joined, except that the weld size need not exceed the thickness of the thinner part. For this exception, particular care shall be taken to provide sufficient preheat for soundness of the weld. Weld sizes larger than the thinner part joined are permitted if required by calculated strength. In the as-welded condition, the distance between the edge of the base metal and the toe of the weld may be less than 1.6 mm provided the weld size is dearly verifiable.

Intermittent fillet welds are permitted to transfer calculated stress across a joint or faying surface when the strength required is less than that developed by a continuous fillet weld of the smallest permitted size, and to join components of built-up members. The effective length of any segment of intermittent fillet welding shall be not less than 4 times the weld size, with a minimum of38 mm.

5.

In lap joints, the minimum lap shall be 5 times the thickness of the thinner part joined, but not less than 25 mm. Lap joints joining plates or bars subjected to axial stress shall be fillet welded along the end of both lapped parts, except where the deflection of the lapped part is sufficiently restrained to prevent opening of the joint under maximum loading.

The maximum size of fillet welds that is permitted along edges of connected parts shall be:

6.

Fillet welds in holes or slots are pern1itted to transmit shear in lap joints or to prevent the buckling or separation of lapped parts and to join components of built-up members. Such fillet welds may overlap, subject to the provision of Section 510.3. Fillet welds in holes or slots are not to be considered plug or slot welds.

7.

Slide or end tlllet welds terminating at ends or sides, respectively, ~f parts or members shalL wherever practicable, be returned continuously- around the comers for a distance not less than 2 times the nominal size of the weld. This provision shall apply to side and top fillet welds connecting brackets,

510.3.3.2 Limitations 1.

2.

• •

Material less than 6 mm thick, not greater than the thickness of the material. Material 6 mm or more in thickne'>s, not greater than the thickness of the material minus 1.6 mm, unless the weld is especially designated on the drawings to be built out to obtain full-throat thickness



5-35

beam seats ~nd similar connections, on the plane about which bending moments are computed. For framing angles and simple end-plate connections which depend upon flexibility of the outstanding legs tor connection flexibility, end returns shall not exceed four times the nominal size of the weld. Fillet welds that occur on opposite sides of a common to both welds End returns shall be indicated on the design and details drawings. 510.3.4 Plug and Slot Welds 510.3.4.1 Effective Area. The effective shearing area of piug and slot welds shall be considered as the nominal cross-sectional area of the hole or slot in the plane of the faying surface.

The length of slot for a slot weld shall not exceed 10 times the thickness of the weld. The width of the slot shall be not less than the thickness of the part containing it plus g mm, nor shall it be larger than 2Y4 times the thickness of the weld. The ends of the slot shall e semicircular or shall have the comers rounded to a radius not less than the thickness of the part containing it, except those ends which extend to the edge of the part.

6.

The thickness of plug or slots welds in material 16 mm. or less in thickness shall be equal to the thickness of the material. In material over 16 mm. thick, the thickness of the we14 shall be at least 112 the thickness of the material but not less than 16 mm.

510.3.5 Allowable Stresses

510.3.4.2 Limitations

2.

5.

Plug or slot welds are permitted to transmit shear in lap joints or to prevent buckling of lapped parts and to join component parts ofbuilt-up members.

510.3.5.1 Except as modified by the provisions of Section 511.5, welds shall be proportioned to meet the stress requirements given in Table 510-5.

The diameter of the hole for a plug weld shall not be less than the thickness of the part containing it plus 8 mm, rounded to the next larger odd 1.6 mm, nor greater than the minimum diameter plus 3 mm or 21;4 times the thickness ofthe weld.

510.3.6 Combination of Welds

3.

The minimum center-to-center spacing of plug welds shall be four times the diameter of the hole.

4.

The minimum spacing of lines of slot welds in a direction transverse to their length shall be 4 times the width of the slot The minimum center-to-center spacing in a longitudinal direction on any line shall be 2 times the length ofthe slot.

510.3.6.1 If two or more of the general types of weld (groove, fillet, plug, slot) are combined in a single joint, the effective capacity of each shall be separately computed with reference to the axis of the group in order to determine the allowable capacity of the combination. 510.3.7 Mixed Weld Metal 510.3.7.1 When notch-toughness is specitied, the process consumables for all weld metal, tack welds, root pass and subsequent passes, deposited in a joint shall be compatible to assure notch-tough composite weld metal.

National StrudJU81 Code of ,the Philippines, Volume 1

STRUCTURAL STEEL

5-36

TABLE 510-5 Allowable Stress on Weldsf Type of Weld and Stress"

Required Weld Strength Levelb•c

Allowable Stress

Complete-penetration Groove Welds --------------------------~ ..... -------------~ Tension normal to pttp('f1VP Same as base metal "Matching" weld metal shall be used. area I COInpression noimartO--:same as'base met'ilf

·····----T-

effective area _________~------.-. .----.---I

Tension or compression : Same as base metal I .

I i Weld metal wIth a strength level equal to or less than . f ld ! " h'" • permitte • d. ara11e1t 0 axIS 0 we -.-----...... ; mate mg weld metaJ IS I Shear on effective area I

! Partial-penetration Groove Weldsd

Sameas- base metal I.

--I I -----1

-----T Same as base m~ I

Comp.ression normal to effectIve area Tension or compression 'parallel to axis of weld" Shear parallel to axis of weld

.--1-----------

---J

i 0.30 * nominal tensile

'I'

I strength of weld metal

! (MPa)

Tension normal to effective area

to.30 * nominal tensile

W Id I 'th h I I i "e ~et,~ WI a st:engt . eve equal i matchmg weld metal IS permItted.

to or less than

: strength of weld metal '

: (MPa). except tensile stress

; on base metal shall not

i exceed 0.60 x yield stress

I Fillet Welds

Shear on effective area

--._--_.. _----_ ...._,---_. --_.-;--'--

Tension or compression _paralleL!.o. ofweld<

:L.--·---·-----c - - - - - - - :

Weld metal with a strength level equal to or less than "matching" weld metal is permitted.

Plug and Slot Welds Shear parallel 10 faying surfaces (on effective area)

_______________.

, 0.30 * nominal tensile .• , strength of weld metal

i

",.(M~al

________

WeJd metal with a strength level equal to or less than "matching" weld metal is permitted.

a For

definition of efTective area. see Section 5·1 OJ.

bFoT "matching" weld metal. sec Table 4. L LAWS Dtt

cWeld metal one strength le\cl stronger than "matching" weld mctal will be permitted.

dSee Section 51O.3.2.2 for a limitation on use of partial-penetration groove welded joints.

"Fillet welds and parLial-penetration groove welds joining the component elements of built-up members, such as flange-to-web

connections. may bc designed without regard to the tensile or compressive stress in these elements parallel to the axis of welds.

f The desi of connected material is oO\'emed hv Sections 504 throu h 507.



510.3.S Preheat for Heavy Shapes 510.3.S.1 For ASTM A6 Group 4 and 5 shapes and welded built-up members made of plates more than 50 rom thick, a equal to or greater than 177°C shall be used when making groove weld splices.

510.4 BOLTS, THREADED PARTS AND RIVETS 510.4.1 High-Strength Bolts Except as otherwise provided in this . Specification, use of high-strength bolts shall conform to the provision of the Specifications for Structural Joints "-Using ASTM A325 or A490 Bolts approved by the Research Council on Structural Connections of the Engineering Foundation (RCSC). 510.4.1.2 If required to be tightened to more than 50% of their minimum specified tensile strength, ASTM A449 bolts in tension and bearing-type shear connections shall have an ASTM F436 hardened washer installed under the bolt head, and the nuts shall meet the requirements of ASTM A563. 510.4.2 Size and Use of Holes 510.4.2.1 The maximum sizes of holes for bolts are given in Table 510-6, except that larger holes, required for tolerance on location of anchor bolts in concrete foundations, are permitted in column base details. 510.4.2.2 Standard holes shall be provided in member-to member connections, unless oversized, short-slotted or long-slotted holes in bolted connections are approved by the designer. Finger shims up to 6 mm may be introduced into slip-criti<;al connections designed on the basis of standard holes without reducing the allowable shear stress of the fastener. 510.4.2.3 Oversized holes are permitted in any or all plies of slip-critical connections, but they shall not be used in bearing-type connections. Hardened washers shall be installed over oversized holes in an outer ply.

5-37

holes are permitted without regard to direction of loading in slip-critical connections, but shaH be normal to the direction of load in bearing-type connections. Where long-slotted holes are used in an outer ply, plate washers or a continuous bar with standard holes, having a size sufficient to completely cover the slot after installation, shall be provided. In high-strength bolted connections, such plate washers or continuous bars shall be not less than 8 mm thick and shall be of structural grade material, but need not be hardened. If hardened washers are required for use of high-strength bolts, the hardened washers shall be placed over the outer surface of the plate washer or bar. 510.4.2.6 When A490 bolts over 25 mm diameter are used in slotted or oversize holes in external plies, a single hardened washer conforming to ASTM F436, except 8 mm minimum thickness, shall be used in lieu of the standard washer. 510.4.3 Effective Bearing Area 510.4.3.1 The effective bearing area of bolts, threaded parts and rivets shall be the diameter multiplied by the length in bearing, except that for countersunk bolts and rivets 112 the depth of the countersink shall be deducted. 510.4.4 Allowable Tension and Shear 510.4.4.1 Allowable tension and shear stresses on bolts, threaded parts and rivets shall be as given in Tab I e 5 i 0-7, in MPa of the nominal body area of rivets (before driving) or the unthreaded nominal body area of bolts and threadeQ parts other than upset rods (see footnote c, Table 510-7) High-strength bolts supporting applied load by direct tension shall be so proportioned that their average tensile stress, computed on the basis of nominal bolt area and independent of any initial tightening force, will not exceed the appropriate stress given in Table 510-7. The applied load shall be the sum of the external load any tension resulting from prying action produced by deformation of the connected parts. 510.4.4.2 When specified by the designer, the nominal slip resistance for connections having special faying surface conditions may be increased to the applicable values in the RCSC Specifications tor Structural Joints Using ASTM A325 or A490 Bolts.

510.4.2.4 Short-slotted holes are permitted in any or all plies of slip-critical or bearing-type connections. The slots are permitted without regard to direction of loading in slip critical connections, but the length shall be normal to the direction of the load in bearing-type connections. Washer shall be installed over short-slotted holes in an outer ply; when high-strength bolts are used, such washer shall be hardened.

510.4.4.3 Finger shims up to 6 mm may be introduced into slip-critical connections designed on the basis of standard holes without reducing the allowable shear stress of the fastener to that specified for slotted holes.

510.4.2.5 Long-slotted holes are permitted in only one of .the connected parts of either a slip-critical or bearing-type COnnection at an individual faying surface. Long-slotted

510.4.4.4 Design for bolts, threaded parts and rivets subject to fatigue loading shall be in accordance with Section 511.5, 1. 5


STRUCTURAL STEEL

5-38

wbere:

Bolt Dia. 12 16 20 22 25 ;::: 28

TABLE 510-6

Nominal Hole Dimensions, mm

Hole Dimensions Standard Oversize Short-slot Long-slot (Dia.) (Dia.) (Width x (Width x length) length) 14 14 x 17 16 14x32 17 21 17 x 22 17 x 40 21 24 21 x 25 21 x 48 ._.... 27 24 24x28 24x55 27 x JJ 27x 63 (d+- 1.6) x (d+l.6)x d+L6 d+8 (2,5 xd) (d+ 10)

~~"

510.4.5 Combined Tension and Sbear in Bearing-type Connections 510.4.5.1 Bolts and rivets subject to combined shear and tension shall be so proportioned that the tension stress F/ in ksi on the nominal body area Ab produced by forces applied ~o the connected parts, shall nOt exceed the values computed from the equations in Table 510-8, where f", the shear stress produced by the same forces, shall not exceed the value for shear given in Table 510-7. When allowable stresses are increased for wind or seismic loads in accordance with Section 501.5.2, the constants in the equations listed on Table 510-8 shall be increased by 113, but the coefficient applied to fv shall not be increased.

Fp 2.

allowable bearing stress, MPa

In long-slotted holes with the axis of the perpendicular to the direction ofload and with two more bolts in the line of force, Fp

510.4.7.2 On the projected area of the bolt or rivet closest the edge in standard or short-slotted holes with the distance less than 15d and in all connections with a bolt in the line afforce:

where: distance from the free edge to center of the bolt, mm d = bolt diameter, mm 510.4.7.3 If deformation around the hole is not a design consideration and adequate spacing and edge distance is as required by Section 510.4.8 and 5104.9, the following equation is permitted in lieu of Equation (510-1): F~

and the limit

In

1.50/-;,

Equation (510-3) shall be increased to

L5f~<.

510.4.6 Combined Tension and Shear in Slip-Critical Joints 510.4.6.1 For A325 and A490 bolts used in slip-critical connections, the maximum shear stress allowed by Table 510-7 shall be multiplied by the reduction factor (1 - fAtl Th)' where it is the average tensile stress due to a direct load applied to all of the bolts in a connection and Tb is the pretension load of the bolt specified in Table 510.3.7. When allowable stresses are increased for wind or seismic loads in accordance with the provisions of Section 501.5.2, the reduced allowable shear stress shall be increased by 1/3. 510.4.7 Allowable Bearing at Bolt Holes 510.4.7.1 On the projected area of bolts and rivets in shear connections with the end distance in the line of force not less than 1lj7£l and the distance center to center of bolts not less than 3d: 1.

= l.OOf;,

In standard-or short-slotted holes with two or more bolts in the line of force,

(510-1)


5-39


TABLE 510-7 Allowable Stress on

MPa

Allowable She~ {FJ Description of Fasteners

Slip-Critical Connectionse.i

Allowable g Tension (Pt)

Oversized and Short slotted Holes

Long-slotted Holes

Bearing type connections!

0.33F a,c,h

o

O.33F a.b

O.22F h

b

d

117

103

82.7

68.9

14Sf

303 d

117

103

82.7

68.9

20t

d

145

]24

103

89.6

193f

372d

145

124

103

89.6

276

303

372

f

permitted in shear planes. tensile capacity of the threaded portion of an upset rode, based upon the cros!l-sectional area at its majof thread diameter Ah shall be than the nominal body area ofthe rod before upsetting times 0.60F,. A325 and A490 bolts subject to tensile fatigue loading, see Section 51 L5.I.5. Class A (slip coefficient 0.33). Clean mill scale and blast-cleaned surfaces with Class A coatings. When specified by the designth. measured parallel to the line of force. exceed 1250 mm.• tabulated yalues shall be reduced by 20%. 'See Section 501.5.2. . . ~See Table 2. NlUllerical Values Section for values for specific ASTM steel specifications. IFor limitations on use of oyersized and slotted holes, see Section 510.4.2. j For Direction of load . relative to axis of slot.

National Structural Code of the Philippines, Volume 'I

STRUCTURAL STEEL

510.4.8 Minimum Spacing

510.4.9 Minimum Edge Distanee

510.4.8.1 The.· distance between centers of standard, oversized or slotted fastener holes shall not be less 2-2/3 times the nominal diameter of the fastener' nor less than that required by the following paragraph, if applicable.

510.4.9.1 The distance from the center of a standard hole to. an edge of a connected part shall be not less than . applicable value from Table 510-10 nor the value from Equation (510-6), as applicable.

510.4.8.2 Along a line of transmitted forces, the distance between centers of holes s shall be not less than 3d when Fp is determined by Equations (510-1) and (510-2). Otherwise, the distance between centers of holes shall not be less than the following:

510.4.9.2 Along a line of transmitted force, in the direction . . of the force, the distance from the center of a standard to the edge of the connected part L" shall be not less LSd when Fp is determined by Equations (510-1) (510-2). Otherwise the edge shall be not less than

a.

For standard holes: (51{}"5)

where P

= force transmitted by one fastener to the critical connected part, kN

Fu = specified minimum tensile strength of the critical connected part, MPa

where P, F'b t are defined in Section 510.4.8. 510.4.9.3 The distance from the center of an oversized or slotted hole to an edge of an oversized or slotted hole to an edge of a connected part shall be not less than required for a standard hole plus the applicable increment C2 from Table 51{}"11.

thickness of the critical connected part, mm 510.4.10 Maximum Edge Distance and Spacing

11.

For oversized and slotted holes, the distance required for standard holes in subparagraph a, (above), plus the applicable increment C1 from Table 510-9, but the clear distance between holes shall not be less than on diameter.

TABLE 510..8

Allowable Tension Stress Ft for Fasteners in

Bearing-type CODnections

Description ofFasteners

I Threads Included in i

Threads Excluded from Shear Plane

Shear Plane

.,,----.---.l~(303)2 . --------T A307 bolts ~ A325 bolts

---,--,,-- i

179.2 - 1.8.f., s; 137.8

-4.39//

I

-'

~(303)2 -2.15//

SlO.4.10.lThe maximum distance from the center of any rivet or bolt to the nearest edge of parts in contact shall be 12 times the thickness of the connected part under consideration, but shall not exceed 150 mm. Bolted joints in unpainted steel exposed to atmospheric corrosion require special limitations on pitch and edge distance. 510.4.10.2 For unpainted, built-up members made of weathering steel which will be exposed to atmospheric corrosion, the spacing of fasteners connecting a plate and a shape or two-plate components in contact shall not exceed 14 times the thickness of the thinnest part nor 175 mm, and the maximum edge distance shall not exceed eight times the thickness of the thinnest part, or 125 mm.

- - -..--....----~.-...- . - - - - - - -

A490 bolts I ~(372)2 -3.75// I ~(372)2 - 1.82// --.--..- . --t--------\-----.. Threaded I

parts, A449 \ 0.4 3Fu - 1.8/~ S; bolts' over. 0.33F~1 ?8-'!!.~ dia. 1 _ _ _ _. _....__

I

0.43FII - L4fv S; 0. 33Fu

I

~02 Gr_ I i 207 1.3.f., S; 159 nvets I ---_·..----1-.. "..-------_..__·_-~502 Gr. 2 i 262 1.3j,. S; 200

--

rivets

• A distance oDd is preferred.



5-41

I 1

TABLE 510-9

Values of S adn Increment C mm

Slotted Holes Parallel to Line of Force Over Perpen dicular sized to Line Short-slots Hole Long-slots ofForce

0 0 0

3.0

5.0 6.0

5.0 6.0 .~

..

8.0

l.5d-1.6 36 1.5d-1.6

~-

"When length of slot is less than maximum allowed in Table 510-6, C] may be reduced by the difference between the maximum and actual slot lengths.

SI0.4.n Long Grips SI0.4.11.1 AJ07 bolts which carry calculated stress, with a grip exceeding five diameters, shall have their number increased 1% for each additional 1.6 mm. in the grip.

510.6.1 Eccentric Connections 510.6.1.1 Intersecting axially stressed members shall have their gravity axes intersect at one point, if practicable; if not, provision shall be made for bending and shearing stresses due to the eccentricity.

TABLE Sl0-10

Miuimum Edge Distancet mm

Center of Standard Bole· to Ed e of Conneded Part

Nominal At Rolled Edges of Bolt or At Sheared River Plates, Shapes or Edges Dia. Bars, Gas Cut or mm Saw-cut Ed esb 12 22 20....__.......... _.. 16 28 22 32 25 20

28

510.5 ALLOWABLE SHEAR RUPTURE

-.. r.. . -·---·-28 50 38

. '·1---··-_·

;~ . "j ..~ "1~:·-···

OV!;32

510.5.1 At beam end connections where the top flange is coped, and in similar situations where failure might occur by shear along a plane through the fasteners, or by a combination of shear along a plane through the fasteners plus tension along a perpendicular plane:

r-

1.7/:Di-a~

1

1.25~Dia.--

• For oversized or slotted holes, see Table 510·11. b All edge distances in this column may be reduced 3 mm when the hole is at a point where stress does not exceed 25% of the maximum design strength in the element. • These may be 32 mm at the ends of beam connection an les.

(510-7) acting on the net shear area Av and,

Fp

=0.50F"

(510-8)

acting on the net tension area At. 510.S.2 The minimum net failure path on the periphery of welded connections shall be checked.'

TABLE 510-11

Values of Edge Distance Increment C2~ mm

Nornin If---~---·-"·--~-r-·---l Slotted Holes a1 Dia. Over-! P~ndicular to E~~ of sized i Short Long" Parallel Hole I Slots Fasten Slotsa to Edge er $22 __ ~1..~5__+___3~.O~ __~ 25 .~~ 3.0 3.0 O.75d o ~_..?~8 3.~ . O_....l. __5.. .._.0. . . _~...L.....L.'_ _ . _

.. _ _ _ _

510.6 CONNECTING ELEMENTS 510.S.1 This section applies to the design of connecting elements, such as stiffeners, gussets, angles and brackets and the panel zones of beam-to-column connections.

• When length of slot is less than maximum allowable (sec Table 510-6), ('2 may be reduced by one-half the difference between the maximum and actual slot lengths.

510.6.2 AUowable Shear Rupture 510,6.2.1 For situations where failure might occur by shear along a plane through the fasteners. or by a combination of shear along a plane through the fasteners plus tension along a perpendicular plane, see Section 510.5

See SectioD 502.3 and Commentary Figure.~ C-.I4.1, C-J.U and C-J4.4 of the l\1anual of Steel Construction, AlIowa!-:le Stress Design, qlh Editi,'n.


STRUCTURAL STEEL

TABLE 510-12

Minimum Pretension for Ful -ti Bolt Size,

A325 Bolts

teoed Bolts, ~ A490Bolts

53.378 -+_....._._....... _.__._ _ ...._--_.66.723

84.516 __________ 0106.757 124.550 155.687 20 1 - - - - --:- ---173.480 -----217.962 22 --_._--_.. __ ._-- _._--- _ . 25 226.859 ... -- -.-- 284.686 ...- --- 28 249.100 355.857 ._._-_.. _ --------_._---_.. .. 32 315.823 453.718 .. ---- .. --.------- -.- 35 378.098 538.234 ----------------._- 38 458.166 658.336 • Equal to 0.70 of minimum tensile strength of bolts as specified in ASTM specifications for A325 and A490 bolts with UNC threads. --.---~---

-~

.-~~

-~.-

~---.--~-

.-~--.---."----

510.9 ALLOWABLE BEARING STRESS 510.9.1 On contact area of milled surfaced and ends of fitted bearing stiffeners; on projected area of pins in reamed, drilled or bored holes: Fp

0.90F/

510.9.2 Expansion rollers and rockers, Newtons per linear .

millimeter:

-~.---~"'----

_(F~

-~----

Fp -

-~

-89.6)O.66d

137.8

(510-10)

where d is the diameter of roller or rocker, mm

510.10 COLUMN BASES AND BEARING ON 510.7 FILLERS

~ONRYANDCONCRETE

510.7.1 In welded construction, any filler 6 nun or more in thickness shall extend beyond the edges of the splice plate and shall be welded to the part on which it is fitted with Bufficient weld to transmit the splice plate stress, applied at the surface of the finer as an eccentric load. The welds joining the splice plate to the filler shall be sufficient to transmit the splice stress and shall be long enough to avoid overstressing the fillet along the toe of the weld. Any filler less than 6 mm thick shall have its edges flush with the edges of the splice plate and the weld size shall be sum of the size necessary to carry the splice plate stress plus the thickness ofthe filler plate.

510.10.1 Proper provision shall be made to transfer the column loads moments to the footings and foundations. 510.10.2 In the absence of code regulations the following stresses apply: On sandstone and limestone ............. .. Fp= 2.75MPa On brick in cement mortar ................. . Fp= 1.72 MFa On the full area of a concrete support..... . Fp = 0.351'0 On less than the full area of a conclete support.............. Fp 0.35f'c ~A21 AI -50.70f'c where

510.7.2 When bolts or rivets carrying computed stress pass through fillers thicker than 6 mm, except in slip-critical connections assembled with high-strength bolts the fillers shall be extended beyond the splice material and the fiUer extension shall be secured by enough bolts or rivets to distribute the total stress in the member uniformly over the combined section of the member and the filler, or an equivalent number of fasteners shall be included in the connection. Fillers between 6 mm and 20 mm thick, inclusive, need not be extended and developed, provided the allowance shear stress in the bolts is reduced by the factor, 0.4 (1-6), where t is the total thickness of the fillers, upto20mm.

1'c AJ

= specified compressive strength of concrete, MPa

= area

of steel concentrically bearing on a concrete support, mm2 A;? = maximum area of the portion of the supporting surface that is geometrically similar to and 2 concentric with the loaded area, mm

510.11 ANCHOR BOLTS 510.11.1 Anchor bolts shall be designed to provided resistance to all conditions on completed structures of tension and shear at the bases of columns, including the net tensile components of any bending moment which may result from fixation or partial fixation ofcolumns.

510.8 SPLICES 510.8.1 Groove welded splices in plate girders and beams shall develop the full strength of the smaller spliced section. Other types of splices in cross sections of plate girders and beams shall develop the strength required by the stresses at the point of splice.

• When parts in contact have different yield stresses, the smaller value.


F;.. shall

be

SPECIAL DESIGN CONSIDERATIONS

5-43

511.2.2.2 If the length of loading measured across the member flange is less than O.15h, where b is the member flange width, Equation (511-1) need not be checked.

SECTION 511- SPECIAL DESIGN CONSIDERA TIONS

511.2.3 Local Web Yielding

511.1 SCOPE .511.1 This Section covers member strength design considerations related to concentrated forces, ponding, a. torsion and fatigue.

511.2 WEBS AND FLANGES UNDER CONCEN TRATED FORCES

511.2.3.1 Bearing stiffeners shall be provided if the compressive stress at the web toe of the fillets resulting from concentrated loads exceeds O.66T;~.. When the force to be resisted is a concentrated load producing tension or compression., applied at a distance from the member end that is greater than the depth of the member,

R - - - - ~ O.66FJ' t..,(N +Sk)

511.2.3 Design Basis 511.2.1.1 Members with concentrated loads applied normaP' to one flange and symmetric to the web shall have a flange and web proportioned to satisfy the local flange bending, web yielding strength, web crippling and sidesway web buckling criteria to both flanges shall have a web proportioned to satisfy the web yielding web crippling and column web buckling criteria of Sections 511.2.3, 511.2.4 and 511.2.6. 5U.2.1.2 Where pairs of stiffeners are provided on opposite sides of the web, at concentrated loads, and extend at least half the depth of the member, Sections 511.2.2 and 511.2.3 need not be checked. 511.2.1.3 For column webs subject to high shears, see Section 511.2.7; for bearing stiffeners see Section 511.2.8. 511.2.2 Local Flange Bending 511.2.1.1 A pair of stiffeners shall be provided opposite the tension flange or flange plate of the beam or girder into the member when the thickness of the member flange If is less than ..

framin/'

12.6SJP~

Fyc wbere:

Fyc

When the force to be resisted is a concentrated load applied at or near the end ofthe member,

R - - - - ' , - ~ O.66F

I.,.(N + 2.Sk) y

wbere

= concentrated load or reaction N

I.,. "" thickness ofweb, mm '

N = length of bearing (not less than k for end reactions),

mm k = distance from outer face of flange to web toe of fillet, mm 511.2.4 Web Crippling 511.2.4.1 Bearing stiffeners shall be provided in the webs of members under concentrated loads, when compressive force exceeds the following limits:

When the concentrated load is applied at a distance not less than d/2 from the end ofthe member:

1772t.'[1 +{;X:;

(511-1) b.

yield stress; MPa Pbf = the computed force delivered by the flange or moment connection plate multiplied by 5/3, when the computed force is due to live and dead load only, or by 4/3, when the computed force is due to live and dead load in conjunction with wind or earthquake forces, N Except where other codes may govern. For example. see ~ti~n 4(0) "Reoommended Lateral Force Requirements and Commentary." Structural Engineers Association ofCalifomia. 197.5.

(511-3)

R

R=

co~umn

(511-2)

fk,.tf

ll•

(511-4)

When the concentrated load is applied less than a distance

d/2 from the end of the member:

R= 893t.'[1+

{;X:; fk,.tf II.

(511-5)

where:

Fyw= specified minimum yield stress ofbeam web, MPa d =overall depth of the member, rom

It =flange thickness, mm


STRUCTURAL STEEL

511.Z.4.2 If stiffeners are provided and extend at least one half the web depth, Equations (511-4) and (511-5) need not be checked.

511.2.8 Stiffener Requirements for Concentrated Loads 511.2.8.1 Stiffeners shall be placed in pairs at unframed ends or at points of concentrated loads on the interior of beams, girders or columns if required by Section 511.2.2 through 511.2.6, as applicabIe.

511.2.5 Sidesway Web Buckling 511.2.5.1 Bearing stiffeners shall be provided in the webs of members with flanges not restrained against relative movement by stiffeners or lateral bracing and subject to concentrated compressive loads, when the compressive force exceeds the following limits: a.

511.2.8.2a If stiffeners are required by Section 51 L2.4 or

511.2.6 the stiffeners shall be designed as axially

compressed members (columns) in accordance with requirements of Section 505.3 with an effective length

equal to O.75h, a cross section composed of two stiffeners

and a strip of the web having a width of 25t".. at interior

stiffeners and 121,.. at the ends of members.

If the loaded flange is restrained against rotation and (dJt",)/(lIhp is less than 2.3: R

h.

511.2.3.2 If required by Sections 511.2.2, 511.23 or Equation (511-9), stiffeners need not extend more than one

half the depth ofthe web, except as follows:

46,8801,/ h

[I

)3]

+ O.4[dc / tw llbf

(511-6)

511.2.8~3

When the load normal to the flange is tensile, the

stiffeners shall be welded to the loaded flange. When the

load normal to the flange is compressive, the stiffeners shall

either bear on or be welded to the loaded flange.

If the loaded flange is not restrained against rotation and (dJt".)I(llhl ) is less than 1.7:

r [ \31j

R = 46,8801,;J 0.4 d() (~ h II hf

l

J

(511-7)

where:

I largest laterally unbraced length along their flange at

the point ofload, mm hi flange width, mm de (d - 2k) = web depth clear of fillets, mm

511.2.8.4 When flanges or moment connection plates for end connections of beams and girders are welded to the flange of an 1- or H-shape column, a pair of column-web stiffeners having a combined cross-sectional area A" not less than that computed from Equation (51 1-9) shall be provided whenever the calculated value of A y [ is positive. (511-9)

Equations (511-6) and (511-7) need not be checked providing (dJtw)/(llb r) exceeds 2.3 or 1.7. respectively, or for webs subject to uniformly distributed load.

511.2.6.1 For unstiffened portion of webs members under concentrated loads to both flanges, a stiffeners or a pair of stiffeners shall be provided opposite the compression flange when the web depth clear of fillets de is greater than 10.81...

3

511.2.8.5 Stiffeners required by the provisions of Equation (511-9) and Sections 511.2.2 and 51 L2.6 shall comply with the following criteria:

(511-8)

where: t"y; = thickness of column web, mm 511.2.7 Compression Members witb Web Panels Subject to 10gb Shear

where: J' ys stiffeners yield stress, MPa k distance between outer face of column flange and web toe of its fillet, if column is a rolled shape. or equivalent distance if column is a welded shape, mm (r, thickness of flange or moment connection plate delivering concentrated torce, mm

,=

511.2.6 Compression Buckling of the Web

1.

2.

511.2.7.1 Members subject to high shear in the web should be checked for conformance with Section 506.5'

The width of each stiffener plus 112 the thickness of the column web shall be not less than 1/3 the width of the flange or moment connection plate delivering the concentrated force. The thickness of stitfeners shall be not less than one-half the thickness of the flange or plate delivering the concentrated load. 3.

• See Commentary Section E6 of the 9'h Edition of Manual of Steel Construction

The weld joining stiffeners to the column web shall be sized to carry the force in the stiffener caused by

Assocmtion of Structural Engineers of the Philippines


unbalanced moments on opposite sides of the column.

511.5 FATIGUE 511.5.1 Members and their connections subject to fatigue loading shall be proportioned in accordance with the provisions ofthis Article.

511.3 PONDING 511.3.1 The roof system shall be investigated by structural analysis to assure adequate strength and stability under ponding conditions, unless the roof surface is provided with sufficient slope toward points of the drainage or adequate individual drains to prevent the accumulation of rainwater. 511.3.2 The roof system shall be considered stable and not requiring further investigation if: C p +O.9Cy

~0.25

(51l~1O)

(51l-11)

511.5.1.1 Members and connections subject to fatigue loading shall be proportioned in accordance with the provisions of this Section. 511.5.1.2 Fatigue, as used in this Specification, is defined as the damage that may result in fracture after a sufficient number of fluctuations of stress. Stress range is defin¢ as the magnitude of these fluctuations. In the case of a stress reversal, the stress range shall be computed as the numerical sum of maximum repeated tensile and compressive stresses or the sum of maximum shearing stresses of opposite direction at a given point, resulting from differing arrangement of live load.

where: 511.!U.3 Loading Conditions; Type and Location of Material

4

(

' _ 5061...1_ p

p -

c., Lp

=

L, S Iv

=

is

ld

Ip

In the design of members and connections subject to

506Sr s 4

repeated variation of live load, consideration shall be given to the number of stress cycles, the expected range of stress and the type and location of member or detail.

column spacing in direction of girder (length of primary members), m spacing of secondary members, m spacing of secondary members, m moment of inertia of primary members, mm" moment of inertia of secondary members, mm4 moment of inertia of the steel deck supported on secondary members, mm" per m

Loading conditions shall be classified according to Table 511-1.

r,

51) .3.3 For trusses and steel joists, the moment of inertia shall be decreased 15% when used in the above equation. A steel deck shall be considered a secondary member when it is directly supported by the primary members. 511.3.4 Total bending stress due to dead loads, gravity live loads (if any) and ponding shall not exceed 0.80Fy for primary and secondary members. Stresses due to wind or seismic forces need not be included in a ponding analysis.

511.4 TORSION 511.4.1 The effects of torsion shall be considered in the design of members and the normal and shearing stresses due to torsion shall be added to those from all other loads, with the resultants not exceeding the allowable values.

National Structul'ill Code of the Philippines, Volume 1

STRUCTURAL STEEL

TABLE 511-1 Number of Loadina Cycles Loading Condition I From i

2.o,.oOOa I 10.0'1..0.00 I I 5OO,O.oQ_--.-l Ov~r 2,OOO,00
!

I 2 --_.__ .... _-3

--~--

-.-------~

4

~

To

IO.o,OOOD 5.oO,.oOOc 2,000,00.0

.-~

.-~

• Approximately equivalent to two (2) applications every day

for 25 years.

b Approximately equivalent to ten (I 0) applications every day

for 25 years.

C Approximately equivalent to fifty (50) applications every day

for 25 vears.

d Appro~ately equivalent to two hundred (200) applications

every day for 25 years.

The type and location of material shall be categorized according to Table 511-2. 511.5.1.4 Allowable Stress Range The maximum stress shall not exceed the basic allowable stress provided in Sections 501 through 513 of this Specification and the maximum range of stress shall not • exceed that given in Table 511-3. 511.5.1.5 Tensile Fatigue When subject to tensile fati.b'Ue loading, the tensile stress in A325 or A490 bolts due to the combined applied load . and prying forces shall not exceed the following values, and the prying force shall not exceed 6.0%. of the externally applied load.

J

.__ ,_~l:llllJ>er of9!de~==~r=-A}25__ ~29_ Not more than 2.0,.0.0.0 i 44 ! 54 i I'Fr~~ 2.0,00.0 5.0.0,.0.0.0-'''''-- '-1-40'--1- 49ri10rethan 5.0000.0 ·-----r"-j'i-r---'38-i .:::::.2...:::. _ _ _ __ _____-1-_..___._ _ , _________

i

to

1.

,~,._._ •••••_

••_ _ _

Bolts must be Table 510-12

~_~.

tensioned

.1

.~

to the

requirements

of

The use of other bolts and threaded parts subjected to tensile fatigue loading is not recommended, Few members or connections in conventional buildings need to be designed for fatigue, since most load changes in such structures occur only a small number of times or produce only minor stress fluctuations. The occurrence of full design wind or earthquake loads is too infrequent to warrant consideration in fatigue design. However, crane runways and supporting structures for machinery and equipment are often subject to fatigue loading conditions.



5-47

TABLE 511-2

ClassifICations Jllu~trative

Situation with rolled or surface. Flame-cut edges

Example Nos. (See 511 1,2

Kind of Stress· T or Rev.

ofl B

3,4,5,6

To~Re~.--!-···B'

3,4,5,6

in members without attachments, built-up plates

!

-,

TorRev.

TorRev. TorRev.

5 5 5

-

"T" signifies range in tensile stress only; "Rev." signifies a range involving reversal oftcnsile or compressive stress; "s" signifies range in shear, including shear stress reversal. These examples are provided as guidelines and are not intended to exclude other reasonably similar situations. Allowable fatigue stress range for transverse partial-penetration and transverse fillet welds is II function of the effective throat, depth M thickness. See Frank and Fisher (l . and


STRUCTURAL STEEL

5-48

TABLE 511-2 (continued) and Location of Matf'rial Stress General Condition Groove Welds

· !

, :

Situation Base metal and weld metal at full-penetration groove welded splices of parts of similar cross section ground flush. with grinding in the direction of applied stress and with weld soundness established by radiographic or ultrasonic inspection in accordance with the requirements of 9.25.2 or 9253 of AWS D1.1

Kind of a Stress : T or Rev • .

i :

. ; Base metal and weld metal at full-penetratIOn groove welded splices at transitions in width or thickness, with welds ground ! to provide slopes no steeper than I to 2 Y2 with grinding in the : direction of applied stress.. and with weld soundness: established by radiographic or ultrasonic inspection in! accordance with the requirements of9.25.2 or 9.25.3 of AWS ; i D1.1 i A514 base metal T or Rev.

:

i

'

i

i i

B'

l2,13

~~~:!::=I :~~~eldmetal at'-fiill-penetrarlongroove-wclaed-H ~i-~~~~l--{--+' 10, a~I;Jj

· splices, with or without transitions having slopes no greater I than 1 to 2Y:a when reinforcement is not removed but weld I I soundness is established by radiographic or ultrasonic!

i inspection

Partial Penetration Groove Welds Fillet-welded Connections

I[

I.

i

I

I

in accordance with requirements of 9.25.2 or I ! 9.25.3 of AWS D1.1 ' Weld metal of partial-penetration transverse groovewelds:t T or R~v.--i--·F-c-'" based on effective throat area of the weld or welds I II

I

-+-

1-16" I

I • Base metal at junction of axially loaded members with · welded end connections. Welds shall be disposed about the axis ofthe member so as to balance weld stresses • b$25 mm

TorRev

C

See Notec Fillet Welds

or intermittent longitudinal or

S

Plug or Slot Welds Mechanically Fastened Connections Base metal at net section bolted bearing connections



5-49

TABLE 511-2 (continued) aDd Material

Stress

Situation

Base metal at details attached by full-penetration groove

welds subject to longitudinal and/or transverse loading w.hen

the detail embodies a transition radius R with the weld

termination ground smooth and for transverse loading, the

weld sound-ness established by radiographic or ultrasonic

inspect-ion in accordance with 9.25.2 or 9.25.3 of AWS D1.1

Kind of

Stressa

llIu8trative Example Nos. (See 511

Longitudinal loading

R>600mm 600mm>R> 150mm , 150 mm > R > 50 mm 50mm>R

T or Rev. TorRev. T or Rev. T or Rev.

B C D E

14 14 14 14

T or Rev. T or Rev. TorRev. TorRev.

B C D

14 14 14 14,15

TorRev. T or Rev. TorRev. TorRev.

C C D

E

14 14 14 14,15

50 mm>R

TorRev. Tor Rev.

D E

J4 14,15

Detail base metal for transverse loading: unequal thickness and reinforcement not removed aliR

T or Rev.

E

14,15

T or Rev'. T or Rev. Tor Rev.

C D

19 19 19

Detail base metal for transverse loading: equal thickness and reinforcement removed

R>600mm

600 mm > R > 150 mm

150 mm > R > 50 mm

150mm>R

E

Detail base metal for transverse loading: equal thickness and reinforcement not removed

R>600mm

600mm>R> 150mm

150 mm > R > 50 mm

50mm>R

Detail base metal for transverse loading: unequal thickness and reinforcement removed R> 50mm

Detail base metal for transverse loading R> 150mm I 150 mm > R > 50 mm 50 mm >R


E

STRUCTURAL STEEL

TABLE 511-2 (tontinued)

T:ypeand Loc' atlOnofMa' tena I

General Condition Attachments (continued)

Kind of Stress·

Situation Base metal at detail attached by full-penetration groove welds subject to longitudinal loading

50 nun 12b or 100mm when b:s: 25 nun • TorRev. a > 12b or 100 mm when b > 25 mm Base metal at detail attached by fillet welds or parti.alpenetration groove welds subject to longitudinal loading

!

i

Stress Category (see Table 511-3)

Illustrative Example Nos. (See Fi~. 511-1)'

D E E'

15 15 15

I

a< 50 mm

TorRev.

C

50 mm < a < 12b or 100 mm a > 12b or 100 nun when b :s: 25 mm a> 12b or 100 nun when b > 25 mm

TorRev. TorRev. TorRev.

D E E'

15,23,24 25,26 15,23,24,26 15,23,24,26 15,23,24,26

R>50mm I TorRev. R:S:50mm I TorRev. Fillet-welded attachments~herethe-wet(itefmination embodies a transition radius, weld termination ground I smooth. and main material subject to longitudinal loading:

D E

19 19

D E C

19 19 22

I Base

,

metal attached by fillet welds or partial-penetration groove welds SUbjected to longitudinal load-ing when the weld termination embodies a transition radius with the weld termination ground smooth:

I

!

I Detail base metal for transverse loading:

H>50mm R<50nun

Base -metalai" stUd-type"shearooMeci", attaChed by

I' TorRev. TorRev. fillett o r Rev

i weld or automatic end weld

_

rs--~~-~'-------'---

. . .______ .~~~ str~~~_~..!lQmin'l.L~Iea of~!l!.
----

. S

F •

Category

(from Table 511-2) A

B

...

TABLE 511-3 Allowable Stress Ran e. MPa Loading Loading Loading Condition Condition Condition 1 2 3 434 255 200 158 145 110 ------t---.- ..

---~ ---.-~--~ --------~+-----------

Flexural stress range of 82.7 MPa permitted at toe of stiffener welds on flanges.


Loading Condition 4

SERVICEABILITY DESIGN CONSIDERAnONS

SECTION 512 - SERVICEABILITY DESIGN ·CONSIDERATIONS

5-51

512.4.2 Vibration 512.4.2.1 Beams and girders supporting large open floor areas free of partitions or other sources of damping shall be designed with due regard for vibration.

512.1 SCOPE 512.1.1 This Section provides design guidance for serviceability considerations not covered elsewhere. Serviceability is a state in which the function of a building, its appearance, maintainability, durability and comfort of its occupants. are pre~rved under normal usage. 512.1.2 Limiting values of structural behavior to ensure serviceability (e.g., maximum deflections, accelerations, etc.) shall be chosen with due regard to the intended function ofthe structure.

512.5 CONNECTION SLIP 512.5.1 For the design of slip-resistant connection see Section 510,4.

512.6 CORROSION 512.6.1 When appropriate, structural components shall be designed to tolerate corrosion or shall be protected against corrosion that impairs the strength or serviceability of the structure.

512.2 CAMBER 512.2.1 If any special camber requirements are necessary to bring a loaded member into proper relation with the work of other trades, the requirements shall be set forth in the design documents.

512.6.2 Where beams are exposed they shall be sealed against corrosion of interior surfaces or spaced sufficiently far apart to permit cleaning and painting.

512.2.2 Trusses of24.4 m or greater span generally shall be cambered for approximately the dead-load deflection. Crane girders of 22.9 m or greater span generally shall be cambered for approximately the dead-load deflection plus 112 the live-.load deflection. 512.2.3 Beams and trusses detailed without specified camber shall be fabricated so that after erection any camber due to rolling or shop assembly shall be upward. If camber involves the erection of any member under a preload, this shall be noted in the design documents.

512.3 EXPANSION AND CONTRACTION 512.3.1 Provision shall be made expansion and contraction appropriate to the service. conditions ofthe structure.

512.4 DEFLECTION, VIBRATION AND DRIFT 512.4.1 Deflection 5J2.4.1.1 !!earns and girders supporting floors and roofs shall be proportioned with due regard to the deflection produced by the design loads. Beams and girders supporting plastered ceiling shall be so proportioned that the maximum live-load deflection does not exceed 1/360 of the span.


STRUCTURAL STEEL

SECTION 513 - FABRICATION, ERECTION AND QUALITY CONTROL 513.1 SHOP DRAWINGS

513.2.3.1 Planing or finishing of sheared or thermally cut edges of plates or shapes will not be required unless specifically called for in the design documents or included in a stipulated edge preparation for welding. 513.2.4 Welded Construction

513.1.1 Shop drawings giving complete information necessary for the fabrication of the component parts of the structure, including the location, type and size of all welds, bolts and rivets, shall be prepared in advanCe of the actual fabrication. These drawings shall be clearly distinguish between shop and field welds and bolts and shall clearly identify type of bigh-strength bolted connection (snug-tight or fully-tightened bearing, or slip-critical), 513.1.2 Shop drawings shall be in conformity with the best practice and with due regard to speed and economy in fabrication and erection.

513.2 FABRICATION 513.2.1 Cambering, Curving and Straightening 512.2.1.1 Local application of heat or mechanical means are permitted to introduce or correct camber, curvature and straightness. The temperature of heated areas, as measured by approved methods, shaU not exceed 565°C for A852 steel, 593°C for AS 14 steel nor 649°C for other steels. The same limits apply for equivalent grades of A709 steels.

",~I'

513.2.3 Planning of Edges

513.2.2 Thermal Cutting 513.2.2.1 Thermally cut free edges which will be subject to substantial tensile stress shall be free of gouges greater than 5 rom. Gouges greater than 1,6 rom deep and sharp notches shall be removed by grinding or repaired by welding. Thermally cut edges which are to have weld deposited upon them, shall be reasonably free of notches or gouges. 513.2.2.2 All reentrant comers shall be shaped to a smooth transition. If specific contour is required, it must be shown on the contract documents. 513.2.2.3 Beam copes and weld access holes shall meet the geometrical requirements of Section 510.2.8. Beam copes and weld access holes in ASTM A6 Group 4 and 5 shapes and welded built-up shapes with material thickness greater than 50 rum shall be preheated to a temperature of not less than 65.6oC prior to thermal cutting.

513.2.4.1 The technique of welding, the workmanship, appearance and quality of welds and the methods used in correcting nonconforming work shall be in accordance with "Section 3-Workmansbip" and "Section4-Technique" of the AWS Structural Welding Code-Steel, D 1.1. 513.2.5 High-Strength Bolted Construction-Assembly 513.2.5.1 All parts of bolted members shall be pinned or bolted and held together rigidly white assembling. Use of a drift pin in bolt holes during assembling shall not distort the metal or enlarge the holes. Poor matching of holes shall be cause for rejection. 513.2.5.2 If the thickness of the material is not greater than the nominal diameter of the bolt plus 3 mrn, the holes may be punChed. If the thickness of the material is greater than the nominal diameter of the bolts plus 3 mm, the holes shall be either drilled or sub-punched holes and the drill for all sub-drilled holes shall be at least 1.6 mm smaller than the nominal diameter of the bolt. Holes in A514 steel plates over 12 rum thick shall be drilled. 513.2,5.3 Surfaces of bigh-strength-bolted parts in contact with bolt head and nut shall not have a slope of more than 1:20 with respect to a plane normal to the bolt axis. Where the surface of a high-strength-bolted part has a slope of more than 1:20, a beveled washer shall be used to compensate for the lack of parallelism. High-strength bolted parts shall fits solidly together when assembled and shall not be separated by gaskets or any other interposed compressible materials. 513.2.5.4 The orientation of fully inserted finger shims, with a total thickness of not more than 6 mrn within a joint, is independent of the direction ofapplication of the load. 513.2.5.5 When assembled, all joints surfaces, including surfaces adjacent to the bolt head and nut, shall be free of scale, except tight mill scale and shall be free of scale, except tight mill scale and shall be free of dirt or other foreign material. Burrs that would prevent solid seating of the connection parts in the snug-tight condition shall be removed. Contact surfaces within slip~critical connections shall be free of oil, paint, lacquer or other coatings, except as listed in Table 3 of the RCSC Specifications for Structural Joints Using ASTM A325 or A490 Bolts.


FABRICATION, ERECTION AND QUAUTY CONTROL

513.2.5.6 The use of high-strength bolts shall conform to the requirements of the RCSC Specifications for Structural Joints Using ASTM A325 or A490 Bolts.

5·53

with concrete need not be painted. Unless specifically excluded shall be given one coat of shop paint. 513.3.2 Inaccessible Surfaces

513.2.6 Compression Joints. 513.2.6.1 Compression joints which depend on contact bearing as part of the splice capacity shall have bearing surfaces of individual fabricated pieces prepared by milling, sawing or other means. 513.2.7 Dimensional Tolerances

513.3.2.1 Except for contact surfaces, inaccessible after shop assembly shall be cleaned and painted prior to assembly, if required by the design documents. 513.3.3 Contact Surfaces

513.2.7.1 Dimensional tolerances shall be as permitted in the Code of Standard Practice of the American Institute of Steel Construction, Inc.

513.3.3.1 Paint is permitted unconditionally in bearing-type connections. For slip-critical connections, the faying surface requirements shall be in accordance with the RCSC Specifications for Structural Joints Using ASTM A32S or A490 Bolts, paragraph 3.(b)

513.2.8 Finishing of Column Bases

513.3.4 Finished Surfaces

513.2.8.1 Column bases and base plates shall be finished in accordance with the following requirements:

513.3.4.1 Machine-finished surfaces shall be protected against corrosion by a rust-inhibiting coating that can be removed prior to erection, or which has characteristics that make removal prior to erection unnecessary.

a.

b.

Rolled steel bearing plates 50 mm or less in thickness are permitted without milling,' provided a satisfactory contact bearing is obtained; rolled steel bearing plates over 50 mm but not over 100 mm in thickness may be straightened by pressing, or if presses are not available, by milling for all bearing surfaces (except as noted in subparagraphs (c) and (d) of this section), to obtain a satisfactory contact bearing; rolled steel plates over 100 mm thick shall be milled for all bearing surfaces (except as noted in subparagraphs (c) and (d) ofthis Section). Column bases other than rolled steel bearing plates shall be milled for all bearing surfaces (except as noted in subparagraphs (c) and (d) ofthis Section). The bottom surfaces of bearing plates and column bases which are grouted to insure full bearing contact on foundations need not be milled. The top surfaces of base plates with column full penetration welded need not be pressed or milled.

513.3 SHOP PAINTING

513.3.1.1 Shop painting and surfaces preparation shall be in ac<:ordlan<::e with the provisions of the Code of Standard Practice of the American Institute of Steel Construction,

513.3.1.2 Unless otherwise specified, steelwork which will be concealed by interior building finish or will be in contact

513.3.5 Surfaces Adjacent to Field Welds 513.3.5.1 Unless otherwise specified in the design documents, surfaces within SO mm of any field weld locations shall be free of materials than would prevent proper welding or produce toxic fumes during welding.

513.4 ERECTION 513.4.1 Alignment of Column Bases 513.4.1.1 Column bases shall be set level and to correct elevation with full bearing on concrete or masonry. 513.4.2 Bracing 513.4.2.1 The frame of steel skeleton buildings shall be carried up true and plumb within the limits defined in the Code of Standard Practice of the American Institute of Steel Construction. Temporary bracing shall be provided, in accordance with the requirements of the Code of Standard Practice, wherever necessary to take care of all loads to which the structure may be subjected including equipment and the operation of same. Such bracing shall be left in place as long as I?-ay be required for safety. 513.4.2.2 Wherever piles of materials erection equipment or other loads are supported during erection, proper provision shall be made to take care of stresses resulting from such loads.

·See Commentaty Section J8 of the Manual of Steel Construction, A·llowable Stress Design, 91h Edition.


----~----

...

STRUCTURAL STEEL

5-54

513.4.3.1 No permanent bolting or welding shall be performed until as much of the structure as will be stiffened 513.4.4 Fit-ofColumn Compression Joints 513.4.4.1 Lack of contact bearing not exceeding a gap of 1.6 nun regardless of the type of connections used (partial-penetration, groove-welded or bolted), shall be acceptable. If the gap exceeds 1.6 nun, but is less than 6 mm, and if an engineering investigation shows sufficient contact area does not exist, the gap shall be packed with non-tapered steel shims. Shims may be of mild steel, regardless ofthe grade of the main material.

thereby has been properly aligned. 513.5.3 Rejections 513.5.3.1 Material or workmanship not in conformances with the -provisions of this specification be rejected at any time during the progress of the The fabricator shall receive copies of all reports !urmslled to the purchaser by the inspection agency. 513.5.4 Inspection of Welding 513.5.4.1 The inspection of welding shall be performed . accordance with the provisions of Section 6 of the AWS Structural Welding Code-Steel, 01.1.

513.4.5 Field Welding 513.4.5.1 Shop paint on surfi1ces adjacent to welds shall be wire-brushed to reduce paint film to a minimum. 513.4.6 Field Painting 513.4.6.1 Responsibility for touch-up painting, cleaning and field-painting shall be allocated in accordance with accepted local practices, and this allocation shall be set forth explicitly in the design documents. 513.4.7 Field Connections

513.5.4.2 When nondestructive testing is required, process, extent and standards of acceptance defined clearly in the design documents. 513.5.5 Inspection of Slip-Critical, High-Strengtb Bolted Connections 513.5.5.1 The inspection of slip-critical, high-strength bolted connections shall be in accordance with provisions of the RCSC Allowable Stress Design Specifications for Structural Joints Using ASTM A325 or A490 Bolts.

513.4.7.1 As erection progresses, the work shall be securely bolted or welded to take care of all dead load, wind and erection stresses.

513.5.6 Identification of Steel

513.5 QUALITY CONTROL

~tten

513.5.1 The fabricator shall provide quality control procedures to the extent that he deems necessary to assure that all work is performed in accordance with this Specification. In addition to the fabricator's quality control procedures, material and workmanship at all times D;lay be subject inspection by qualified inspectors representing the purchases. If such inspection by representatives of the purchaser will be required, it shall be so stated in design documents.

513.5.6.1 The fabricator shall be able to demonstrate by procedure and by actual practice a method of material application and identification, visible at least through the "fit-up" operation, of the main structural elements of a shipping piece. 513.5.6.2 The identification method shall be capable of verifying proper material applicable as it relates to: 1. 2. 3.

Material specification designation Heat number, if required Material test reports for special requirements

513.5.2 Cooperation 513.5.2.1 A far as possible, all inspection by representatives of the purchaser shall be made at the fabricator's plant. The fabricator shall cooperate with the inspector, permitting access for inspection to all places where work is being done. Tbe purchaser's inspector shall schedule his work for minimum interruption to the work of the fabricator.


PlASTIC DESIGN

SECTION 514 - PLASTIC DESIGN

514.1.1 Subject to the limitations contained herein, simple and (iontinuous beams, braced and unbraced planar rigid frames, and similar parts of structures rigidly constructed so as to be continuous over at least one interior support,' are permitted to be proportioned on the basis of plastic design, i.e., on the basis of their maximum strength. This strength, as determined by rational analysis, shall be not less than that required to support a factored load equal to 1.7 times the given live load and dead load, or 1.3 times these loads acting in conjunction with 1.3 times any specified wind or earthquake forces. 514.1.2 Rigid frames shall satisfy the requirements for Type 1 construction in the plane of the frame, as provided in Section 501.2.2. This does not preclude the use of some simple connections, provided provisions of Section 514.3 are satisfied. Type 2 construction is permitted for members between rigid frames. Connections joining a portion of structure designed on the basis of plastic behavior with a po~ion not so designed need be no more rigid than ordtnary seat-and-top-angle or ordinary web connections. 514.1.3 Where plastic design is used as the basis for proportioning continuous beams and structural frames the provisi~ns relating to allowable stress are waived. E~cept as modtfied by these rules, however, all other provisions of Sections 501 through 513 shall govern. 514.1.4 It is not recommended that crane runways be designed continuous over interior vertical supports on the basis of maximum strength. However, rigid frame bents supporting crane runways may be considered as coming within the scope ofthe rules.

514.2 STRUCTURAL STEEL 514.2.1 Structural steel shall conform to one of the following specifications: Structural Steel, ASTM A36 High-Strength Low-Alloy Structural Steel, ASTM A242 High-Strength Low-Alloy Structural Manganese Vanadium Steel, ASTM A441

•As

used here, "interior support" includes a rigid-frame knee formed by the junction of a column and a sloping or horizontal beam or girder.

Structural Steel With 290 MPa Minimum Yield Point, ASTMA529 High-Strength Low-Alloy Columbium-Vanadium Steel With 345 MPa Minimum Yield Point to l00-mm Thick, ASTM A588

514.3 BASIS FOR MAXIMUM STRENGm DETERMINATION 514.3.1 For one-or two-story frames, the maximum strength is permitted to be determined by a routine plastic procedure and ignore the frame instability effect (p.o.). For braced multi-story frames, provisions shall be made to include the frame instability effect in the design of bracing system and frame members. For unbraced multi-story frames, the frame instability effect shall be included directly in the calculations for maximum strength. 514.3.2 Stability of Braced Frames 514.3.2.1 The vertical bracing system for plastically designed braced multi-story frame shall be adequate, as determined by an analysis, to: 1. 2.

Prevent buckling of the structure under factored gravity loads Maintain the lateral stability of the structure including the overturning effects of drift, und~ factored gravity plus factored horizontal loads.

514.3.2.2 It is permitted to consider that the vertical bracing system functions together with in-plane shear resisting exterior and interior walls, floor slabs and roof decks, if these walls, slabs and decks are secured to the s~ctural frames. The columns, girders, beams and dIagonal members, when used as the vertical bracing system, could be considered to comprise a vertical cantilever, simply connected truss in the analyses for frame buckling and lateral stability. Axial deformation of all members in the vertical bracing system shaH be included in the lateral stability analysis. The axial force in these members caused by factored gravity plus factored horizontal loads shall not exceed 0.85Py , where Py is the product of yield stress times the profile area of the member. 514.3.2.3 Girders and beams included in the vertical bracing system of a braced multi~story frame shall be proportioned for axial force and moment caused by the concurrent factored horizontal and gravity loads, in accordance with Equation (514-2), with Per taken as the maximum axial strength of the beam, based on the actual slenderness ratio between braced points in the plane of bending.

National Structyral Code of the Philippines, Volume 1

STRUCTURAL STEEL

514.3.2 Stability of Unbraced Frames

514.5 SHEAR

514.3.2.1 The strength of an unbraced multi-story frame shall be determined by an analysis which includes the effect of frame instability and column axial deformation. Such a frame shall be designed to be stable under (1) factored gravity loads and (2) factored gravity loads plus factored horizontal loads. The axial force in the columns at factored load levels shall not exceed 0.75Py

514.5.1 Unless reinforced by diagonal stiffeners or a doubler plate, the webs of columns, beams and girders, including areas within the boundaries of the connections, shall be so proportioned that,

514.4 COLUMNS 514.4.1 In the plane of bending of columns which would develop a plastic hinge at ultimate loading, the slenderness ratio llr shall not exceed Ce , defined in Section 505.3.

where:

V shear that would be produced by the required

factored loading, N d depth of the member, rom tw =0 web thickness, rom

514.6 WEB CRIPPLING 514.4.2 The maximum strength of an axially loaded compression member shall be taken as,

514.6.1 Web stiffeners are required on a member at a point ofload applications where a plastic hinge would form.

(514-1 ) where A is gross of the member and Fa, as defined by Equation (505-1), is based upon the applicable slenderness ratio. 514.4.3 Members subject to combined axial load bending moment shall be proportioned to satisfy the following interaction formulas, (514-2)

514.7 MINIMUM THICKNESS (WIDTH TIDCKNESS RATIOS)

(514-3)

514.7.1 The width-thickness ratio for flanges of rolled W, M or S shapes similar built-up, single-web shapes SUbjected to compression involving hinge rotation under ultimate loading shall not exceed the following values:

in which: M = maximum factored moment, kN-m P factored axial load, kN Pe = Euler buckling load, kN = (23/12)F'.,A, where F',A is as defined in Section 508.2. e", = coefficient defined in Section 508, L Mm= maximum moment that can be resisted by the member in the absence of axial load, kN-m Mp plastic moment, kN-m =F,Z Z = piastic section modulus, mm) For columns braced in the weak direction: (514-4)

M1'I/=Mpx

= },07 1'1/

[

).jF;\\

(// r l • ' AJI'~::S; Mpx 8297'

FvJMPa)

bllt,

248 290 310 345 379 414 448

8.5 8.0 7.4 7.0 6.6 6.3 6.0

(514-5)

I

i

514.7.2 It is permitted to take the thickness of sloping flanges as their average thickness. 514.7.3 The width-thickness ratio of similarly compressed plates in box sections and cover plates shall not exceed For this purpose, 500/ y . the width of a cover plate shall be taken as the distance between longitudinal lines of connecting rivets, high-strength bolts or welds.

JF

For columns unbraced in the weak direction:

M

514.6.2 At points on a member where the concentrated load delivered by the flanges of a member framing into it would produce web crippling opposite the compression flange or high-tensile stress in the connection of the tension flange, web stiffeners are required in accordance with the provisions of Section 511,2.

/


PLASTIC DESIGN

514.7.4 The depth~thickness ratio of webs of members sUbject to plastic bending shall not exceed the value given by Equation (514-7) or (514-8), as applicable,

p)

p-::;0.27

Py

Py

d 1082 ( -:;; ~ 1-1.4- when t

yFy d t

=

675

P

yFy

Py

~ when

fer 9480 M - = - - when -0.5>->-1.0 ry Fy Mp

(

514-10)

(514~7)

wbere: ry = radius of gyration of the member about its weak. axis, mm

> 0.27

(514-8)

M

= lesser of the moments at the ends of the unbraced

segment, kN-m

M/Mp= end moment ratio, positive when the segment is bent in reverse curvature and negative when bent in single curvature.

514.8 CONNECTIONS 514.8.1 All connections, the rigidity ofwhich is essential to the continuity assumed as the basis of the analysis, shall be capable of resisting the moments, shears and axial loads to which they would be subjected by the full factored loading, or any probable partial distribution thereof 514.8.2 Comer connections (haunches) that are tapered or curved for architectural reasons shall be so proportioned that the full plastic bending strength of the section adjacent to the connection can be developed, if required. 514.8.3 Stiffeners shall be used, as required, to preserve the flange continuity of interrupted members at their junction with other members in a continuous frame. Such stiffeners shall be placed in pairs on opposite sides of the web of the member which extends continuously through the joint. 514.8.4 High-strength bolts, A307 bolts, rivets and welds shall be proportioned to resist the forces produced at factored load, using stresses equal to 1.7 times those given in Sections 501 through 513. In general, groove welds are preferable to fillet welds, but their use in mandatory. 514.8.5 High-strength bolts are permitted in joints having painted contact surfaces when these joints are of such size that the slip required to produce bearing would not interfere with the formation, at factored loading, of the plastic hinges assumed in the design.

514.9.2 The foregoing provisions need not apply in the region of the last hinge to form in the failure mechanism assumed as the basis for proportioning a given member, nor in members oriented with their weak. axis normal to the plane of bending. However, in the region of the last hinge to form, and in regions not adjacent to a plastic hinge, the maximum distance between points of lateral support shall be such as to satisfy the requirements of Equations (506-5), (506-6), or (506-7), as well as Equations (508-1) and (508-2). For this case, the values of fa and fb shall be computed from the moment and axial force at factored loading, divided by the applicable load factor. 514.9.3 Members built into a masonry wall and having their web perpendicular to this wall can be assumed to laterally supported with respect to their weak. axis of bending.

514.10 FABRICATION 514.10.1 The provisions of Sections 501 through 513 with respect workmanship shall govern the fabrication of structures, or portions of structures, designed on the basis of maximum strength, subject to the following limitations: 1.

The use of sheared edges shall be avoided in locations subject to plastic hinge rotation at factored loading. If used, they shall be finished smooth by grinding, chipping or planing.

2.

In locations subject to plastic hinge rotation at factored loading, holes for rivets or bolts in the tension area shall be sub-punched and reamed or drilled full size.

514.9 LATERAL BRACING 514.9.1 Members shall be braced adequately to resist ,lateral and torsional displacements at the plastic hinge locations associated with the failure mechanisms. The laterally unsupported distance La from such braced hinge locations to similarly terminated from Equation (514-9) or (514-10), as applicable,

f

'-9480

~=--+25 when

ry

Fy

+1.0>

M >-0.5 Mp .

(514-9)


STRUCTURAL STEEL

SECTION 515 - SEISMIC PROVISIONS FOR STRUCTURAL STEEL BUILDINGS IN SEISMIC ZONE 4 515.1 SCOPE 515.1.1 The provisions contained in this Section are a supplement to the Specifications from Sections 501 through 514. Additional design and detailing requirements are provided to reach the levels of inelastic strength and stability requires to meet the design objectives of this Specification, particularly fur the detailed design of buildings and structures that are subjected to substantial earthquake effects. 515.1.2 When the load combinations of Section 201 sub paragraph (e) for Allowable Stress Design are used, structural steel buildings shall be designed in accordance with the provisions of Sections 501 through 514 and this Section where applicable.

,

515.2 GENERAL 515.2.1 Design and construction of steel framing in lateral force-resisting systems in Seismic Zone 4 shall conform to the requirements ofthis Section.

K-bradng is that form of bracing where a pair of braces located on one side of a column terminates at a single point within the clear column height. Link Beam is that part of a beam in an eccentrically braced frame which is designed to yield shear and/or bending so that buckling of the bracing members prevented. Strength is that strength prescribed in Section 515.4.2. V-bracing is that form of chevron bracing that intersects a beam from above and inverted V -bracing is that form of chevron bracing that intersects a beam from below. X-bracing is that form of bracing where a pair of diagonal. braces cross near mid-length of the bracing members.

515.4 MATERIALS 515.4.1 Quality 5] 5.4.1.1 Structural steel used in lateral force resisting systems shall conform to A36, A441, ASOO, AS01, A572 (Grades 42 and SO), A913 (Grades 50 and 65) and A588. Structural steel confomling to A283 (Grade D) may be use.d for base plates and anchor bolts. l!.:X('EP110N: Other steel listed in the reference standards may be used for the follOWing:

515.3 DEFINITIONS Allowable Stresses are prescribed in Sections 501 through 514 of this Specification.

a. h.

One-story buildings Light-:framed wall .\),stems in accordance with Section 515.12

Chevron Bracing is that form of bracing where a pair of braces located either above or below a beam terminates at a single point within the clear beam span.

515.4.2 Member Strength

Connection is the group of elements that connect the members to the joint.

515.4.2.1 When this section requires the strength of the member be developed, the following shall be used:

Diagonal Bracing is that form of bracing that diagonally connects joints at different levels. Eccentric Braced Frame (EBF) is a diagonal braced frame in which at least one end of each bracing member connects to a beam a short distance from a beam-to-column connection or from another beam-to-brace connection. Girder is the horizontal member in a seismic frame. The words beam and girder may be used interchangeably..

Full Penetration welds Partial penetration and fillet welds Bolts and fillet welds

Joint is the entire assemblage at the intersections of the members.


A 1.7F$

F,

1. 7 Fs

SEISMIC PROVISIONS FOR STRUCTURAL STEEL BUILDING IN SEISMIC ZONE 4

The above load combinations need only be used when specifically referred to.

== Flexural Strength.

Axial dead load Axial load on member due to earthquake = AXial live load =: Compressive axial strength of member == tensile axial strength of member :: shear strength of member = plastic section modulus =:

=

515.4.2.2 Where Fs is the allowable stress value defined in Allowable Stress Design in Sections 505 and 506. For the purpose of determining the member or connection strengths, the allowable stress values shall not be increased by the one-third allowable stress increase per Section 203.4. -515.4.2.3 Members need not be compact unless otherwise required by this Section.

515.5.2 Column Splices 515.5.2.1 Column splices shall have sufficient strength to develop the column forces determined in Section 515.5.1.1 items (1) and (2). Welded column splices that are subject to net tensile forces shall comply with the more critical of the following: l.

Partial penetration welds shall be designed to resist 150 percent of the force determined from Section 515.5.1.1 item (2).

2.

Welding shall develop not less than 50 percent of the flange area strength of the smaller column.

515.5.2.2 Splices employing partial penetration welds shall be located at least 900 mm from girder flanges.

515.5 COLUMN REQUIREMENTS

515.5.3 Slenderness Evaluation

515.5.1 Column Strength

This sub-section is applicable when the proVlslOns are applied to the effective length determination of columns of moment frames resisting earthquake forces. In the plane of the earthquake forces the factor K may be taken as unity when all ofthe following conditions are met:

515.5.1.1 Columns shall satisfy the load combinations required by Section 203.4 at allowable stress limits with stress increases allowed by Section 203.4.2. In addition, in Seismic Zone 4, columns in frames shall have the strength to resist the axial force resulting from the following load combinations in item 1 and 2.

1.

Axial Compression

The column is either continuous or fixed at each joint. The maximum axial compressive stress, la, does not exceed O.4Fy under design loads. • Calculated story drift ratios are less than the values given in Section 208.5.8.

2.

Axial Tension

515.6 ORDINARY MOMENT FRAME REQUIREMENTS EXCEPTIONS: The axial load combinations as outlined above: 1.

2.

Need not exceed either of the maximum force that can be transferred to the column, by elements of the structure, or the limit as determined by the overturning uplift which the foundation is capable of resisting. Need not apply to columns in moment-resisting (5 J5-3) or frames complying with Equation Equation (5 J5-4) where fa is equal to or less than O. 3Fy for all load combinations.

515.6.1 Ordinary moment frames (OMF) shall be designed to resist the load combinations in Section 203.4. 515.6.2 All beam-to-column connections in OMFs which resist earthquake forces shall meet one of the following requirements: l.

Fully restrained (Type FR or Type 1) conforming to Section 515.7.l.

2.

Fully restrained (Type F.R. or Type 1) connections with the design strengths of the connections capable of resisting a combination of gravity loads and 00 times the design seismic forces.


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3.

Partially restrained (Type P.R. connections are permitted provided:

or

Type

3)

1. The connections are designed to resist the load combinatio... ' ~n Sections 203.3 or 203.4 and, 2. . The connections have been demonstrated by cyclic test to have adequate rotation capacity to accommodate a story drift due to times the design seismic forces.

no

515.6.3 The moment frame drift calculations shall include the contribution due to the rotation and distortion of connections.

been reduced, such as for bolt holes. Bolted connections of flanges plates of beam- column joints, shall have the net to-gross area ratio AelAg equal to or greater than l.2Fy IFu.

515.7.2 Panel Zone 515.7.2.1 Strength The shear strength of the joint shall be capable of resisting the shear induced by beam bending moments due to gravity loads plus 1.85 times the prescribed seismic forces, but the shear strength need not exceed that required to develop 0.8Ws of the girders framing into the column flanges at the joint. The joint panel zone shear strength may be obtained from the following formula:

515.6.4 See Section 501.2.2 for the definitions of fully restrained and partially restrained connections.

515.7 SPECIAL MOMENT-RESISTING FRAME (SMRF) REQUIREMENTS 515.7.1 Girder-to-Column Connection 515.7.1.1 Required Strength The girder-to-column connection shall be develop the lesser of the following:

where: be = the width ofthe column flange, mm db = the depth of the beam, mm de = the column depth, mm t = the total thickness of the panel zone including doubler plates, mm ti = the thickness ofthe column flange, mm

adequate to

1.

The strength of the girder in flexure.

2.

The moment corresponding to development of the panel zone shear strength as determined from Equation (515-1).

515.7.2.2 Thickness The panel zone thickness, tz , shall conform to the following formula: (515-2)

where: = the panel zone depth between continuity plates, mm W z = the panel zone width between column flanges, mm dz

Where a connection is not designed to contribute flexural resistance at the joint, it need not develop the required strength above if it can be shown to meet the deformation compatibility requirements of Section 202.8.2.3.

For this purpose, the tz shall not include any doubler plate thickness unless the doubler plate is connected to the column web with plug welds adequate to prevent local buckling of the plate.

515.7.1.2 Connection Strength 515.7.2.3 Doubler Plates Connection configurations utilizing welds or high-strength bolts shall demonstrate, by approved cyclic test results or calculations, the ability to sustain inelastic rotation and develop the strength criteria in Section 515.7.1.1 considering the effect of steel over strength and strain hardening.

515.7.1.3 Flange Detail Limitations

Doubler plates provided to reduce panel zone shear stress or to reduce the web depth thickness ratio shall be placed not more than 2 mm from the column web and shall be welded across the plate width top and bottom with at least 5 mm fillet weld. They shall be either butt or fillet welded to the column flanges to develop the shear strength of the doubler plate. Weld strength shall be as given in Section 515.4.2.

For steel whose specified ultimate strength is less than 1.5 times the specified yield strength, plastic hinges shall not form at locations in which the beam flange area has



is defined for the purpose of this exception as a single line of columns, or parallel lines of columns located within 10 percent of the plan dimension perpendicular to the line of columns; or

515.7.3 Width-Thickness Ratio Girders shall comply with Section 506, except that the flange width-thickness ratio, bf l2ft shall not exceed The width- 0.31~E I Fy . thickness ratio of column sections the requirements of Section 502.6. shall meet The outside wall width-thickness ratio of rectangular tubes used for columns shall not exceed unless otherwise stiffened.

(c)

0.65~EI Fy

515.7.4 Continuity Plates When determining the need for tension flange continuity plates, the value of Phfshall be taken as 1.8(bv1Fyb.

IZAFyc

fa)/IMc >1.0

(515-3)

(5]5-4)

where, (fa > 0) Me ::: the moment at column center line due to the development of plastic hinging in the beam accounting for over-strength and strain hardening, kN-m Mpz= the sum of beam moments when the panel zone shear strength reaches the value specified in Equation (515-1), kN-m

EXCEPTION: Columns meeting the compactness limitations for beams given ill Section 515.7.3 need flot comply with this reqlliremmt provided they conform to one of the follOWing conditions: 1.

Columns with fa less than O.4F;. for all load combinations, other than loads spec!fied in Sectioll 515.5.1 and (a)

(b)

Which are used il1 the top story of a multistory bUilding with building period greater than O. 7 second; Where the Slim of their resistance is less than 20 percent qf the shear ill a story. alld is less than 33 percent of the shear on each qf the column lilies wi/hill th(lt story. A column line

When the design for combined axial compression and bending is proportioned to satisfy Allowable Stress Design without the one-third permissible stress increase.

2.

Columns in any story which has a lateral shear strength 50 percent greater than that qf the story above.

3.

Columns which lateral strengths are not included ill the design to resist code-required shears.

515.7.5 Strength Ratio 515.7.5.1 At any moment frame the joint, the column girder moment strength ratio in the following formula shall be satisfied:

6-61

515.7.6 Trusses in SMRSF 515.7.6.1 Trusses may be used as horizontal members in SMRF if the sum of the truss seismic force flexural strength exceeds the sum of the column seismic force flexural strengths immediately above and below the truss by a factor of at least 1.25. For this determination the strengths of the members shall be reduced by the gravity load effects. In buildings of more than one story, the column axial stress shall not exceed 0.4 f~ and the ratio of the unbraced column height to' the least radius of gyration shall not exceed 60. Columns shall have allowable stresses reduced 25 percent when one end frame into a truss, and 50 percent when both ends frame into trusses. The connection of truss chords to the column shall develop the lesser ofth~ following:

1.

The strength of the truss chord.

2.

The chord force necessary to develop 125 percent of the flexural strength ofthe column.

515.7.7 Girder-Column Joint Restraint 515.7.7.1 Restrained Joint Where it can be shown that the columns of SMRF remain elastic, the flanges of the columns need be laterally supported only at the level of the girder top flange. Columns may be assumed to remain elastic if one of the following conditions is satisfied: 1.

The ratio in Equation (515-3) or (515-4) is greater than] .25.


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2.

3.

The flexural strength of the column is at least 1.25 times the moment that corresponds to a total panel zone shear strength. Girder flexural strength or panel zone strength will limit column stress (fa+fbx+fhy) to Fy of the column.

The column will remain elastic under gravity loads plus times the design seismic forces.

no

Where the column cannot be shown to remain elastic, the column flanges shall be laterally supported at the levels of the girder top and bottom flanges. The column flange lateral support shall be capable of resisting a force equal to one percent of the girder flange capacity at allowable stress and at a limiting displacement perpendicular to the frame 5 mm. Required bracing members may brace the column flanges either directly, or indirectly through the column web or girder flanges.

515.7.10 Moment Frame Drift Calculation 515.7.10.1 Moment frame drift calculations shall include bending and shear contributions from the clear girder and column spans, column axial deformation, and the rotation: and distortion ofthe panel zone.

EXCEPTIONS: 1.

Drift calculations may be based on column and girder center lines where either of the follOWing conditions are met: (a) It can be demonstrated that the drift so computedfor frames of similar cOl~figuration is typically within 15 percent of that determined above. (b) The column panel zone strellgth call develop 0.8 2M. of the girders framing to the column .panges at the joint.

515.7.7.2 Unrestrained Joint Columns without lateral support transverse to a joint shall t::anform to the requirements of Section 501.4, with the column considered as pin ended and the length taken as the distance between lateral supports conforming with Section 515.7.7.1. The column stress,Ja, shall be determined from gravity loads plus the lesser ofthe following:

no times the design seismic forces.

.2.

Column arial deformations maybe neglected if they contribute less than 10 percent to the total drift.

515.8 REQUIREMENTS FOR BRACED

FRAMES

515.8.1 General

The forces corresponding to either 125 percent of the girder flexural strength or the panel zone shear Strength. The stress,h" shall include the effects of the bracing force specified in Section 515.7.7.1 and P..1 effects.

IIr for such columns shall not exceed 60.

515.8.1.1 The provisions of this section apply to all braced frames, except Special Concentrically Braced Frames designed in accordance with Section 515.9 or Eccentrically Braced Frames (EBF) designed in accordance with Section 515.10. Those members which resist seismic forces totally or partially by shear or flexure shall be designed 10 accordance with Section 515. g except Section 515.8.3.

At truss frames, the culumn shall be braced at each truss chord for a lateral force of one percent of the compression yield strength ofthe truss chord.

515.8.2 Braciog Members

515.7.8 Beam Braciog

515.8.2.1 Slenderness In Seismic Zone 4, the Ilr for bracing members shall not exceed 4 .3~ E I Fy except as permitted in Sections 515. g.4

Both flanges of beams shall be braced directly or indirectly. The beam bracing between column centerlines shall not exceed 96rp. In addition, braces shall be placed at concentrated loads where a hinge may form. 515.7.9 Changes in Beam Flange Area Abrupt changes in beam flange area are not permitted within possible plastic hinge regions of special moment resistant frames.

and 515.8.5. 515.8.2.2 Stress Reduction The allowable stress, Fa.< for bracing members resisting seismic forces in compression is given by the following formula:

Fas= f3Fa


(515-4)


Where: p : .: the stress reduction factor determine',d from the following formula:

5.03

Rectangular tubes shall have outside width-thickness ratio not exceeding O.65~ E ! Fy .

EXCEPTION:

1

P== --Kl---'-

Compression elements stiffened to resist local buckling.

l+(·I_) 2ec

Fa ::.: the allowable axial compression stress, allowed in ASD.

515.8.3 Bracing connedions. 515.8.3.1 Forces.

EXCEPTION:

Bracing connections shall have the strength to resist the least of the following:

Bracing members carrying gravity load.. may be designed llsing the column strength reqllirement and load combinations ofSection 515.5.1.

2.

515.S.2.3 Latera) forte distribution

3.

The seismic lateral force along any line of bracing shall be distributed to the various members so that neither the sum of the horizontal component.s of the forces in members acting in tension nor the sum of the horizontal components of forces in members acting in compression exceeds 70 percent of the total force.

Bracing connections shall, as a minim~ satisfy the load combinations required by Section 2.I.I.e at allowable stress design limits with stress increases allowed by Section 2.1. 1. c. These combinations shall include the provisions for Sections 515.8.2.2 and 515.8.4.1.

EXCEPTION: Where compression bracing acting alone has the strength, neglecting the strength-reduction factor A to resist no times the design seismic force, such distribution is Iwl required. A line of bracing is defined, for the purpose of this provision, as a single line, or parallel lines located within 10 percent of the dimension of the structure perpendicular to the line ofbracing.

1.

The tensile strength of the bracing, Pst. J.i" times the force in the brace due to design seismic forces, in combination with gravity loads. The maximum force that can be transferred to the brace by the system.

Beam-to-column connections for beams, that are part of the bracing system shall have 'the capacity to transfer the force determined above. Where eccentricities in the frame geometry or connection load path exist, the affected members and connections shall have the strength to resist all secondary forces resulting from the eccentricities fn combination with all primary forces using the lesser of the forces determined above. 515.8.3.2 Net area. In bolted brace connections, the ratio of effective net section area to gross section area shall satisfy the formula:

515.8.2.4 Built-up members The llr of individual parts of built-up bracing members between stitches when computed about a line perpendicular to the axis through the parts, shall not be greater than 75 percent ofthe llr of the member as a whole. 515.S.2.5 Compression elements in brates The width-thickness ratio of stiffened and unstiffened compression elements used in braces shall be as shown in Table 502.1 for compact sections.

where: Ae effective net area as defined in ASD. Fu =:: minimum tensile strength.

F

= stress in brace as determined in Section 515.8.3.1 a = fraction of the member force from Section 515.8.3.1 ·that is transferred across a particular section.

The width-ihickness ratio of angle sections shall be limited to O.31~E I Fy. Circular sections shall have outside diameter-waIl thickness ratio not exceeding 7. 63E!/y.

National Structural Code of

the


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515.8.4 Bracing configuration.

515.9 REQUIREMENTS SPECIAL CONCENTRICALLY BRACED FRAME

515.8.4.1 Chevron bracing Chevron bracing shall conform with the following: 1.

2. 3.

Bracing members shall be designed for 1.5 times the otherwise prescribed seismic forces, in addition to the requirement of Section 515.8.2.2. The beam intersected by chevron braces shall be continuous between columns. Where chevron braces intersect a beam from below, i.e. inverted V brace, the beam shall be capable of supporting all tributary gravity loads presuming the bracing not to exist.

EXCEPTION:

515.9.1 General The provisions of this section apply to special concentrically braced frame structures as defined in Section 2.2.2. All members and connections in special braced frames shall be designed and detailed to resist shear and flexure caused by eccentricities in the geometry of the members comprising the frame in accordance with Section 515.9. Any member intersected by a brace shall be continuous through the connection. Horizontal bracing that transfers forces between horizontally offset bracing in the vertical plane shall be subject to the requirements of Section 515.9, except Sections 515.9.2.3; 515.8.4.1, Item 3; and 515.8.4.2. Horizontal bracing other than the above is not subjected to the requirements of Section 515.9.

This limitation need not apply to penthouses, one-story building or top story ofbuilding.

515.9.2 Bracing Members

51~.8.4.2

515.9.2.1 Slenderness

K-bracing

K-bracing is prohibited except as permitted by Section '515.8.5. 515.8.4.3 Non-concentric bracing Non-concentric bracing shall conform with the following: 1. 2.

Any member intersected by the brace shall be continuous through the connection. When the eccentricity of the brace is greater than the depth of the intersected member at the eccentric location, the affected member shall have the strength to resist the forces prescribed in Section 515.8.2.2, including the effects of all secondary forces resulting from eccentricities.

The kllr

for

bracing

members

shall

not

exceed

5.87.JE I Fy except as permitted in Section 515.9.6. 515.9.2.2 Lateral-force distribution The seismic lateral force along any line of bracing shall be distributed to various members so that neither the sum of the horizontal components of forces in members acting in compression or tension exceed 70 percent of the total force.

EXCEPTION:

Where compression bracing acting alone has the strength to resist no times the design seismic force. such distribution is not required

515.8.5 One- and two- story building. Braced frames not meeting the requirements of Sections 515.8.2 through 515.8.4 may be used in buildings not over two stories in height and in roof structures, if the braces have the strength to resist Do times the design seismic forces. 515.8.6 Non-building Structures. Non-building structures with Rw values defined by Table 2.21 need comply only with the provisions of Section 515.8.3.

A line of bracing is defined, for the purposes of this provision, as a single line or parallel lines within 10 percent of the dimension of the structure perpendicular to the line ofbracing. 515.9.2.3 Built-up members The spacing of stitches shall be such that the slenderness ratio (/ir) of individual elements between the stitches does not exceed 0.4 times the governing slenderness ratio of the built-up members. The total shear strength of the stitches shall be at least equal to the tensile strength of each element The spacing of the stitches shall be uniform and not less than two stitches shall be used. Bolted stitches shall not belocated within the middle one fourth of the clear brace length.


REQUIREMENTS SPECIAL CONCENTRICALLY BRACED FRAME

5-65

515.9.3.3 Gusset Plates

lrhere it can be shown that the braces can buckle without Causing shear in the stitches, the spacing of the stitches shall be such that the slenderness ratio (llr) of the uldividual element between the stitches does not exceed (J.75 times the governing slenderness ratio of the built-up member. 515.9.2.4 Compression elements in braces The width-thickness ratio of the compression elements used in braces shall meet the requirements of ASD Table 502.1, for compact sections. The width-thickness ratio of angle section shall be limited to O.3I~ E I Fy. Circular sections shall have outside diameter-wall thickness ratio . lnot exceeding 7.63E!FJ" rectangular tubes shalt have 'outside wall width-thickness ratio not exceeding

O.65~E I Fy

End connections of braces shall provide a flexural strength in excess ofthat ofthe brace gross section about the critical buckling axis.

EXCEPTION: Where the out-£?f-plane buckling strength of the brace is less than the in-plane buckling strength, the brace is permitted to terminate on a single gusset plate connection with a setback oftwo times the gusset thickness from a line about which the gusset plate may bend unrestrained by the columll or beam joints. The gusset plate shall be designed to carry the compressive strength of the brace without buckling. 515.9.4 Bracing configuration 515.9.4.1 Chevron bracing Chevron bracing shall conform with the following:

tCompression elements stiffened to resist local buckling.

1.

The beam intersected by chevron braces shall be continuous between columns.

2.

Where chevron braces intersect a beam from below, i.e., inverted V brace, the beam shall be capable of supporting all tributary gravity toads presuming the bracing not to exist.

3.

A beam intersected by chevron braces shall have the strength to support the following tributary gravit)i loads and unbalanced brace force combinations:

;·515.9.3 Bracing connectioDs

Bracing connections shall have the strength to resist the lesser of the following: The strength of brace in axial tension, Pst.

flo times the force in the brace due to the design

1.2D + O.SL + Pb 0.9D- P b

seismic forces, in combination with gravity loads. The maximum force that can be transferred to the brace by the system. Hr""'T'" connections shall, as a minimum. satisfy the load

required by Section 2.1.1 at allowable stress s with stress increases allowed by Section 2.] .l.c. to-column connections for beams that are part of the ng system shall have the capacity to transfer the force ed above. Where eccentricities in the frame or connection load path exist, the affected lPrtll~p"" and connectrons shall have the strength to resist secondary forces resulting from the eccentricities in . . with all primary forces using the lesser of the determined above.

(SIS-8) (SIS-9)

Where:

D L == Ph ==

4.

tributary dead load tributary live load the maximum unbalanced post~buckling force that can be applied to the beam by the braces. For this purpose, the maximum unbalanced force may be computed using a minimum of PSI for the tension and a maximum of 0.3P,c for the compressioll. brace. Both flanges of beams at the point of intersection of chevron braces shall be laterally supported directly or indirectly.

9.3.2 Net area bolted brace connections, the ratio of effective net area to gross section shall satisfY Equation (S] S-6) Section 5158.3.2.


STRUCTURAL STEEL

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EXCEPTION:

515.10.4 Link Beam Rotation The rotation of the link segment relative to the rest of

Limitations 2 and 3 need not apply to penthouses, one beam at a total frame drift of Lk times the drift story buildings or the top story ojhuilding.'" for prescribed seismic forces, shall not exceed th~ following:

515.9.4.2 K-Bradng 1.

0.090 radians for link segments having clear lengths of 1.6M/Y. or less.

2.

0.30 radians for link segments having clear of 3.0 M/Vs or greater.

3.

A value obtained by linear interpolation for lengths between the above limits.

K bracing is prohibited.

515.9.5 Columns Columns in braced frames shall meet the requirements of Section 515.7.3. In addition to meeting the requirements of Section 515.5.1 and 515.5.2, columns splices shall be designed to develop the full shear strength and 50 percent of the full moment strength of the section. Splices shall be located in the middle one third of the column clear height.

515.9.6

Non-building structures

515.10.5 Link beam web The web of the link beam shall be single thickness without doubler plate reinforcement. No openings shall be placed in the web of a link beam. The web shear shall not exceed 0.8Vs, under prescribe lateral forces.

Non-building structures with R", values defined by Table 2.21 need comply only with the provisions of Sections 515.8.3.1 and 515.8.3.2.

515.10.6 Beam connection braces

515.10 ECCENTRIC BRACED FRAME (EBF) REQUIREMENTS

Brace-to-beam connections shall develop the compression strength of the brace and transfer this force to the beam web. No part of the brace-to-beam connection shall extend into the web area of a link beam.

515.10.1General Eccentrically braced frames accordance with this section.

515.10.7 Link beam stiffeners shall

be

designed

In

515.10.2 Link beam There shall be a link beam provided at least at one end of each brace. Beams in EBF's shall comply with the requirements of Sec. 4.5.1.4.1, except that the flange width-thickness ratio, h/2t" shall not exceed OJ I~ HII'y .

Link beam shall have full depth web stiffeners on both sides of the beam web at the brace end of the link beam. In addition, for link beams with clear lengths within the limits of Section 515.10.4 Item 3, full depth stiffeners shall be placed a distance hI from each end of the link. The stiffeners shall have a combined width not less than br 2tw and Ii thickness not less than 0.75 t", or Less than 10 mm.

515.10.8 Intenoediate stiffeners Intermediate full depth web stiffeners shall be provided in either of the following conditions:

515.10.3 Link beam strength Link beam shear strength V" and flexural strength, /0.1." are the strengths as defined in Section 5 J5.4.1. Where the link beam strength is governed by shear, the flexural and axial capacities within the link shall be calculated using the beam flanges only. A reduced flexural strength Mrs. for use in Sections 515.10.8 and 515.10.13 is defined as Z(F,. - {,,), Wherefo is less than 0.15 [~.,fo may be neglected. "

Where the link beam strength is controlled by Vs. Where the link beam strength is controlled by flexure and the shear determined by applying the reduced flell.'Ural strength., M". exceeds 0.45 !~df.

515.10.9 Web stiffener spacing Where intermediate web stiffeners are required, the spacing

shall c.onfoml to the requirements given below.

For Link beams with a rotation angle of 0.09 radian, the

spacing shall not exceed 381,r - £115.


REQUIREMENTS SPEQAL CONCENTRICALLY BRACED FRAME

For link beams with a rotation angle of 0.03 radian or less the spacing shall not exceed 56/,. - dIS. Interpolation may be used for rotation angles between 0.03 and 0.09 radian.

5-67

strength. Each brace and beam assembly outside the link shall have combined reduced flexural strengths, Mm at least 1.3 times the forces corresponding to the controlling link beam strength.

515.10.10 Web Stiffener Location 515.10.14 Column strength For beams 610mm in depth and greater, intermediate full depth web stiffeners are required on both sides of the web. Such web stiffeners are required only on one side of the beam web for beams less than 610mm in depth. The stiffener thickness, I,., of one side stiffeners shall be not less than 10mm and the width shall not be less than

Columns shall be designed to remain elastic at 1.25 times the strength of the EBF bay, as defined in Section 515.10.13. Column strength need not exceed the requirements of Section 515.5.

(hI2) - t,..

515.10.15 Roof link beam

515.10.l1Stiffener Welds

A link beam is not required in roof beams for EBF over five stories. 515.10.16 Concentric brace in combination

Fillet welds connecting the stiffener to the beam web shall develop a stiffener force of AsFy . Fillet welds connecting the stiffener to the flanges shall develop a stiffener force of A sFJ4.

Where:

As! b =

hI of stiffener. width ofstiffener plate

515.10.12 Link beam-column connection Length of link beam connected to the column flange shall not exceed L6MIV,

The first story of an EBF bay over five stories in height may be concentrically braced if this story can be shown to have an elastic capacity 50 percent greater than the yield capacity of the story frames above the first story. 515.10.17 Axial forces Axial forces in beams ofEBF frames due to braces and due to transfer of seismic force to the end of the frames shall be included in the frame calculations. 515.10.18 Beam flanges

Where a link beam is connected to the column flange the following requirements shall be met: The beam flanges shall have full penetration welds to the column. Where the link beam strength is controlled by shear as per Section 515.10.8 the web connection shall be welded to develop the full link beam web shear strength. Where the link beam is connected to the column web, the beam flanges shall have full penetration welds to the connection plates and the web connection shall be welded to develop the link beam web shear strength. Rotation between the link beam and the column shall not exceed 0.015 radian at a total frame drift of L1A/.

Top and bottom flanges of EBF frame beams shall be laterally braced at the ends of link beams and at intervalS' not exceeding 0.45J E I Fy times the beam flange width. End bracing shall be designed to resist 6.0 percent of the beam flange strength, defined as F;bf If Intermediate bracing shall be designed to resist 1.0 percent of the beam flange force at the brace point using the link beam strength determined in Sec. 515. 10.13. 515.10.19 Beam-column connection Beam connections to columns may be designed as pins in the plane of the beam web if the link beam is not adjacent to the column. Such connection must have capacity to resist a torsional moment of 0.01 f~.b;lt1.

515.10.13 Brace and beam strength. The controlling link beam strength is either the shear strength, Vs, or the reduced flexural strength, Mrs, whichever results in the lesser force in the brace. Each brace and beam outside the link shall have the axial strength or reduced flexural strength, Mrs, at least 1.5 times the forces corresponding to the controlling link beam


of the


STRUCTURAL STEEL

SECTION 515.11 REQUIREMENTS SPECIAL TRUSS MOMENT FRAMES

gravity loads and lateral forces necessary to develop maximum amplified vertical shear force in all special segments, VS!h given by the following formula: 3.4M.

.

V-"""-L-+O.l 1E1

(L

Ly)...

.

L3

.

+LL.5(Pg ,+0.3P",)sma

515.11.IGeneraI Special truss moment frames of steel shall be designed in accordance with this section. 515.11.2 Special segment Each horizontal truss which is part of the moment frame shall have a special segment located within the middle one half length of the truss. Such trusses shall be limited to span lengths between columns not to exceed 15240mm and overall depth not to exceed 1829mm. The length of the special segment shall have a range from 0.1 to 0.5 times the truss span length. The length-to-depth ratio of any panel in the special segment shall be limited to a maximum of 0.67. All panels within the special segment shall be either Vierendeel or X-braced, not a combination thereof • Where diagonal members are used in the special segment, they shall be arrange in an X pattern separated by vertical members. Such diagonal members shall have the strength to resist a force at least equal to 0.25 times the diagonal member tension strength. Bolted connections shall not be used for web members within the special segment. Splicing of chord members shall not be permitted within the special segment or within a one-half panel length from the ends of the special segment. Axial stresses in diagonal web members due to concentrated dead load plus live loads acting within the special segment shall not exceed 0.03 Fy •

where:

EI flexural stiffness ofthe chord members.

L = span length ofthe truss.

= 0.9 times the length of the special segment.

Ls flexural strength of the chord members.

Ms Psc = axial compression strength of the diagonal

member. axial tension strength of diagonal members. angle that the diagonal member make with the horizontal 515.11.S

Connections

Connections of all elements in the truss frames, including those within the truss, shall conform to the requirements of Section 208.6.2. 515.11.6

Compactness

Diagonal web members of the special segment shall be made of flat bars. The width-thickness ratio of such flat bars shall not exceed 2.5. The width-thickness ratio of angles, and flanges and webs of T sections used for chord members in the special segment shall not exceed

0.31JE I Fy.

515.11.3 Special segment members strength

515.11.7Lateral bracing

In the fully yielded state, the special segment shall develop vertical shear strength through flexural strength of the chord members and through axial tension and compression strength of diagonal web members. The top and bottom chord members in the special segment shall be made of identical sections and shall provide at least 25 percent of the required vertical shear strength. The maximum axial stress in the chord members shall not exceed 0.4 Fy . Diagonal members. in any panel of the special segment shall be made of identical sections. The end connections of diagonal web members in the special segment shall have strength to resist a minimum force equal to Pst of the member.

Top and bottom chords of the trusses shall be laterally

braced at the ends of the segment, and at intervals not to

exceed Lp along the entire length ofthe truss.

where:

515.11.4 Non-special segment members strength

515.11.8Materials

All members and connections of special truss moment frames, except those in Section 515.11.3, shall have strength to resist t~e forces due to combination of specified

The material specifications of Section 501.3 are superseded by the requirements of Section 515.4.1 for all elements in the special trusses.

Lp

~ 176r,~:,

Each lateral brace at the ends of and within the special segment shall have strength to resist at least 5 percent of Pst of the chord member. Lateral braces outside of the special segment shall have strength to resist at least 2.5 percent of . P3t of the chord member.



SECTION 516 • SEISMIC PROVISIONS FOR STRUCTURAL STEEL BUILDINGS IN SEISMIC . ZONE 2

accommodate a story drift due to design seismic forces.

See Chapter 5 for definition offully restrained connections.

Design and construction of steel framing in lateral~force resisting systems in Seismic Zone 2 shall conform to the requirements of this code. Additionally, in Seismic Zone 2, such framing shall conform to the requirements of this section.

516.2 Definitions

Definitions shall be as prescribed in Section 515.3.

~16.5 SPECIAL MOMENT (SMRF) REQUIREMENTS

1.

The strength of the girder in flexure. The moment corresponding to development of the panel zone shear strength as determined from Formula (11-1).

EX('EPTION:

EXCEPTION:

Ordinary moment frames in accordance with Section

516.4.

MOMENT

FRAME

Ordinary moment frames (OMF) shall be designed to resist the load combination of Section 203.4 for Allowable Stress Design. All beam-to-column connections in OMFs that resist earthquake forces shall meet one of the follo,",,1.ng requirements: Fully restrained (Type F.R. or Type 1) conforming to Section 516.5.1. Fully restrained (Type F.R. or Type 1) connections with the design strength of the connections capable of resisting a combination of gravity loads and times the design seismic forces.

no

3.

FRAME

516.5.1.1 Required Strength. The girder4a-column connection shall be adequate to develop the lesser of the following:

Materials shall be as prescribed in Section 515.4.

2.

RESISTING

516.5.1 Girder-to-column connections

2.

516.3 Materials

1.

no times the

3.3 The moment frame drift calculations shall include the contribution due to the rotation and distortion of the connection.

516.1 General

516.4 ORDINARY REQUIREMENTS

5-69

Partially restrained (Type P.R. or Type connections are permitted as follows:

3)

3. 1 The connections are designed to resist the load combinations in Section 203.4 for Allowable Stress Design., and 3.2 The connection have been demonstrated by cyclic tests to have adequate rotation capacity to

Where a connection is not designed to contribute flexural resistance at the joint, it need not develop the required strength if it can be shown to meet the deformation compatibility requirements of Section 1633.2.4

516.5.1.2. Connection Strength. The girder to column connection may be considered to be adequate to develop the flexural strength of the girder if it conforms to the following:' • 1. 2.

The flanges have full-penetration butt welds to the columns. The girder-ta-web connections shall be capable of resisting the girder shear determined for the combination of gravity loads and the seismic shear forces which result from the compliance with Section 516.5.1.1. This connection strength need not exceed that required to develop gravity load plus times the girder shear resulting from the design seismic forces.

no

Where the flexural strength of the girder flanges is greater than 70 percent of the flexural strength of the entire section [ i.e. bt{d-lpFy>O. 7Z;xF)'] the web connection may be made by means ofwelding or high strength bolting. F or girders not meeting the criteria in the paragraph above, the girder web-to-column connection shall be made by means of welding the web directly or through shear tabs to the column. That welding shall have a strength capable of development at least 20 percent of the flexural strength of the girder web. The girder shear shall be resisted by means of additional welds or friction-type high strength bolts or both.


STRUCTURAL STEEL

5-70

516.5.1.3 Alternate connection. Connection configurations utilizing welds or high-strength bolts not conforming with Section 516.5.1.2 may be used if they are shown by test or calculation to meet the criteria in Section 516.5. L L Where conformance is shown by calculation, 125 percent of the strength of the connecting elements may be used. 516.5.1.4 Flange detail limitations. For steel whose specified strength is less than 1,5 time the specified yield strength, plastic hinges shall not form at locations in which the beam flange area has been reduced, such as for bolt holes. Bolted connections of flange plates of beam-column joints shall have the net-to-gross area ratio A,/Ag equal to greater than I.2F;F.,. 516.5.2 Trusses in SMRF. Trusses may be used as horizontal members in SMRF if the sum of the truss seismic force flexural strength exceeds the sum of the column seismic force flexural strength immediately above and below the truss by a factor of at least 1.25. For this determination, the strengths of the members shall be reduced by the gravity load effects. In buildings of more than one story, the column axial stress shall not exceed O.4Fy and the ratio of the un~raced column height to the least radius of gyration shall not exceed 60. The connection of the truss chords to the column shall develop the lesser ofthe following: 1. The strength of the truss chord. 2. The chord force necessary to develop 125 percent of the flexural strength of the column.

column flanges directly or indirectly through the column web or the girder flanges. 515.5.3.2 Unrestrained joint Columns without lateral support transverse to a joint shall conform to the requirements of Division m,.with the columns considered as a pin ended and the length taken as the distance between lateral supports conforming with Section 516.5.3. L The column stress Fa, shall be determined from the gravity loads plus the lesser of the following:

no

times the design seismic forces. The forces corresponding to either 125 percent of the girder flexural strength or the panel zone shear strength.

1. 2.

The stress, /by> shall include the effects of the bracing force specified in Section 516.5.3.1 and PA effects. L'r for such columns shall not exceed 60.

At truss frames, the columns shall be braced at each truss chord for a lateral force equal to one percent of the corresponding yield strength ofthe chord. 516.5.4 Changes in beam flange area. Abrupt changes in beam flange area are not permitted within possible plastic hinge regions of the special moment-resistant frames. 516.6 Requirements for Braced Frames

516.5.3 Girder-column joint restraint 516.5.3.1 Restrained joint. Where it can be shown that the columns of SMRF remain elastic, the flanges of the columns need be laterally supported only at the level of the girder top flange. Columns may be assumed to remain elastic if one of the following conditions is satisfied: 1. The ratio in Formula (515-3) or (515-4) is grater than 1.25. 2. The flexural strength of the column is at least 1.25 times the moment that corresponds to the panel zone shear strength. 3. Girder flexural strength or panel zone strength will limit column stress (fu+."'-,+/h).) to f~, of the column. 4. The column will remain elastic under gravity load plus no time the design seismic forces.

516.6.1 General The provisions of this section apply to all braced frames, except special concentrically braced frames designed in accordance with Section 515.9 and eccentrically braced frames designed in accordance with Section 515.10. Those members which resist seismic forces totally or partially by shear or flexure shall be designed in accordance with Section 516.5. 516.6.2 Bracing members 516.6.2.1 Stress rednction. The allowable stress, Fa., for bracing members resisting seismic forces in compression shall be determined from the following formula: . Fas /3Fa (516-1) where:

P Where the column cannot be shown to remain elastic, the column flanges shall be laterally supported at the levels of the girder top and bottom flanges. The column flange lateral support shall be capable of resisting a force equal to one percent of the girder flange capacity at the allowable stresses [ and at a limiting displacement perpendicular to the frame of 5.08 mm]. Required bracing members may brace the

=

the stress-reduction factor determined from the following formula: B

=

ll{l + [(K/ir)/2CcIJ > 0.8

Fa= the allowable axial compressive stress allowed in DivisionID.


l


supporting all tributary gravity loads presuming the bracing not to exist.

EXCEPTION: Bracing members carrying gravity loads may be designed using the column strength requirement and the load combination of Sectio11515.5.1, Item 1.

516.6.2.2 Built-up members. The llr of individual parts of built-up bracing members between stitches, when computed about a line perpendicular to the axis through the parts, shall not be greater than 75 percent of the Ilr of the member as a whole. 516.6.2.3 Compression elements in brates. The width-to thickness ratio of stiffened and unstiffened compression elements used in braces shall be shown this Chapter.

516.6.3.1 Forces. Bracing connections shall be designed the lesser of the following: 1.

3.

EXCEPTION: These limitations need not apply to penthouses, one-story blli/dings or the top story if buildings.

516.6.5 One- and two-story buildings. Braced frames not meeting the requirements of Section 516.6.2 and 516.6.4 may not be used in buildings not over two stories in height and in roof structures as defined in Chapter 15 if the braces have the strength to resist times the design seismic forces.

no

516.6.6 Nonbuilding structures. Nonbuilding structures with R values defined by Table 208-13, need comply only with the provisions of Section 516.6.3.

516.6.3 Bracing connections

2.

5-71

The tensile strength of the bracing. time the force in the brace due to design seismic forces. The maximum force that can be transferred to the brace by the system

no

516.7 Special Concentrically Braced Frames. Special concentrically braced frames shall comply with the requirements of Section 515.9, 516.8 Eccentrically Braced Frames. Eccentrically braced frames shaH comply with the requirements of Section 515.1 O.

Beam-to-column connections for beams that are part of the bracing system shall have the capacity to transfer the force determined above.

516.9 Nondestructive Testing. Nondestructive testing shall comply with the provisions of Section 1703 of 1997 Uniform Building Code.

516.6.3.2 Net Area. 1n bolted connections, the ratio of effective net section area to gross section area shall satisfy the formula:

516.10 Special Truss Moment Frames. Special truss moment frames shall comply with the requirements of Section 51 5.11.

Ae 1.2aF* ::::--- Ag Fu = =

a.

=

(516-3)

effective net area as defined in Division III. gross area of member. minimum tensile strength. stress in the brace due to forces determined in Section 515.8.3.1. fraction of the member force from Section 515.8.3.1 that is transferred across a particular net section.

516.6.4 Bracing conftguration for chevron and K bracing. Bracing members shall be designed for 1.5 times the otherwise prescribed forces. The beam intersected by chevron braces shall be continuous between columns. Where chevron braces intersect a beam from below, i.e., inverted V brace, the beam shall be capable of


5-72

SECTION 517 WALL SYSTEMS

STRUCTURAL STEEL

LIGHT FRAMED

517.1 General. A steel stud wall system consists of vertical steel studs with stee~ structural wood or gypsum shear panels, used to resist horizontal wind or earthquake.

SEC.518 - INSPECTION Tension groove welded connections between primary members of the frames which are part of the lateral load resisting system shall be tested by non-destructive methods for compliance with AWSD 1.1-90 and job specifications. A program for this testing shall be established by the engineer.

In Seismic Zone 4, steel stud wall systems may be used to resist the specified seismic forces in buildings not over five stories high. Such systems shall comply with the following:

The IIr ofthe brace may exceed 200 and is unlimited. All boundary members, chords, and collectors, shall be designed and detailed to transmit the induced axial forces. 3. Connection of the diagonal bracing member, top chord splices, boundary members and collectors shall be designed to develop the full tensile strength of the member or flo times the otherwise prescribed seismic forces. 4. Vertical and diagonal members of the braced bay shall be anchored so the bottom track is not required to resist uplift forces by bending ofthe track web. 5. ' Both flanges of studs in a bracing panel shall be braced to prevent lateral torsional buckling. Wire tied bridging shall not be considered to provide such restraint. 6. Screws shall not be used to resist lateral forces by pullout resistance. Provision shall be made for pretensioning or other 7. methods of installation of tension only bracing to guard against loose diagonal straps. 1. 2.

517.2 Boundary members and ancborage. Boundary members and the uplift anchorage thereto shall have the strength to resist the forces determined by the load combinations in Section 515.5.1.

517.3 Wood structural panel sbeatbing. \\'here wood structural panels provide lateral resistance, the design and construction of such walls shall be in accordance with the additional requirements of this .section. Perimeter members at openings shall be provided and shall be detailed to distribute the shearing stresses. Wood sheathing shall not be used to splice these members. Wood structural panels shall be manufactured using exterior glue. Wall studs and track shall have a minimum uncoated base metal thickness of not less than 0.8mm and shall not have an uncoated base metal thickness greater l.lOmm.


5-73

NUMERICAL VALUES

TABLE 1

Allowable Stress (MPa) F~,

(MPa)

0.40Fy b,.

0.75F/

91.0 96.5 100.0

170.9 181.3 186.1

217.1 223.3

276 290 310

110.3 115.8 124.1

]24.1 l30.3 139.9

165.4 173.7 186.1

182.0 190.9 204.7

206.8 217.1 233.0

248.2 260.6 279.2

317 345 379

126.8 137.8 151.6

142.7 155.1 170.9

190.2 206.8 227.5

209.6 227.5 250.2

237.8 258.5 284.7

285.4 310.2 341.2

414 448 483

165.4 179.2 193.0

186.1 202.0 217.1

248.2 268.8 289.5

273.0 295.7

310.2 336.4

372.3 403.3 434.3

279.2 310.2

372.3 413.6

248.2 620 275.7 689 a See Article 504.1, 504.3 Tension b See Article 504.3, 506.4, 51Ll Shear See Article 506, I, 506.2 Bending d See Article 510,8 Bearing C See Article 507.3 Shear in Plate Girders

558.4 620,5

C


of

the Philippines, Volume

1

STRUCTURAL STEEL

6-74

NUMERICAL VALUES TABLE 2

5 .:::

ASTM Desig nation

Fy

FI<

(MPa)

(MFa)

Connected Part ofDesignated Steel Tension Bearing 0.5Fa 1.2Fb

Bolt or Threaded Part of Designated Steel Tension 0.33F c

Shear 0.22Ft

131.6 A242 A441 A588 rIO

~ p..,

483 462 434 414

241.3 230.9 217.1 206.8

579.1 554.3 521.2 496.4

310

155.1

372.3

400

199.9

479.8

276 290 290 345 414 448 689 620 310 345 310 345 379 414 448 483 345 345

414 448 483 517 552 586 483 448

189.6 199.9 206.8 224.0 258.5 275.7 379.2 344.7 224.0 241.3 206.8 224.0 241.3 258.5 275.7 293.0 241.3 224.0

455.0 479.8 496.4 537.7 620.5 661.8 910.1 827.3 537.7 579.1 496.4 537.7 579.1 620.5 661.8 703.2 579.1 537.7

483

621-758

310.2

744.6

345 317 290 276f

A500 227/269g 290/317g 317/345 g

1$

1 1:

159.2 152.3 143.4 136.5

f-o! .... 0" I

.] I ~I '"0 !li i Q)I

A572

.,gl (/)

~"

~

A514

ui' Q,)

1i

s::

"," Q,)

c..

.! (/)

A606 A607

136.5 148.2 170.9 182.0 250.2 227.5

70.3 76.5 88.2 93.7 128.9 117.2

91.0 98.5 113.7 ]21.3 166.8 151.6

634 182.0 827 273.0 140.6 724 123.4 159.2 558 239.2 !Xl ]36.5 204.7 621 105.4 400 • On effective net area, see Articles 504.1, 510.4. b Produced by fastener in shear, see Article 510.3.7. Note that smaller maximum design bearing stresses, as a function of hole spacing, may be required by Articles 510.3.& and 510.3.9. C On nominal body area, see Table 510-7. d Threads not excluded from shear plane, see Table 510-7. e Threads excluded from shear plane, see Table 510-7. f For A441 material only. g Smaller value for circular shapes, larger value for square or rectangular shapes. Note: For dimensional and size limitations, see the appropriate ASTM Specification.

""

~

0


L_~_~~~~" __ ,~

5-75

NUMERICAL VALUES

TABLE 3 VALUESofC. For Determining Allowable Stress When KlI,. :s Cc for Steel of Any Yield Stress

Kill'

Kill'

KIll'

Co

Cc

Co

Cc

Co

Cc

Co

0.01 0.02 0.03 0.04 0.05

0.599 0.597 0.596 0.594 0.593

. 0.26 0.27 0.28 0.29 0.30

0.548 0.546 0.543 0.540 0.538

0.51 0.52 0.53 0.54 0.55

0.47:2 0.469 0.465 0.462 0.458

0.76 0.77 0.78 0.79 0.80

0.375 0.371 0.366 0.362 0.357

0.06 0.07 0.08 0.09 0.10

0.591 0.589 0.588 0.586 0.584

0.31 0.32 0.33 0.34 0.35

0.535 0.532 0.529 0.527 0.524

0.56 0.57 0.58 0.59 0.60

0.455 0.451 0.447 0.444 0.440

0.81 0.82 0.83 0.84 0.85

0.353 0.348 0.344 0.339 0.335

0.11 0.12 0.13 0.14 0.15

0.582 0.580 0.578 0.576 0.574

0.36 0.37 0.38 0.39 0.40

0.521 0.518 0.515 0.512 0.509

0.61 0.62 0.63 0.64 0.65

0.436 0.432 0.428 0.424 0.420

0.86 0.87 0.88 0.89 0.90

0.330 0.325 0.321 0.316 0.311

0.16 0.17 0.18 0.19 0.20

0.572 0.570 0.568 0.565 0.563

0.41 0.42 0.43 0.44 0.45

0.506 0.502 0.499 0.496 0.493

0.66 0.67 0.68 0.69 0.70

0.416 0.412 0.408 0.404 0.400

0.91 0.92 0.93 0.94 0.95

0.306 0.301 0.296 0.291 0.286

0.21 0.22 0.23 0.24 0.25

0.561 0.558 0.556 0.553 0.551

0.46 0.47 0.48 0.49 0.50

0.489 0.486 0.483 0.479 0.476

0.71 0.72 0.73 0.74 0.75

0.396 0.392 0.388 0.384 0.379

0.96 0.97 0.98 0.99 1.00

0.281 0.276 0.271 0.266 0.261

Kit r

• When ratios exceed the noncompact section limits of Article 502.5.1, use C' c Fa = CaQaQsF;. (Appendix Article 502.5).

Kllr in lieU{9f


values and equation

-

1 ~

'\; fj "t:I

= ...

-f:)f)

~

STRUCTURAL STEEL

5-76

NUMERICAL VALUES

F ,(MPa) ___L _____

,L-

227 241 248 269

107.0 102.0 97.7 93.8 1-----------4----·------+---------~~---79.8 75.7 -


.. ---~

5-77

TABLE 5

Specification Section and Ratios

248

1701j"F;

10.8

10.0

9.6

5001 jF;

31.7

29.3

j"F;

106.7 42.8

16801 675/

414

448

9.2

8.4

8.1

28.0

26.9

24.5

23.6

98.7

94.4

90.5

82.6

79.4

39.6

37.9

33.2

31.9

53.,JC;

49.,JC;

47..jC;

45..jC;

41..jC;

40..jC;

119'[c;

110'[c;

1OS..jC;

101'[c;

92..jC;

89..jC;

12.7

11. 7

11.2

10.7

9.8

9.4

15.8

14.7

14.0

13.4

12.3

11.8

19.6

18.7

18.0

16.4

15.8

6251j"F;

36.7

35.1

33.7

30.7

29.5

8321j"F;

48.9

46.7

44.8

40.9

39.3

j"F;

39.0

37.3

78.6

71.7

66.0

55.0

50.8

310

283

260

217

200

322

282

261

243

207

192

333

309

295

283

258

248

250/

.JF;

3331 jF; 502-1

6341

91.7

52501 jF;

31.4


r

~-~.~,---------'

~-,-

STRUCTURAL STEEL

5·78

TABLE 6 VALUES of Ml M2

!!1~

Ml

Cb

M2

Cb

Cb

_, _ _ .~

-1.00 -0.99 -0.98 -0.97 -0.96

l.000 1.005 1.009 l.014 1.018

-0.59 -0.58 -0.57 -0.56

1,228 1.235 l.242 1.249 1.256

-0.19 -0.18 -0.17 -0.16

L552 1.56J 1.571 J .580 1.590

·0.95 -0.94 -0.93 -0.92 -0.91

l.023 l.028 1.033 1.038 1.043

-0.55 -0.54 -0.53 -0.52 -0.51

1.263 J,270 1.278 1.285 1.293

-0.15 -0.14 -0.13 -0.12 -0.11

-0.90 -0.89 -0.88 -0.87 -0.86

1.048 1.053 l.058 1.064 l.069

-0.50 -0.49 -0.48 -0.47 -0.46

1.300 1.308 1.315 1.323 1.330

-0.85 -0.84 -0.83 -0.82 -0.81

l.074 1.080 1.085 1.091 1.096

-0.45 -0.44 -OA3 -OA2 -0.41

-0.80 -0.79 -0.78 -0.77 -0.76

1.102 LI08 1.114 1.119 LI25

-0.75 -0.74 -0.73 -0.72 -0.71

! ._i i

M2 ..

Cb

-----~--,--.-~,----.-

0.20 0.21 0,22 0.23 0,24

1.972 1,984 1.996 2,007 2,019

1.599 1.609 1.619 1.628 1.638

0.25 0.26 0.27 0.28 0.29

2.031 2.043 2.055 2.068 2.080

-0.10 -0.09 -0.08 -0.07 -0.06

1.648 l.658 1.668 1.678 1.688

0.30 0.31 0.32 0.33 0.34

2.092 2.104 2.117 2.129 2.142

1.338 1.346 1.354 1.362 1.370

-0.05 -0.04 -0.03 -0.02 -0.01

1.698 1.708 1.719 1.729 1.740

0.35 0.36 0.37 0.38 0.39

2.154 2.167 2.180 2.192 2.205

-0.40 -0.39 -0.38 -0.37 -0.36

1.378 1.386 1.394 1.403 1.411

0.00 0.01 0.02 0.03 0.04

1.750 1.761 1.771 1.782 1.792

OAO 0.41 0.42 0.43 0.44

2.218 2.231 2.244 2.257 2.270

1.131 1.137 1.143 1.150 1.156

-0.35 -0.34 -0.33 -0.32 -0.31

l.419 1.428 1.436 1.445 1.453

0.05 0.06 0.07 0.08 0.09

1.803 1.814 1.825 ' 1.836 1.847

0.45 0.46 :2: 0.47

2.283 2.296 2.300

-0.70 -0.69 -0.68 -0.67 -0.66

1.162 1.168 1.175 1.181 1.188

-0.30 -0.29 -0.28 -0.27 -0.26

1.462 1.471 1.480 1.488 1.497

0.10 0.11 0.12 0.13 0.14

1.858 1.869 1.880 1.892 1.903

-0.65 -0.64 -0.63 -0.62 -0.61

1.194 1.201 1.208 1.214 1.221

-0.25 -0.24 -0.23 -0.22 -0.21

1.506 1.515 1.524 1.534 1.543

0.15 0.16 0.17 0.18 0.19

1.914 1.926 1.937 1.949 1.960

Note 1: C b ::: 1.75+ l.05(M1/M2 ) + 0.3(M1/M2 )2 :s; 2.3 Note 2: MI/M2 positive for reverse curvature and negative for single curvature.


NUMERICAL VALUES TABLE 7

Cm

MI M2

Cm

MI M2

Cm

MI M2

-0.95 :'0.94 -0.93 -0.92 -0.91

1.000 0.996 0.992 0.988 0.984 0.980 0.976 0.972 0.968 0.964

-0.60 -0.59 -0.58 -0.57 -0.56 -0.55 -0.54 -0.53 -0.52 -0.51

0.840 0.836 0.832 0.828 0.824 0.820 0.816 0.812 0.808 0.804

-0.20 -0.19 -0.18 -0.17 -0.16 -0.15 ·0.14 -0.13 -0.12 -0.11

0.680 0.676 0.672 0.668 0.664 0.660 0.656 0.652 0.648 0.644

0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.30

-0.90 -0.89 -0.88 -0.87 -0.86 :.0.85 -0.84 -0.83 -0.82 -0.81

0.960 0.956 0.952 0.948 0.944 0.940 0.936 0.932 0.928 0.924

-0.50 -0.49 -0.48 -0.47 -0.46 -0.45 -0.44 -0.43 -0.42 -0.41

0.800 0.796 0.792 0.788 0.784 0.780 0.776 0.772 0.768 0.764

-0.80 -0.79 -0.78 -0.77 -0.76 -0.75 -0.74 -0.73 -0.72 -0.71

0.920

0.916 0.912 0.908 0.904 0.900 0.896 0.892 0.888 0.884

-0.40 -0.39 -0.38 -0.37 -0.36 -0.35 -0.34 -0.33 -0.32 -0.31

0.760 0.756 0.752 0.748 0.744 0.740 0.736 0.732 0.728 0.724

-0.10 -0.09 -0.08 -0.07 -0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

0.640 0.636 0.632 0.628 0.624 0.620 0.616 0.612 0.608 0.604 0.600

0.596 0.592 0.588 0.584 0.580 0.576 0.572 0.568 0.564 0.560

-0.70 -0.69 -0.68 -0.67 -0.66 -0.65 -0.64 -0.63 -0.62 -0.61

0.880 0.876 0.872 0.868 0.864 0.860 0.856 0.852 0.848 0.844

-0.30 -0.29 -0.28 -0.27 -0.26 -0.25 -0.24 -0.23 -0.22 -0.21

0.720 0.716 0.712 0.708 0.704 0.700 0.696 0.692 0.688 0.684

0.11 0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20

0.556 0.552 0.548 0.544 0.540 0.536 0.532 0.528 0.524 0.520

0.51 0.52 0.53 0.54 0.55 0.56 0.57 0.58 0.59 0.60

-1.00 .;.0.99 -0.98 -0.97 ~0.96

Ml.

M2

Cm

0.516 '0.512 0.508 0.504 0.500 0.496 0.492 0.488 0.484 0.480

0.61 0.62 0.63 0.64 0.65 0.66 0.67 0.68 0.69 0.70

0.356 0.352 0.348 0.344 0.340 0.336' 0.332 0.328 0.324 0.320

0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.38 0.39 0.40

0.476 0.472 0.468 0.464 0.460 0.456 0.452 0.448 0.444 0.440

0.71 0.72 0.73 0.74 0.75 0.76 0.77 0.78 0.79 0.80

0.316 0.312 0.308 0.304 0.300 0.296 0.292 0.288 0.284 0.280

0.41 0.42 0.43 0.44 0.45 0.46 0.47 0.48 0.49 0.50

0.436 0.432 0.428 0.424 0.420 0.416 0.412 0.408

0.276 0.272 0.268 0.264

0.400

0.81 0.82 0.83 0.84 0.85 0.86 0.87 0.88 0.89 0.90

0.256 0.252 0.248 0.244 0.240

0.396 0.392 0.388 0.384 0.380 0.376 0.372 0.368 0.364 0.360

0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 1.00

0.236 0.232 0.228 0.224 0.220 0.216 0.212 0.208 0.204 0.200

Note 1: C =0.60-0.40(M 1 IM 2 )

Note 2: M'JM2 positive for reverse curvature and negative for single curvature.

. National Structural Code of the Philippines, Volume 1

Cm

OA04

0.26~

STRUCTURAL STEEL

5.00

NUMERICAL VALUES

TABLE 8 VALUES of F'e For Use in Equation 508-1), for Steel of Any Yield Stress

K1b

F'e

K1b

F'e

'b

(MPa)

'b

(MPa)

rb

F'e (MPa)

21 22 23 24 25

2334.70 2127.28 1946.32 1787.51 1647.37

51 52 53 54 55

395.85 380.77 366.54 353.09 340.36

81 82 83 84 85

156.93 153.12 149.46 145.92 142.51

112 113 114 115

26 27 28 29 30

1523.08 1412.35 1313.27 1224.26 1144.00

56 57 58 59 60

328.32 316.90 306.07 295.78 286.00

86 87 88 89 90

13921 IJ6.03 132.96 129.98 127.11

31 32 33 34 35

1071.39 1005.47 945.46 890.66 840.49

61 62 63 64 65

276.70 267.85 259.41 251.37 243.69

91 92 93 94 95

36 37 38 39 40

794.45 752.08 713.02 676.93 643.50

66 67 68 69 70

236.36 2Z9.36 222.67 21626 210.12

41 42 43 44 45

612.49 583.68 556.84 531.82 508.45'

71 72 73 74 75

46 47 48 49 50

486.58 466.09 446.88 428.82 411.84

76 77 78 79 80

-

<

Note:

K1b

K1b

F'e

rb

(MPa)

I -K1b

rb

51.79 51.06 50.35 49.65 48.97

171 172 173 174 175

35.21 34.80 34.40 34.01 33.62

146 147 148 149 150

48.30 47.65 47.01 46.38 45.76

176 177 178 179 180

33.24 32.86 32.50 32.13 31.78

70.32 69.18 68.05 66.96 65.89

151 152 153 154 155

45.16 44.56 43.98 43.41 42.86

181 182 183 184 185

31.43 31.08 30.74 30.41 30.08

126 127 128 129 130

64.85 63.84 62.84 61.87 60.92

156 157 158 159 160

42.31 41.77 41.24 40.73 40.22

186 187 188 189 190

29.76 29.44 29.13 28.82 28.52

100.93 98.96 97.05 95.19 93.39

131 132 133 134 135

60.00 59.09 58.21 57.34 56.49

161 162 163 164 165

39.72 39.23 38.75 38.28 37.82

191 192 193 194 195

28.22 27.93 27.64 27.36 27.08

91.63 89.93 88.27 86.66 85.09

136 137 138 139 140

55.67 54.86 54.06 53.29 52.53

166 167 168 169 170

37.36 36.92 36.48 36.05 35.63

196 197 198 199 200

26.80 26.53 26.26 26.00 25.74

rh

83.56 82.08 80.63 79.22 77.85

141 142 143 144 145

116 117 118 119 ]20

76.52 75.21 73.94 72.71 71.50

124.33 121.65 119.04 116.52 114.08

121 122 123 124 125

96 97 98 99 100

111.72 109.43 107.21 105.05 102.96

204.25 198.61 193.21 188.02 183.04

101 102 103 104 105

178.26 173.66 169.23 164.97 160.88

106 107 108 109 110

III

2

F' =

12.1t E

e

23(K1 b Ir/)2

K1b

F'e (MPa)

F'e (MPa)


-

CHAPTER 6

WOOD TABLE OF CONTENTS SECTION 601 - GENERAL ...................................................................................................... 6-1

601. 1

Scope............. ................................... ..... 6-1

601.2

Design Method ......................... ~.. . . . ... 6-1

SECTION 602 - DEFINI·TION ...............................................-.................................................. 6-1

602.1

Definitions ..... ..... .................... ... ........... 6-1

SECTION 603 - MIN"IM'UM QUALITY ................................................................................. 6-2

603.1 603.2 603.3 603.4

Quality and Identification ...................... Minimum Capacity or Grade ................. Timber Connectors and Fasteners .......... Fabrication, Installation and Manufacture.

6-2 6-2 6-2 6-3

603.5 603.6 603.7 603.8

Dried Fire-retardant-treated Wood... , ..... Size of Structural Members.. ............. Shrinkage.................................. ,. Rejection. .. , ................... ' ........ ,., .. ,

6-3

6-3

6-3

6-3

SECTION 604 - DESIGN AND CONSTRUCTION REQUIREMENTS ............................ 6-4•

604.1

General .................................... ,............ 6-4

SECTION 605 - DECAY AND TERMITE PROTECTION .................................................. 6-4

6OS.1 6OS.2 60S.3 6OS.4 6OS.S 60S.6

Preparation ofBuilding Site .................. Wood Support Embedded in Ground ..... Under-floor Clearance ......................... , Plates, Sills and Sleepers .............. ......... Columns and Posts .................................. Girders Entering Masonry or Concrete Walls.......................................................

6-4 6-4

6-4 6-S 6-S 6-S

60S.7 60S.8 60S.9 60S.10 60S.11 60S.12 60S.13

Under-floorVentilation.. ,.......... , .. , ...... Wood and Earth Separation ........ ,..... Wood Supporting Roofs and Floors......... Moisture Content of Treated Wood., .. " ... Retaining Walls................................ Weather Exposure ............................. Water Splash ...................................

6-S

6-S

6-S

6-5

6-5

6-S

6-6

SECTION 606 - WOOD SUPPORTING MASONRY OR CONCRETE ............................. 6-6

606.1

Dead Load ............ ,............................... , 6-6

SECTION 607 - WALLFRAMING 607.1

Horizontal Force .................................... 6-6

....................................................•...................................

6-7

Wall Framing .. ,..................... ,.... ,.......... 6-7

SECTION 608 - FLOOR FRAMING 60S. 1

606.2

..................................................................................... 6-8

Floor Frarnings .................................. ,... 6-S

National Structural Co1:le of the

Phllipplhes, Volume

1

WOOD

6-ii

SECTION 609 - EXTERIOR WALL CO'VERIN"GS ............................................................. 6-9

609.1 609.2 609.3 609.4

General ........ ... ........ .... ......... ...... .. ..... ..... Siding .................................................. Plywood ................................................ Shingles or Shakes ...........................

6-9 6-9 6-9 6-10

609.5 609.6 609.7

Particleboard ......... .. ...... ... ....... ........... 6-10

Hardboard ........................................... 6-10

Nailing ................................................. 6-10

SECTION 610 - INTERIOR PANELING ............................................................................. 6-11

610.1

Interior Paneling ..... ......... ............. ......... 6-11

SECTION 611 - SHEATIDNG .................................................................................................6-11

611. 1 Structural Floor Sheathing ............ ......... 6-11

611.2

Structural Roof Sheathing ..... ...... ...... 6-II

SECTION 612 - MECHANICALLY LAMINATED FLOORS AND DECKS ................. 6-12

612.1 Mechanically Laminated Floors

and Decks ... ... ... ......... ... ... ... ... ... ....

6-12

• SECTION 613 - POST-BEAM CONN'ECTION .................................................................. 6-12

613.1

Post-Beam Connection .......................... 6-12

SECTION 614 - WOOD SHEAR WALLS AND DIAPHRAGMS 614.1 General .................................................. 6-12 614.2 Wood Members Resisting Horizontal Forces Contributed by Masonry and Concrete ... ......... ... ................ ........ 6-13 614.3 Diagonally Sheathed Diaphragms 6-13

SECTION 615 - STRESSES

614.4 614.5 614.6

.................................... 6-12

Particleboard Diaphragms .................... 6-14

Wood Shear Walls and Diaphragms

in Seismic Zone 4 ............................. 6-14

Fiberboard Sheathing Diaphragms ....... 6-15

.................................................................................................. 6-15

615.1 General.................................................. 6-15 615.2 Stresses in Piles Used

as Structural Members ......................... 6-15

615.3

Adjustment of Stresses ........................ 6-15

SECTION 616 - HORIZONTAL MEMBER DESIGN ....................................................... 6-18

616.1 616.2 616.3 616.4 616.5

Beam Span ........................................ c... Flexure ..... ................. ................ .... ........ Horizontal Shear ....................... ............ Horizontal Shear in Notched Beams ...... Design ofJoints in Shear ............ ............

6-18 6-18 6-18 6-19 6-19

616.6 616.7 616.8

Compression Perpendicular to Grain ... 6-19

Lateral Support .................................... 6-20

Lateral Support of Arches,

Compression Chords of Trusses and Studs ......... .... ............. ................ 6-20

SECTION 617 - COLlJMN DESIGN .................................................................................... 6-21

617.1 617.2

I

Column Classifications ....................... 6-21 Limitation on I d Ratio................. 6-21

617.3 617.4

Simple Solid-column Design............. Tapered Column...........................


6-21

6-22

Table of Contents

6·iii

SECTION 618 - FLEXURAL AND AXIAL LOADING COMBINED .............................. 6-23

618.1 618.2 618.3

Flexure and Axial Tension ................... 6-23 Flexure and Axial Compression .... ........ 6-23 Spaced Columns .. ...... ....... ..... ........ ...... 6-23

618.4 618.5

Truss Compression Chords ................... 6-23

Compression at Angle to Grain ............ 6-24

SECTION 619 - TIMBER CONNECTORS AND FASTENERS ....................................... 6-24

619.1 619.2 619.3

General ................................................ 6-24 Bolts .................................................... 6-24 Nails and Spikes ..... ..... ... .......... ........ ... 6-24

619.4 619.5

Joist Hangers and Framing Anchors ..... 6-25

Miscellaneous Fasteners .. ...... ..... ......... 6-25

SECTION 620 - CONVENTIONAL LIGHT-FRAME CONSTRUCTION

DESIGN PROVISIONS ............ _................................................................ 6-25

General.... ....... ........ ..... ............ ............ 620.1 620.2 Design ofPortions ... .............................. 620.3 Additional Requirements for Conventional Construction in High-wind Areas ............................ 620.4 Additional Requirements for Conventional Construction in Seismic Zone 2 ........................ ......

6-25 6-25

6-25

6-26

620.5

Additional Requirements

for Conventional Construction

in Seismic Zone 4 ............................. . 620.6 Girders ................................................ . 620.7 Floor Joists ........................................... . 620.8 Subflooring .......................................... . 620.9 Particleboard Underlayment ................ . 620.10 Wall Framing ...................................... .

6-26

6-27

6-27

6-28

6-28

6-28

SECTION 621 - METAL PLATE CONNECTED WOOD TRUSS DESIGN ................... 6-31

621.1 621.2

Design and Fabrication ........................ 6-31 Performance ......................................... 6-31

621.3 621.4

In-plant Inspection ............................... 6-31

Marking ................................................ 6-31


GENERAL & DEFINITION


SECTION 602 - DEFINITION

601.1 Scope.

602.1 Definitions.

The quality and design of wood members and their fastenings shall conform to the provisions ofthis chapter.

The following terms used in this chapter snall have the meanings indicated in this section:

601.2 Design Method.

Design shall be based on one of the following methods.

BLOCKED DIAPHRAGM is a diaphragm in which all sheathing edges not occurring on framing members are supported on and connected to blocking.

601.2.1 Allowable stress design. Design using allowable stress design methods shall. resist the different load combinations in accordance< with the applicable requirements of Section 604.

CONVENTIONAL LIGHT-FRAME CONSTRUCTION is a type of construction whose primary structural elements are formed by a system of repetitive wood-framing members.

601.2.2 Conventional light-frame construction. The design and construction of conventional light-frame wood structures shall be in accordance with the applicable requirements of Section 604.

DIAPHRAGM is a horizontal or nearly horizontal system acting to transmit lateral forces to the vertical resisting elements. When the term "diaphragm is used, it includes horizontal bracing systems. FIBERBOARD is a fibrous-felted, homogeneous panel made from lignocellulosic fibers (usually wood or crane) having a density of less than 497 kg/m3 but more than 160 kglm3 . GLUED BUILT-UP MEMBERS are structural elements, the sections of which are composed of built-up lumber, wood structural panels or wood structural panels in combination with lumber, all parts bonded together with adhesive. GRADE (Lumber), the classification of lumber in regard to strength and utility in accordance with the grading rules of an approved lumber grading agency. HARDBOARD is a fibrous-felted, homogeneous panel made from lignocellulosic fibers consolidated under heat and pressure in a· hot press to a density not less than 497 kglm3 . NOMINAL SIZE (Lumber), the commercial size designation of width and depth, in standard sawn lumber grades; somewhat larger than the standard net '3ize of dressed lumber, in accordance with UBC Standard 23-1, "Classification, Definition and Methods of Grading for All Species ofLumber"', for sawn lumber. NORMAL LOADING, a design load that stressed a member or fastening to the full allowable stress tabulated in this chapter. This loading may be applied for approximately I 0 years, either continuously or cumu1atively, and 90 percent ofthis load may be applied for the remainder ofthe life ofthe member or fastening.

National

Structural Code of tile Phifippines, Volume 1

WOOD

6·2

PARTICLEBOARD is a manufactured panel product consisting of particles of wood or combinations of wood particles and wood fibers bonded together with synthetic resins or other suitable bonding system by as bonding pr'ocess, in accordance with approved nationally recognized standard. PLYWOOD is a panel oflaminated veneers conforming to UBC Standard 23-2, "Construction and Industrial Plywood" and UBC Standard 23-3, "Performance Standard for Wood based Structural-Use Panels". ROTATION is the torsional movement of a diaphragm about a vertical axis. SUBDIAPHRAGM is a portion of a larger wood diaphragm designed to anchor and transfer local forces to primary diaphragm struts and the main diaphragm. TREATED WOOD, is wood treated with an approved preservative under treating and quality control procedures. WOOD OF NATURAL RESISTANCE TO DECAY OR TI.:RMITES is the heartwood of the species set forth below. Corner sapwood is permitted on 5 percent of the pieces provided 90 percent or more of the width of each side on which it occurs is heartwood. Recognized species are:

Decay resistant: Narra, Kamagong, Dao, Tangile. Termite resistant: Narra, Kamagong. WOOD STRUCTURAL PANEL is a structural panel product composed primarily of wood and meeting the requirement of UBC Standard 23-2 or 23~3. Wood structural panels include all-veneer plywood, composite panels containing a combination of veneer and wood-based material, and mat-formed panel such as oriented stranded board and waferboard.

SECTION 603 - MINIMUM QUALITY 603.1 Quality and Identification. All lumber, wood structural panels, particleboard, timber, end-jointed lumber, fiberboard sheathing (when used structurally), hardboard siding (when used structurally), piles and poles regulated by this chapter shall conform to the applicable standards or grading rules specified in this code and shall be so identified by the grade mark or a certificate ofinspection issued by an approved agency. All preservatively treated wood required to be treated shall be identified by the quality mark of an approved inspection agency.

603.2 Minimum Capacity or Grade. Minimum capacity of structural framing members may be established by performance tests. When the tests are not made, capacity shall be based on allowable stresses and design criteria specified in this code. Studs, joists, rafters, foundation plates or sills, planking 50 mm or more in depth, beams, stringers, posts, structural sheathing and similar load-bearing members shall be of at least the minimum grades set forth in Table Nos. 61 or Table 6.2 Approved end-jointed lumber may be used interchangeably with solid-sawn members of the same species and grade. Such use shall include, but not be limited to, light-framing joists, planks and decking. Wood structural panel shall be of grades specified in UBC Standard 23-2 and UBC Standard 23-3.

603.3 Timber Connectors and Fasteners. Safe loads and design practices for types of connectors and fasteners not mentioned or fully covered in Section 619, may be determined in a manner approved by the building officiaL The number and size of nails connecting wood members shall not be less than that set forth in Tables 6.3 and 6.4. Other connections shall be fastened to provide equivalent strength. End and edge distances and nail penetrations shall be in accordance with the applicable provisions of Section 619. Fasteners for pressure-preservative treated and fire retardant treated wood shall be of hot-dipped zinc coated

I


MINIMUM QUALITY

galvanized, stainless steel, silicon bronze or copper. Fasteners required to be corrosion resistant shall be either zinc-coated fasteners, aluminum alloy wire fasteners or stainless steel fasteners Connections depending on joist hangers or framing anchors, ties, and other mechanical fastenings not otherwise covered may be used where approved.

6-3

603.7 Shrinkage. Consideration shall be given in the design to the possible effect of cross-grain dimensional changes considered vertically which may occur in lumber fabricated in a given condition.

603.8 Rejection. 603.4 Fabrication, Installation and Manufacture. 603.4.1 General. Preparation, fabrication and installation of wood members and their fastenings shall conform to accepted engineering practices and to the requirements of this code. All members shall be framed, anchored, tied and braced to develop the strength and rigidity necessary for the purposes for which they are used.

The building official may deny permission for the use of a wood member where permissible grade characteristics or defects are present in such a combination that they affect the serviceability of the member.

603.4.2 Timber connectors and fasteners. The installation of timber connectors and fasteners shall be in accordance with the provisions set forth in Section 619. 603.4.3 Metal-plate-connected wood trusses. Metal-plate connected wood trusses shall conform to the provisions of Section 618. Each manufacturer of trusses using metal plate connectors shall retain an approved agency having no financial interest in the plant being inspected to make nonscheduled inspections of truss fabrication, delivery, and operations. The inspection shall cover all phases of truss operation, including lumber .storage, handling, cutting, fixtures, presses or rollers, fabrication, bundling and banding, handling and delivery.

603.5 Dried Fire-retardant-treated Wood. Approved fire-retardant-treated wood shall be dried, following treatment, to a maximum moisture content as foHows: solid-sawn lumber 50 mm in thickness or less to 19 percent, and plywood to 15 percent.

603.6 Size of Structural Members. Sizes of lumber referred to in this code are nominal sizes. Computations to determine the required sizes of members shall be based on the net dimensions (actual size) and not the nominal sizes. The rough siZe lumber shall not be less than the nominal size and the reduction in face dimensions of dressed lumber shall not be more than 6 mm of the nominal size.


6-4

WOOD

SECTION 604 - DESIGN AND CONSTRUCTION REQUIREMENTS

SECTION 605 - DECAY AND TERMITE PROTECTION

604.1 General.

605.1 Preparation of Building Site.

The following design requirements apply.

All stumps and roots shall be removed from the soil to a depth of at least 300 mm below the surface of the ground in the area to be occupied by the building.

604.1.1 All wood structures shall be designed and constructed in accordance with the requirements of Section 601 up to Section 613. 604.1.2 Wind and earthquake load-resisting systems for all engineered wood structures shall be designed and constructed in accordance with the requirements of Section 614. 604.1.3 The design and construction of wood structures using allowable stress design methods shall be in accordance with Section 615 and Section 618. 604.1.4 The design and construction of conventional light frame wood structures shall be in accordance with Section 620. 604.1.5 The design and installation of timber connectors and fasteners shall be in accordance with Section 619. 604.1.6 Metal-plate-connected wood trusses shall conform to the provisions of Section 621.

All wood forms which have been used in placing concrete, if within the ground or between foundation sills and the ground, shall be removed before a building is occupied or used for any purpose. Before completion, loose or casual wood shall be removed from direct contact with the ground under the building.

605.2 Wood Support Embedded in Ground. Wood embedded in the ground or in direct contact with the earth and used for the support of permanent structures shall be treated wood unless continuously submerged in fresh water. Round or rectangular posts, poles and sawn timber columns supporting permanent structures which are embedded in concrete or masonry in direct contact with the earth or embedded in concrete or masonry exposed to the weather shall be treated wood. The wood shall be treated for ground contact.

605.3 Under-floor Clearance. When wood joists or the bottom of wood structural floors without joists are located closer than 450 mm or wood girders are located closer than 300 mm to exposed ground in crawl spaces or unexcavated areas located within the periphery of the building foundation, the floor assembly including posts, girders, joists and subfloor, shall be approved wood of natural resistance to decay as listed in Section 605.4 or treated wood. When the above under-floor clearances are required, the under-floor area shall be accessible. Accessible under-floor areas shall be provided with a minimum 450 mm by 600 mm opening unobstructed by pipes, ducts and similar construction. All under-floor access opening shall be effectively screened or covered. Pipes, ducts and other construction shall not interfere with the accessibility to or within under-floor areas.


DECAY AND TERMITE PROTECTION

6(l5.4 Plates, Sills and Sleepers. All foundation plates or sills and sleepers on a concrete or masonry slab, which is in dire<:;t contact with eerth, and sills that rest on concrete or masonry foundations, shall be treated wood, all marked or branded by an approved agency. Foundation wood marked or branded by an approved agency may be used for sills in localities subject to moderate hazard, where termite damage is not frequent and when specifically approved by the building official. In localities where hazard of termite is slight, any species of wood permitted by this chapter may be used for sills when specifically approved by the building official.

605.5 Columns and Posts. Columns and posts located on concrete or masonry floors or decks exposed to the weather or to water splash or in basements and which support permanent structures shall be supported by concrete piers or metal pedestals projecting above floors unless approved wood of natural resistance to decay or treated wood is used. The pedestal shall project at least 150 mm above exposed earth and at least 25 mm above such floors. Individual concrete or masonry piers shall project at least 200 mm above exposed ground unless the columns or posts they support are of approved wood of natural resistance to decay or treated wood is used.

605.6 Girders Entering Masonry or Concrete Walls.

6-5

above, provided the under-floor ground surface area covered with an approved vapor barrier.

IS

605.8 Wood and Earth Separation. Protection of wood against deterioration as set forth in the previous sections for specified applications is required. In addition, wood used in construction of permanent structures and located nearer than 150 mm to earth shall be treated wood or wood of natural resistance to decay. Where located on concrete slabs placed on earth, wood shall be treated wood or wood of natural resistance top decay. Where not subject to water splash or to exterior moisture and located on concrete having a minimum thickness of 75 mm with an impervious membrane installed between concrete and earth, the wood may be untreated and of any species. Where planter boxes are installed adjacent to wood frame walls a 50 mm air space shall be provided between the planter and the wall. Flashing shall be installed when the air space is less than 150 mm in width. Where flashing is used, provisions shall be made to permit circulation of the air in the air space. The wood frame shall be provided with an exterior wall covering conforming to the provisions of Section 609.

605.9 Wood Supporting Roofs and Floors. Wood structural members supporting moisture permeable floors or roofs which are exposed to the weather such as concrete or masonry slabs shall be approved wood @If natural resistance to decay or treated wood unless separated from such floors or roofs by an impervious moisture barrier.

Ends of wood girder entering masonry or .concrete walls shall be provided with a 13 mm air space on tops, sides and ends unless approved wood of natural resistance to decay or treated wood is used.

605.10 Moisture Content of Treated Wood.

605.7 Under-floor Ventilation.

When wood pressure treated with a water-borne preservative is used in enclosed locations where drying in service cannot readily occur, such wood shall be at a moisture content of 19 percent or less before being covered with insulation, interior wall finish floor covering or other material.

Under-floor areas shall be ventilated by an approved mechanical means or by openings in exterior foundation walls. Such openings shall have a net area of not less than 0.067 m2 for each 10 m2 of under-floor area. Openings shall be located as close to comers as practical and shall provide cross ventilation. The required area of such openings shall be approximately equally distributed along the length of at least two opposite sides. They shall be covered with corrosion-resistant wire mesh with mesh openings of 6 mm dimension. Where moisture due to climate and groundwater conditions is not considered excessive, the building official may allow operable louvers and may allow the required net area of vent opening to be reduced to 10 percent of the

605.11 Retaining Walls. Wood used in retaining or crio walls shall be treated wood.

605.12 Weather Exposure. All wood structural panels, when designed to be exposed in outdoor application, shall be of exterior type, except as provided in Section 605.2 In geographical areas where experience has demonstrated a specific need, approved

National Structural Code of the Philippines. Volame 1

6-6

WOOD

wood of natural resistance to decay or treated wood shall be used for those portions of wood members which form the structural support of buildings, balconies, porches, or similar permanent building appurtenances when such members are exposed to the weather without adequate protection from a roof, eave, overhang or other covering to prevent moisture or water accumulation on the surface or at joints between members. Depending on local experience, such members may include: horizontal members such as girders, joists and decking; or vertical members such as posts, poles and columns; or both horizontal and vertical members.

SECTION 606 - WOOD SUPPORTING MASONRY OR CONCRETE 606.1 Dead Load. Wood members shall not be used to permanently support dead load ofany masonry or concrete.

EXCEPTIONS:

1.

Masonry or cOllcrele nOll-sln/clural floor or ro(y surfaCing not more than 100 mm thick maybe supported by wood members.

2.

Any stn/cture may rest upon wood piles constnlcted in accordance with the requirements of Chapter 011 "Foundations and Retaining Walls".

3.

Veneer of brick or concrete stone may be supported by approved treated wood foundations when the maximum height of veneer does 110t exceed 9000 mm above the foundations. Such veneer used as all interior wall finish may also be supported on wood floors which are designed to support the additional load, and be designed to limit the deflection and shrinkage to J.. 600 of the span qf the supporting members.

4.

Glass block masonry having an installed weight qf 97.6 kg.1rl or less. When glass block is supported 011 }I'ood floors, the .floors shall be designed to limit deflection and shrinkage to 1/600 of the span of the supporting members alld the allowable stresses for the framing members shall be reduced in accordance with Section 615.3.4.

605.13 Water Splash. Where wood-frame walls and partitions are covered on the interior with plaster, tile or similar materials and are subject to water splash, the framing shall be protected with approved waterproof paper conforming to Section on "Weather Protection".

606.2 Horizontal Force. Wood members shall not be used to resist horizontal forces contributed by masonry or concrete construction in buildings over one story in height.

EXCEPTIONS: I.

Wood floor and roof members may be used in horizontal tntsses and diaphragms to- resist horizontal forces imposed by wind, earthquake or earth pre~sure. proVided such forces are not resisted by rotation ofthe tntss or diaphragm.

2.

Vertical wood stntctural panel-sheathed shear walls may be used to provide resistance to wind or earthquake forces in two-story buildings ofmasonry


6-7 WOOD SUPPORTING MASONRY OR CONCRETE & WALL FRAMING

or concrete construction, provided the following requirements are met:

SECTION 607 - WALL FRAMJNG

Story-to story wall heights shall not exceed 3600 mm.

607.1

Horizontal diaphragm shall not be considered to transmit lateral forces by rotation or cantilever action. Deflection of horizontal. and vertical diaphragms shall not permit per-story deflection of supported masonry or concrete walls to exceed 0.005 times each story height. Wood structural panel sheathing in horizontal diaphragms shall have all unsupported edges blocked Wood strUctural panel sheathing for both stories of vertical diaphragms shall have all unsupported edges blocked and for the lower walls have a minimum thickness of 12 mm.

wan Framing.

The framing of exterior and interior walls shall be in accordance with provisions specified in Section 620 unless a specific design is furnished. Wood studs walls and bearing partitions shall not support more than two floors and a roof unless an analysis satisfactory to the building official shows that shrinkage of wood framing will not have adverse upon the structure nor any plumbing, electrical, mechanical systems nor other equipment installed therein due to the excessive shrinkage or differential movements caused by shrinkage. The analysis shall also show that the roof drainage system and the foregoing systems or equipment will not be adversely affected or, as an alternate, such systems shall be designed to accommodate the differential shrinkage or movements.

There shall be no out-of-plane horizontal offsets between the first and second stories of wood structural panel shear walls.

National Structural Code of the Philippines, Vohme 1

WOOD

6-8

of mineral fiber or ~s fiber or other approved non rigid materials.

SECTION 608 - FLOOR FRAMING. 608.1 Floor Framing.

4.

Wood-joisted floors shall be framed and constructed and anchored to supporting wood stud or masonry walls.

4.1.1 Floor-Ceiling Assemblies.

Fire block and draft stops shall be in accordance with the following provision: I.

2.

1. I

In combustible construction, firestopping and draftstopping shall be installed to cut off all concealed draft openings (both vertical and horizontal) and shall form an effective barrier between floors, between a top story and a roof or attic space, and shall subdivide attic spaces, concealed roof spaces and floor-ceiling assemblies. The integrity of all fire and draft stops shall be maintained. Firestopping shall be provided in the following location: In concealed spaces of stud walls and partitions, including furred spaces, at the ceiling and floor levels and at 250 mm intervals along the length of the wall.

Draftstopping shall be provided in the locations:

4.1.2 Single-family dwellings. When there is usable space above and below the concealed space of a floor ceiling assembly in a single-family dwelling, draft stops shall be installed so that the area of the concealed space does not exceed 93 sq. m. Draftstopping shall divide the concealed space into approximately equal areas.

4.1.3 Two or more dwelling units and hotels. Draft stops shall be installed in floor-ceiling assemblies of building having more than one dwelling unit and in hotels. Such draft stops shall be in line with walls separating tenants from each other and separating tenants from other areas. 4.1.4 Other uses. Draft stops shall be installed in floor ceiling assemblies of buildings or portions of buildings used for other than dwelling or hotel occupancies so that the area of concealed space does not exceed 93 sq. m. and so that the horizontal dimension between stops does not exceed 18.30 m.

EXCEPTION:

EXCEPTION:

Fire stops may be omitted at floor and ceiling levels when approved smoke-actllates fire dampers are installed at these leve/.<;.

Where approved automatic sprinklers are installed within the concealed space, the area between draft stops may be 278 sq. m. and the horizontal dimension may be 30.50 m.

2.2

4.2

At all interconnections between concealed vertical and horizontal spaces such as those that occurs at soffits, drop ceiling and cove ceilings.

2.3 In concealed spaces between stairs stringers at the top and bottom of the run and between studs along and in line with the run of stairs if the walls under the stairs are unfinished 2.4 In openings around vents, pipes, ducts, chimneys, fireplaces and similar openings which afford a passage for the fire at ceiling and floor levels, with noncombustible materials.

....:J.

Firestopping shall consist of 50 mm nominal lumber or one thickness of 18 mm plywood with joints backed by 18 mm plywood or one thickness of 19 mm Type 2-M particleboard. Fire stops may also be of gypsum board, cement asbestos board, mineral fiber, glass fiber or other approved materials securely fastened in place. Walls having parallel or staggered studs for sound-transmission control shall have stops

Attics.

4.2.1 Single-family dwellings. None required.

4.2.2 Two or more dwelling unit and hotels. Drafts stops shall be installed in the attics, mansards, overhangs, false fronts set out from walls and similar concealed spaces of buildings containing more than one dwelling unit and hotels. Such drafts stop shall be above and in line with walls separating tenants from each other and from other uses. EXCEPTION: 1.

Draft stops may be omitted along one ofthe corridor walls, prOVided draft stops at tenant separation walls extend to the remaining corridor draft stop.

2.

Where approved sprinklers are installed. draftstoppillg may be as specified ill the exception below.


FLOOR FRAMING & EXTERIOR WALL COVERINGS

4.2.3 Other uses. Draft stops shall be installed in attics, mansards, over-bangs, false fronts set out from walls and similar concealed spaces of buildings having uses other than dwellings or hotels so that the area between draft stops does not exceed 27S sq. m. and the greatest horizontal dimension does not exceed IS.30 m.

EXCEPTION: Where approved automatic sprinklers are illStalled, the area between the draft stops may be 836 sq. m. and the greatest horizontal dimension may he 30.50 m.

Draft stopping materials shall be not less than 12 mm gypsum board, 9 mm plywood, 9 mm Type 2-M particleboard or other approved materials adequately supported. Openings in the partitions shall be protected by self-closing doors with automatic latches constructed as required for the partitions.

6-9

SECTION 609 - EXTERIOR WALL COVERINGS 609.1 General. Exterior wood stud walls shall be covered on the outside with the materials and in the manner specified in this section or elsewhere in this code. Studs or sheathing shall be covered on the outside face with a weather-resistive barrier when required. Exterior wall coverings of the minimum thickness specified in this section are based upon a maximum stud spacing of 400 mm unless otherwise specified.

609.2 Siding. Solid wood siding shall have an average thickness of 9 mm unless placed over sheathing permitted by this code. Siding patterns known as rustic, drop siding or shiplap shall have an average thickness in place of not less than 15 mm and shall have a minimum thickness measured not less than 9 mm. Bevel siding shall have a minimum thickness measured at the butt section of not less than 11 rom and a tip thickness of not less than 5 mm. Siding of lesser dimensions may be used, provided such wall covering is placed over sheathing which conforms to the provisions specified elsewhere in this code. All weatherboarding or siding shall be securely nailed to each stud with not less than one nail, or to solid 25 mm nominal wood sheathing or 12 mm plywood sheathing or 13 rom particleboard sheathing with not less than one line of nails spaced not more than 600 rom on center in each piece of the weatherboarding or siding. Wood board siding applied horizontally, diagonally or vertically shall be nailed to studs, nailing strips or blocking set maximum 600 mm on center. Fasteners shall be nails or screws with a penetration of not less than 40 mm into studs. studs and wood sheathing combined, or blocking. Distance between such fastenings shall not exceed 600 mm for horizontally or vertically applied sidings and SOO mm for diagonally applied sidings.

609.3 Plywood. Where plywood is used for covering the exterior of outside walls, it shall be of the exterior type not less than 9 mm thick. Plywood panel siding shall be installed in accordance with Table 6.5. Unless applied over 25 mm wood sheathing or 12 mm wood structural panel sheathing or 13 mm particleboard sheathing joints shaU occur over framing members and shall be protected with a continuous wood


6-10

WOOD

batten, approved caulking, flashing, vertical or horizontal shiplaps or joints shall be lapped horizontally or otherwise made waterproof.

609.4 Shingles or Shakes. Wood shingles or shakes and asbestos cement shingles may be used for exterior wall covering, provided the :frame of the .structure is covered with building paper. All shingles or shakes attached to sheathing other than wood sheathing shall be secured with approved corrosion-resistant fasteners or on furring strips attached to the studs. Wood shingles or shakes may be applied over fiberboard shingle backer and sheathing with annular grooved nails. The thickness of wood shingles or shakes between wood nailing boards shall not be less than 9 mm. Wood shingles or shakes and asbestos shingles or siding may be nailed directly to approved fiberboard nailbase sheathing not less than 13 mm nominal thickness with annular grooved nails.

Nail size and spacing shall follow Table 6.8 and shall penetrate framing 38 nun. Lap siding shall overlap 2S mm minimum and be nailed through both courses and into framing members with nails located 13 mm from bottom of the overlapped course. Square-edged nongrooved panels shall be nailed 9 mm from the perimeter of the panel and intermediately into studs. Shiplap edge panel siding with 9 mm shiplap shall be nailed 9 mm from the edges on both sides of the shiplap. The 19 mm shiplap shall be nailed 9 mm from the edge and penetrate through both the overlap and underlap. Top and bottom edges of the panel shall be nailed 9 mm from the edge. Shiplap and lap siding shall not be force fit. Square-edged panels shall maintain a 2 mm gap at joints. All joints and edges of siding shall be over framing members, and shall be made resistant to weather penetration with battens, horizontal overlaps or ship laps to the satisfaction ofthe building official. A 3 mm gap shall be provided around all openings.

609.7 Nailing. The weather exposure of wood shingle or shake siding used on exterior walls shall not exceed maximum set forth in Tat>le 6.6.

All fasteners used for the attachment of siding shall be of a corrosion-resistant type.

609.5 Particleboard. When particleboard is used for covering the exterior of outside walls, it shall be of the M-l, M-S and M-2 Exterior Glue grades. Particleboard panel siding shall be installed in accordance with Table 6.7 and 6.3. Panel shall be gapped 3 mm and nails shall be spaced not less than 9 mm from edges and ends of sheathing. Unless applied over 16 mm net wood sheathing or 13 mm plywood sheathing or 13 mm particleboard sheathing, joints shall occur over framing members and shall be covered with a continuous wood batt; or joints shall be lapped horizontally or otherwise made waterproof to the satisfaction of the building official. Particleboard shall he sealed and protected with exterior quality finishes.

609.6 Hardboard. When hardboard siding is used for covering the outside of exterior walls, it shall conform to Table 6.8 Lap siding shall be installed horizontally and applied to sheathed or unsheathed walls. Corner bracing shall be installed in conformance with Section 620.6. A weather-resistive barrier shall be installed under the lap siding. Square-edg~ non-grooved panels and shiplap grooved or non-grooved siding shall be applied vertically to sheathed or unsheathed walls. Siding that is grooved shall not be less than 6 mm thick in the groove.

Association of Structural Engineers of the PhiHppines

INTERIOR PANELING & SHEATHING

SECTION 610 -INTERIOR PANELING 610.1 Interior PaneUng. All softwood wood structural panels shall conform to the provisions of the previous Chapter and shall be installed in accordance with Table 6.3 Panels shall comply with UBC Standard 23-3.

SECTION 611 - SHEATHING

designed to support all loads specified in this code and shall be capable of supporting concentrated loads of not less than 1.33 kN without failure. The concentrated load shall be applied by a loaded disk, 75 mm or smaller in diameter. Structural roof sheathing shall meet the following requirement: L

Deflection under uniform design live and dead load limited to 1/180 of the span between supporting rafters or beams and 1/240 under live load only.

Roof sheathing conforming to the provisions of Tables 6.9 or 6. 10 and 6.11 shall be deemed to meet the requirements of this section. Wood structural panel roof sheathing shall be bonded by intermediate or exterior glue. Wood structural panel roof sheathing exposed on the underside shall be bonded with exterior glue.

611.1 Structural Floor Sheathing. Structural floor sheathing shall be designed in accordance with the general provisions of this code and the special provisions in this section. Sheathing use as sub flooring shall be designed to support all loads specified in this code and shall be capable of supporting concentrated loads of not less than 1.33 kN without failure. The concentrated load shall be applied by a loaded disc, 75 mm or smaller in diameter. Flooring, including the finish floor, underlayment and subfloor, where used, shall meet the following requirements: 1.

Deflection under uniform design load limited to 11360 of the span between supporting joists or beams.

2.

Deflection of flooring relative to joists under a 25 mm·diameter concentrated load of 890 kN limited to 3 mm or less when loaded midway between supporting joists or beams not over 600 mm on center and 1/360 of the span for spans over 600 mm.

6-11

Floor sheathing conforming to the provisions of Tables 6.9, 6.10, 6.12, or 6.13 shall he deemed to meet the requirements of this section.

611.2 Structural Roof Sheathing. Structural roof sheathing shall be designed in accordance with the general provisions of 'this code and the special 'provisiohs in this section. Structural roof sheathing shall be


6-12

WOOD

SECTION 612 - MECHANICALLY LAMINATED FLOORS AND DECKS

SECTION 613 - POST-BEA~1 CONNECTION

612.1 MechanicaUy Laminated Floors and Decks.

613.1 Post-Beam Connection.

A laminated lumber floor or deck built up of wood members set on edge, when meeting the following requirements, may be designed as a solid floor or roof deck of the same thickness, and continuous span may be designed on the basis of the full cross section using the simple span moment coefficient.

Where post and beam or girder construction is used, the design shall be in accordance with the provisions of this code. Positive connection shall be provided to ensure against uplift and lateral displacement.

Nail length shall not be less than two and one half times the net thickness of each lamination. When deck supports are 1200 mm on center or less, side nails shall be spaced not more than 750 mm on center and staggered one third of the spacing in adjacent laminations. When supports are spaced more than 1200 mm on center, side nails shall be spaced not more than 450 mm on center alternately near top and bottom edges, and also staggered one third of the spacing in adjacent laminations. Two side nails shall be used at each eAd of butt-jointed pieces. Laminations shall be toenailed to supports with 20d or larger common nails. When supports are 1200 mm on center or less, alternate laminations shall be toenailed to alternate supports; when supports are spaced more than 1200 mm on center, alternate laminations shall be toenailed to every support. A single-span deck shall have all laminations full length.

A continuous deck of two spans shall have not more than every fourth lamination spliced within quarter points adjoining supports. Joints shall be closely butted over supports or staggered across the deck but within the adjoining quarter spans. No lamination shall be spliced more than twice in any span.

SECTION 614 - WOOD SHEAR WALLS AND DIAPHRAGMS 614.1 General. Particleboard vertical diaphragms and lumber and wood structural panel horizontal and vertical diaphragms may be used to resist horizontal forces in horizontal and vertical distributing or resisting elements. provided the deflection in the plane of the diaphragms. as determined by calculations, tests or analogies drawn therefrom, does not exceed the permissible deflection of attached distributing or resisting elements. See UBC Standard 23-2 for a method of calculating the deflection of a blocked wood structural panel diaphragm. Permissible deflection shall be that deflection up to which a diaphragm and any attached distributing or resisting element will maintain its structural integrity under assumed load conditions, i.e. continue to support assumed loads without danger to occupant of the structure. Connections and anchorages capable of resisting the design forces shall be provided between the diaphragms and the resisting elements. Openings in diaphragm which materially affect their strength shall be fully detailed on the plans and shall have their edges adequately reinforced to transfer a\1 shearing stresses. Size and shape of each horizontal diaphragm and shear wall shall be limited as set forth in Table 6.5. The height of a shear wall shall be detlned as: 1.

The maximum clear height from foundation to bottom of diaphragm framing above, or

2.

The maximum clear height from top of diaphragm to bottom of diaphragm framing above.


MECHANICALt.Y LAMINATED FLOORS AND DECKS, POST-BEAM CONNECTION & WOOD SHEAR WALLS AND DIAPHRAGMS

The width of a shear wall shall be defined as the width of sheathing. Where shear walls with openings are designed for force transfer around the openings, the limitations of Table 6.14 shall apply to the overall shear wall including openings and to each wall pier at the side of an opening. The height f a wall pier shall be defined as the clear height of the pier at the side of an opening. The width of a wall pier shall be defined as the sheathed width of the pier at the side of an opening. Design for force transfer shall be based on a rational analysis In buildings of wood-frame construction where rotation is provided for, the depth ofthe diaphragm normal to the open side shall not exceed 7500 mm nor two thirds the diaphragm width, whichever is the smaller depth. Straight sheathing shall not be permitted to resist shears in diaphragms acting in rotation.

EXCEPTIONS:

One-story, wood-framed slmclures with the depth normal to the open side nol greater than 7500 mm may have a depth equal to the width.

2.

masonry or concrete buildings, lumber and wood panel diaphragms shall not be considered as tral1snlitting lateral forces by rotation. Diaphragm sheathing nails or other approved sheathing "cClnfliectiors shall be driven flush but shall not fracture the

4.2 Wood Members Resisting Horizontal Forces by Masonry and Concrete.

U"~H"p,"

by masonry or concrete construction in over one story in height.

""rood floor and roof members may be used ill horizontal trusses and diaphragms to resist horizonlal forces imposed by wind, earthquake or earth pressure. pnwided slich forces are 1101 resisted hy I'otatioll l!f the trusses or diaphragm.

Vertical plywood~eathed shear walls may be used to prOVide resistance to wind or earthquake forces in two story bUildings of masonry or concrete constmction, provided the following requirements are met:

2.1 Story-ta-story 3600mm.

wall heights

shall not

exceed

2.2 Horizontal diaphragms shall not be considered to transmit lateral forces by rotation or cantilever action. 2.3 Deflections of horizontal and vertical diaphragms shall not permit per-story deflections of supported masonry or concrete walls to exceed 0.005 times each story height. 2.4 Wood stmctural panel sheathing in horizontal diaphragms shall have all unsupported edges blocked. Wood structural panel sheathing for both stories of vertical diaphragms shall have all unsupported edges blocked alld for the lower story walls hmJe a minimum thickness of 12 mm. 2.5

Where calculations show that diaphragm deflections call be tolerated. the depth normal 10 the open end may be increased to a depth-Io-width ratio 1I0t greater than 1 !'2: 1for diagonal sheathing or 2: 1 for special diagonal sheathed or plywood or particleboard diaphragms.

6-13

Where shall be no ollt-oj-plane horizontal offsets between the first and second stories of plywood shear walls.

614.3 Diagonally Sheathed Diaphragms.

•

614.3.1 Conventional lumber diaphragm construction. Such lumber diaphragms shall be made up of 25 mm nominal sheathing boards laid at an angle of approximately 45 degrees to supports. Sheathing boards shall be directly nailed to each intermediate bearing member with not less than two 8d nails for 25 mm by 150 mm nominal boards and three 8d nails for boards 200 mm or wider; and in addition, three 8d nails and four 8d nails shall be used for 150 mm and 200 mm boards, respectively, at the diaphragm boundaries. End joints in adjacent boards shall be separated by at least one joist or stud space, and there shall be at least two boards between joints on the same support. Boundary members at edges of diaphragms shall be designed to resist direct tensile or compressive chord stresses and adequately tied together at comers.

614.3.2 Special lumber diaphragm construction. Special diagonally sheathed diaphragms shall conform to conventional construction and in addition, shall have all elements designed in conformance with the provisions of this code. Each chord or portion thereof maybe considered as a beam loaded with a uniform load per meter equal to 50 percent of

National Stru~1 Code of the Philippines, Volume 1

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WOOD

the unit shear due to diaphragm action. The load shall be assumed as acting normal to the chord, in the plane of the diaphragm and either towards or away from the diaphragm. The span of chord, or potion thereof, shall be the distance between structural members of the diaphragm such as the joists, studs and blocking, which serve to transfer the assumed load to the sheathing. Special diagonally sheathed diaphragms shall include conventional diaphragms sheathed with two layers of diagonal sheathing at 90 degrees to each other and on the same face ofthe supporting members.

614.3.3 Wood structural panel diaphragm. Horizontal and vertical diaphragms sheathed with wood structural panels may be used to resist horizontal forces for horizontal diaphragm and for vertical diaphragms, or may be calculated by principles of mechanics without limitation by using values of nail strength and wood structural panel shear values as specified elsewhere in this code. Wood structural panels for horizontal diaphragms shall be as set forth in Tables 6.10 and 6.11 for corresponding joist spacing and loads. Wood structural panels in shear walls shall be at least 8 mm thick for studs spaced 400 mm on ~enter and 9 mm thick where studs are spaced 600 mm on center. Maximum spans for wood structural panel subfloor underlayment shall be as set forth in Table 6.12. Wood structural panels used for horizontal and vertical diaphragms shall conform to UBC Standard 23-2 and UBC Standard 23-3. All boundary members shall be proportioned and spliced where necessary to transmit direct stresses. Framing members shall be at least 50 mm nominal in the dimensions to which the plywood is attached. In general, panel edges shall bear on the framing members and butt along their centerlines. Nails shall be placed not less than 9 mm in from the panel edge, shall be spaced not more than 150 mm on center along panel edge bearings, and shall be firmly driven into the framing members. No unblocked panels less than 300 mm wide shall be used. Diaphragms with panel edges supP011ed in accordance with Tables 6.10, 6.11 and 6.12 shall not be considered as blocked diagrams unless blocking or other means of shear transfer is provided.

614.4 Particleboard Diaphragms. Vertical diaphragms sheathed with particleboard may be used to resists horizontal forces.

All boundary members shall be proportioned and spliced where necessary to transmit direct stresses. Framing members shall be at least 50 mm nominal in the dimension to which the particleboard is attached. In general, panel edges shall bear on the framing members and butt along their centerlines. Nails shall be placed not less than 9 mm in from the panel edge, shall be spaced not more than 150 mm on center along panel edge bearings, and shall be firmly driven into the framing members. No unblocked panels less than 300 mm wide shall be used. Diaphragms with panel edges supported in accordance with Table 6.13 shall not be considered as blocked diaphragms unless blocking or other means of shear transfer is provided.

614.5 Wood Shear Walls and Diaphragms in Seismic Zone 4. 614.5.1 Scope. Design and construction of wood shear walls and diaphragms in Seismic Zone 4 shall conform to the requirements ofthis section. 614.5.2 Framing. Collector members shall be provided to transmit tension and compression forces. Perimeter members at openings shall be provided and shall be detailed to distribute the shearing stresses. Diaphragm sheathing shall not be used to splice these members. Diaphragm chords and ties shall be placed in, or tangent to, the plane of the diaphragm framing unless it can be demonstrated that the moments, shear and deflections and deformations resulting from other arrangements can be tolerated.

614.5.3 Wood structural panel. Wood structural panels shall be manufactured using exterior glue. Wood structural panel diaphragms and shear walls shall be constructed with wood structural panel sheets not less than 1200 mm by 2400 mm, except at boundaries and changes in framing where minimum sheet dimension shall be 600 mm unless all edges of the undersized sheets are supported by framing members or blocking. Framing members or blocking shall be provided at the edges of all sheets in shear walls. Wood structural panel sheathing may be used for splicing members, other than those noted in Section 614.5.2, where the additional nailing required to develop the transfer of forces will not cause cross-grain bending or cross-grain tension in the nailed member.


STRESSES

614.5.4 Heavy wood panels. Diagonally sheathed panels utilizing 50 mm nominal boards may be used to resist the same permissible shear as 25 mm nominal lumber, except that 16d nails shall be used instead of8d.

6-15

SECTION 615 - STRESSES 615.1 General.

Panels utilizing straight decking overlaid with plywood may be used to resist shear forces using the same shear values as permitted for the wood structural panel alone. Wood structural panel joints parallel to the decking shall be . located at least 25 mm offset from any parallel decking joint.

Except as herein provided, stresses shall not exceed the allowable unit stresses for the respective species and grades or fabricated products as set forth in Table 6.1 and Table 6.15 for lumber.

Heavy decking panels utilizing dowel pins, or vertically laminated panels connected by nailing units to one another, resist shear forces based on the permissible shear values of their connectors.

The repetitive member adjustment factors for Fb may be used for the design of an assembly of repetitive framing such as joists, rafters and studs not over 100 mm in thickness spaced not more than 600 mm, not less than three in number and joined by transverse load-distributing elements adequate to support the design load'.

614.5.5 Particleboard. Particleboard shall not be less than Type M "Exterior Glue". Shear walls shall be sheathed with particleboard sheets not less than 1200mm by 2400 mm except at boundaries and changes in framing. The required nail size and spacing in Table 6.3 apply to panel edges only. All panel edges shall be backed with 50 mm nominal or wider framing. Sheets are permitted to be installed either horizontally or vertically. For 9 mm particleboard sheets installed with the long dimension parallel to the studs spaced 600 mm on center, nails shall be spaced at 150 mm on center along intermediate framing members. For all other conditions, nails of the same size shall be spaced at 300 mm on center along intermediate framing members.

Values for species and grades not tabulated shall be approved by the building official.

615.2 Stresses Members.

in

Piles

Used

as

Structural

Induced stresses for normal loading of round poles or piles when used as a structural member, except modulus of elasticity which shall be the same as for sawn lumber, shall not exceed 60 percent of the basic unit working stresses for the species as forth in Table 6.1

615.3 Adjustment of Stresses. 614.6 Fiberboard Sheathing Diaphragms. Wood stud walls sheathed with fiberboard sheathing may be used to resist horizontal forces not exceeding those set forth in this section. The fiberboard sheathing, 1200 mm by 2400 mm, shall be applied vertically to wood studs not less than 50 mm nominal in thickness spaced 400 mm on center. Nailing shall be provided at the perimeter of the sheathing board and at the intermediate studs. Blocking not less than 50 mm nominal in thickness shall be provided at horizontal joints when wall height exceeds length of sheathing panel, and sheathing shall be fastened to the blocking with nails sized spaced 75 mm on centers each side of joint. Nails shall be spaced not less than 9 mm from edges and ends of . sheathing. Marginal studs of shear walls or shear-resisting elements shall be adequately anchored at the top and bottom and designed to resist all forces. The maximum height-width ratio shall be 1'12: 1.

615.3.1 General. The allowable unit stresses specified in this chapter shall be subject to the adjustments set forth in the footnotes to the appropriate stress tables and to the requirements of this section. 615.3.2 Preservative treatment. The values for wood pressure impregnated with an approved process and preservative need no adjustment for treatment but are subjected to other adjustments. 615.3.3 Fire-retardant teatment. The values for lumber and plywood pressure impregnated with approved fire retardant chemicals, including fastener values, shall be recommended by the treater and submitted to the building official for approval. Submittal to the building official shall include an substantiating data. Such values shall be developed from approved test methods and procedures that consider potential strength-reduction characteristics. including effects of elevated temperatures and moisture. Other adjustments are applicable, except that the impact load-duration factor shall not apply


6-16

WOOD

615.3.4 Duration ofload. Values for wood and mechanical fastenings (when the wood determines the load capacity) are subjected to the following adjustments for the various duration of loading: ].

2.

Where a member is fully stressed to the maximum allowable stress, either continuously or cumulatively, for more than 10 years under the conditions of maximum design load, the values shall not exceed 90 percent of those in the tables. When the accumulated duration of the full maximum load during the life of the member does not exceed the period indicated below, the values may be increased in the table as follows:

25 percent for seven days duration, as for roof loads 33 113 percent for earthquake 33 1/3 percent for wind (for connections and fasteners) 60 percent for wind (members only) 100 percent for impact The foregoing examples are not cumulative. For combined • duration of loadings the resultant structural members shall not be smaller than the required for the longer duration of loading. The duration of load factors in this item shall not apply to compression-perpendicular-to-grain design values based on a deformation limit, or to modulus of elasticity.

3.

Values for normal loading conditions may be used without regard to impact if the stress induced by impact does not exceed the values for normal loading.

615.3.5 Size factor adjustment. When the depth of a rectangular sawn . lumber bending member 125 mm or thicker exceeds 300 mm, the bending values, F", shall be multiplied by the size factor, CF, as determined by the Equation (615-1):

CF -_ (300)119 d

(615-1)

615.3.6 Slenderness factor and flexural stress. When the depth of a bending member exceeds its breadth, lateral support may be required and the slenderness factor Cs shall be calculated by the following Equation:

(615-2) Where:

Cs slenderness factor.

Ie

effective length of beam, mm from the following table.

d

depth of beam, mm.

b

breadth ofbeam, mm.

EFFECflVE LENGTH OF BEAMS

TYPE OF BEAM SPAN AND NATURE OF LOAD

Single-span beam, load concentrated at the center. Single-span beam, uniformly distributed load. Single-span beam, equal end moments. Cantilever beam, load concentrated at unsupported end. Cantilever beam, uniformly distributed load. Cantilever beam, uniformly distributed load with concentrated load at cantilever end. Single-span or cantilever beam, any other load.

VALUE OF EFFECTIVE LENGTH,le

1.611u 1.9Uu 1.841u 1.691u 1.06lu 1.691u l.9Uu

Lu = unsupported length ofbeam, mm

Where:

CF = size factor.

d = depth ofbeam in mm.

beams of circular cross section that have a diameter greater than 340 rom, or 300 rom or larger square beams loaded in the plane of the diagonal, the size factor CF may be determined on the basis of an equivalent conventionally loaded square beam ofthe same cross-sectional area.

FOT

Size factor adjustments are cumulative with form factor adjustments specified in Section 615.3.7, except for lumber I beam and box beams, but are not cumulative with slenderness factor adjustments specified in Section 6]5.3.6. The size factor adjustment shall not apply to visually graded lumber 50 mm to 100 mm thick or to machine stress-rated lumber.

The effective lengths, Ie in the table are based on an /uld ratio of 17. For other fufd ratios, these effective lengths may be multiplied by a factor equal to 0.85+2.55/(fufd) except that this factor shall not apply to a single-span beam with equal end moments (Je=L84Ju) or to a single span or cantilever beam with any load (le=L92Ju).


STRESSES

When the slenderness factor Cs does not exceed 10, the full allowable unit stress in bending Fb may be used. When the slenderness factor Cs is greater than 10 but does not exceed Ck, the allowable unit stress in bending Fb shall b~ determined from the following equation:

(615-3)

Where:

Ck 0.811~E/ Fb E

Fb

(615-4) .

modulus of elasticity. =

allowable unit stress for extreme fiber in bending.

6-17

provided throughout the length of the beam, the unsupported Itt is the distance between such points of end bearing, or the length of the cantilever. When a beam is provided with a lateral support to prevent rotational and lateral displacement at intermediate points as well as the ends, unsupported length III is the distance between such points of intermediate lateral support. 615.3.7 Form factor adjustments. The allowable unit stress in bending for non-prismatic members shall not exceed the value established by multiplying such stress by the form factor Cfdetermined as follows: FORM FACTOR (C1)

BEAM SECTION

Circular Square (with diagonal vertical) Lumber I Beams and Box Beam

Fb' = allowable unit stress for extreme fiber in bending, adjusted for slenderness.

+J..I3 )2 O.SI 1+ [( 25~.j --d

2

When the slenderness factor Cs is greater than Ck but less than 50, the allowable unit stress in bending F'h shall be determined by the following Equation: L-'

r

_

b-

0.4381::

[

(--~) \25.-1

1.180 1.414

1

1 Cg

(615-6)

+88

Where: (615-5)

( 'S 2

Cr

=

form factor

In no case shall Cs exceed 50.

Cg

=

support factor

The design values for extreme fiber in bending, 1'1" and modulus elasticity, E, used in the formulas for F'h shall be modified to account for moisture service condition, duration of loading, temperature and type of treatment in accordance with the Section 615.3 except that the modification for size factor shown in Section 615.3.5 shall not be take. Design values for extreme fiber in bending adjusted for slenderness factor, F'b, are not subject to further modifications for moisture service condition, duration of loading. temperature, type of treatment' or size.

p

= ratio

The design value for extreme fiber in bending. F 'b, shall not exceed the fujI design value for extreme fiber in bending, Fb, modified as allowed in this section, including the size factor adjustment. When the compression edge of a beam is supported throughout its length to prevent its lateral displacement, and the ends at points of bearing have lateral support to prevent rotation, the unsupported length 111 may be taken as zero.

(615-7) (6

8p + 3/i)(1

q) + q

of depth of compression flange to full depth ofbeam.

q = ratio of thickness of web or webs to the full width

of beam.

The form factor adjustment shall be cumulative with the size factor adjustment, except for lumber 1 beams and box beams. 615.3.8 Modulus of elasticity adjustment. The use of average modulus of elasticity E values are appropriate for the design of normal wood structural members and assemblies. In special applications where deflections are critical to the stability of structures or structural components, and where exposed to varying temperature and relative humidity under sustained loading conditions, Ihe average values of the modulus of elasticity E listed in Table 6.1 shall be reduced to account for variability. Coefficients of variation C 1, in the modulus of elasticity E fOT lumber as follows:

When lateral support is provided to prevent rotation at the points of end bearing but no other lateral support is


6-18

Visually graded sawn lumber Machine stress-rated sawn lumber

WOOD

Cv 0.25 0.11

The average modulus of elasticity E values listed in the table shall be multiplied by r-cv , or 1-1.65Cv to obtain a modulus of elasticity E value exceeded by 84 percent or 95 percent individual pieces, respectively. The duration-of-Ioad adjustments specified in Section 615.3.4 do not apply to modulus of elasticity values.

615.3.9 Temperature. The allowable unit stress for untreated and preservative-treated wood specified in this chapter and as modified in this section apply to uses within the range of climatic temperature ordinarily encountered in buildings. Wood members shall not be used in areas subject to temperatures above 66°C unless the exposure is infrequent and any permanent loss in strength is accounted for in the design. The allowable unit stress for fire-retardant-treated solid sawn lumber and plywood, including fasteners values, sqJJject to prolonged elevated temperatures from manufacturing or equipment processes, but not exceeding 66°C, shan be developed from approved test methods that properly consider potential strength-reduction characteristics, including effects of heat and moisture.

615.3.10 Moisture service condition. Where sawn lumber and fastenings are exposed to service conditions causing the wood to possess more than 19 percent moisture content, the tabulated design values shall be reduced as specified in Table 6.16 615.3.11 Bolted joints. Bolt values used in conjunction with metal side plates shall be in accordance with Section 619.

SECTION 616 - HORIZONTAL MEMBER DESIGN 616.1 Beam Span. For simple beams, the span shall be taken as the distance from face to face of support, plus one half the required length· of bearing at each end; for continuous beams, the span is the distance between centers of bearings on support over which the beam is continuous.

616.2 Flexure. 616.2.1 Circular cross section. A beam of circular cross section may be assumed to have the sam.e strength in flexure as a square beam having the same cross-sectional area. If a circular beam is tapered, it shall be considered a beam of variable cross section. 616.2.2 Notching. Ifpossible, notching of beams should be avoided. Notches in sawn lumber bending members shall not exceed one-sixth the depth of the member apd shall not be located in the middle third of the span. Where members are notches at the ends, the notch depth shall not exceed one- fourth the beam depth. The tension side of the sawn lumber bending members of 100 mm or greater nominal thickness shall not be notch except at ends of members. Cantilevered portions of beams less than 100 mm in normal thickness shall not be notched unless the reduced section properties and lumber defects are considered in the design. 616.2.3 Lateral moment distribution. Lateral moment distIibution of a CQncentrated load from a critically loaded beam to adjacent parallel beams shall be calculated.

616.3 HoriZontal Shear. The maximum horizontal shear stress in a solid-sawn wood shall .not exceed that calculated by means of Equation (616-1):

3V

f"

= 2bd

(616-1)

The actual unit shear fv shall not exceed the allowable for the species and the grade as given in Table 6.1 adjusted for duration ofloading, as provided in Section 615.3.4. When calculating the shear force)/' distribution of load to adjacent parallel beams by flooring or other members may be considered, and all loads within a distance from either


HORIZONTAL MEMBER DESIGN

support equal to the depth of the beam may be neglected for beams support by full bearing on one surface and loads applied to the opposite surface.

6-19

Where: d

total depth ofbeam.

d' = actual depth ofbeam at notch.

616.4 Horizontal Shear in Notched Beams. e

When rectangular-shaped girder, beams or joists are notched at points of support on the tension side, they shall meet the design requirements of that section in bending and in shear. The horizontal shear stress at such point shall not exceed the value calculated by Equation (616-2):

Eccentric connector and bolted joints and beams support by connectors or bolt shall be designed so that .fi· in Equation (616-5) does not exceed the allowable unit stresses in horizontal shear.

total depth of beam.

= actual depth of beam at notch.

(616-5)

Wben girder, beams or joists with circular cross section are notched at points of support on the tension side, they shall JTleet the design requirements of that section in bending and in shear. The actual shear stress at such point shall not exceed the value calculated by Equation (616-3): (616-3)

Where:

An

The shear for the notch on the compression side shall be further limited to the value determined for a beam of depth d' if e exceed d'.

(616-2)

Where:

d'

distance notch extends inside the inner edge of support.

616.5 Design of Joints in Shear.

-~(~J

Fv - 2bd' d'

d

=

=

cross-sectional area of notched member.

d

total depth of beam.

dn

actual depth of beam at notch.

For bending members with other than rectangular or circular cross section and notched at point of support on the tension side, the actual shear stress parallel to grain shall be calculated in accordance with conventional engineering mechanics. When girders, beams or JOIsts are notched at point of support on the compression side, they shall meet design requirement for that net section in bending and in shear. The shear at such point shall not exceed the value calculated by : (616-4)

Where:

de (with connectors) the depth of the member less the distance from the unloaded edge of the member to the nearest edge of the nearest connector. djf (with bolts or log screws) = the depth of the member less the distance from the unloaded edge of the member to the center of the nearest bolt or lag screw. 8

Allowable unit stresses in shear for joint involving bolts or connectors loaded perpendicular to grain may be 50 percent greater than the horizontal shear values as set forth in Table 6.1 and, provided that the joint occurs at least five times the depth of the member from its end. When the joint is less than five times the depth of the member from its end, the included shear stress is calculated by: (616-6)

and the 50 percent increase in design values tor shear in joints does not apply.

616.6 Compression Perpendicular to Grain. In application where deformation is critical. Equation (616-7) shall be used to calculate the compression perpendicular-to-grain design values.

National StructUral Code of f.tJe PhRippines. Volume 1

6·20

WOOD

Fe.!.' = 0.73 FC.L

(616-7)

Where:

Fc.!.

=

Fe.!. '

compression-perpendicular-to-grain values from Tables 6.1. critical compression-perpendicular-to-grain value.

616.7 Lateral Support. Solid-sawn rectangular lumber beams, rafter and joist shall be supported laterally to prevent rotation or lateral displacement in accordance with the following: If the ratio of depth to thickness, based on nominal dimensions, is: 1.

Two to 1, no lateral support is required.

The duration of load modification factors given in Section 615.3.4 shall not apply to compression-perpendicular-to grain values for sawn lumber.

2.

The allowable unit stresses for compression perpendicular to grain in Table Nos. 6.1 and 6.17 apply to bearings of any length at the ends of the beam and to all bearings 150 mm or more in length at any other location.

Three to 1 or 4 to 1, the ends shall be held in position, as by full-depth solid blocking, bridging, nailing or bolting to other framing members, approved hangers or other acceptable means.

3.

Five to 1, one edge shall be held in line for its entire length.

4. .

Six to 1, bridging, full-depth solid blocking or cross bracing shall be installed at intervals not exceeding 2.4 meters unless:

4.1

Both edges of the member are held in line or,

For bearing of less than 150 mm in length and not nearer than 75 mm to the end of a member, the maximum allowable load per square mm may be obtained by multiplying the allowable unit stresses in compression perpendicular to grain by the factor indicated by: (616-8)

in which lb is the length of bearing in mm measured along the grain ofthe wood. The multiplying factors for indicated length of bearing on such small areas as plates and washers may be: I

Length of Bearing

150 13

25

38

50

15

100

or More

1.19

1.13

1.10

1.00

(mm)

Factor

1.15

1.38 I 1.25

In using the preceding equation and table for round washers or bearing areas, use a length equal to the diameter. In joists supported on a ribbon or ledger board and spiked to the studding, the allowable stress in compression perpendicular to grain may be increased 50 percent.

4.2 The compression edge of the member is supported throughout its length to prevent lateral displacement, as by adequate sheathing or subflooring , and the ends and all points of bearing have lateral support to prevent rotation. 5.

Seven to 1, both edges shall be held in line for their entire length.

If a beam is subject to both flexure and compression parallel to grain, the ratio may be as much as 5 to 1 if one edge is held firmly inline. Ifunder any combination ofload the unbraced edge of the member is in tension, the ratio may be 6 to 1. In lieu of providing lateral support by the methods specified in items 2 through 5 above, the allowable stresses shall be reduced by the slenderness factor set forth in Section 615.3.6.

616.8 Lateral Support of Arches, Compression Chords of Trusses and Studs. Where roof joist or purlins are used between arches or compression chords, the largest value of Ie I d, calculated using the depth of the arch or compression chord or calculated using the breadth (least dimension) of the arch or compression chord between points of intermittent lateral support, shall be used. The roof joist or purlins shall be placed to account for shrinkage (for example, by placing the

Association of Structural Engineers of the P~ilippines

COLUMN DESIGN

6-21

1 !

upper edges of unseasoned joist approximately 5 percent of the joist depth above the tops of the arch or chord) but also placed low enough to provide adequate lateral support.

SECTION 617 - COLUMN DESIGN 617.1 Column Classifications.

Where roof joist or purlins are placed on top of an arch or compression chord and are securely fastened to the arch or compression chord, the largest value of Ie / d, calculated using the depth of the arch or compression chord or calculated using the breadth (least dimension) .ofthe arch or compression chord between points of intermittent lateral support, shall be used. Where planks are placed on top of an arch or compression chord and securely fastened to the arch or compression chord, or when sheathing is nailed properly to the top chord of trussed rafter, the depth rather than the breadth of the arch, compression chord or trussed rafter may be used as the least dimension in determining Ie / d Where stud walls in light-frame construction are adequately sheathed on at least one side, the depth rather than breadth of the stud, may be taken as the least dimension in calculating the Ie / d ratio.

617.1.1 Simple solid-wood columns. Simple column

consist of a single piece or of;pieces properly glued together to form a single member. 617.1.2 Spaced

column, connector joined. Spaced columns are formed of two or more individual members with their longitudinal axes paralleL separated at the ends and middle points of their length by blocking and joined at . the ends' by timber connectors capable of developing the required shear resistance.

617.1.3 Built-up columns. Built-up columns, other than

connector-joined spaced columns and glued-laminated columns, shall not be designed as solid columns.

617.2 Limitation on 1/ d Ratio. For simple solid columns, 1/ d shall not exceed 50. For individual members of a spaced column, see UBC Standard No. 25-15, "Design Standard for Spaced Wood Column Design" or Division II of Uniform Building Code, Volume 2, 1994

617.3 Simple Solid-column Design. The effective column length, Ie shall be used in design Equations given in this section. The effective column length, Ie shall be determined in accordance with good engineering practice. Actual column length, I, may be multiplied by the factors given in the following table to determine effective column length, Ie. Allowable unit stresses in newton per square millimeter of cross-sectional area of square or rectangular simple solid columns shall be determined by the following formulas, but such unit stresses shall not exceed values for compression, parallel to grain Fe in Table 6.1 adjusted in accordance with provision of this section.

Where: c'

0.8 for sawn lumber.

c' "'" 0,85 for round timber piles.

National SbuctunII Code of the Philippines, Volume 1

6-22

WOOD

Where: dmin Fc* = tabulated compression design value multiplied by all of the applicable adjustment factors. KcE

dmax = the maximum dimension, d, for that face of the column.

0.3 for visually graded lumber-

Support Conditions:

0.418 for products such as machine stress-rated sawn lumber.

KcE

,

!

... Buckling Modes

I

I

I I

I

I

;

I

I I

;

I I

I

,

I

\

I

~

\ I I

I I

I

I I I I I

I

I I

, \

I

1.00

T I

I

I

2.10

The design of a column of round cross section shall be based on the design calculations for a square column of the same cross-sectional area and having the same degree of taper.

2.4

Rotation fixed, translation fixed Rotation free, translation fixed End Condition Code

a= 0.50 a= 0.70

For all other support conditions:

t

0.65

a= 0.70 a 0.30

I

I I

I

Large end fixed, small end unsupported Small end fixed, large end unsupported Both ends simply supported: Tapered toward one end Tapered toward both ends

I I I I I

I

t

Design buckling factoI', Ke when ideal conditions approxi mated

~

I I I I I I I

\ I

I

I

l

+ I

I

I

I

;

...•

I

I

y

I I

the minimum dimensiofl, d, for that face ofthe column.

Rotation fixed, translation free Rotation free, translation free

Note: Ie Kle

617.4 Tapered Columns. When designing a tapered column with a rectangular cross section, tapered at one or both ends, the representative dimension, d rep for each face of the column shall be derived as follows:


FLEXURAL AND AXIAL LOADING COMBINED

SECTION 618 - FLEXURAL:AND AXIAL LOADING COMBINED

618.1 Flexure and Axial Tension. Members subjected to both flexure and axial tension shall be so proportioned that

:'S

(618-1)

1

and

<

618.3 Spaced Columns. In the case of spaced columns, this combined stress formula maybe applied only if the bending is in a direction parallel to the greater d of the individual member.

618.4 Truss Compression Chords.

Fb *

tabulated bending design value multiplied by all applicable adjustment factors except CF .

Fb **

tabulated bending design value multiplied by all

applicable adjustment factor except CF.

Fe

allowable tension design value parallel to grain,

N/rom2 •

.k

design in the plane of bending the slenderness ratio, teld, in the plane of bendin~ shall be used to -calculate Fe and J and (2) when checking the design perpendicular to the plane of bending the slenderness ratio, le Id, in the plane of bending shall be used to calculate F'c and J shall be set equal to zero.

(618-2)

Where:

Effect of buckling of a 50 rom by 100 mm or smaller truss compression chord having effective buckling lengths of2400 mm or less and with 9 rom or thicker plywood sheathing nailed to the narrow face of the chord in accordance with the appropriate standards shall be determined from the equation:

c.,. = I+O. 62Ie Eo. 05

actual unit stress in tension parallel to grain .

.f, :=

6-23

actual unit stress for extreme fiber in bending.

Where: CT

618.2 Flexure and Axial Compression.

(618-3)

Ie

The value of J shall be derived as (618-4)

K 11

K =0.671

[I

~Fc-

(618-5)

= effective buckling length used in design of chord for compression loading.

Eo.05= 0.589E for visually graded lumber.

E

Id"':'l1

= buckling of the stiffness factor. 0.819E for machine-stress-rated lumber.

Members subjected to both flexure and axial compression shaH be proportioned that

J

(618-6)

Modulus of elasticity from tables of allowable unit stress, N/mm2 .

The values of CT determined from this equation are for wood seasoned to a moisture content of 19 percent or less at the time the plywood is nailed to the chord. For wood that is unseasoned at the time of plywood attachment, CT shall be determined from the Equation (618-7): (618-7)

except that J shall not be less than zero nor greater than one (0 S; J::;; 1).

Fe and K shall be determined in accordance with the provision in Section 617.3, except (1) when checking the

For chords with an effective buckling length greater than 2400 rom, Ct shall be taken as the value for a chord having an effective length of 2400 rom.

National Structural Code 01 the Philippines, Volume 1

WOOD

6-24

The buckling stiffness factor does not apply to short columns or trusses used under wet conditions. The allowable unit compressive stress shall be modified by the buckling stiffness factor when a truss chord is subjected to combined flexure and compression and the bending moment in the direction that induces compression stresses in the chord face to which the plywood is attached. The buckling stiffness factor Cr shall apply as follows: Short column ( lei d of 11 or less ): (618-8)

F'c = Fe

Intermediate columns (fe" d greater than 11 but less than K): (618-9)

K = 0.671JCr FE . . c

(618-10)

Lbng column (Ie; d of K or greater ): F' _ 0.30F:C r

c-

(618-11)

V" I d)2

The allowable unit stress in compression at an angle of load to grain between 0° and 90° shall be computed from the Hankinson Equation as folIows:

'e}' + ..cl. Co.F'(J

. S1I1-

619.1 GeneraL Timber connectors and fasteners may be used to transmit forces between wood members and between wood and metal members. The allowable loads and installation of timber connectors and fasteners shall be in accordance with the provision set forth in UBC Standard No. 25-17, "Timber Connector Joints, Bolted Joints, Drift Bolts and Wood Screws, Lag Screws; Metal Plate Connected Wood Truss Design, and Nails and Staples" or Division III of Chapter23Uriiform Building Code, Volume 2, 1994. For connectors and fasteners where the wood is wet a time of fabrication or wet in service, the allowable load shall be modified in accordance with UBC Standard No. 25-17. The allowable loads and installation of timber connectors shall be as set forth in Tables 6.2, 6.17, 6.19, and 6.20. Safe loads and design practices for types of connectors and fasteners not mentioned or fully covered in UBC Standard No. 25-17 may be determined in a manner approved by the building official.

619.2 Bolts. Safe loads in leN for bolts in shear in seasoned lumber shall not exceed the values set forth in Table 6.17.

618.5 Compression at Angle to Grain.

L' I' c

SECTION 619 - TIMBER CONNECTORS AND FASTENERS.

Allowable shear values used to connect a wood to concrete or masonry are permitted to be determined as one half the tabulated double shear values for a wood member twice the thickness of the member attached to the concrete or masonry.

(618-12)

Allowable values J'~ shall be adjusted for duration of load before lise in Hankinson's Equation. Values of Fn and are not subjected to duration of load modifications.

619.3 Nails and Spikes. 619.3.1 Safe lateral strength. A common wire nail driven perpendicular to grain of the wood. when used to fasten wood members together, shall not be subjected to a greater load causing shear and bending than the safe lateral strength of the wire nail or spike as set forth in Table 6.21. A wire nail driven parallel to the grain of the wood shall not be subjected more than two thirds of the lateral load allowed when driven perpendicular to the grain. Toenails shall not be subjected more than five sixths of the lateral load allowed for nails driven perpendicular to the grain. 619.3.2 Safe resistance to withdrawal. A w.ire nail driven perpendicular to grain of wood shall not be subjected to a greater load, tending to cause withdrawal, than the safe


TIMBER CONNECTORS AND FASTENERS & CONVENTIONAL LIGHT-FRAME CONSTRUCTION DESIGN PROVISIONS

resistance of the nail to withdrawal, as set forth in Table 6.21. 619.3.3 Spacing and penetration. Common wire nails shall have penetration into the piece receiving the point. as set forth in Table 6.21. Nails or spikes for which the wire gauges or lengths are not set forth in Table 6.21 shall have a required penetration of not less than 11 diameters, and allowable loads may be interpolated. Design values shall be increased when the penetration of nails into the member holding the point is larger than the required by this item. For wood-to-wood joints, the spacing center to center of nails in the direction of stress shall not be less than one half of the required penetration. Edge or end distances in the direction of stress shall not be less one half of the required penetration. All spacing and edge and end distances shall be such as to avoid splitting of the wood. Holes for nails, where necessary to prevent splitting, shall be bored of a diameter smaller than that ofthe nails.

6-25

SECTION 620 ~ CONVENTIONAL LIGHT-FRAME CONSTRUCTION DESIGN PROVISIONS 620.1 General. The requirements in this section are intended for conventional light-frame construction. Other methods may be used provided a satisfactory design is submitted showing compliance with other provisions ofthis code. Only the following occupancies may be constructed in accordance with this division: 1.

One-, two- or three-story buildings housing Group R Occupancies.

2.

One-story Occupancy Category 4 buildings, as defined in Table 6.24, when constructed on a slab on-grade floor.

619.4 Joist Hangers and Framing Anchors 3.

Group U Occupancies.

Connections depending upon joist hangers or framing anchors, ties and other mechanical fastenings not otherwise covered may be used where approved

4.

Top-story walls and roofs of Occupancy Category 4 buildings not exceeding two story's of wood framing.

619.5 Miscellaneous Fasteners.

5.

Interior non-load bearing partitions, ceilings and curtain walls in all occupancies.

619.5.1 Drift bolts or drift pins. Connections involving the use of drift bolts or pins, wood and screws and lag screws shall be designed in accordance with the provisions set forth in UBC Standard No. 25-17. 619.5.1.1 Withdrawal design values. Drift bolt and drift pin connections loaded in withdrawal shall be design in accordance with good engineering practice. 619.5.1.2 Lateral design values. Allowable lateral design values for drift bolts and drift pins driven in the side grain of wood shall not exceed 75 percent of the allowable lateral design values for common bolts of the same diameter and length in main member. Additional penetration of pin into members should be provided in lieu ofthe washer, head. and nut on a common bolt. ·619.5.2 Spike grids. Wood-to-wood connections involving spike grids for lateral load transfer shall be designed in accordance with good engineering practice.

Other approved repetitive wood members may be used in lieu of solid-sawn lumber in conventional construction provided these members comply with the provisions of this code.

620.2 Design of Portions. When a building of otherwise conventional construction contains non-conventional structural elements, those elements shall be designed in accordance with Sec:tion on "Rationality of Design Method" on the previous chapter.

620.3 Additional Requirements for Conventional Construction in High-wind Areas. Appendix Chapter 23 of the Uniform Building Code, Volume 2, 1994 provisions for conventional construction in high-wind areas shall apply when specifically adopted.


6-26

WOOD

620.4 Additional Requirements for Conventional Construction in Seismic Zone 2. 620.4.1 Braced wall lines. Where the basic wind speed is not greater than 129 kmlh, buildings shall be provided with exterior and interior braced wall lines. Spacing shall not exceed 10.20 meters on center in both the longitudinal and transverse directions in each story. 620.4.2 Braced wall lines for high wind. Where the basic wind speed exceeds 129 kmlh, buildings shall be provided with exterior and interior braced wall lines. Spacing shall not exceed 7.50 meters on center in both longitudinal and transverse directions in each story.

EXCEPTION:

lateral-force-resisting system designed to resist the forces specified in Chapter on Structural Forces. One or more of the following shall be considered to constitute an unusual shape: 620.5.3.1 When exterior braced wall panels, as required by Section 620.10.3, are not in one plane vertically from the foundation to the uppermost story in which they are required.

EXCEPTION: Floors with cantilevers or setbacks Ilot exceedingfour times the nominal depth of the .floor joists may ,support braced wall panels prOVided: I.

Floor joists are 50 mm by 250 mm or larger and spaced at not more than 400 mm on center.

In one- and two-story Group R. Division 3 buildings. interior braced wall line spacing may be increased to 1Iot more than 10.20 meters on center in order to accommodate lone single room per dwelling unit not exceeding 83.6m2• Ihe building offiCial may require additional walls to contain braced panels when this exception is used.

2.

The ratio ofthe hack spall to the cantilever is at least 2 to 1.

3.

Floor joists at ends of braced wall panels are doubled.

620.4.3 Veneer. Anchored masonry and stone wall veneer shall not exceed 125 mm in thickness.

4.

620.4.4 Unusually shaped buildings. When of unusual shape as defined in Section 620.5.3, buildings of light frame construction in Seismic Zone 2 shall have a lateral force-resisting system designed to resist the forces specified . in Chapter 2.

A continuous rim joists is connected to ends of all cantilevered joists. The rim joist may he spliced using a metal tie flot les.<; than 1.-17 mm (16 galvanized gage) and 38 mm wide fastened with six 16dnails.

5.

Gravity loads carried at the end of cantilevered joists are limited to uniform wall and roof load and the reactions from headers having a span of 2400 mm or less.

620.5 Additional Requirements for Conventional Construction in Seismic Zone 4. 620.5.1 Braced wall lines. Buildings shall be provided with exterior and interior braced wall lines. Spacing shall not exceed 7500 mm on center in both the longitudinal and transverse directions in each story.

EXCEPTION: In one- and two-story Group R. Division 3 bUildings, interior braced wall line spacing may be increased to not more than 10200 mm on center in order to accommodate one single room per dwelling unit not exceeding 83.61m2. The building offiCial may require additional walls to contain braced panels when this exception is used 620.5.2 Veneer. Anchored masonry and stone wall veneer shall not exceed 125 mm in thickness and shall not extend above the first story. 620.5.3 Unusually shaped b\lildings. When of unusual shape, buildings of light-frame construction shall have a

620.5.3.2 When a section of floor or roof is not laterally supported by braced wall lines on all edges.

EXCEPTION: Portions of roofs or floors which do not support braced wall panels above may extend up to 1800 mm beyond a braced wall line. 620.5.3.3 When the end of a required braced wall panel extends more than 300 mm over an opening in the wall below. This provision is applicable to braced wall panels offset in plane and to braced wall panels offset out of plane as permitted by Section 620.5.3.1.

EXCEPTION: Braced wall panels may extend over an opening not more than 2400 mm in width when the header is a 100 mm by 300 mm or larger member.


CONVENTIONAL LIGHT-FRAME CONSTRUCTION DESIGN PROVISIONS

620.5:3.4 When an opening in a floor or roof exceeds the . lesser of 3600 mm or 50 percent of the least floor or roof dimension. 620.5.3.5 Construction where portions of a floor level are vertically offset such that the framing members on either side of the offset cannot be lapped or tied together in an approved manner as required by Section 620.7.3.

EXCEPTION: Framing supported directly byfoundations. 620.5.3.6 When braced wall lines do not occur in two perpendicular directions. 620.5.3.7 Other configurations which, in the opinion of the building official, create irregularities or discontinuities which are not addressed by this Section. 620.5.4 Lumber roof decks. Lumber roof decks shall have solid sheathing. 620.5.5 Interior braced wall support. In one-story buildings, interior braced wall lines shall be supported on continuous foundations at intervals not exceeding 15000 mm. In buildings more than one-story in height, all interior braced wall panels shall be supported on continuous foundations.

EXCEPTION: Two-story bUildings may have interior braced wall lines :,upported on contimlous foundations at intervals not exceeding 15000 mm prOVided: 1.

Cripple wall height does not exceed 1200 mm.

2,

First floor braced wall panels are supported 011 doubled floor joist, amtimlous blocking or floor heams.

3,

Distance between bracing lines does not exceed twice the building width parallel to the braced wall line.

6-27

The end of beams or girders supported on masonry or concrete shall not have less than 75 mm of bearing.

620.7 Floor Joists. 620.7.1 General. The limits of defects by grade in joists and planks for seasoned wood are set forth in Table 6. IS. 620.7.2 Bearing. Except where supported on a 25 mm by ] 00 mm ribbon strip and nailed to the adjoining stud, the ends of each joist shall not have less than 38 mm of bearing on wood or metal, or less than 75 mm on masonry. 620.7.3 Framing details. Joists shall be supported laterally at the ends and at each support by solid blocking except where the ends of joists are nailed to a header, band or rim joist or to an adjoining stud or by other approved means. Solid blocking shall not be less 50 mm in thickness and the full depth ofjoist. Notches on the ends of joists shall not exceed one-fourth the joist depth. Holes bored in joists shall not be within 50 mm of the top or bottom of the joist, and the diameter of any such hole shall not exceed one-third the depth of the joist. Notches in the top or bottom ofjoists shall not exceed one-sixth the depth and shall not be located in the middle third of the span. Joist framing from opposite sides of a beam, girder or partition shall be lapped at least 75 mm or the opposing joists shall be tied together in an approved manner. Joists framing into the side of a· wood girder shall be supported by framing anchors or on ledger strips not less than 50 mm by 50 mm. 620.7.4 Framing. around openings. Trimmer and header joists shall be doubled, or of lumber of equivalent cross section, when the span of the header exceeds 1200 mm. The ends of header joists more than 1800 mm long shall be supported by framing anchors or joist hangers unless bearing on a beam, partition or wall. Tail joists over 3600 mm long shall be supported at header by framing anchors or on ledger strips not less than 50 mm by 50 mm. 620.7.5 Supporting bearing partitions. Bearing partitions perpendicular to joists shal1 not be offset from supporting girders, walls or partitions more than the joist depth.

620.6 Girders. Girders for single-story construction or girders supporting loads from a single floor shan not be less than 100mm by 150 mm for spans ] 800 mm or less, provided that girders are spaced not more than 2400 mm on center. Other girders shall be designed to support the loads specified in this code. Girder end joints shall occur over supports. When a girder is spliced over a support, an adequate tie shall be provided.

Joists under and parallel to bearing partitions shall be doubled. 620.7.6 Blocking. Floor joists shall be blocked when required by the provisions of Section 620.7.3.


WOOD

6-28

620.8 Subtlooring.

620.10 Wall Framing.

620.8.1 Lumber subfloor. Sheathing used as a structural sub:'floor shall confonn to the limitations set forth in Table 6.9.

620.10.1 Size. beigltjt and spacing. The size, height and spacing of studs shall be in accordance with Table 6.23 except that utility grade studs shall not be spaced more than 400 mm on center, or support more than a roof and ceiling, or exceed 2400 mm in height for exterior walls and load bearing walls or 3000 mm for interior nonload-bearing walls.

Joints in subflooring shall occur over supports unless end matched lumber is used in which case each piece shall bear on at least two joists. Subflooring may be omitted when joist spacing does not exceed 400 mm and 25 mm nominal tongue-and-groove wood strip flooring is applied perpendicular to the joists.

620.8.2 Wood structural panels. Where used as structural . subflooring, wood structural panels shall be as set forth in . Tables 6.10 and 6.11. Wood structural panel combination subfloor underlayment shall have maximum spans as set forth in Table 6.12. When wood structural panel floors are glued to joists with an adhesive in accordance with the adhesive manufacturer's dvections, fasteners may be spaced a maximum of 300 mm on center at all supports.

620.8.3 Plank flooring. Plank flooring shall be designed in accordance with the general provisions of this code. In lieu of such design, 50 mm tongue-and-groove planking may be used in accordance with Table 6.22. Joints in such planking may be randomly spaced, provided the system is applied to not less than three continuous spans, planks are center-matched and end-matched or splined, each plank bears on at least one support and joints are separated by at least 600 mm in adjacent pieces. 25 mm nominal strip square-edged flooring, 13 mm tongue-and-groove flooring or 9 mm wood structural panel shall be applied at right angles to the span of the planks. The 9 mm plywood shall be applied with the tace grain at right angles to the span of the planks.

620.8.4 Particleboard. Where used as structural subflooring or as combined subfloor underlayment, particieboard shall be as set forth in Table 6.13.

620.9 Particleboanl Underlayment. In accordance with approved recognized standards, particleboard floor underlayment shall confonn to Type PBU. Underlayment shall not be less than 6 mm in thickness and shall be identified by the grade mark of an approved inspection agency. Underlayment shall be installed in accordance with this code and as recommended by the manutacturer.

620.10.2 Framing details. Studs shall be placed with their wide dimension perpendicular to the wall. Not less than three studs shall be installed at each corner of an exterior wall

EXCEPTIONS: At comers, a third stud may be omitted through the use of wood. spacers or backup cleats of 9 mm wood stnlctural panel, 9 mm Type M "Exterior Glue" particle-board, 25 mm lumber or other approved devices that will serve as all adequate backing for the attachment offaCing materials. Where fire resistance ratings or shear values are im l01ved, wood. spacers, backup cleats or other devices shall 1101 be used unless specifically approvedfor such use. Bearing and exterior wall studs shall be capped with double top plates installed to provide overlapping at corners and at intersections with other partitions. End joints in double top plates shall be offset at leaSt 2400 mm.

EXCEPTIONS: A single top plate may be used, prOVided the plate is adequately tied at jOints, corners and intersecting walls by at least the equivalent of 75 mm by 150 mm by 0.9 mm galvanized steel that is nailed to each wall or segment l~f wall by six 8d nails or equivalent, provided the rcifters, joists or fntsses are centered over the ,<;tuds with a tolerance of110 more than 25 mm. When bearing studs are spaced at 600 mm intervals and top plates are less than 50 mm by 150 mm or 70 mm by 100 mm members and when the floor joists, floor trusses or roof trusses which they support are spaced at more than 406 mm intervals, such joists or trusses shall bear within 125 mm of the studs beneath or a third plate shall be installed. Tnterior nonbearing partitions may be capped with a single top plate installed to provide overlapping at corners and at intersections with other walls and partitions. The plate shall be continuously tied at joints by solid blocking at least 400 mm in length and equal in size to the plate or by 3 mm by 38 mm metal ties with spliced sections fastened with two 16d nails on each side of the joint.


CONVENTIONAL UGHT-FRAME CONSTRUCTION DESIGN PROVISIONS

6-29

Studs shall have full bearing on a plate or sill not less than 50 mm in thickness having a width not less than that of the wall studs.

For Method 5, each brar;ed wall panel must be at least 2400 mm in length when a.pplied to one face of a braced wall panel and 1200mm when applied to both faces.

620.10.3 Bracing. Braced wall lines shall consists of braced wall panels which meet the requirements for location, type and amount of bracing specified in Table 6.24 and are in line or offset from each other by not more than 1200 mm. Braced wall panels shall start at not more than 2400 mm from each end of a braced wall line. All braced wall panels shall be clearly indicated on the plans. Construction of braced wall panels shall be by one of the following methods:

All vertical joints of panel sheathing shall occur over studs. Horizontal joints shall occur over blocking equal in size to the studding except where waived by the installation requirements for the specific sheathing materials.

1.

2.

Nominal 25 mm by 100 mm continuous diagonal braces let into top and bottom plates and intervening studs, placed at an angle not more than 60 degrees or less than 45 degrees from the horizontal, and attached to the framing in confonnance with Table 6.3. Wood boards of 16 mm net ffilfllmum thickness applied diagonally on studs spaced not over 600 mm on center.

3.

Wood structural panel sheathing with a thickness not less than S mm for 400 mm stud spacing and not less than 9 mm for 600 mm stud spacing in accordance with Tables 6.5 and 6.25.

4.

Fiberboard sheathing 1200 mm by 2400 mm panels not less than 13 mm thick applied vertically on studs spaced not over 406 mm on center when installed in ac.cordance with Section 614.6 and Table 6.27.

5.

Gypsum board (sheathing 13 mm thick by 1200 mm wide, wallboard or veneer base) on studs spaced not over 600 mm on center and nailed at 175 mm on center with nails as required by Table 6.2S.

6.

Particleboard wall sheathing panels where installed in accordance with Table 6.29.

7. 8.

Portland cement plaster on studs spaced 400 mm on center installed in accordance with Table 6.2S. Hardboard panel siding when installed in accordance with Section 609.6 and Table 6.S.

Method I is not permitted in Seismic Zones 2B and 4. For cripple wall bracing, see Section 620.10.5. For Methods 2, 3, 4, 6 and S, each braced panel must be at least 1200 mm in length, covering three stud spaces where studs are spaced 400 mm apart and covering two stud spaces where studs are spaced 600 mm apart.

Braced wall panel sole plates shall be nailed to the floor framing and top plates shall be connected to the framing above in accordance with Table 6.3. Sills shall be bolted to the foundation or slab. Where joists are perpendicular to braced wall lines above, blocking shall be provided under and in line with the braced wall panels.

620.10.4 Alternate braced wall panels. Any braced wall panel required by Section 620.10.3 may be replaced by an alternate braced wall panel constructed in accordance with the following: l.

In one-story buildings, each panel shall have a length

of not less than SOO mm and a height of not more than 3000 mm. Each panel shall be sheathed on one face with 9 mm plywood sheathing nailed with Sd common or galvanized box nails in accordance with Table 6.3 and blocked at all plywood edges. Two anchor bolts installed shall be provided in each panel. Anchor bolts shall be placed at panel quarter points. Each panel end stud shall have a tie-down device fastened to the foundation, capable of providing an approved uplift capacity of not less than S16.5 kg. The tie-down device shall be installed in accordance with the manufacturer's recommendations. The panels shall be supported directly on a foundation or on floor framing supported directly on a foundation which is continuous across the entire length of the braced wall line. This foundation shall be reinforced with not less than one 12 mm bar top and bottom. 2.

In the first story of two-story buildings, each braced wall panel shall be in accordance with Section 620.10.4, item 1, except that the plywood sheathing shall be provided on both faces, three anchor bolts shall be placed at one-fifth points, and tie-down device uplift capacity shall not be less than 1360.Skg.

620.10.5 Cripple walls. Foundation cripple walls shall be framed of studs not less in size than the studding above with a minimum length of 350 mm, or shall be framed if solid blocking. When exceeding 1200 mm in height, such walls shall be framed of studs having the size required for an additional story.


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WOOD

Cripple walls having a stud height exceeding 350 mm shall be braced in accordance with Table 6.26. Solid blocking or wood structural panel sheathing may be used to brace cripple walls having a stud height of 350 mm or less. In Seismic Zone 4, Method 7 is not permitted for bracing any cripple wall studs. Spacing of boundary nailing for required wall bracing shall not exceed 150 mm on center along the foundation plate and the top plate of the cripple walL Nail size, nail spacing for field nailing and more restrictive boundary nailing requirements shall be as required elsewhere in the code for the specific bracing material used. 620.10.6 Headers. Headers and lintels shall conform to the requirements set forth in this paragraph and together with their supporting systems shall be designed to support the loads specified in this code. All openings 1200 mm wide or less in bearing walls shall be provided with headers consisting of either two pieces of 50 mm framing lumber placed on edge and securely fastened together or 100 mm lumber of equivalent cross section. All openings more than 1200 mm wide shall be provided with headers or lintels. Each end of lintel or header shall have a length of bearing bf not less than 38 mm for the full width of the lintel. 620.10.7 Pipes in waDs. Stud partitions containing plumbing, heating, or other pipes shall be so framed and the joists underneath so spaced as to give proper clearance for the piping. Where a partition containing such piping runs parallel to the floor joists, the joists underneath such partitions shall be doubled and spaced to permit the passage of such pipes and shall be bridged. Where plumbing, heating or other pipes are placed in or partly in a partition, necessitating the cutting of the soles or plates, a metal tie not less than 1.47 mm (16 galvanized gage) and 38 mm wide shall be fastened to each plate across and to each side ofthe opening with not less than six 16d nails.

stud. Bored holes not greater than 60 percent of the width of the stud are permitted in nonbearing partitions or in any wall where each bored stud is doubled, provided not more than two such successive doubled studs are so bored. In no case shall the edge of the bored hole be nearer than 16 mm to the edge of the stud. Bored holes shall not be located at the same section of stud as a cut or notch.

620.10.11 Roof and ceiling framing. 620.10.11.1 General. The framing details required in this section apply to roofs having a minimum slope of 3 units vertical in 12 units horizontal (25% slope) or greater. When the roof slope is less than 3 units vertical in 12 units horizontal (25% slope), members supP.Orting rafters and ceiling joists such as ridge board, hips al'ld valley shall be designed as beams. 620.10.11.2 Framing. Rafters shall be framed directly opposite each other at the ridge. There shall be a ridge board at least 25 mm nominal thickness at all ridges and not less in depth than the cut end ofthe rafter. At all valleys and hips there shall be a single valley or hip rafter not less than 50 mm nominal thickness and not less than the cut of the rafter. 620.10.11.3 Notches and holes. Notching at the ends of rafters or ceiling joists shall not exceed one fourth the depth. Notches in the top or bottom of the rafter or ceiling joist shall not exceed one sixth the depth and shall not be located in the middle one third of the span, except that a notch not exceeding one third of the depth is permitted in the top of the rafter or ceiling joist not further from the face ofthe support than the depth ofthe member.

Holes bored in rafters or ceiling joists shall not be within 50 mm of the top and bottom and their diameter shall not exceed one third the depth ofthe member.

620.10.8 Bridging. Unless covered by interior or exterior wall coverings or sheathing meeting the minimum requirements of this code, all stud partitions or walls with studs having a height-to-least thickness ratio exceeding 50 shall have bridging not less than 50 mm in thickness and of the same width as the studs fitted snugly and nailed thereto to provide adequate lateral support.

620.10.11.4 Framing around openings. Trimmer and header rafters shall be doubled, or of lumber of equivalent cross section, when the span of the header exceeds 1200 mm. The ends of header rafters more than 1800 mm long shall be supported by framing anchors or rafter hangers unless bearing on a beam, partition or walL

620.10.9 Cutting and notching. In exterior walls and bearing partitions, any wood stud may be cut or notched to a depth not exceeding 25 percent of its width. Cutting or notching of studs to a depth not greater than 40 percent of the width of the stud is permitted in nonbearing partitions supporting no loads other than the weight of the partition.

620.10.11.5 Rafter ties. Rafter shall be nailed to adjacent ceiling joists to form a continuous tie between exterior walls when such joists are parallel to the rafters. Where not parallel, rafter shall be tied to 25 mm by 100 mm (nominal) minimum-size crossties. Rafter ties shall be spaced not more than 1200 mm on center.

620.10.10 Bored holes. A hole not greater in diameter than 40 percent of the stud width may be bored in any wood

620.10.11.6 Purlins. Purlins to support roof loads may be installed to reduce the span of rafters within allowable


METAL PLATE CONNECTED WOOD TRUSS DESIGN

limits and shall be supported by struts to bearing walls. The maximum span of 50 mm by 100 mmpurlins shall be 1200 mm. The maximum span of the 50mm by 150 mm purlins shall be 1800 mm but in no case shall the purlins be smaller than 50 mm by 100 mm members. The unbraced length of struts shall not exceed 2400 mm and the minimum slope of the struts shall not be less than 45 degrees from the horizontal.

6-31

SECTION 621 - METAL PLATE CONNECTED WOOD TRlJSS DESIGN 621.1 Design and Fabrication.

620.10.11.7 Blocking. Roof rafters and ceiling joists shall be supported laterally to prevent rotation and lateral displacement when required by Section 616. Roof trusses shall be supported laterally at points of bearing by solid blocking to prevent rotation and lateral displacement.

The design and fabrication of metal plate connected wood trusses shall be in accordance with ANSlrrPI 1-1995, National Design Standard for Metal Plate Connected Wood Truss Construction, of the Truss Plate Institute.

620.10.11.8 Roof sbeatbing. Roof sheathing shall be in accordance with Tables 6.10 and 6.11 for wood structural panels, and Table 6.9 for lumber.

621.2 Performance.

Joints in lumber sheathing shall occur over support unless · approved end-matched is used, in which case each piece shall on at leaSt two supports.

bear

.'

"

· Wood. structUral panels used. for roof sheathing shall be bo:nded by intermediate or exterior gIue. Wood' structural . .p;aneI roof sheathjng exposed on the underside shall 'be boi1d~ with e~erior gIue.

Full-scale load tests in accordance with ANSUTPI 2 may be required at the option of the building official to provide a means of demonstrating that trummum adequate performance is obtainable from specific metal plate connector plates, various lumber types and grades, a particular truss design and a particular fabrication procedure. ANSIrrPI 2 provides procedures for testing and evaluating wood trusses designed in accordance with ANSUTPI1.

621.3 In-plant Inspection. 620.iojl.9 Roof planking. Planking shall be .designed in · accordance with the general provisions of this code. In

lieu of such design, 50

mm ton~e-and-groove planking

. may be usea it;l accordance with Table 6.22. Joints in such

'planking may b~ randomly spaced, provided the system is applied to' not .\ess than three continuous spans, planks are c~riter-matched and end-matched or splined, each plank · bears on at least one' support, and joints are separated by at least 600 mm in adjacent pieces.

620.10.11.10 Ent Facilities. In Seismic Zone 4, exterior exit balco~ies,. stairs and simila~ exit facilities shall be positivei y . iuichored to the primary. structure at not over 2400 mm Oil center or shall be designed for lateral forces. Such attachment' shaH not be accomplished by used of toenails or nails silbject to withdrawal.

Each truss manufacturer shall retain an approved agency having no financial interest in the plant being inspected to make nonscheduled inspections shall cover all phrases of the truss operation, including lumber storage, handling, cutting, fixtures, presses or rollers, fabrication bundling and banding, handling, and delivery.

621.4 Marking. Each truss shall be legibly branded, marked or otherwise have permanently affixed thereto the following information located within 600 mm of the center of the span on the face of the bottom chord: 1.

Identity ofthe company manufacturing the truss.

2.

The design load.

3.

The spacing oftrusses.


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6-32

Table 6.1 - WORKING STRESSES FOR VISUALLY STRESS-GRADED UNSEASONED STRUCTURAL TIMBER OF pmuPPINE WOODS.

Species (Common and Botanical Names)

Bending and tension paraUel to

80% Stress Grade Modulus of Compression Compression elasticity in paraUel to perpendicula . grain rto grain bending

I

Shear paraUel to grain

~rain

(1)

L

(3)

(4)

(5)

(6)

MPa

1000 MPa

MPa

MPa

MPa

26.3 25.0 28.7 25.8 24.0 21.8 31.3 24.5

8.22 9.36 8.30 9.63 6.54 8.33 9.72 9.78

14.5 15.6 15.8 16.0 15.4 13.7 21.60 15.8

5.91 4.31 8.70 6.03 6.34 4.97 10.2 6.27

2.95 2.64 3.02 2.78 2.88 2.61 3.38

186 18.9 18.1 16.2 20.8 21.8 20.9 19.0 18.8 184 19.8 16.5 20.5 18.9 18.0 16.6

5.35 6.57 6.36 5.43 6.84 8.47 7.20 7.56 6.82 8.04 7.92 4.66 6.72 6.66 5.94 6.53

10.8 11.4 11.3 9.44 13.5 13.2 11.7 ILl 11.9 10.6 11.8 10.5 11.4 11.12 11.4 10.0

3.90 3.27 3.41 2.27 3.52 4.26 439 ;1.95 4.84 3.46 2.98 3.83 3.70 2.32 3.07 2.50

2.06 2.24 2.18 1.92 2.36 2.40 2.47 2.35 2.29 1.96 2.18 2.71

16.5 16.6 16.3 14.3 15.0 13.9 13.8 16.8 15.4 15.7 16.2 13.8 14.7 15.7

7.31 6.48 6.38 6.06 5.83 5.41 5.94 6.30 6.50 5.56 5.98 6.66 5.67

9.56 9.89 9.20 8.16 8.96 8.18 8.54 9.51 9.33 K83 9.17 8.38 8.29 8.83

2.20 2.33 2.48 1.99 2.02 1.72 1.96 2.92 3.07 2.78 2.73 1.88 2.94

1.73 1.82 1.98 1.90 1.84 1.48 1.59 1.85 2.07 2.06 1.98 1.68 1.56 1.88

19.5

5.83

8.54

2.65

2.39

11.8 12.6 13.2 12.8 11.9 12.6

5.47 4.75 4.13 5.36 2.75 409

6.27 7.33 6.85 7.46 7.23 7.87

1.44 1.30 2.00 1.97 3.32

1.47 1.20 1.66 1.44 2.07 1.%

High Strength Group Agoho (Casuarina equisetifolia Forst) Liusin [pa.rina.ri corymbosa (Blume) Miq.] Malabayabas (Tristania spp.) Manggacbapui (Hopea spp.) Molave (Vitex parviflorn Juss.) Narig (Vatica spp.) Sasalit [Teijmanniodendron ahernianum (Merr) Bkh.] Yahl (Shorea spp.)

II.

(2)

249

Moderately High Strength Group Antipolo (Arthocarpus spp.) Binggas (Terrninalia spp.) Bokbok CXanthophyllum excelsum (Blume) Miq.) Dao (Dracontomelon spp.) Gatasan [Garcinia venulosa (Blanco) ChoisY1 Ouijo (Shorea spp.) Kamagong (Diospyros spp.) Kamatog [Erythrophloeum densiflorum (Elm) Merr) Katmon (Dillenia spp) Kato (Amoora spp.) Lomarau (Swintorua foxworthyi Elm.) Mahogany, Big-leafed (Swintonia macrophylla King) Makaasim (Sysygium nitidum Benth) Maiakauayan [Decusocarpus philippinensis (Foxw.) de Laub·1 Narra (Pterocarpus indicus WiUd) Puhutan (Mangilera spp.)

III. Medirun Strength Group Apitong Oipterocarpus spp.) Bagtikan [Parashorea malaanonan (Bianco) Merr.] Dangkalan (Calophyllum spp.) Gisau (Canarium spp.) Lanutan-bagyo [Gonystylus macrophyllum (miq.) Airy Shaw] Lauan (Shorea spp.) Malaanonang (Shorea spp.) Maiasaging (Agiaia spp.) Malugai (pametia spp.) Miau (Dysoxylum spp.) Nato (PaLaquium spp.) Pa10sapis (Anisoptera spp,) Pine (pinus spp.) Salakin (Aphanarnixis spp.) Vidallanutan [Hibiscus campylosiphon Turcz. vat. glabrecens

(liar. Ex. Peri.:.) 1

5.33

2.33

lAO 2.14 1.91 2.05

IV. Model1lteiy Low Strength Group Almaciga [Agathis dammara (Lamb.) Rilh.] Bayok (Pterospermmn spp.) Lingo-lingo (Vitex tnrczaninowii Merr.) Mangasinoro (Shorea spp.) Raintree [Samanea saman (Jacq.) Merr.] Yemane (Gmelina arborea R. Br.)

~


HO

I

WOOD

6-33

Tahle6.1 (Continued) J3"1o Stress

~-

Spedes (Common and Botanical Names)

Bending and tension parallel to 2r8in

(1)

(7)

i I•

Modulus ot", ela.~ticity in bending (8)

Gra~

Compression paranel to grain

Compression perpendicular to grain

Shear parallel to

(9)

(10)

(11)

I

grain

I

1000

I.

Hill.h Strength Group Agoho (Casuarina equisetirolia Forst) Liusin ll'arinari corymbosa (Blume) Miq.l Malabayahas (Tristania spp.) Manggachapui (Horea spp) Molayc (Vitex parvitlora .fUSS) Narig (Vatica spp.)

Sasalit [Tcijrnanniodcndrnn ahernianum (Mcrr) Bi;h.J

Yakal (Shorca spp.)

I,

I

II.

Moderately Hill.h Strength Group Antipol0 (Arthocarpu~ spp.) Hinggas (Tcrrninalia spp.)

Eo!..h,)!" (Xanthopln'Uumexcdsum (Blume) Miq.]

Dan (Dracontnmcloll spp.)

Galas"n [Garciniu n:nulosa (Blanco) Choisy]

Uuijo C:ihorea "pp)

Kamngong I ni(lsp~ Tns Spp)

Kamatog iFrvthrophlocmn densitlonun (Elm) Merr.l

Kalmon(Dillenia spp)

Kaltl U\moom spp.)

Lomuruu (S~inhmia ()"worthYl Elm.) Mahogany. Big-leafed (Swintonia rnacrophylla King)

Makaasim (S\'S\'gium nili<.lum Benth)

Malukaul1vun Il)<:cllsOcm1)lL~ phihppincnsis (Foxw.) <.lc l.ullh.1

Nurra (Plewcarpu.s indicus Will<.l)

PuhUlan (Mangilem spp.!

1II.

IV.

--.-

MPa

MFa

MPa

MPa

20.7 19.7 22.6 20.3 18.9 17.2 24.7 19.3

6.47 7.37 6.53 7.58 5.15 6.56 7.65 7.70

11.4 12.3 12.5 12.6 12.J 10.8 17.0 12.0

4.65 3.39 6.85 4.75 5.00·

2.32 2.08 2.38 2.19 2.27 2.06 2.67 1.96

14.7 14.9 14.3

4.21 5.17 5.01 4.28 5.39 6.67 5.67 5.95 5.37 6.33 6.24 3.67 5.29 5.24 4.68 5.15

8.53 8.98 8.90 7.43 10.6 10.4 9.21 8.79 9.38 IU4 9.30 8.24 8.95 8.79 7.88

307 2.57 2.68 1.79 2.77 3.35 3.46 3.11 3.81 2.73 2.34 301 2.92 1.83 2.42 1.97

7.53 7.79 7.24 6.43 7()(i 6.44

1.73 1.84 1.96 1.56 1.59 1.35

12.8 16.4 17.1 16.6 15.0 14.8 14.5 15.6 130

16.1 14.9 14.2 13.1

8.97

5.76 5.10 503 4.20 4.77 4.59 4.26 4.08 4.% 5.12 4.38 4.71 5.24 4.47

13.0 \3.1 12.8 11.2 11.8

10.9 Ill.'!

13.3 12.1 12.3 12.7 10.9 11.6 12.4

,

I

1.62 177

1.72 1.51 1.86 1.89 1.95 1.85 1.80 1.54

1.71 2.13 1.89 1.69 1.51 1.61

I

1.54

7.49 7.35 6.96 7.22 6.60 6.53

2.30 2.42 2.19 184 2.15 1.48

(91)

2.32

IAR

2.09

1.88

1.13 t03

1.16 0.95 L31 1.14 1.63

4 ..59

6.73

l),~6

4.10

4'M

'J <)4

".74

5.7R

1t!.4

3.2)

i'.'.O

422

539 5.f{7 5.70

q .}{\

I

I

2.1(, ~

i

!

'_W'

22

, i

_


1.36· 1.43 1.56 1.49 1.45 1.17 125 146 1.03 1.62 1.56

6.72

1.5 4

937

---...

3.92 8.07 4.94

I

Medium Strength Group Apitong Dipl,-,rocarplls spp.) Baglikun (pamshorea malaanonan (Blanco) l\1tl'TT I Dangkalan (Calophyllmn spp.) OiS<1U (Canarium spp.) Lanulan-bagyolGonystylus macroph\lIum (miq.) Air}' Shawl LawHl (Shorea spp.) Malaunonang (Shorea spr.) l\1alasaging. (Aglai« spp.) Malugai (p()lllclia spp.) Miau (Dys,)xylum spp.)

Nato (palaql1ilUn spp.)

Palosapis (Anisoptera spr.)

Pine ( Pinus spp.!

Salakin (AphunamJ"l~ 'pp.)

Vl<.lallanutan [llihi,cl1:; cumpylo"iphon Tnre? \ aT. glnhrccen"

(I'lar Ex. Perk.) J Moderatcl~' Low Strength Group Almaciga [Agatlw; dU1l111IDr<1 (] .amh.) l~ ilh.} Bayok (l'lcrot>pemHlIll 'PI'. I ! .ingo-ling,o !Vilex [[Irezunino\\ ii M~rr.1 Mangasinoro (Shorea
MPa

(,20

I

1.53 1.55 2.61 2.68

1.33 1.23

1.55

6-34

WOOD

Table 6.1 (Continued)

Species (Common and Botanical Names)

--

II.

f

(I)

High Strength Group Agoho (Casuarina equiselifolia Fmst) Liusin [Parinari corymbnsa iBltune) Miq.1 Malabayabas (Tristania spp.) Manggachapui (Hopea spp.) Molave (Vitex parvitlora Ju:;s.) Narig (Vatica spp.) Sasalit [TeijmaIIDiodendron ahernianum (Mcrr) Bkh.] Yakal (Shorea spp.) Moderately High Stre~th Group Antipo\o (Arthocarpus spp.) Binggas Crcrminalia spp.) Bokbok (Xanthophyilmn excelstun (Blume) Miq.1 Dao O)raconlomelon spp.) Gatasan IGarcilUa venulosa (Blanco) Choisy] Uuijo (Shorea spp.) Kmnugong (Diospyros spp.) Kamatl1g [Ervlhropbloeum densifl('mm (Elm) Mcrr.]

Killmon (Dillenia spp)

Kalo (Amoora spp.)

Lomarau (:'>winlonia foxworthyi Elm.)

Mahogany, Big-leafed (Swintonia macrophylla King.)

Makausim (Sysvgium nitidum lk'llth)

Malukm.lll\'un IDecusocarpus philippinensi~ (Fn~,\'.) de Laub. J

NtlITU (Pterocarpus indicus Wind)

Puhulan (Mangilera spp.l

III. Medium Strength Group Apilong DipterocarplL' spp.) Bag.tikan [paroshorea rnalaanonan (Blanco) Merr.) lYdngkalan (Calophyllum spp.) (ii,;au (Canarium spp.) Lanulan-oollYo [G(myslylus rnacropbyllum (miq.) Airy Shawl I ~'llUlI1 (Shorea spp.) Maluunonang (:'>horca spp.) Milia,aging (Aglaia spp.) Malugai (Pometia spp.) Miau (l~'s()~'vlum spp.) Nulo iPalaquiuIn spp.) l'alosapis (Ani~()ptcm sppJ Pinc{Pinus 'pp.) Siliakin (I\phanami,j, spp.) Vid"llanulun rHihiscll~ campylosiph(m Turcz. Hlr. glahrec~'O, tHur. h.l'erk.) I IV.

I I

..

I.

II

M()de.....teI~· Low Strength Group Almaci)!
l

50% Stress Grade Compression Bcndingand M~dulus ofl Compression elasticity in , parallel to

perpendicular teadon parallel to I to grain bending I g.....in i

grain ._M_ I j ! (13) I (14) (15) (12)

I

MPa

1000

MPa

16.4 15.6 17.9 16.1 15.0 13.6 19.6 \:)3

5.14 5.R; 5.19 6.02 4.09 5.20 6.08 3.11

9.06 9376 9390 10.0

3.34 4.11 3.97 3.39 4.27 5.30 4.50 4.72 4.26

6.77 7.13 7.06

\ Hi 1\.8 1\.3 10.1 13.0 13.6 I:l.1 119 J L7 11.5 12.4

10.3 12.8 11.8 11.2

lOA

IOJ

I

I

5.02 4.95 2.91 4.20 4.16 3.71 4.08

4.57 40j 3.99 3.33 3.79 3.64 :1.38 3.71

MPa

I I I

II

l\,iPa

3.6<)

184

2.69 5.44 3.77

:i.92

L65 /.89 1.74 1.80 1.63 2.l2 1.55

2.44 2.04 2.13 1.42 2.20 2.66 2.74 2.47 3.03 2.17 2.R6 2.39 231 1.45 1.92 l.56

1.29 1.40 1.36 1.20 1.47 L50 154 1.47 1.43 L23 1.36 1.69 l.50 IJ4 1.20 1.28

I.OR \.14 l.24 l.IR Ll5 0.93 0.99 1.I6 1.30 L29

L50

GAO

8A2

i

I

i

\0.4 10.2 8.93 9.39 R.6R 8.63 10.5 9.62 'i.go 10.1 R.65

4.0(, 3.18 3.73

9.1'.1

·U6

5.18

9X'

3.54

55~

137 1.46 155 1.24 1.26 1.07 12.3 1.83 1.92 1.74 14(; 1.70 U8

1.84

12.2

3.64

5.34

1.6(,

735

3.42

7.8')

2 ~>7

3.<)2 4.58

0.90 O.Rl

4.6() 4.52 4.92

123 2.07

R27 7.'JR

7.43 7.R6

3.94

-

5.24

,


(16)

Ml'a

3.11

5.90

5.97 6.18 5.75 5.10 5.60 5.11 534 595 5.83 5.52 57.

I

3.96

%0 8.5') 13.5 9.55

8.22 7.31 6.98 7.44 6.62 7.3R 6.54 7.10 6.9R 712 6.25

·c:---

Shear parallel to grain

-

2.13

124 1.05

0.98 UR

I

i

0.92

(175 1.04 O')()

l.](} 1.23

I

6-35

Table 6.2 - GROtJPING OF SPECIES FOR DETERMINING ALLOWABLE LOADS FOR TIMBER JOINTS ,..--

I

Species

II

Relative

Species

Density

(3)

IV

III

Relative

Species

Density

(4)

Relative

I,

Density

i

Species (7)

(6)

, Relative Density (8)

(1)

(2)

Malabayabas

0.90

Makaasim

0.74

Sasalit

.90

Kamagong

.72

Dangakalan

.58

Raintree

.48

Agoho

.84

Ouijo

.70

Apitong

.57

Bayok

.44

Limin

.79

Binggas

.70

Sa1akin

.56

Ahnaciga

.42

Yakal

.76

Katmon

.68

Pine

.55

Manggasinoro

.42

Narig

.72

Gatasan

.67

Lanutan-bagyo

.53

Yemane

.42

Manggachapui

.71

Bok-bok

.64

Miau

.52

Molave

.69

Kamatog

.64

Palosapis

.52

Lomarau

.64

Ma\asaging

.51

Kato

.59

Vidal Lanutan

.50

Pahutan

.55

C'risau

.50

Mahogany, big leaf

.54

Nato

.49

Antipolo

.52

Bagtikan

.44

Narra

.52

Malaanonang

.41

Malakauayan

.50

Lauan

Dao

.48

(5) Malugai

0.61

i

SOURCE: Philippine Timber Design Standards (J. E. Rocafort and J. 0. Siopongco) November, 1991 (FPRDI Terminal Report)


Lingo-lingo

0.48

•

6-36

WOOD

Table 6.3 - NAILING SCHEDULE

2-100 100 at 400 mm o.c. 3-100 400mm 2-l6d

end nail 16d at 600 mm o.c. 16d at 400 mm o.c. 8-J6d 3-8d 8d at 150 mm o.c. 100 at 400 mmo.c. 4-8d 3-16d

13 mm and less 15mm-19mm 22mm-25mm 29mm-32mm

Combination 19 mm and less 22mm-25mm 29mm-32mm

20mm


WOOD

6-37

rlOTES FOR TABLE 6.3 , Common or box nails may be used except where ntherwise stated. , Nails spaced at 150 mm on center at edges, 300 mm at intermediate SUpp"rts except 150 mm at all support. where spans are 1200 mm or me,re. For nailing of wood slrucln,-..u panel and particleboard diaphragms and shear walls, refer to Sections 614.3.3 and 61~.4. Nails ter wall sheathing may be common, box or casing. 3 Common or det,>nned shank. 'Common. S Deformed shank, 6 Corrosion-resistant siding or casing nails conforming to the requirements of Section 6033. 7 Fasteners spaced 75 mm on center at ex1erior edges and 150 mm on center at intermediate supports. 'Corrosion-resistant roofing nails with II mm head and 38 mm length for 13 mm sheathing and 44 mm length for 20 mm sheathing confurmin!! to th~ rc<]uiromcnts of Section 603.3. • Corrosion-resistant staples with nominal II mm crown 29 lum length lor 13 mm sheathing and 38 mm length tor 20 mm sheathing contenning to the requirement> of Section 603.3. '·Panel supports at 400 mm (500 mm if strength axi.• in the long direction of the panel, unless otherwi"" marked). Casing or finish nails spaced 150 mm on panel edges. 300 mm at intermediate supports. 11 Panel Sllpports at 600 mm. Casing or finish nails spaced 150 mm on panel edges, 300 mm at intermediate supports.

Table 6.4 - WOOD STRUCTURAL PANEL ROOF SHEATHING NAILING SCHEDULE ROOF FASTENING 2 NAILS

3

Fastening Schedule

(rnrn on center) 150 150 f--..--~~---'"c.·---__I-""..--·------__+---·--~-·----··1--·---------;--_. 150 150 100 150 150 300 I~ I~ ""~-....."""'- ..--""""---"'.. '".-.+-.---.---"'---~-+-.~--.-.---:-"'--:;.---+----...--.--""---.~-+-.-.---.--.------+."'-~--"'."'.-."'"'--_. 150 150 150 300 300 , Applies only to mean roof heights up to 10500 mm. For mean roof height' over 10700 mm, the nailing shall be designed. , The roof fastening zones are shown below:

.

-----T I I I I I I I I I fj\ I I \.!J I I I I I I I -/.------l-

- . . 1200 mm

r---

1500 rnrn (INCLUDING 300 mm. OVERHANG)

I I I

leD I I

ROOFRIIXlE

ROOF FASTENING ZONES 3 Edge spacing also applies over roof framing at gable-end walls. 4 Use 8d ring-shank nails in this zone if mean roof height is greater than 7500 mm.

National structural Code of the PbiJippines. Volmne 1

WOOD

6-38

Table 6.5 - EXPOSED PLYWOOD PANEL SIDING MINIMUM TIDCKNESS1

9

MINIMUM NUMBER OF PLIES

=

13

STUD SPACING PLYWOOD SIDING APPLIED DIRECTLY TO STUDS OR OVER SHEATIDNG

3

=

4

600

I Thickness of grooved panels is measured at bottom of grooves. "May he 600 mm if plywood siding applied with face grain perpendicular to studs or over one of the following: (I) 25 mm board sheathing, (2) 11 mm wood structural panel sheathing or (3) 9 mm wood structural panel sheathing with strength a.xis (which is the long direction of the panel unless otherwise marked) of sheatllingperpendicular to studs.

Table 6.6 - WOOD SHINGLE AND SHAKE SIDE WALL EXPOSURES

1_'_' S~GLE OR SHAKE Length and Type

i

400 =

shingles

j

450= shingles GO mm shingles 1-'-----' 450 mm resawn shakes i

MAXIMUM WEATHER EXPOSURES
400 ---- 288 500 -

_.

" '

,___450 mm ouu'e;" '¥:~: shakes 600 mm resawn shakes

-

-~

-

Table 6.7 -ALLOWABLE SPANS FOR EXPOSED PARTICLEBOARD PANEL SIDING

I

GRADE

STUD SPACING

MINIMUM TIDCKNESS -·----··-------------Sidil;g . - - - -...

Continuous Support

Exterior Ceilings and Soffits Direcllo Supports

16mm

9mm

9mm

16mm

9mm

Direct to Studs ..-- ....... ...

M-I M-S M-2 --Exterior
--~.

400

-"'---"'--'"

"--~-'-'-'

.----..

600

9mm

..---------- I


WOOD

6-39

Table 6.8 - HARDBOARD SIDING MINIMAL SIDING

I

Nominal Thickness (mm)

I

NAIL SPACING

FRAMING (50mm x l00mm)

~

NAIL SIZE 1,%

General

Bracing Panels 3

.......

Maximum Spacing

_._!.:_.__~AP SIDING 9 9

400mmo.c.

8d

400 mrno.c.

Not applicable

4oomrno.0.

IOd

4oommo.c.

Not applicable

9

6OOmmo.c.

6d

9

6OOmmo.o.

8d

Direct to Studs

9

400mmo.o.

6d

Over Sheathing

9

400 nun 0.0.

8d

Direct to Studs -~-~-.-".--.~~--------

.....

______ Over S~~thing ~ _ _._. ~~QUARE EDGE P~.I- SIDING Direct to Studs ---~-~-~-.-~-'

..--"~-----.-- ..

Over Sheathing ,~.

".".~

____

.~_~4

____ ·__·_

150 mrn 0.0. edges; 300 mm o.c. at intermediate suPPOrts 150 mID 0.0. edges; 300 mrn o.c. at interroedia te supports

-.----..

~

100 mrn o.c. edges; 200mmo.c. intermediate sUE:E2rts 100 mrn o.c. edges; 200nuno.c. intermediate support:i._

..1,____§!!fP~AP EDGE P~L SID~~ . :--_..

I

150 mm 0.0. edges; 300 mm o.c. at intennediate supports 150 mm 0.0, edges; 300 mrn 0.0. at intermediatc supports

100 nun o.c. edges; 200 mrn o.c. intermediate SU~_ 100 mrn 0.0. edges; 200mmo.o. intermediate supports

Nails shall be corrosion resistant in accordance with Section 619. 2 Minimum acceptable nail dimensions (mm). I

L Shank diameter Head diameter 3When used to comply with Section 620.103.

Table 6.9 - ALLOWABLE SPANS FOR LUMBER FLOOR AND ROOF SHEATIDNG 1,1

__-.

~···-------rl-

SPAN 600 400

-------::c-::::::-:= ==-=-==::-====-=-=~--:-~:--::==:-:-:--:::--=--:--==----------,

Perpendicu..la,r_t.o_-"-''--____ ....._ _ _---1I--_ __ ·-··---S;.raced Dry3 ----

..

19 .. - - --\---_. -------_.-._---' _-_

'Installation details shall conform to Section 620.8.1 and 620.1 1.1 for floor and roof sheathing, respectively. roofsheathing conforming with this table shall be deemed to meet the design criteria of Section 620.1 0.11. , Maximum 19 percent moisture content.

Z Floor or

National 'Structural Code of the Philippines, Vois.me 1

20

17

WOOD

6-40

Table 6.10 - ALLOWABLE SPANS AND LOADS FOR WOOD STRUCfURAL PANEL SHEATHING AND SINGLE-FLOOR GRADES CONTINUOUS OVER TWO OR MORE SPANS WIT STRENGTH AXIS PERPENDICULAR TO SUPPORTS 1,2 :--SHEATHING GRADES

L_p!~~~~r~!l Ra~~ RooJIFloor Span

FLOOR'

Panel Thickness (mm)

r-----::-::-:::-- Maxim~_Span \r~t With FAige Su rt"

Without Edge Su rt

300

300 400

8

12/0

1-----1-6/~0----·+---~8:-,-:9---·----400-

Maximum Span (rnm:l

+---------------I--------------~·--------------·--r_---------------_+

20/0 2410 24116 32/16

500 500

600

600 600 700 800 f·······------40-~12:-0-----i----::-:::--:-:---:'-:---::-::---t---- i-000---r----·---- · ------+-----------··--+-·---·--·---· .--- -+-.. ....-.--- 800 ~-.--.-------.___I----'-:--'--::-~-___I---------t-------. 48/24 .... __-+____-'-__c___··__·+____ · __· 1200 900 ._.._._._.__

·I______..-.----... +.-..-.------.-.--.... ..j--.- _______ 54/32 25 1350 1000

-------_.-+-----.!_-----+---

60/48 22, 25,_2_9_--l_ _ _1_50_0___--'-_ _ _lk_'O_ O _ _-'---::-_--= __ . _...L.._ _ _ _ _ _+ SINGLE-FLOOR GRADES ROOF'

Panel Span Rating

Maximum Span (mm) LoadS (kilone\'
... _.-..--L~---.

Panel Thickness

Withf..dge rt° Su

(rnm)

Roof/Floor Span

Without Edge Su rt

600 800 ]200

Total Load

___12:....0_0-:-_-1 FLOOR' Maximwn Spall (mml

Live Load

400

600 1.92 ---.-------+. - - -2.40 - -...-----1----.----..-.-...-.-.- 800 1.92 1.44 -f-------·----··----r----·-- ---..--.---+-

~----·--=-----·--·---l'-----::_::'__---'___::---I-·-------····

1.68 2.40

900

f·-·..·-~------------t---"···-:----::---t···-----::1200

1000

1500 ____

~

conforn~ing

1200 __________

1.20 1.92

-",----_... ---" ..

2.40

~__________

2.40 _L-________ . . __________ ~

~

with this table shall be deemed to meet the design criteria of Section fi.ll_ under live land plus dead loud, under live load only. or shall be supported with blocking unless 6 mm minimum thickness underlayment or 38 mm of appr
or floor is 19 mm wood strip_ Allowable uniform load based on deflection of '. '60 of span is 4.79 kNtm' except the span lightweight concrete is placed mtin'./. of 1200 mm on center is based on a tOlllllnad of 3.11 kNim.

5 Allo';able load at maximum spnn. • Tongue-and-groove edges, panel edge clips (one midw.), between each support excepi two equally spaced hetween supports 1200 mm nn center). lumber blocking. Or (llher. Only lumber blocking shall satisfy blocked diaphragms requirements.

7 For 13 mm panel, maximum span sh.n be 600 mm_

• May be 600 mm on center where 19 mm wood strip tlooring is installed at right angles tn joist.

, May be 600 mm on center tbr floors where 38 mm of cellular or lightweight concrete is applied orer the panels_

'f".

Table 611- ALLOWABLE LOAD FOR WOOD STRtlCTURAL PANEL ROOF SHEATHING CONTINUOtlS OVER TWO OR MORE SPANS AND STRENGTH AXIS PARALLEL TO SUPPORTS (Plywood structural panels are five--ply, five-layer unless otherwise noted)l,2

PANEL GRADE

THICKNESS (mm)

MAXIMUM SPAN (mm)

Structural 1

II

600 600 600 600 600

0.958

12 13

16 18, 19

Li\'c

3.353 4.311

Other Grades Covered in

II

400

12

600

1'.12 .. i!.958

240

UBC Standard 23-2 or 23-3

13

hOO

1.10

1.44

2.iu3

()OO .

.~-

11(1

._.-< -_.

-

600

'Uniform of edge supports. •

3 For composite and four-ply plywood sttllcturnl panel. load shall be reduced by 0.72 kN nc

Edges shall be blo"ked with lumhcr C'r othet "l'l'rn\ed


1\

r"

WOOD

Table 6.12 - ALLOWABLE SPAN FOR WOOD STRUcrURAL PANEL COMBINATION SUBFLOOR-UNDERLAYMENT (SINGLE FLOOR)I,l

Panels Continuous over Two or More Spans and Strength Axis Perpendicular to Supports

I

13

16

19

=~- - -s-p-a-~·-:-~-m-'~·4~ -·- - tr- - - ~- - ·~- -4-0- -;-:-~-.-·~-=-~- - - - -:r- - - ~ - -5-=-o-o-~-~-o

·--=-.c-=-.--------·-

:~-.=--~=.-~6=·-0=-~=-~=-.c=-.=- ~=--~=-_~:t- ~=- -~-=-~=-8=-0=-0-=-o-=·-.c=-.=- ~=-=- - =- t_- ~-~~,~~:-~-j

, Spans limited to value shown because of possible effects of concentrated loads. Allowable unifonn loads based on deflection of '/'.0 of span is 4.79 kN/m'. except allowable total unifonn load for 29 mm wood structural panels over joists spaced 1200 mm on center is 3.11 kN/m 2 Panel edges shall have approved tongue-and-groove joints or shall be supported with blocking, unless 6 mm minimum thickness underlayment or 38 mm of approved cellular or lightweight concrete is placed over the subfloor, or finish floor is 19 mm wood strip. 2 Floor panels confonning with this table shall be deemed to meet the design criteria of Section 611. 3 Applicable to all grades of sanded exterior-type plywood. See UBC Standard 23-2 for plywood species groups. 4 Applicable to underlayment grade and C-C (plugged) plywood. and single Hoor grade wood structural panels.

Table 6.13 - ALLOWABLE SPANS FOR PARTICLEBOARD SUBFLOOR AND COMBINED SUBFLOOR

UNDERLAYMENT 1, 1

THICKNESS (mm)

GRADE

I______MAX!_MUM S!,_A~~~.Q~_S!!!!'5>~!~~!!l)~______._ I Subfloor Combined Subfloor-Underlayment'"

_._ . . _____:~_____ l

2-M-W

19 2-M-3

19

._~~

I I

___=_·-·-___-_~~-_-_4_0_0_-==_=~-_--.~

600

600

500

500

__

, All panels are continuous over two or more spans.

Floor sheathing confonning with this table shall be deemed to meet the design criteria of Section 6.11.

3 Uniform deflection limitation: '/,.. of the span under 4.79 kN/m' minimum load.

• Edges shall have tongue-and-groove joints or shall be supported with blocking. The tongue-and-groove panels arc installed with the long dimension perpendicular to supports. , A tinish wearing surface is to be applied to the top of the panel. 2

Table 6.14 - MAXIMUM DIAPHRAGM DIMENSION RATIOS HORIZONTAL DIAPHRAGMS -. Maximum Span-Width Ratios

MATERIAL

VERTICAL D1APHRAGl\'!~ __ Maximum Height-Width Ratios

1.

Diagonal sheathing, conventional

3:1

1: I'

2.

Diagonal sheathing, special

4:1

3.

Wood structural panels and particleboard, nailed all edges

4:1

2:e 2:12

4.

Wood structural panels intermediate joints.

_.

and particleboard,

blocking

omitted at

4:1

, In Seismic Zone 2, the maximum ratio may be 2: I. 2 In Seismic Zone 2, the maximum ratio may be 3'.';:1. ) Not permitted. .


3

-----------

-_. -_._---

6-42

WOOD

Table 6.15 - LIMITS OF DEFECfS BY GRADE IN JOISTS AND PLANKS FOR SEASONED WOOD Stress Grade 800/.

Stress Grade 63%

Not permitted Not permitted

2

6

Not clustered

Not clustered

18

25

32

V. ofthiekness

Y.i of thickness

Kind of Defeds A-

Stress Grade 50·/0

NATURAL DEFECTS

1.

Wonn holes, average diameter (maximum allowable size in rom) a. b.

2.

3.

Individual

Quaritity limi tation

Slope of Grain (lTIllximum variation in rom from longitudinal axis per 300 rom within middle half of length) Checks and Shakes a.

Size of each check and shake, or if in combination, the sum of the sizes of ali checks and shakes within middle half of depth of thc piece shall not exceed:

3/8

of thickness

End penetration: Checks and splits at the middle half of the depth of the V. of thickness V. of thickness %of thickness piece shall not extend a distance _____________~~~(ea~t=er~·~~(ea~t=er~than~~:~___________1--------------------_+------------________~------------------~ b.

Knoo (Maximum allowable size of individual knot rom*)

III

Narrow face edge of wide face within the middle third oflength of piece 011

Along center line of wide face

Narrow face on edge of wide face within the middle third oflength of piece

Along eenter line of wide tlICe

Narrow face on edge of \\ide face \\~thin the middle third oflength of piece

Along center line ofwidetace

Nominal width of lace, in rom

50 75 100 125 150 200 250 300 350 400

6

12 18 25 30 35 38 45 48 50 50

450 andover

18 25 30 38 50 55 65 70 75

12 18 25 30 45 50 55 65 70 75 75

30 38 50 60 80 90 100 100 100

18 25 38 50 60

70 80 90

95 100 100

38 50 60 75 100 110 125 125 125

*The S1?.e of knots on the narrow lAce within the middle third of length may he increased proportionately towards the end, or tlte piece of n,ice tbe size permitted on the narrow face but not to exceed that allowable along the center line of the wide face. The .ize of knots on the edge of wide tace within the middle third of length may he increased proportionately towards the center of the wide and towards the ends of the piece In the size pcmlitted alnng the center line orthe wide lace. The ,UIIl of the sizes or all knnts in any 150 mm oflength of the piece shall not exceed nvice the maximum permissible size ofknnts. Two knots ofnmxirnunl ,hall not he allo\\ed in the same 15001111 of length on any face. Clu~1er knot. and knots in group shall not be permitted.

lace


I

WOOD

6-43

Table 6.1S ( continued) Stre~.

r

I 13.

Grade 80%

Kind of Defects HANDLINe;. lvlANlWACTURE PROCESSING DEFECTS L

Stress Grade 63%

Stress Grade SO·/.

12

12

]5

15

20

12

OR

Want: (maximum allowable size in mm) Nominal lace dimension in mm

.'

50

75

100

125

3

r; {,

ISO

200

250

300

350

400

450 and OYcf

2.

Tom grain (allowable depth in mm)

3.

Skips, allowable size not to exceed: surface area (Width mm x length) Depthmm Quantity

10 12 15 18 20 25 30

28 38 45 50

2

2

12

15

15

20

25

""

k"

25

width x ]00 I I skip per 5 m or shorter len

30

38

\\idth x

45

50

55

;\

100

"idth x 100

3

2

I skip per 5 m or Rhorter

len th

Table 6.16 - WOOD SCREWS-ALLOWABLE LOADS IN SEASONED WOOD-NORMAL DURATION

Screw Size

I

Gauge

Diameter (mm)

Withdrawal Load from Side Grain per 25 mm of Penetration of Threaded Portion, (N)

Lateral Load in Side Grain, (N)

Species Group

Species Group

II

I

j

III

I

IV

II

I

III

I IV

4

1985

1370

950

3100

2665

2190

1825

2315

1710

1180

820

2295

1970

1620

1350

7.468

12130

1570

1085

750

1935

1665

1370

1140

16

6.807

I 1940

1430

985

685

1610

1380

1135

945

14

6.147

1750

1290

890

620

1315

1130

925

770

12

5.486

1565

1155

795

550

1045

900

740

615

10

4.826

1375

1015

700

485

810

695

570

475

9

4.496

1280

945

650

450

700

605

495

415

8

4.166

1185

875

605

420

605

520

425

355

7

3.835

1095

805

555

385

510

440

360

300

6 ...

3.505

1000

735

510

355

425

365

300

250

24

9.449

2695

20

8.128

18

1

i

SOURCE: PhlhpplOe Timber dcs1l!1l Standards (J. E. Rocafort and J. O. SlOpongco) November,I991 (FPRDI Tenninal Report)


WOOD

Table 6.17 - ALLOWABLE LOADS IN kN ON ONE BOLT IN SEASONED WOOD LOAD AT BOTH ENDS (DOUBLE

SHEAR) NORMAL DURATION

SPEOES GROUP (Refer to listing in Table 6.2) Length of Bolt in Main Memher L (mm)

Bolt d (mm)

m

D

I

IV Parallel to I PerpendiGrain cularto Grain

ParaDelto Grain

Petpendicularto Grain

ParaDel to Grain

Petpendicularto Grain

Parallel to Grain

Perpendicularto Grain

P

Q

P

Q

P

Q

P

Q

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

J3 16 20 22 25

7.08 8.75 11.0 12.1 13.7

3.76 4.19 4.85 5.04 5.47

4.86 6.01 7.55 8.30 9.43

1.98 2.21 2.56 2.66 2.89

4.20 5.20 6.53 7.19 8.16

2.07 2.30 2.67 2.77 3.01

3.26 4.01 5.02 5.52 6.27

1.82 2.02 2.35 2.43 2.64

50

13 16 20 22 25

8.38 10.8 13.7 15.1 17.2

4.70 5.23 6.07 6.30 6.83

5.75 7.42 9.38 10.3 11.8

2.48 2.76 3.20 3.32 3.61

4.98 6.43 RI2 8.95 10.2

2.59 2.88 3.34 3.46 3.76

3.99 5.00 6.27 6.90 7.84

2.27 2.53 2.93 3.04 3.30

65

13 16 20 22 25

9.29 13.0 17.4 19.3 22.2

6.11 6.80 7.89 8.19 8.88

6.38 8.95 11.9 13.2 15.2

3.23 3.59 4.16 4.32 4.69

5.52 7.74 10.3 11.4 13.2

3.36 3.74 4.34 4.50 4.89

4.68 6.29 8.10 8.97 10.2

2.95 3.29 3.84 3.% 4.29

75

13 16 20 22 25

9.35 13.8 19.4 21.9 25.5

6.84 7.85 9.10 9.45 10.2

6.42 9.48 13.3 15.0 17.5

3.61 4.14 4.81 4.99 5.41

5.56 8.21 11.5 13.0 15.2

3.76 4.32 5.01 5.20 5.64

4.79 6.85 9.22 10.2 118

3.30 3.79 4.40 4.56 4.95

80

13 16 20 22 25

9.41 14.1 20.3 22.9 26.9

7.14 8.37 9.71 10.1 10.9

6.45 9.66 14.0 15.7 18.4

3.77 4.42 5.13 5.32 5.77

5.59 8.36 12.1 13.6 16.0

3.93 4.61 5.34 5.54 6.01

4.84 7.09 9.77 10.9 12.5

3.45 4.05 4.69 4.87 5.28

90

13 16 20 22 25

9.39 14.3 21.3 24.9 29.4

13 16 20 22 25

9040 14.2 22.0 25.9 31.8

7.42 9.20 10.9 11.3 12.3 7.40 9.84 12.1 12.6 13.7

6.44 9.79 14.6 17.1 20.2 6.45 9.78 15.1 17.8 21.8

3.92 4.86 5.77 5.98 6.49 3.91 5.19 6.41 6.65 7.21

5.58 8.48 12.7 14.8 17.5 5.58 8.47 13.1 15.4 18.9

4.08 5.06 6.04 6.24 6.77 4.07 5.41 6.68 7.35 7.52

4.84 7.28 10.5 12.0 13.9 4.84 7.34

ILl 12.8 15.3

3.59 4.45 5.28 5.48 5.94 3.58 4.76 5.87 6.45 6.60

13 16 20 22 25 28

9.38 14.2 22.3 26.90 34.4 41.8

6.92 10.1 14.3 15.3 11.1 18.5

6.44 9.77 15.3 18.5 23.6 28.7

3.65 5.33 7.53 8.10 9.02 9.78

5.57 8.46 13.2 16.0 20A 24.8

3.81 5.56 7.85 8.44 9.40 10.2

4.83 7.33 11.5 13.8 11.3 20.5

3.34 4.89 6.89 7.42 8.26 8.95

(1)

I 40

I

Diameferof

100

125

I


WOOD

6-45

Table 6.17 (continued)

SPEOES GROUP (Refer to listing in Table 6.2) Length of

Diameter of Bolt d

Bolt in Main Member L

II

I

Parallel to Grain

Perpendi·cWarto Grain

(mm)

I

Parallel to Grain

IV

ill

I PerpendieIllar to Grain

i

~

Parallel to Grain

Perpendi cWarto Grain

P

Q

P

(7)

(8)

(9)

(1O}

PerpendieIllar to Grain

Parallel to Grain I

P

Q

P

Q

I

(2)

(3)

(4)

(5)

(6)

I

I3 ]6 20 22 25 28

9.38 14.2 22.2 27.0 34.8 43.1

6.51 9.85 14.8 164 18.7 20.8

6.44 9.76 15.2 18.5 23.9 29.6

3.44 5.20 7.79 8.65 9.88 11.0

5.57 845 13.2 16.0 20.7 25.6

3.58 5.42 !U2 9.01 10.3 11.4

4.83 7.33 11.4 13.9 17.7 21.7

3.14 4.76 7.14 7.92 9.04 10.0

16 20 22 25 28

14.2 223 26.9 34.6 43.5

9.59 14.7 16.7 19.7 21.9

9.76 15.3 18.5 23.8 29.9

5.06 7.78 8.84 104 11.6

8.45 13.2 16.0 20.6 25.9

5.28 9.21 10.9 12.1

7.33 11.5 13.8 17.8 22.1

4.64 7.13 8.09 9.54

16 20 22 25 28

14.2 22.2 26.9 34.8 43.7

8.84 14.1 16.6 20.8 24.6

9.72 15.2 18.5 23.9 30.0

4.66 7.45 8.75 11.0 13.0

8.42 13.2 16.0 20.6 25.9

4.86 7.76 9.12 11.4 13.5

7.32 114 13.9 17.9 22.5

4.27 6.82 8.01 10.0 11.9

190

16 20 22 25 28

14.2 22.2 26.9 34.8 43.6

8.59 13.8 16.3 20.7 25.0

9.75 15.3 18.5 23.9 29.9

4.54 7.30 8.63 10.9 13.2

8.44 13.2 16.0 20.7 25.9

4.73 7.61 899 11.4 13.8

7.30 114 13.9 179 22.5

4.15 6.69 7.90 10.0 121

200

16 20 22 25 28

14.2 22.2 26.8 34.6 43.6

837 13.5 16.1 20.5 25.3

9.90 15.2 18.4 23.8 29.9

4.42 7.13 8.48 10.8 13.3

844 13.2 16.0 20.0 25.9

4.61 7.40 8.84 J3.9

730 11.4 13.9 17.8 22.4

4.05 6.50 • 7.77 9.91 12.2

20 22 25 28 32 20 22 25 28 32

22.2 26.8 34.7 43.5 56.8 22.2 26.8 34.7 43.6 57.0

12.7 15.1 19.7 24.8 31.9 12.4 14.8 19.4 24.6 31.9

15.2 184 23.8 29.9 39.0 15.2 18.4 23.8 29.9 39.1

6.69 7.98 104 13.\ 16.8 6.54 7.83 10.2 13.0 16.8

13.2 15.9 20.6 25.9 33.8 13.2 16.0 20.6 25.9 33.9

6.97 8.32 10.9 13.7 17.5 6.81 8.15 10.7 13.5 17.5

11.4 13.9 17.9 22.5 29.3 11.4 13.8 17.'i 22.5 29.4

6.12 7.31 9.54 12.0 15.4 5.98 7.16 9.37 11.9 15.4

7.93 10.4 13.2 17.3

13.R 17.9 22.4 29.2

6.97 9.09 J 1.6 15.2

9.94 12.6 17.0

17.\J 22.4 293

In3

!

(I)

140

i

150

180

230

~2W

1 255

i

L:.

i

i

I

I i

8.11

I

IL3

Q

10.6

I

i

-J I

i

22 25 28 32

25 28 32

26.8 34.7 43.5 56.7

I i

I

34.6 43.4 56.9

I

18.4 23.8 29.8 38.9

14.4 18.8 24.0 31.5

7.61 9.93 12.7 16.6

15.9 20.6 25.8 33.7

953 12.1

20.6 25.8 33.8

I

"jl' I

23.0

30.8

29.9

I I

390~~~~

I I

I I

I

I


.L-

I i

III 14.9

I

WOOD

6-46

Table 6 17 (continued)

··----1 SPECIES GROUP (Refer to listing in Table 6.2)

I i

!

(I)

I 290

305

Diameter of Bolt d (mm)

II

I

I Perpendl-

Parallel to Grain

I

cular to Grain

Parallel to Grain

Perpendlcular to Grain

I

rv

III

I

Parallel to Grain

Perpendicularto Grain

P

Q

Parallel to Grdin

I

Pcrpcndi cular to Grain

I

P

Q

,:

(9)

( 10)

17.9 29.3

8.60 11.0 14.7

17.& 22.4 29.3

8.36 10.7 14.4

P

Q

P

Q

(2)

(3)

(4)

(5)

(6)

(7)

(8)

25 28 32

34.7 43.5 56.&

17.8 22.7 30A

23.8 29.9 39.0

9.39 12.0 16.1

20.6 25.9 33.7

9.79 12.5 16.7

22.+

25 28 32

34.7 43.4 56.8

17.3 22.2 29.8

9.13 11.7 15.8

20.6 25.8 33.8

9.51 12.2 16.4

I

I

I

23.8 29.8 39.0

I

I I

I I

i

Table 6.18 - ALLOWABLE LOADS IN SEASONED WOOD (NORMAL DURATJON) FOR ONE SHEAR-PLATE UNIT AND

BOLT IN SINGLE SHEAR

Shear Plate diam. (mm)

I diam. Bolt (mm)

Number offaee ofpiccc with

Net dUeknessof lumber
Minimu med~

distance (mm)

Loaded parallel to grain (0; Allowable load per co~or unit and bolt (kN)

oonDeC-

65

III

14.01

11.70

10.10

2

40 minimum

10.90

9.074

7.828

50

13.26

11.03

9519

67 & thicker 40 minimum

14.01 19.75

11.70 16.46

10.10 14.19

2J.l7

17.66

15.21

45 minimum

14.10

11.74

10.14

50

15.75

13.12

11.30

66

18.46

15.39

13.25

75

20.10

16.72

14.46

90 & thicker 40 minimum

21.17 1957

17.66 16.46

15.21 14.19

45

. 45 & thicker

I

II

40minimwn

1

I 100

I

1 20

2

1

distance (mm)

Unloaded edge i (minimum)

Speeies Group

!

Loaded-

I

Allowable Load per eo~or unit and bolt (kN)

ed~

I

II

III

45 minimum 70 or more

8.140 9.830

6.761 8.184

5.872 7.072

45 minimum 70 or more 45 or more 70 or more 45 minimum 70 or more 70 minimum 95 or more 70 minimum 95 or more

6.316 7.651 9.296 8.140 9.830 11.480 \3.830 12.280 14.810

5.293 6.361 6.405 7.740 6.761 !U84 9563 11.52 10.23 12.37

4.537 5.471 5.516 6.672 5.871 7.072 8.229 9.964 8.807 10.680

70 minimum 95 or more 70 minimum 95 or more 70 minimum 95 or more 70 minimum 95 or more 70 minimum 95 or more 70 minimum 95 or more 70 minimum

8.184 9.875 9.118 11.030 10.720 12.940 11.650 14.060 12.280 14.810 11.480 13.830 12.010

6.805 8.229 7.606 9.163 8.940 10.760 9.697 11.740 10.230 12.370 9.563 11.520 10.230

5.871 7.117 6.583 7.917 7.695 9.296 8.362 10.100 8.807 10.680 8.229 9.964 8.807

45

70

20

E.

I

Speeies Group

tors of same bolt

Loaded perpendicular to grain (90;

7.W5

I

70

50


l

6-47

Table 6.18 ( Continued)

Shear Plate diam. (mm)

Bolt diaJR. (mm)

i

100

Number offace of piece with connec tors of same bolt

22

Net thkknessof lumber (mm)

Loaded parallel to grain (0">

Minimu medge distance (mm)

Loaded perpendicular to grain (90·)

Allowable load per connector unit and bolt (kN) Species Group

45 & thicker

I

II

III

21.17

17.66

15.21

i

70 2

14.10

11.74

10.]4

50& thicker

16.19

]3.12

11.30

66 minimum

18.46

15.39

13.26

75 & thicker

20.10

16.72

14.46

90 minimum

Loadededge

15.21

l

i

!

Unloaded edge (minimum)

i

Species Group

I

I

II

III

95 or more

14.810

12.370

1O.6RO

70 minimum 95 or more 70 minimum 95 or more 70 minimum 95 or more 70 minimum 95 or more 70 minimum 95 or more

8.]84 9.875 9.1]8 11.030 10.720 \2.940 11.650 14.060 12.280 14.810

6.805 8.229 7.606 9.163 8.940 10.760 9.697 11.740 10.230 12.370

5.918 7.]]7 6.583 7.917 7.695 9.296 8.362 10.100 8.807 1O.6R

I

70

45 minimum

I

Allowable Load per connector unit and bolt (kN)

Edge distance (mm)

i

I

Table 6.19 - ALLOWABLE LOADS IN SEASONED WOOD (NORMAL DURATION) FOR ONE TOOTHED-RING UNIT AND DOLT IN SINGLE SHEAR Loaded parallel to grain

Toothed

RinK diam. (mm)

No.. of

Bolt diam. (mm)

fa~of

piece with connec

Net thickness oflumbcr (mm)

Minimu medge distance (mm)

Allowa~le Load per connector anit and bolt (kN)

-ton of I

25 minimum

5.338

40& thicker

5.871

i

II

I

4.804

5.293

2

12

16

i

I

2

Unloaded edge (minimu m)

~~

Allowable Load per connector unit and bolt (kN) Species Group

Loadededge

I

I

i

I

II

I

• III

i

4.181

32 minimum

3558

3.203

2.758

4.581

50 or more 32 minimum

4.048 3.914

3.647 3.514

3.158 3.069

50 or more

4.448

4003

i

I !

-

+(19

40 minimum

5.338

4.804

4.181

32 l1l1I1lmum

3.558

3.203

2.758

50& thicker

5.871

5.293

4.581


4.048 3.914

3.647 3.514

:U58 J.069

4.448

25 minimum

R.006

7.206

6.227

40& thicker

1001

8.985

7.823

40 minimum 50

i

32

45 65

I I

III

32 50

Edge distance (rom)

Specics Group

same bolt

I

Loaded perpendicular to grain

(0")

! SO or more

45 minimluu

5.338

4.003 4.804

3.469 4.181

62ormorc 45 minimum

6.094 6.h72

5.471 6.005

4.759 5.204

62 or more

7562

6.805

5.916

4.804 5.471

4.nQ 4.759

5.293

..k"SI

45 8.006

7.206

6.227


5.338 6.094

I

8,852

7.%2

6.894

45

5.916

I

,National Struct}iral Code of the Philippines, Volume 1

.. J

WOOD

6-48 Table 6.19 (continued)

Loaded parallel to grain Toothed Ring diam. (mm)

No. of face of piece with connec -tors of same bolt

Bolt diam. (mm)

Net thickness of lumber (mm)

medge distance (mm)

Allowable Load per connector unit and bolt (kN)

I

Species Group

I

65& thicker 25 .. mmlmum

I

II

III

2

20

f

I

III

6.716 6.Q72 7.562

6.049 6.005 6.805

5.249 5.204 5.916

9.385

8.140

55 minimum

6.939

6.227

5.427

10.94

80 or more 55 minimum 80 or more

8.229 9.385 I L120

7.428 8.451 10.010

6A50 7.295 8.674

55minimwn 80 or more

6.939 8.229

6.227 7.428

5.427 6.450

7.606 9.029 8.718 10.320 9.385 11.120

6.850 8.095 7.828 9.296 . 8.451 10.010

5.916 7.028 6.805 8.051 7.295 8.674

12.63

55

lOA I

9.385

8.140

50

1139

10.27

8.896

65

\3.03

J 1.74

10.19

75& thicker

14.06

12.63

10.94

55 minimwn 80 or more 55minimwn 80 or more 55 minimum 80 or more

25 minimum

12.54

11.30

9.786


8.362 10050

7.517 9.029

6.494 7.828

40& thicker

16.32

14.68

12.72


10.850 13030

9.786 11.743

8.451 10.19


8.362 to.050

7.517 9.029

6.494 7.828


9.029 10.850

8.\39 9.786

7.072 8.451


10.190 12.230

9.163 10.990

7.962 9.519


10.850

9.700 11.740

8,451 10.19

! 12.54

50

I

II

IOAI

70

IUO

9.786

!

I

I

40 minimum

40 minimum

2

Species Group

Loadededge

7.828

-.

20

""

8.985

70

100

Unloaded edge (minimu m)

10.01

55 85

AUowable Load per connector unit and bolt (kN)

Edge distance (mm)

62 or more 45 minimum 62 or more

14.06

40& thicker

I

Loaded perpendicular to grain (90")

(0")

MiniulU

13.57

12.19

10.59

65

1530

13.74

li.n

75& tJlickcr

16.32

14Ji8

12.72

13.030

I

I

,


I

i

WOOD

6-49

Table 6.20 - ALLOWABLE LOADS IN SEASONED WOOD (NORMAL DURATION) FOR ONE SPLIT-RING UNIT AND BOLT IN SINGLE SHEAR

Bolt

Split Ring diam. (mm)

diam.

(mm)

No. of face of plea: with 00_ fonof same bolt

Net thiclmess of lumber (mm)

Minimu

medge distance (mm)

I

(0")

~Wable Load per .

emmector unit and bolt (kN)

i

Species Group

r----

I

I

n

64

m

20

100

2

. ooDJ'ledor unit

bolt (kN)

!

Species Group

edge

I

n

m

i

11.03

9.252

7.%2

45 minimum

6.583

5.471

4.715

40& thicker

13.25

lLl2

9.519


7.784 7.873

6.494 6583

5.560 5.649

70 or more

9.385

U84

6.672

45

40 minimum

11.03

9.252

7.962

45minimmn

6.583

5.471

4.715

50& thicker

13.25

11.12

9519


7.784 7.872

6.494 6.583

5.560 5.649

25 minimum

17.03

14.19

12.23

70 or more 70 mininllun

9.385 9.815

7.784 8.229

6.672 7.117

40& thicker

25.53

21.26

18.37


11.830 14.810

9.875 12.320

8.496 10.630

17.92

14.90

12.90


17.790 10.360

14.810 8.629

12.770 7.473

50

20.599

17.17

1·t81

95 or more 70 minimum 95 ormorc

12.450 11.970 14320

10.360 9.963 11.970

8.985 8585' 10.320

66

25.04

20.90

18.06 70 minimum 95 or more 70 minimum

14.540 17.440 14.810

12.100 14.540 12.320

10.450 12540 10.630

95 or more

17.790

14.810

12.770

40 minimum

75& thicker '--.-.

I .-_Lod and '":~

Loaded-

m)

45

I

!(~U

I

25 minimum

12 2

Edge distance (mm)

Unloaded

i

1

Loaded perpendic:uIar to grain (90")

Loaded paraDel to grain

70

25.53

21.26

1107

70

I

National StructlBal Code of the Philippines, Volume 1

I

WOOD

6-50

Table 6.21 - COMMON WIRE NAILS AND SPIKES-ALLOWABLE WAD IN SEASONED WOOD-NORMAL DURATION

Size of NaB or Spike

Designation

Length

Diameter

(mm)

(mml

Withdrawal Load from Side Grain per 25 mm ofPeoeiration of NaB or Spike into the Member Holding the Point (N)

Lateral Load in Side Grain, (N)

Species Group

Species Group

I

n

m

IV

(11

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

N

60d 50d 40d 30d 20d 16d IOd

150

140

125

115

100

90

75

65

50

6.680 6.198 5.715 5.258 4.877 4.115 3.759 3.327 2.870

805

750

690

685

590

495

455

550

510

470

435

400

340

310

275

235

340

315

290

265

245

210

190

170

145

215

200

180

170

155

130

120

105

90

1320

1180

1045

920

825

215

180

150

140

125

115

100

90

80

75

9.525 7.925 7.188 7.188 6.680 6.198 5.715 5.258 4.877 4.877

1035

705

590

535

536

495

460

425

390

360

360

435

360

325

325

305

280

260

240

220

220

275

230

205

205

195

180

165

150

140

140

2020

1535

1325

1325

1185

1060

940

830

740

740

A

L

8d

S

6d

S

3/8 3/8 60d 50d

P

40d

30d 20d 16d 12d IOd

• K E S

400

345

860

780

780

725

675

620

570

530

530

I

640

555

465

370

n ~ (10)

1135

1010

895

790

705

550

480

400

320

1735

1320

1140

1140

1020

910

805

710

635

635

m

IV

(11)

(12)

930

830

735

650

580

450

395

325

260

775

695

615

540

485

375

33'0

275

220

1425

1085

935

935

1190

905

780

780

700

625

5j5

490

435

435

840

750

665

585

525

525

SOURCE: Philippine Timber design Standards (1. E. Rocafort and J. O. SiojJ9llgco) November,1991 (FPRDI Terminal Report)

Table 6.22 - ALLOWABLE SPANS FOR SOmrnTONGUE AND GROOVE DECKING

SPANl (mm)

DEFLECI10NLIMlT

LIVE LOAD (kN/m;

Roofs 11240

0_958 1200

11360

11240

1.437 1.916 0.958

1350

1.437 1.916 0.958

1500

1.437 1.916

E

/

(N/mml)

(Nlmm;

I--

11360 11240 11360 11240 ]/360 ]/240 ]1360 11240 11360 11240 11360 11240

11360 11240 11360

1171.30

1.102

.....

~

1?(j3~ _ _.__

1.722

1763.84 - 2645.76 2342.60 .. 3527.68 1667.38 .- 2101.45 2501:07--- 2790·~L __. _ _ 1 - - - - - -3334.76 - .-.... - - - - 4995.25 2287.48 3445.~ _ _

2.274

·-----:5iTi.38

2.894

4547.40 6890.00

1.447 1.860 1.378 1.860

2.412

Association of stnactural Engineers of the Philippines

I-~

-

._----

3410.55

WOOD

6-51

TABLE 6.22 (Continued)

SPAN1

LIVE LOAD

(mm)

(kN/ml)

DEFLECflON LIMIT

0.958 1650

1.437

1800

1950

2100

2250

1.916

3.445

0.958

2.480

1.437

3.307

1.916

4.143

0.958

2.894

1.437

3.858

1.916

4.823

0.958

3.376

1.437

4.478

1.916

5.581

0.958

3.858

1.437

5.168

1.916

6.408

0.958 2400 1.437 Floors 11360

1.916

I

Spans are based on simple beam action with 0.48 kNlm' dead load and provisions for a l334 N concentrated load on a 300 mm. width of fluor declciJig. Ramfom lay-up permitted in aooordan~ with the provisions of Section 620.8.3 or 620.1 0.11.9. Lumberthiclrness assumed at 38 mm, net.

TABLE 6.23 - SIZE, HEIGHT AND SPACING OF WOOD STUDS

STUD SIZE

Laterally UDSUJlported

StudHeighr (mm) 30 J{ 75 2

55 82

NON-BEARING WALLS Laterally Unsupported Spacing

StudHeighr
250 250

105 x 125 130 J{ 150

250 250

J{

Supporting Two Floors, Roof and CeiIiDg

SpadDg(mm)

(mm)

100 100

J{

BEARING WALLS Supportiug One Supportiug Roof Floor, Roof and and Ceiling Only CeiIiDg

(mmJ 400

600 600 600

400 600 600

4200

600

400

4200

600

600

400

4800 6000

600 600 600

distances betWeen points of lattnI support placed perpendicular to the plane of the wall. Increa._ in unsupported height 1m: permiUed where jusIified by an analysis. 2 Shall not be used in exImior walls. 1 Listed heights &Ie

National St.n.IctUIaI Code of 1he Philippines, Volume 1

WOOD

Table 6.24 - BRACED WALL PANELS!

SEISMIC ZONE

CONDITION

,~

One-story, top of two or three-story 0, I and2A

,

1

First- story oftwo-story or second-story of three-story First-story of three-story

X

CONSTRUCTION METH002. 1 \13 2 4 5 7 r X X X X X X

BRACED PANEL LOCATION AND LENGTH" '

8 X

-

...

X

X

X

X

X

X

X

X

X

X

X5

X

X

X

X

X

X

X

X

x:o

X

X

5

Each end and not more than 7500 mm on center

~~~.~-----

2B,3 and 4

One-story, top of two-story or three-story First-story of two-story or second of three-story

I

I

Each end and not more than 7500 mm on center -_.

f---

X

X

X

X

X·

X

Each end and not more than 7500 mm on center but not less than 25% of

building length' First-story of three-story X

X

X

X5

X

I x:o

X

Each end and not more than 7500 mm on center but not less than 40% of building length?

This table specifies minimum requirements for braced panels which form interior or eKterior braced wall lines.

See Section 620.10.3 for fun description.

See Section 620.10.4 ror alternate braced panel requirement.

4 Building length is the dimension parallel to the braced waJllength.

5 Gypsum wallboard applied to supports at 400 mm on center.

• Not permitted for bracing cripple walls in Seismic Zone 4. See Section 620.10.5.

7 The required lengths shall be doubled ror gypsum board applied to only one fi1ce of a braced wall panel.

1

2

3

TABLE 625 - CRIPPLE WALL BRACING

SEISMIC ZONE

AMOUNT OF CRIPPLE WALL BRACINGl , I

CONDITION

9 mm wood structural

with 8d at 150/300 minimum 9 mm wood structural panel with 8d at 100 1300 mm nailing on 50 peruent of \V'dlilength minimum or 9 mm wood structural with Rd at 150 1 300 mm of w~~~ length ~inimum 9 mm wood structural with 8d at 150/300 mrn of wall

4

t------······~·----r_~--~~--~--~_+~----~----~----·

~----:::-.~~~=---J-~:::::..:~'L:::-:::.:::.::::J:x.:::-=.:~--I.

9 mrn wood structural panel with Rd ~t_150 1300 mm nailing 01l}..9 percent of waillength miniDlum 9 mm wood structural panel with 8d at 100 1 300 mm nailing on 40 percent of wall1ength minimwn

0,1,2 and 3

t

2

Two-story above cripple wall

or 9 mm wood structural panel with 8d at 150 1 300 mm nailing on 60 percent of wal! length minimwn

Braced panel length shall be at least two times the height of the cripple wall, but not less than 1200 mm.

All panels "'long a wall shall be nearly equal in length and shall be nearly equally spaced along the length ofthe wall.


.(~

,~~

6-53

WOOD

Table 6.26- WOOD STRUCTURAL PANEL WALL SHEATHING1

(Not exposed to the weather, strength axis parallel or perpendicular to studs)

I MINIMUM TIDCKNESS

l.=-=~9':)I'~.~-~ l__ !

II, 12, 13

PANEL SPAN RATING

_. ---,

[--·-------1=:~~~~:~~~~~~i~~~d ~;~~~;620:i'o~3J ,

Siding Nailed to Studs 400

Sheathing Parallel to Studs

600

400

-------,

T Sheathing Perpendicular

'

to Studs

400

--,----,------_._--+

(,(jO

600

24/(l. 24/16. 32/16 Wa_I_I_2_4_,_o,_c_'---e_ _ _61_.lO _ _ _--'-_ _ _ __

In reference to Section 620, I 03, blocking. of horizonwl joints is not required,

Table 6.27 - ALLOWABLE SHEARS FOR WIND OR SEISMIC LOADING ON VERTICAL DIAPHRAGMS OF FIBERBOARD SHEATHING BOARD CONSTRUCTION FOR TYPE V CONSTRUCTION ONLY , - - - - - - - - - - - - - - - - - - - -... -------------,--SHE--A-R-=V-,-A-LCC"U=E"""IN::c:-:7=-=S-m-m-N:-c:-A-=-=lL:-C"S=-PA--:cC-=-INC::-G"l SIZE AND APPLICATION

NAIL SIZE

13 x 1200 x 2400 mm

No, I I gage galyanized TOoting nail 38 mm long. II mmhead

AROUND PERIMETER AND 150 mm AT INTERMEDIATE POINTS

------_ ...__.'--------

!

256 I

FiOOrboard sheathing dinphmgms shan not be used to bmcc concrete or masonry waIl,_ The ,hearYruue may be 778 N for 13 ~ 1200 by 2400 mm tiberboard nail-hase sheathing.,

National Structural Code of the Plu1ippines, Volume 1

J I

6-54

WOOD

Table 6.28 - ALLOWABLE SHEAR FOR WIND OR SEISMIC FORCES IN POUNDS PER FOOT FOR VERTICAL DIAPHRAGMS OF LATH AND PLASTER OR GYPSUM BOARD FRAME WALL ASSEMBLIES I

TYPE OF MATERIAL

1.

Expanded metal, or woven wire lath and portland cement plaster

2.

Gypsum lath

3.

Gypsum board

sheathing

THICKNESS OF MATERIAL (mm)

WALL CONSTRUC TION

22 nun

NAIL SPACING1 MAXIMUM (mm)

SHEAR VALUE (mm)

Unblocked

150

2628

No. II gage, 38 nun long, II nun head No. 16 gage staple, 22 nun legs

9 nun lath and 13 nun plaster

Unblocked

125

1460

No. 13 gage staple, 29 mm long, 7 mm head, plasterboard blued nail

13 nun x 600 rnm x 2,400 1llll1

Unblocked

100

1095

No. II gage, 44 nun long, II nun head, diamondpoint, galvanized

" _ , 1200

~IOC'"

1~3"~ x 1200 nun' Un~IOCked 4.

,

Gypsum wallboard or veneer base

13 nun

I

MINIMUM NAIL SIZEl (mm)

2555

175

1460

175

1460

100

1825

175

1825

5d cooler (2.18 nun dia., 41 mm long, 6 mm head) orwalIboard (2.18 nun dia. 41mnt long, 7mmhead)

Unblocked

Blocked

r-.---- 100

Unblocked

2190

175

1679

.-

._.

16mm

100

2117

6d cooler (133 nun dia., 47 nun long, 6 nun head) or wallboard (232 nun dia. 47 mm long, 7 nunhcad)

..._.

Blocked

175

2117 ..

Blocked Two ply

•

~

.....

-~

---_._.-.__ .

100

2555

Base ply: 225 Face ply: 175

3650

i

Base ply 6d cooler (2.33 nun diu. 47 m111long, 6 mm head) or wallboard (232 mm dill. 47 mm long, 7 mm head) Face ply - 8d cooler (2.87 nun dia., 59 mm long, 7 nun head) or wallboard (2.87 nun dia., 59 rrun 1 IOllg, 9 mm head)

I

I These vertical diaphragms shall not be used to resist loads imposed by masonry or c

6·55

Table 6.29 - ALLOWABLE SPANS FOR PARTICLEBOARD WALL SHEATHING) (Not exposed to the weather. long dimension of the panel parallel or perpendicular to studs) STUD SPACING (mm) TIDCKNESS (mm)

GRADE

Sheathing under Co\cerings

Specified in Section 620.10.3

Parallel or Perpendicular to Studs

Siding Nailed to Studs

9

M-I

---_._-_ ......- •. __ ._-

I-··-······-·-·-~~~-~~~--+~--··-----·-----

M-S

I - - - - - - - - - - - - - ... t - - . - - - - -..--~--M-2 "Exterior Glue 13

-.-

400

400

lin reference to Section 620.103, hlocking of horizontal joints is not required.

Table 6.30 SClENTIFrC NAME OF PHILIPPINE TIMBER ~PECIES

I.

Malabayabas (Tristania spp.) includes:

8.

Malabayabas (T. decorticata Merr.) Tiga (T. micrantha Merr.)

2.

DangakaIan (C obliquinenium Merr) BitantdJol (C. blancoi FL & Tr.) Bitaog (C. inophyllum U

Manggachapui I.Hopea spp.) includes: 9.

Dalingdingan (H, foxworthyi Elm.)

Manggachapui (H. acuminala Merr.) Yakal-saplungan LH. plagata (BIanco) Vid.j 3.

10.

Yakal (Shorea spp.) includes:

Lauan I.Shorea spp_) includes:

Almon (S. almon Fm.:w.) Lauan, Red (S. negros(''I1sis Foxw.) Lauan, While (S. cOI1lorta Vid.)

Ma),apis [S. squamata (l'urcz. Dyer.]

Tangilc IS. polyspenna (Blanco) Merr.]

Yakal (S.astylosa Foxw.) Yakal-gisok (8.gisok Foxw.) Yakal-Malx)lo (S. ciliata King) Yakal-malibato (S. rnalibato Foxw.)

II. 5.

GiSl!U (Canarium spp.) includes:

Dulil [C. hirsutum Willd. Forma multipinnatum

(Llanos) H..1. Lam]

Gisau (C. "TIeseanum Engl.) Pagsabingin-bulog tC. calophyllum Perle) Piling-liilan [C.luzonicum (Blume) A. f'lTay!

Narig (Vaties spp.) includes: Narig ('I. manggachapui Blanco spp. tnanggachapoi)

Narig, Thick-leafed ('I. pachyphylla Merr.)

4.

Dangkalan (Callophyllum spp.) includes:

Malaanonang (Shorea spp.) includes:

Antipolo (Arthocarpus spp.) includes: Antipolo [A. blanco (Elm.) Merr.] Anubing (A ovato Blanco)

Kubi (A nitida Trec. Spp. Nitida) Nangka (A heterophylla Lam.)

Kalunti LS. hopeilolia (Hcim). Sym.]

Malaanonang (S. polila Vid.

12.

Malasaging (AgJaia spp.) includes:

TIo-ilo LA. iloilo (Blanco) Men.]

Kuling-manok [A. luzoniensis (Vid.) Merr. & Rolle] Malasaging (A diffusa ML--rr.)

Binggas (Terminalia spp.) includes: Binggas [T. citrina (CIaerln) Roxb·1

Kalumpit (T. microcarpa Deone) Lanipau (T. copeIandii Elm.)

Sakat (T. Nitens Fres!.) Talisai-gubat (T. foetidissima Griff.)

13.

Malugai (P. pinnata Forst.)

Malugai-liitan (p. pinnata forma responda Jacobs)

14.

Dao tIJracontomelon spp.) includes: Dao [D. dao (Blanco) Merr. & Rolfe} Lamio [D. edule (Blanco) Skeels.]

Malugai (pometia spp.) includes:

Miau (Dyso;,;ylum spp.) includes: Kuling-babui (0. altissisum Mcrr.) Miau (D. euphlebium Merr.)

National Struclural Code of the Phirlppines, Volume 1

•

6-56

WOOD

TABLE 6.30 (Continued)

15.

Ouijo (Shorea spp.) includes:

19.

Ouija IS. guiso (Blanco) Blume] Malaguijo (S. plagata Foxw.) 16.

17.

20,

2L

22.

Salakin (Aphanamixis spp.) includes: Kangko (A perrotleliana A .Iuss) Salakin LA. cumingiana (C. Dc,)]

Kato (Amoora spp.) includes: 23,

Bayok (Pterospennum spp.) includes: Bayok (p. diversifolium Blume) Bayok-bayokan (P. niveum Vid,)

Pahutan (Mangifera spp,) inclUdes: 24. Pahulan <.M. altissima Blanco Pahong-liitan (M. merriUii Mukh.)

13.

Pine (Pinus spp.) includes:

Pin!.", Benguet (p. kesiya Royle~. Gordon)

Pine, Mindoro (P. mcil"llsil Jungh & de Vr.)

Kato (A shermana Merr.) Katong-Iakihan (A macrocarpa Merr.) 18.

Palosapis (Anisoptera spp.) includes: Afu (A bnmnea Foxw.)

Dagang (A, auren Fo;.',\\,,)

Katmin (Dillenia spp,) includes: Katmon (D. philippinensis Rolfe) Katmon-bayani (D. megalantha Merr.) Malakatmon [D. luzoniensis (Vid.) Martel1iJ

IL

Malak-malak IP. philippense (perr.) C. B, Rob.]

Maniknik (p. tenuipeliolatwn Merr.)

Nato [P.luzoniensis (E-ViU,) Vidl

PaJak-palak (p. lanceolalwn Dlanco)

Kamagong (Diospyros spp.) includes: Anang 11 pyrrhocarpa Miq.)

Anang-guIod (0. inclusa Merr.)

Ata-ata (D, mindanaesis Merr.)

Bolong-eta (0. pilosanthem Blanco)

Kamagong (D. philippinensis (Resr.) Gurke]

Kamagong, Ponce (D. poncei Merr.)

Katilma (D. nitida Merr.)

Nato (Palaquium spp.) includes:

Apitong (Dipterocarpus spp.) includes:

Manggasinoro lShorea spp.) includes: Manggasinoro IS, assamica Dyer. forma philippinensis (Brandis) Sym.] Manggasinorong -Iakihan (S. "irencens Parijs)

Apitong (D. grandiflorus Blanco)

Apitong, Basilan (D. basilanicus Foxw.)

Apilong, Broad-winged (0. speciosus Brandis)

Hagakhak tD. warbugii Brandis)

Malapanau (D. Kerni King)

Panau (D. grandis Blume)

Panau, Leaf-tailed <.0. caudatus FO);w,)


CHAPTER 7

MASONRY TABLE OF CONTENTS SECTION 701 - GENERAL •...••••..•••••.•••.••••.••••••••...••••.•.•••..•••••••.••••.••••••••••••••••••••.••••••••••.••••••...•• 7- t 701.1 Scope ......... ............. ................ ......... 7-1 701.2 Design Methods .......................... 7-1

701.3 Definitions ................................ .. .. . 7-1

701.4 Notations ...................................7-2

SECTION 702 - MATERIAL STANDARDS ••••.•..••••.•••••.•••.•••••••..•.••.•••••••.••.••••..•.•••.•••.•••••••..•... 7-4

702.1

Quality ............................................ 7-4

702.2

Standards of Quality ....................... 7-4

SECTION 703 - MORTAR AND GROlJT •••••••••.••••••.•.•••••.•••••••••..•••••••..•••••..•••••••••••••......••....•••• 7-6

703.1 703.2 703.3

General ........................................... 7-6 Materials ......................................... 7-6 Mortar................................................... 7-6

703.4 703.5

Grout .............................................. 7-6

Additives and Admixtures ................ 7-6

SECTION 704 - CONSTRUCTION ••.•••••••••..•.••••••••••....••••••.•••..••••••.•••••..•••••..••••..••••.••••.•.•••••.••••• 7-7

704.1 General ........................................... 7-7 704.2 Materials Handling, Storage and Preparation ......... ................... ....... 7-7 704.3 Placing Masonry Units .. . ... . .. . ..... . 7-7

704.4 Reinforcement Placing ...................... 704.5 Grouted Masonry. .. .. . . . . ... ... . . . . . . .. . 704.6 Aluminum Equipment... ... ............ 704.7 Joint Reinforcement... ...... ...... ......

7-7

7-8

7-8

7-8

SECTION 705 - QUALITY ASSURANCE ..••••••...•••••..••.••••••••••..••.••.•••..••••••..•••••.•••.•••••••••••••••••• 7-9

705.1 705.2 705.3

General ........................................... 7-9 Scope ............................................... 7-9 Compliance with I'm ....................... 7-9

705.4 705.5

Mortar Testing ............................... 7-11

Grout Testing................................... 7-11

SECTION 706 - GENERAL DESIGN REQUIREMENTS 706.1 General .................................... ..... 7-11 706.2 Working Stress Design and Strength Design Requirements for Unreinforced and Reinforced

Masonry ...................................... 7-14

706.3

7-11

Working Stress Design and

Strength Design Requirements

for Reinforced Masonry ............. 7-16

SECTION 707 - WORKING STRESS DESIGN OF MASONRy........................................ 7-18

707.1 707.2

General ......................................... 7-18 Design of Reinforced Masonry........ 7-19

707.3

Design ofUnreinforced Masonry .... 7-23


TABLE OF CONTENTS

SECTION 708 - STRENGTH DESIGN OF MASONRY 708.1

General ......................................... 7-25

708.2

7-ii

...................................................... 7-25

Reinforced Masonry ..................... 7-26

SECTION 709 - EMPIRICAL DESIGN OF MASONRY ..................................................... 7-35

709.1 709.2 709.3 709.4 709.5

Height ........................................... 7-35 Lateral Stability.................. ...... 7-35 Compressive Stresses...... ......... ... 7-35 Lateral Support........................... 7-36 Minimum Thickness ..................... 7-36

709.6 Bond......................................... 7-36

709.7 Anchorage.................................. 7-37

709-8 Unburned Clay Masonry ................. 7-37

709.9 Stone Masonry ............................ 7-37

SECTION 710 - GUSS MASONRY ....................................................................................... 7-38

710.1 General ......................................... 710.2 Mortar Joints .................... ;............ 710.3 Lateral Support... ..... ....... ...... .... 710.4 Reinforcement... .......................

7-38 7-38 7-38 7-38

710.5 Size ofPanels ................................ 7-38

710.6 Expansion Joints.................. ... ... 7-38

710.7 Re-use of Units.......................... 7-38


,

GENERAL

7-1


TRANSFORMED AREA is the equivalent area of one material to a second based on the ratio of moduli of elasticity of the first material to the second.

701.1 SCOPE.

BOND:

The materials, design, construction and quality assurance of masonry shall be in accordance with this chapter.

ADHESION BOND is the adhesion between masonry units and mortar or grout.

701.2 DESIGN METHODS.

REINFORCING BOND is the adhesion between steel reinforcement and mortar or grout.

Masonry shall comply with the provisions of one of the following design methods in this chapter as well as the requirements of Sections 701 through 705. 701.2.1 Working Stress Design. Masonry designed by the working stress design method shall comply with the provisions of Sections 706 and 707. 701.2.2 Strength Design. Masonry designed by the strength design method shall comply with the provisions of Sections 706 and 708. 701.2.3 Empirical Design. Masonry designed by the empirical design method shall comply with the provisions of Sections 706.1 and 709. 701.2.4 Glass Masonry. Glass masonry shall comply with the provisions of Section 710.

BOND BEAM is a horizontal grouted element within masonry in which reinforcement is embedded. CELL is a void space having a gross cross-sectional area greater than 967 mm2 CLEANOUT is an opening to the bottom of a grout space of sufficient size and spacing to allow the removal of debris. COLLAR JOINT is the mortared or grouted space between wythes of masonry. COLUMN, REINFORCED, lS a vertical structural member in which both the reinforcement and masonry resist compression. COLUMN, UNREINFORCED, is a vertical structural member whose horizontal dimension measured at ri&ht angles to the thickness does not exceed three times the thickness.

701.3 DEFINITIONS. For the purpose of this chapter, certain terms are defined as follows: AREAS: BEDDED AREA is the area of the surface of a masonry unit which is in contact with mortar in the plane of the joint

DIMENSIONS: ACTUAL DIMENSIONS are the measured dimensions of a designated item. The actual dimension shall not vary ITom the specified dimension by more than the amount allowed in the appropriate standard of quality in Section 702.

EFFECTIVE AREA OF REINFORCEMENT is the cross-sectional area of reinforcement multiplied by the cosine of the angle between the reinforcement and the direction for which effective area is to be determined.

NOMINAL DIMENSIONS of masonry units are equal to its specified dimensions plus the thickness of the joint with which the unit is laid.

GROSS AREA is the total cross-sectional area of a specified section.

SPECIFIED DIMENSIONS are the dimensions specified for the manufacture or construction of masonry, masonry units, joints or any other component of a structure.

NET AREA is the gross cross-sectional area minus the area of ungrouted cores, notches, cells and unbedded areas. Net area is the actual surface area of cross section of masonry.

GROUT LIFT is an increment of grout height within the total grout pour.


7-2

MASONRY

GROUT POUR is the total height of masonry wall to be grouted prior to the erection of additional masonry. A grout pour will consist of one or more grout lifts.

CA VITY WALL is a wall containing continuous air space with a minimum width of 51 mm and a maximum width of 114 mm between wythes which are tied with metal ties.

GROUTED MASONRY:

WALL TIE is a mechanical metal fastener which connects wythes of masonry to each other or to other materials.

GROUTED HOLLOW-UNIT MASONRY is that form of grouted masonry construction in which certain designated cells of hollow units are continuously filled with grout. GROUTED MULTIWymE MASONRY is that form of grouted masonry construction in which the space between the wythes is solidly or periodically filled with grout.

WEB is an interior solid portion of a hollow-masonry unit as placed in masonry. WYTHE is the portion of a wall which is one masonry unit in thickness. A collar joint is not considered a wythe.

701.4

JOINTS:

= cross-sectional area of anchor bolt, square

BED JOINT is the mortar joint that is horizontal at the time the masonry units are placed. HEAD JOINT is the mortar joint having a vertical transverse plane. MASONRY UNIT is brick:, tile, stone, glass block or C'oncrete block conforming to the requirements specified in Section 702. HOLLOW-MASONRY UNIT is a masonry unit whose net cross-sectional areas (solid area) in any plane parallel to the surface containing cores, cells or deep frogs is less than 75 percent of its gross cross-sectional area measured in the same plane.

As

SOLID-MASONRY UNIT is a masonry unit whose net cross-sectional area in any plane parallel to the surface containing the cores or cells is at least 75 percent of the gross cross-sectional area measured in the same plane. PRISM is an assemblage of masonry units and mortar with or without grout used as a test specimen for determining properties of the masonry.

REINFORCED MASONRY is that form of masonry construction in. which reinforcement acting in conjunction with the masonry is used to resist forces.

A' s

a

SHELL is the outer portion of a hollow masonry unit as placed in masonry. WALLS: BONDED WALL is a masonry wall in which two or more wythes are bonded to act as a structural unit.

NOTATIONS.

b

millimeter. effective area of masonry, square millimeter. = gross area of wall, square millimeter. = total area of special horizontal reinforcement through wall frame joint, square millimeter. = net area of masonry section bounded by wall thickness and length of section in direction of shear force considered, square millimeter. area oftension (pullout) cone of embedded anchor bolt projected onto surface of masonry, square millimeter. = effective cross-sectional area of reinforcement in column or flexural member, square millimeter. effective area of reinforcement, square millimeter = total cross-sectional area of rectangular tie reinforcement for confined core, square millimeter. area of reinforcement required for shear reinforcement perpendicular to longitudinal reinforcement, square millimeter. effective cross-sectional area of compression reinforcement in flexural member, square millimeter. depth of equivalent rectangular stress block:, millimeter. nominal shear strength of anchor bolt, kilonewtons. allowable tensile force on anchor bolt, kilo newtons nominal tensile strength of anchor bolt, kilonewtons. allowable shear force on anchor bolt, kilonewtons effective width of rectangular member or width of flange for T and I sections, millimeter


1

GENERAL

factored shear force supported by anchor bolt, kilonewtons. = computed tensile force on anchor belt, kilonewtons. = factored tensile force supported by anchor bolt, kilonewtons. = computed shear force on anchor bolt, kilonewtons. = width ofweb in Tor I section, millimeter. = nominal shear strength coefficient as obtained from Table 708-2. = distance from neutral axis to extreme fiber, millimeter. = dead loads, or related internal moments and forces. = distance from compression face of flexural member to centroid oflongitudinal tensile reinforcement,millimeter. = diameter of reinforcing bar, millimeter. diameter of largest beam longitudinal reinforcing bar passing through, or anchored in, a joint, millimeter. diameter of largest pier longitudinal reinforcing bar passing through a joint, millimeter. = load effects of earthquake. or related internal moments and forces. modulus of elasticity of masonry, MPa. = eccentricity ofPufi millimeter. = maximum usable compressive strain of masonry. = loads due to weight and pressure of fluids or related moments and forces. allowable average axial compressive stress in columns for centroidally applied axial load only, MPa. allowable flexural compressive stress in members subjected to bending load only, MPa. = allowable bearing stress in masonry, MPa. = allowable stress in reinforcement, MPa. = allowable compressive stress in column reinforcement, MPa. = allowable flexural tensile stress in masonry, MPa. = allowable shear stress in masonry, MPa. computed axial compressive stress due to design axial load, MPa. computed flexural stress in extreme fiber due to design bending loads only, MPa. = computed compressive stress due to dead load only, MPa. = modulus of rupture, MPa. = computed stress in reinforcement due to design loads, MPa. = computed shear stress due to design load, MPa. = tensile yield stress of reinforcement, MPa.

= tensile yield stress of horizontal

=

c D

d

E

F

F" fa

G H H

.i K k L

Mill

Mser

reinforcement, MPa. specified compressive strength of grout at age of 28 days, MPa. = specified compressive strength of masonry at age of 28 days, MPa. = shear modulus of masonry, MPa. = loads due to weight and pressure of soil, water in soil or related internal moments and forces. height of wall between points of support, millimeter beam depth, millimeter. = cross-sectional dimension of grouted core measured center to center of confining = pier depth in plane of wall frame, millimeter. effective height of wall or column, millimeter. = moment of inertia about neutral axis of cross 4 sectional area, mm = effective moment of inertia, mm4. = gross, cracked moment of inertia of wall cross 4 section, mm = ratio or distance between centroid of flexural compressive forces and centroid of tensile

forces of depth, d.

= reinforcement cover or clear spacing,

whichever is less, millimeter. = ratio of depth of compressive stress in flexural member to depth, d. ~ live loads, or related internal moments and forces. = length of wall, millimeter. = length of wall or segment, millimeter. = embedment depth of anchor bolt, millimeter. • = anchor bolt edge distance, the least distance measured from edge of masonry to surface of anchor bolt. millimeter. = required development length of reinforcement, millimeter. = design moment, kN-m.

= maximum moment in member at stage

deflection is computed, kN-m.

= moment capacity of compression reinforcement in flexural member about centroid oftensile force, kN-m. nominal cracking moment strength in masonry, kN-m. = moment of compressive force in masonry about centroid of tensile force in reinforcement, kN-m. nominal moment strength, kN-m. moment of tensile force in reinforcement about centroid of compressive force in masonry, kN-m. = service moment at midheight of panel, including PA effects. kN-m. factored moment, kN-m.


MASONRY

7-4

n.

= modular ratio.

Po

=EIE $ m

= design axial load, kilonewtons. = allowable centroidal axial load for reinforced

P" P,q

r

S S

T t

u u

w

masonry columns, kilonewtons. nominal balanced design axial strength, kilo newtons. = load from tributary floor or roof area, kilonewtons. = nominal axial strength in masonry, kilo newtons. nominal axial load strength in masonry without flexure, kilonewtons. = factored axial load, kilonewtons. = factored load from tributary floor or roof loads, kilonewtons. = factored weight ofwall tributary to section I.jnder consideration, kilonewtons. weight of wall tributary to section under consideration, kilonewtons. = radius of gyration (based on specified unit dimensions or Tables 710-1, 710-2 and 710-3), millimeter. = ratio of area ofreinforcing bars cut offto total area of reinforcing bars at the section. = section modulus, mm3 . = spacing of stirrups or of bent bars in direction parallel to that of main reinforcement, millimeter. = effects oftemperature, creep, shrinkage and differential settlement. effective thickness of wythe, wall or column, millimeter. = required strength to resist factored loads, or related internal moments and forces. = bond stress per unit of surface area of reinforcing bar, MPa. = total design shear force, kilonewtons. total horizontal joint shear, kilonewtons. = nominal shear strength of masonry, kilonewtons == nominal shear strength, kilonewtons. = nominal shear strength of shear reinforcement, kilonewtons. =required shear strength in masonry, kilonewtons. = wind load, or related internal moments in forces. = factored distributed lateral load. = horizontal deflection at mid height under factored load, millimeter. deflection due to factored loads, millimeter. = ratio ofarea of flexural tensile reinforcement, A., to area bd. = reinforcement ratio producing balanced strain conditions.

Lo

"if 'm
ratio of distributed shear reinforcement on plane perpendicular to plane of A.nv. = sum of perimeters of all longitudinal reinforcement, millimeter. = square root of specified strength of masonry at the age of 28 days, MFa. strength-reduction factor.

SECTION 702 - MATERIAL STANDARDS 702.1 QUALITY. Materials used in masonry shall conform to the requirements stated herein. If no requirements are specified in this section for a material, quality shall be based on generally accepted good practice, subject to the approval of the building official. Reclaimed or previously used masonry units shall meet the applicable requirements as for new masonry units of the same material for their intended use.

702.2 STANDARDS OF QUALITY. The standards listed below labeled a "UBC Standard" are also listed in Chapter 35, Part IT of UBC, and are part of this code. The other standards listed below are recognized standards. See Sections 3503 and 3504 ofUBC.

1.

Aggregates.

1.1 1.2

ASTM CI44, Aggregates for Masonry Mortar ASTM C404, Aggregates for Grout

2.

Cement.

2.1

ASTM C91-93, Cement, Masonry. (plastic cement conforming to the requirements ofUBC Standard 25 1 may be used in lieu of masonry cement when it also conforms to ASTM C 91-93). . 2.2 ASTM C 150, Portland Cement 2.3 ASTM C270

3.

Lime.

3.1 ASTM C 5-79, Quicklime for Structural Purposes 3.2 ASTM C 207-91, Hydrated Lime for Masonry Purposes. When Types N and NA hydrated lime are used in masonry mortar, they shall comply with the provisions of UBC Standard ASTM C 270-95,


1 MATERIAL STANDARDS

Section 21.1506.7, requirement.

excluding

the

plasticity

4.

Masonry units of clay or shale.

4.1 4.2 4.3 4.4

ASTM C 34, Structural Clay Load-bearing Wall Tile ASTM C 56, Structural Clay NOnload-bearing Tile ASTM C 62-87, Building Brick (solid units) ASTM C 126, Ceramic Glazed Structural Clay Facing Tile, Facing Brick and Solid Masonry Units. Load-bearing glazed brick shall conform to the weathering and structural requirements of ASTM C 73-85, Section 21.106, Facing Brick ASTM C 216-86, Facing Brick (solid units) ASTM C 90-85, Hollow Brick ASTM C 67, Sampling and Testing Brick and Structural Clay Tile ASTM C 212, Structural Clay Facing Tile ASTM C 530, Structural Clay Non-Load bearing Screen Tile.

4.5 4.6 4.7 4.8 4.9

5.

Masonry units of concrete.

5.1 ASTM C 55-85, Concrete Building Brick 5.2 ASTM C 90-85; Hollow and Solid Load-bearing Concrete Masonry Units . 5.3 ASTM C 129-85, Non-load bearing Concrete Masonry Units 5.4 ASTM C 140, Sampling and Testing Concrete Masonry Units 5.5 ASTM C 426, Standard Test Method for Drying Shrinkage of Concrete Block

6.

7-5

7.2

All such items not fully embedded in mortar or grout shall either be corrosion resistant or shall be coated after fabrication with copper, zinc or a metal having at least equivalent corrosion-resistant properties.

8.

Mortar.

8.1

ASTM C 270-95, Mortar for Unit Masonry and Reinforced Masonry other than Gypsum 8.2 ASTM C 270, Field Tests Specimens for Mortar 8.3 ASTM C 780, Standard Test Method for Flexural Bond Strength ofMortar Cement

9.

Grout.

9.1

ASTM C 1019-84, Method of Sampling and Testing Grout 9.2 ASTM C 476-83, Grout for Masonry

10.

Reinforcement.

10.1 ASTM A 82, Part I, Joint Reinforcement for Masonry 10.2 ASTM A 615, A 616, A 617, A 706, A 767 and A 775, Deformed and Plain Billet-steel Bars, Rail-steel Deformed and Plain Bars, Axle-steel Deformed and Plain Bars, and Deformed Low-alloy Bars for Concrete Reinforcement 10.3 ASTM A 4%, Part n, Cold-drawn Steel Wire for Concrete Reinforcement

Masonry units of other materials.

6.1

Calcium silicate. ASTM C 73-85, Calcium Silicate Face Brick (Sand lime Brick) 6.2 ASTM C 216, C 62 or C 652, Unburned Clay Masonry Units and Standard Methods of Sampling and ASTM C 67, Testing Unburned Clay Masonry Units 6.3 ACI-704, Cast Stone 6.4 ASTM E 447-84, Test Method for Compressive Strength ofMasonry Prisms

.7.

Connectors.

7.1

Wall ties and anchors made from steel wire shall conform to UBC Standard 21-10, Part n, and other steel wall ties and anchors shall conform to A36 in accordance with UBC Standard 22-1. Wall ties and anchors made from copper, brass or other nonferrous metal shall have a minimum tensile yield strength of 207Mpa


MASONRY

7-6

SECTION 703 - MORTAR AND

GROUT

placement under eXlstmg field conditions, without segregation. Grout shall be specified by one of the following methods: 1.

Proportions of ingredients and any additives shall be based on laboratory or field experience with the grout ingredients and the masonry units to be used. The grout shall be specified by the proportion of its constituents in terms of parts by volume, or

2.

Minimum compressive strength which will produce the required prism strength, or

3.

Proportions by grout type shall be used as given in Table 703-2.

703.1 GENERAL. Mortar and grout shall comply with the provisions of this section. Special mortars, grouts or bonding systems may be used, subject to satisfactory evidence of their capabilities when approved by the building official.

703.2 MATERIALS. Materials used as ingredients in mortar and grout shall conform to the applicable requirements in Section 702. Cementitious materials for grout shall be one or both of the following: lime and portland cement. Cementitious materials for mortar shall be one or more of the following: lime, masonry cement, portland cement and mortar cement. Cementitious materials or additives shall not contain epoxy resins and derivatives, phenols, asbestos fibers or fire clays. Water used in mortar or grout shall be clean and free of del~terious amounts of acid, alkalies or organic material or other harmful substances.

703.3 MORTAR. 7(13.3.1 General. Mortar shall consist of a mixture of .:cmetitious materials and aggregate to which sufficient water and approved additives, if any, have been added to achieve a workable, plastic consistency.

703.5 ADDITIVES AND ADMIXTURES. 703.5.1 General. Additives and admixtures to mortar or grout shall not be used unless approved by the building official. 703.5.2 Air entrainment. Air-entraining substances shall not be used m mortar or grout unless tests are conducted to determine compliance with the requirements ofthis code. 703.5.3 Colors. Only pure mineral oxide, carbon black or synthetic colors may be used. Carbon black shall be limited to a maximum of3 percent ofthe weight of the cement.

703.3.2 Selecting proportions. Mortar with specified proportions of ingredients that differ from the mortar proportions of Table 703-1 may be approved for use when it is demonstrated by laboratory or field experience that this mortar with the specified proportions of ingredients, when combined with the masonry units to be used in the structure, will achieve the specified compressive strength I'IIl" Water content shall be adjusted to provide proper workability under existing field conditions. When the proportion of ingredients is not specified, the proportions by mortar type shall be used as given in Table 703-1.

703.4 GROUT. 703.4.1 ~neraL Grout shall consist of a mixture of cementitious materials and aggregate to which water has been added such that the mixture will flow without ::;egrtgation of the constituents. The specified compressive strength ofgroutJ'g, shall not be less than 13.8 MPa 703.4.2 Selecting proportions. Water content shall be adjusted to provide proper workability and to enable proper


7-7

CONSTRUCTION

SECTION 704 - CONSTRUCTION

EXCEPTION:

704.1 GENERAL.

Dry mixes for mortar and gmll! which are blended in the factory and mixed at the job site shall be mixed in mechanical mixers until workable, but 110t to exceed 10 minutes.

Masonry shall be constructed according to the provision of this section.

704.3 PLACING MASONRY UNITS.

704.2 MATERIALS: HANDLING, STORAGE AND PREPARATION.

704.3.1 Mortar. The mortar shall be sufficiently plastic and units shall be placed with sufficient pressure to extrude mortar from the joint and produce a tight joint. Deep furrowing which produces voids shall not be used.

All materials shall comply with applicable requirements of Section 702. Storage, handling and preparation at the site shall conform also the following:

The initial bed joint thickness shall not be less than 6mm or more than 25 mm; subsequent bed joints shall not be less than 6 mm or more than 16mm in thickness.

Masonry materials shall be stored so that at the time of use the materials are clean and structurally suitable for the intended use.

.., .... 3.

704.3.2 Surfaces. Surfaces to be in contact with mortar or grOllt shall be clean and free of deleterious materials.

All metal reinforcement shall be free from loose rust and other coatings that would inhibit reinforcing bond. At the time of laying, burned clay units and sand lime units shall have an initial rate of absorption not exceeding 1.6 liter per square meter during a period of one minute. In the absorption test, the surface of the unit shall be held 3mm below the surface of the water.

4.

Concrete masonry units shall not be wetted unless otherwise approved.

5.

Materials shall be stored in a manner such that deterioration or intrusion of foreign materials is prevented and that the material will be capable of meeting applicable requirements at the time of mixing or placement.

6.

The method of measuring materials for mortar and grout shall be such that proportions of the materials can be controlled.

7.

Mortar or grout mixed at the job site shall be mixed for a period of time not less than three minutes or more than 10 minutes in a mechanical mixer with the amount of water required to provide the desired workability Hand mixing of small amounts of mortar is permitted. Mortar may be re-tempered. Mortar or grout which has hardened or stiffened due to hydration of the cement shall not be used. In no case shall mOltar be used two and one-half hours, nor grout used one and one half hours, after the initial mixing water has been added to the dry mgredients at the jobsitc.


704.3.3 Solid masonry units. Solid masonry units shall have full head and bed joints. 704.3.4 Hollow-masonry units. All head and bed joints shall be filled solidly with mortar for a distance in from the face of the unit not less than the thickness of the shell. Head joints of open-ends units with beveled ends that are to be fully grouted need not be mortared. The beveled ends shall form a grout key which permits grout within J6mIIlaof the face of the unit. The units sha1l be tightly butted to prevent leakage of grout.

704.4

REINFORCEMENT PLACING.

Reinforcement details shall conform to the requirements of this chapter. Metal reinforcement shall be located in accordance with the plans and specifications. Reinforcement shall be secured against displacement prior to grouting by wire positioners or other suitable devices at intervals not exceeding 200 bar diameters. Tolerances for the placement of reinforcement in walls and flexural elements shall be plus or minus 12.7 mm for d equal to 200 mm or less, 25 mm for d equal to 600 mm or less but greater than 200 mm, and 32 mm for d greater than 600mm Tolerance for longitudinal location of reinforcement shall be± 51 mm

of


MASONRY

704.5 GROUTED MASONRY. 704.5.1 General Conditions. Grouted masonry shall be constructed in such a manner that all elements of the masonry act together as a structural element. Prior to grouting, the grout space shall be clean so that all spaces to be filled with grout do not contain mortar proj ections greater than 12.7 mm, mortar droppings or other foreign material. Grout shall be placed so that all spaces designated to be grouted shall be filled with grout and the grout shall be confined to those specific spaces. Grout materials and water content shall be controlled to provide adequate fluidity for placement without segregation ofthe constituents, and shall be mixed thoroughly. The grouting of any section of wall shall be completed in one day with no interruptions greater than one hour. Between grout pours, a horizontal construction joint shall be formed by stopping all wythes at the same elevation and with the grout stopping a minimum of 38 mm below a mortar joint, except the top of the wall. Where bond beams o~cur, the grout pour shall be stopped a minimum of 12.7 mm below the top of the masonry. Size and height limitations of the grout space or cell shall not be less than shown in Table 704-1. Higher grout pours or smaller cavity widths or cell size than shown in Table 704-1 may be used when approved, if it is demonstrated that grout spaces will be properly filled. Cleanouts shall be provided for all grout pours over 1524 mm in height. Where required, cleanouts shall be provided in the bottom course at every vertical bar but shall not be spaced more than 813 mm on center for solidly grouted masonry. When cleanouts are required, they shall be sealed after inspection and before grouting. Where cleanouts are not provided, special provisions must be made to keep the bottom and sides of the grout spaces, as well as the minimum total clear area as required by Table 704-1, clean and clear prior to grouting.

704.5.2 Construction requirements. Reinforcement shall be placed prior to grouting. Bolts shall be accurately set with templates or by approved equivalent means and held in place to prevent dislocation during grouting. Segregation of the grout materials and damage to the masonry shall be avoided during the grouting process. Grout shall be consolidated by mechanical vibration during placement before loss of plasticity in a manner to fill the grout space. Grout pours greater than 300 mm in height shall be reconsolidated by mechanical vibration to minimize voids due to water loss. Grout pours 300 rom or less in height shall be mechanically vibrated or puddled. In one-storey buildings having wood-frame exterior walls, foundations not over 600 mm high measured from the top of the footing may be constructed of hollow-masonry units laid in running bond without mortared head joints. Any standard shape unit may be used, provided the masonry units permit horizontal flow of grout to adjacent units. Grout shall be solidly poured to the full height in one lift and shall be puddled or mechanically vibrated. In nonstructural elements which do not exceed 2440 mm in height above the highest point of lateral support, including fireplaces and residential chimneys, mortar of pouring consistency may be substituted for grout when the masonry is constructed and grouted in pours of 300 mm or less in height. In multiwythe grouted masonry, vertical barriers of masonry shall be built across the grout space the entire height of the grout pour and spaced not more than 9144 rom horizontally. The grouting of any section of wall between barriers shall be completed in one day with no interruption longer than one hour.

704.6 ALUMINUM EQUIPMENT. Grout shall not be handled nor pumped utilizing aluminum equipment unless it can be demonstrated with the materials and equipment to be used that there will be no deleterious effect on the strength ofthe grout.

704.7 JOINT REINFORCEMENT.

Units may be laid to the full height of the grout pour and grout shall be placed in a continuous pour in grout lifts not exceeding 1830 mm. When approved, grout lifts may be greater than 1830 mm if it can be demonstrated the grout spaces can be properly filled.

Wire joint reinforcement used in the design as principal reinforcement in hollow-unit construction shall be continuous between supports unless splices are made by lapping:

All cells and spaces containing reinforcement shall be filled with grout.

2.

1.

Fifty-four wire diameters in a grouted cell, or Seventy-five wire diameters in the mortared bed joint, or


CONSTRUCTION & QUALITY ASSURANCE

3.

4.

In alternate bed joints of running bond m?sonry a distance not less than 54 diameters plus twice the spacing of the bed ioints, or As required by calculation and specific location in areas of minimum stress, such as points of inflection.

7-9

SECTION 705 - QUALITY ASSURANCE 705.1 GENERAL.

Side wires shall be deformed and shall conform to UBC Standard 21-10, Part 1, Joint Reinforcement for Masonry.

Quality assurance shall be provided to ensure that materials, construction and workmanship are in compliance with the plans and specifications, and the applicable requirements of this chapter. When required, inspection records shall be maintained and made available to the building officiaL

705.2 SCOPE. Quality assurance shall include, but is not limited to, assurance that: 1.

2.

3.

4.

705.3

Masonry units, reinforcement, cement, lime, aggregate and all other materials meet the requirements of the applicable standards of quality and that they are properly stored and prepared for use. Mortar and grout are properly mixed using specified proportions of ingredients. The method of measuring materials for mortar and grout shall be such that proportions of materials are controlled. Construction details, procedures and workmanship are in accordance with the plans and specifications. Placement, splices and reinforcement sizes are in accordance with the provisions of this chapter and the plans and specifications.

COMPLIANCE withFm'

705.3.1 General. Compliance with the requirements for the specified compressive strength of masonry I'm shall be in accordance with one of the sections in this subsection. 705.3.2 Masonry prism testing. The compressive strength of masonry determined in accordance with UBC Standard 21-17 for each set of prisms shall equal or exceed I'm" Compressive strength of prisms shall be based on tests at 28 days. Compressive strength at seven days or three days may be used provided a relationship between seven-day and three-day and 28-day strength has been established for the project prior to the start of construction. Verification by masonry prism testing shall meet the following:

1.

A set offive masonry prisms shall be built and tested in accordance with ASTM E 447 prior to the start of construction. Materials used for the construction of the prisms shall be taken from those specified to be used in the project. Prisms shall be constructed under the observation of the engineer or special

Nationai Struc~u'ral Code of the Philippines, Volume 1

7-10

MASONRY

inspector or an approved agency and tested by an approved agency. 2.

When full allowable stresses are used in design, a set of three prisms shall be built and tested during construction in accordance with ASTM E 447 for each 465 m2 of wall area, but not less than one set of three masonry prisms for the project.

3.

When one half the allowable masonry stresses are used in design, testing during construction is not required. A letter of certification from the supplier of the materials used to verify the f m in accordance with Section 705.3 .2, Item 1, shall be provided at the time of, or prior to, delivery of the materials to the job site to ensure the materials used in construction are representative of the materials used to construct the prisms prior to construction.

1.

When full allowable stresses are used in design, units shall be tested prior to construction and test units during construction for each 465 m2 of wall area for compressive strength to show compliance with the compressive strength required in Table 705-1; and

EXCEPTION: Prior to the start ofconstruction, prism testing may be used in lieu of testing the unit strength. During constroction, prism testing may also be used in lieu of testing the unit strength and the grout as reqUired by Section 705.3.4, Item 4. 2.

When one half the allowable masonry stresses are used in design, testing is not required for the units. A letter of certification from the manufacturer of the units shall be provided at the time of, or prior to, delivery ofthe units to the job site to assure the units comply with the compressive strength required in Table 705-1; and

3.

Mortar shall comply with the mortar type required in Table 70S-I; and.

4.

When full stresses are used in design for concrete masonry, grout shall be tested tor each 465 m2 of wall area, but not less than one test per project, to show compliance with the compressive strength required in Table 705-1, Footnote 4.

5.

When one half the allowable stresses are used in design for concrete masonry, testing is not required for the grout. A letter of certification from the supplier of the grout shall be provided at the time of, or prior to, delivery of the grout to the job site to assure the grout complies with the compressive strength required in Table 705-1, Footnote 4; or

6.

When full allowable stresses are used in design for clay masonry, grout proportions shall be verified by the engineer or special inspector or an approved agency to conform with Table 703-2.

7.

When one half the allowable masonry stresses are used in design for clay masonry, a letter of certification from the supplier of the grout shall be provided at the time of, or prior to. delivery of the grout to the job site to assure the grout contorms to the proportions of Table 703-2.

705.3.3 Masonry prism test record. Compressive strength verification by masonry prism test records shall meet the following: 1.

A masonry prism test record approved by the building official of at least 30 masonry prisms which were built and tested in accordance with ASTM E 447. Prisms shall have been constructed under the observation of an engineer or special inspector or an approved agency and shall have been tested by an approved agency.

2.

Masonry prisms shall be representative of the corresponding construction.

3.

The average compressive strength of the test record shall equal or exceed 1.33 f m'

4.

When full allowable stresses are used in design, a set of three masonry prisms shall be built during construction in accordance with ASTM E 447 for each 465 m2 of wall area, but not less than one set of three prisms for the project.

5.

When one half the allowable masonry stresses are used in design, field testing during construction is not required. A letter of certification from the supplier of the materials to the job site shall be provided at the time of, or prior to, delivery of the materials to assure the materials used in construction are representative of the materials used to develop the prism test record in accordance with Section 705.3.3, Item 1.

705.3.4 Unit strength method. Verification by the unit strength method shall meet the following:

705.3.5 Testing prisms from constructed masonry. When approved by the building official, acceptance of masonry which does not meet the requirements of Section


QUALITY ASSURANCE &

GENERAL DESIGN REQUIREMENTS

705.3.2, 705.3.3 or 705.3.4 shall be permitted to be based on tests of prisms cut from the masonry construction in accordance with the following:

1.

2.

3.

A set of three masonry prisms that are at least 28 days old shall be saw cut from the masonry for each 465 m2 of the wall area that is in question but not less than one set of three masonry prisms for the project. The length, width and height dimensions of the prisms shall comply with the requirements of ASTM E 447. Transporting, preparation and testing of prisms shall be in accordance with ASTM E 447. The compressive strength of prisms shall be the value calculated in accordance with UBC Standard 21-17, Section 21.1707.2, except that the net cross sectional area of the prism shall be based on the net mortar bedded area. Compliance with the requirement for the specified compressive strength of masonry, j'm. shall be considered satisfied provided the modified compressive strength equals or exceeds the specified I'm. Additional testing of specimens cut from locations in question shall be permitted.

705.4 MORTAR TESTING. When required, mortar shall be tested in accordance with ASTMC270.

705.5 GROUT TESTING. When required, grout shall be tested in accordance with ASTM C 476-83.

7-11

SECTION 706 - GENERAL DESIGN REQUIREMENTS 706.1

GENERAL.

706.1.1 ~ope. The design of masonry structures shall comply with the working stress design provisions of Section 707, or the strength design provisions of Section 708 or the empirical design provisions of Section 709, and with the provisions of this section. Unless otherwise stated, all calculations shall be made using or based on specified dimensions. 706.1.2 Plans. Plans submitted for approval !ball describe the required design strengths of masonry materials and inspection requirements for which all parts of the structure were designed, and any load test requirements. 706.1.3 Design loads. See Chapter 2 for design loads. 706.1.4 Stack bond. In bearing and nonbearing walls, except veneer walls, if less than 75 percent of the units in any transverse vertical plane lap the ends of the units below a distance less than one half the height of the unit, or less than one fourth the length of the unit, the wall shall be considered laid in stack bond. 706.1.5 Multiwytbe walls. 706.5.1 General. All wythes of multiwythe walls shall be bonded by grout or tied together by corrosion-resistant wall ties or joint reinforcement conforming to the requirements of Section 702, and as set forth in this section. 706.5.2 Wall ties in cavity wall eonstmetion. Wall ties . shall be of sufficient length· to engage all wythes. The portion of the wall ties within the wythe shall be completely embedded in mortar or grout. The ends of the wall ties shall be bent to 9O-degree angles with an extension not less than 51 nun long. Wall ties not completely embedded in mortar or grout between wythes shall be a single piece with each end engaged in each wythe. There shall be at least one 9.5 nun diameter wall tie for each 0.42 m2 of wall area. For cavity walls in which the width of the cavity is greater than 75 mm, but not more than 115 nun, at least one 9.5 nun diameter wall tie for each 0.28 2 m of wall area shall be provided. Ties in alternate courses shall be staggered. The maximum vertical distance between ties shall not exceed 610 nun and the maximum horizontal distance between ties shall not exceed 914 nun.

National Sbuctural Code of the PbiDppines. Volume 1

MASONRY

7-12

Additional ties spaced not more than 914 rom apart shall be provided around openings within a distance of 305 rom from the edge of the opening. Adjustable wall ties shall meet the following requirements: 1.

2.

ties or joint reinforcement and any exposed face. The thickness of grout or mortar between masonry units and joint reinforcement shall not be less than 6mm, except that 6rom .or smaller diameter reinforcement or bolts may be placed in bed joints which are at least twice the thickness of the reinforcement or bolts.

2

One tie shall be provided for each 0.16 m of wall area. Horizontal and vertical spacing shall not exceed 406 mm. Maximum misalignment of bed joints from one wythe to the other shall be 32 mm. Maximum clearance between the connecting parts of the tie shall be 1.6 mm. When used, pintle ties shall have at least two 4.8 rom diameter pintle legs.

Wall ties of different size and spacing that provide equivalent strength between wythes may be used. 706.1.5.3 Wall ties for grouted multiwythe construction. Wythes of multiwythe walls shall be bonded together with at least 4.8 mm diameter steel wall tie for each 0.19 m2 of area. Wall ties of different size and spacing that provide equivalent strength between wythes may be used. 706.1.5.4 Joint reinforcement. Prefabricated Jomt reinforcement for masonry wall shall have at least one cross 2 wire of at least NO.9 gage steel for each 0.19 m of wall area. The vertical spacing of the joint reinforcement shall not exceed 406 mm. The longitudinal wires shall be thoroughly embedded in the bed joint mortar. The joint reinforcement shall engage all wythes. Where the space between tied wythes is solidly filled with grout or mortar, the allowable stresses and other provisions for masonry bonded walls shall apply. Where the space is not filled, tied walls shall conform to the allowable stress, lateral support, thickness (excluding cavity), height and tie requirements for cavity walls. 706.1.6 Vertical Support. Structural members providing vertical support of masonry shall provide a bearing surface on which the initial bed joint shall not be less than 6mm or more than 25mm in thickness and shall be of noncombustible material, e~cept where masonry is a nonstructural decorative feature or wearing surface.

706.1.9 Pipes and conduits embedded in masonry. Pipes or conduit shall not be embedded in any masonry in a manner that will reduce the capacity of the masonry to less than that necessary for required strength or required fire protection. Placement of pipes or conduits in unfilled cores of hollow unit masonry shall not be considered as embedment.

EXCEPTIONS: 1.

Rigid electric conduits may be embedded in structural masonry when their locations have been detailed on the approved plan .

2.

Any pipe or conduit may pass vertically or horizontally through any masonry by means of a sleeve at least large enough to pass any hub or coupling 011 the pipeline. Such sleeves shall not be placed closer than three diameters, center to center. nor shall they unduly impair the strength of constnlction.

706.1.10 Load Test. When a load test is required, the member or portion ofthe structure under consideration shall be subjected to a superimposed load equal to twice the design live load plus one half of the dead load. This load shall be left in position for a period of 24 hours before removal. If, during the test or upon removal of the load, the member or portion of the structure shows evidence of failure, such changes or modifications as are necessary to make the structure adequate for the rated capacity shall be made; or where approved, a lower rating shall be established, A flexural member shall be considered to have passed the test if the maximum deflection D at the end of the 24-hour period does not exceed the value of Formula (706-1) or (706-2) and the beams and slabs show a recovery of at least 75 percent of the observed deflection within 24 hours after removal of the load.

706.1.7 Lateral support. Lateral support of masonry may be provided by cross walls, columns, pilasters, counter forts or buttresses where spanning horizontally or by floors, beams, girts or roofs where spanning vertically. The clear distance between lateral supports of a beam shall not exceed 32 times the least width of the compression area.

(706-1)

e D

4,00Ot

706.1.8 Protection of ties and joint reinforcement. A minimum of 16mm mortar cover shall be provided between


(706-2)


7-13

706.1.11 Reuse af masonry units. Masonry units may be reused when clean, whole and conforming to the other requirements of this section. All structural properties of masonry of reclaimed units shall be determined by approved test

706.1.12.3 Special provisions for Seismic Zone 4. All masonry structures built in Seismic Zone 4 shall be designed and constructed in accprdance with requirements for Seismic Zone 2 and with the following additional requirements and limitations :

706.1.12 Special provisions in area of seismic risk.

1. Column reinforcement ties. In columns that are stressed by tensile or compressive axial overturning forces from seismic loading, the spacing of column ties shall not exceed 203 mm for the full height of such columns. In all other columns, ties shall be spaced a maximum of 203 mm in the tops and bottoms of the columns for a distance of one sixth of the clear column height, 457 nun, or the maximum column cross-sectional dimension, whichever is greater. Tie spacing for the remaining column height shall not exceed the lesser of 16 bar diameters, 48 tie diameters, the least column cross-sectional dimension, or 457 mm.

706.1.12.1 General. Masonry structures constructed in the seismic zones shown in Figure 208-1 shall be designed in accordance with the design requirements of this chapter and the special provisions for each seismic zone given in this section. 706.1.12.2 Special proVISIons for Seismic Zone 2. Masonry structures in Seismic Zone 2 shall comply with the following special provisions : L

Columns shall be reinforced as specified in Sections 706.3.6,706.3.7 and 701.2.13.

2.

Vertical waH reinforcement of at least 130 mm2 in cross-sectional area shall be provided continuously from support to support at each corner, at each side of each opening, at the ends of walls and at maximum spacing of 1219 mm apart horizontally throughout walls. .

..

.J.

4.

5.

Horizontal wall reinforcement not less than 130 mm2 in cross-sectional area shall be provided (1) at the bottom and top ofwall openings and shall extend not less than 610 mm or less than 40 bar diameters past the opening, (2) continuously at structurally connected roof and floor levels and at the top of walls, (3) at the bottom of walls or in the top of foundations when doweled in walls, and (4) at maximum spacing of 3048 mm unless uniformly distributed joint reinforcement is provided. Reinforcement at the top and bottom of openings when continuous in walls may be used in determining the maximum spacing specified in Item 1 ofthis paragraph. Where stack bond is used, the minimum horizontal reinforcement ratio shall be O.OOO7bt. This ratio shall be satisfied by uniformly distributed joint reinforcement or by horizontal reinforcement spaced not over 1219 mm and fully embedded in grout or mortar. The following materials shall not he used as pa..-t of the vertical or lateral load-resisting system: Type 0 mortar, masonry cement, plastic cement, non-load bearing masonry units and glass blud:

Column ties shall terminate with a minimum. 135-degree hook with extensions not less than six bar diameters or 102 mm. Such extensions shall engage the longitudinal column reinforcement and project into the interior of the column. Hooks shall comply with Section 707.2.2.5, Item 3.

EXCEPTION: Where ties are placed in horizontal bed joints, hooks shall consist of a 90-degree bend having an inside radius of not less thall four tie diameters plus an extension of 32 tie diameters. 2.

Shear Walls.

•

2.1 Reinforcement. The portion of the reinforcement required to resist shear shall be uniformly distributed and shall be joint reinforcement, deformed bars or a combination thereof. The spacing of reinforcement in each direction shall not exceed oile half the length of the element, nor one half the height of the element, nor 1219 mm. Joint reinforcement used in exterior walls and considered in the determination of the shear strength of the member shall be hot-dipped galvanized in accordance with ASTM A 385 & A 641. Reinforcement required to resist in-plane shear shall be terminated with a standard hook as defined in Section 707.2.2.5 or with an extension of proper embedment length beyond the reinforcement at the end of the wall s~ion. The hook or extension may be turned up, down or horizontally. Provisions shall be made not to obstruct grout placement. Wall reinforcement terminating in columns ·or beams shall be fully anchored into these elements. 2.2 Bond. Multi wythe grouted masonry shear walls shall !>e designed with consideration of the adhesion bond

National Structural Code of the Philippines. Voh.me 1

7-14

MASONRY

strength between the grout and masonry units. When bond strengths are not known from previous tests, the bond strength shall be determined by tests. 2.3 WaD reinforcement. All walls shall be reinforced with both vertical and horizontal reinforcement. The sum of the areas of horizontal and vertical reinforcement shall be at least 0.002 times the gross cross-sectional area of the wall, and the minimum area of reinforcement in either direction shall not be less than 0.0007 times the gross cross-sectional area of the waiL The minimum steel requirements for Seismic Zone 2 in Section 706.1.12.3, Items 2 and 3, may be included in the sum. The spacing of reinforcement shall not exceed 1219 rum. The diameter of reinforcement shall not be less than 9.5 rum except that joint reinforcement may be considered as a part or all of the requirement for minimum reinforcement. Reinforcement shall be continuous around wall corners and through intersections. Only reinforcement which is continuous in the wall or element s~all be considered in computing the minimum area of 'reinforcement. Reinforcement with splices conforming to Section 707.2.2.6 shall be considered as continuous reinforcement. 2~4 Stack bond. Where stack bond is used, the minimum horizontal reinforcement ratio shall be 0.0015bt. Where open-end units are used and grouted solid, the minimum horizontal reinforcement ratio shall be O.OOO7bt.

Reinforced hollow-unit stacked bond construction which is part of the seismic-resisting system shall use open-end units so that all head joints are made solid, shall use bond beam units to facilitate the flow of grout and shall be grouted solid. 3. Type N mortar. Type N mortar shall not be used as part of the vertical-or lateral-load-resisting system. 4. Concrete abutting structural masoury. Concrete abutting structural masonry, such as at starter courses or at wall intersections not designed as true separation joints, shall be roughened to a full amplitude of 1.6 rum and shall be bonded to the masonry in accordance with the requirements of this chapter as if it were masonry. Unless keys or proper reinforcement is provided, vertical joints as specified in Section 706.1.4 shall be considered to be stack bond and the reinforcement as required for stack bond shall extend through the joint and be anchored into the concrete.·

706.2 WORK1NG STRESS DESIGN AND STRENGTH 'DESIGN REQUIREMENTS FOR UNREINFORCED AND REINFORCED MASONRY.

706.2.1 General. In addition to the requirements of Section 706.1, the design of masonry structures by the working stress design method and strength design method shall comply with the requirements of this section. Additionally, the design of reinforced masonry structures by these design methods shall comply with th~ requirements of Section 706.3. 706.2.2 Specified compressive strength of masonry. The allowable stresses for the design of masonry shall be based on value of1'm selected for the construction. Verification of the value of 1'm shall be based on compliance with Section 705.3. Unless otherwise specified, 1'm shall be based on 28-day tests. If other than a 28-day test age is used, the value off'", shall be as indicated in design drawings or specifications. Design drawings shall show the value off'", for which each part of the structure is designed. 706.2.3 EFFECTIVE THICKNESS. 706.2.3.1 Single-wythe walls. The effective thickness of single-wythe walls of either solid or hollow units is the specified thickness of the wall. 706.2.3.2 Multiwythe walls. The effective thickness of multiwythe walls is the specified thickness of the wall if the space between wythes is filled with mortar or grout. For walls with an open space between wythes, the effective thickness shall be determined as for cavity walls. 706.2.3.3 Cavity walls. Where both wythes of a cavity wall are axially loaded, each wythe shall be considered to act independently and the effective thickness of each wythe is as defined in Section 706.2.3. L Where only one wythe is axially loaded, the effective thickness of the cavity wall is taken as the square root of the sum of the squares of the specified thicknesses ofthe wythes. Where a cavity wall is composed of a single wythe and a multiwythe, and both sides are axially loaded, each side of the cavity wall shall be considered to act independently and the effective thickness of each side is as defined in Sections 706.2.3.1 and 706.2.3.2. Where only one side is axially loaded, the effective thickness of the cavity wall is the square root of the sum of the squares of the specified thicknesses of the sides. 706.2.3.4 Columns. The effective thickness for rectangular columns in the direction considered is the specified thickness. The effective thickness for non-rectangular columns is the thickness of the square column with the same moment of inertia about its axis as that about the axis considered in the actual column.


GENERAL DEsiGN REQUIREMENTS

706.2.4 Effective height. The effective height of columns and walls shall be taken as the clear height of members laterally supported at the top and bottom in a direction normal to the member axis considered. For members not supported at the top normal to the axis considered, the effective height is twice the height of the member above the support. Effective height less than clear height may be used ifjustified. 706.2.5 Effective area. The effective cross-sectional area shall be based on the minimum bedded area of hollow units, or the gross area of solid units plus any grouted area. Where hollow units are used with cells perpendicular to the direction of stress, the effective area shall be the lesser of the minimum bedded area or the minimum cross-sectional area. Where bed joints are raked, the effective area shall be correspondingly reduced. Effective areas for cavity walls shall be that ofthe loaded wythes. 706.2.6 Effective width of intersecting walls. Where a shear wall is anchored to an intersecting wall or walls, the width of the overhanging flange formed by the intersected wall on either side ofthe shear wall, which may be assumed working with the shear wall for purposes of flexural stiffness calculations, shall not exceed six times the thickness ·of the intersected wall. Limits of the effective flange may be waived if justified. Only the effective area of the wall parallel to the shear forces may be assumed to carry horizontal shear. 706.2.7 Distribution of concentrated vertical loads in walls. The length of wall laid up in running bond which may be considered capable of working 'at the maximum allowable compressive stress to resist vertical concentrated loads shall not exceed the center-to-center distance between such loads, nor the width of bearing area plus four times the wall thickness. Concentrated vertical loads shall not be assumed to be distributed across continuous vertical mortar or control joints unless elements designed to distribute the concentrated vertical loads are employed.

exceeded. A minimum bearing length of 102 rom shall be provided for lintels bearing on masonry. 706.2.10 Structural continuity. Intersecting structural eleIlJents intended to act as a unit shall be anchored together to resist the design forces. 706.2.11 Walls intersecting with floors and roofs. Walls shall be anchored to all floors, roofs or other elements which provide lateral support for the wall. Where floors or roofs are designed to transmit horizontal forces to walls, the anchorage to such walls shall be designed to resist the horizontal force. MODULUS 706.2.12 MATERIALS.

706.2.9 Vertical deflection. Elements supporting masonry shall be designed so that their vertical deflection will not exceed 1/600 of the clear span under total loads. Lintels shall bear on supporting masonry on each end such that allowable stresses in the supporting masonry are not

OF

ELASTICITY

OF

706.2.12.1 Modulus of elasticity of masonry. The moduli for masonry may be estimated as provided below. Actual values, where required, shall be established by test. The modulus of elasticity of masonry shall be determined by the secant method in which the slope of the line for the modulus of elasticity is taken from 0.05 i'm to a point on the curve at 0.33 i'm. These values are not to be reduced by one half as set forth in Section 707.1.2. Modulus of elasticity of clay or shale unit masonry.

Em = 750i'm, 20.5 GPa maximum

(706-3)

Modulus of elasticity of concrete unit masonry. £.", = 750i'm. 20.5 GPa maximum

(70614)

706.2.12.2 Modulus of elasticity of steel. Es = 200GPa

(706-5)

706.2.13 Shear modulus of masonry.

G 706.2.8 Loads on nonbearing walls. Masonry walls used as interior partitions or as exterior surfaces of a building which do not carry vertical loads imposed by other elements of the building shall be designed to carry their own weight plus any superimposed finish and lateral forces. Bonding or anchorage of nonbearing walls shall be adequate to support the walls and to transfer lateral forces to the supporting elements.

7-15

0.4 Em

(706-6)

706.2.14 Placement of embedded anchor bolts. 706.2.14.1 General. Placement requirements for plate anchor bolts, headed anchor bolts and bent bar anchor bolts shall be determined in accordance with this subsection. Bent bar anchor bolts shall have a hook with a 90-degree bend with an inside diameter of three bolt diameters, plus an extension of one and one half bolt diameters at the free end. Plate anchor bolts shall have a plate welded to the shank to provide anchorage equivalent to headed anchor bolts. The effective embedment depth lb for plate or headed anchor bolts shall be the length of embedment measured


,7·16

MASONRY

perpendicular from the surface of the masonry to the bearing surface of the plate or head of the anchorage, and 4. for bent bar anchors shall be the length of embedment measured perpendicular from the surface of the masonry to the bearing surface of the bent end minus one anchor bolt diameter. All bolts shall be grouted in place with at least 25mm of grout between the bolt and the masonry, except that 6.4 mm bolts may be placed in bed joints which area at least 12.7 mm in thickness, 706.2.14.2 Minimum edge distance. The minimum anchor bolt edge distance It.e measured from the edge of the masonry parallel with the anchor bolt to the surface of the anchor bolt shall be 38 mm, 706.2.14.3 Minimum embedment depth. The minimum embedment depth of anchor bolts 4. shall be four bolt diameters but not less than 51 mm.

The 706.3.4 Anchorage of flexural reinforcement. tension or compression in any bar at any section shall be developed on each, side of that section by the required development length. The development length. of the bar may be achieved by a combination of an embedment length, anchorage or, for tension only, hooks. Except at supports or at the free end of cantilevers, every, reinforcing bar shall be extended beyond the point at which it is no longer needed to resist tensile stress for a distance equal to 12 bar diameters or the depth of the beam, whichever is greater. No flexural bar shall be terminated in a tensile zone unless at least one ofthe following conditions is satisfied : 1.

2. The 706.2.14.4 Minimum spacing between bolts. minimum center·to-center distance between anchor bolts shall be four bolt diameters. 3. 706.2.15 Flexural resistance of cavity waUsa For cbmputing the flexural resistance of cavity walls, lateral loads perpendicular to the plane of the wall shall be distributed to the wythes according to their respective flexural rigidities.

706.3 WORKING STRESS DESIGN AND STRENGTH DESIGN REQUIREMENTS FOR REINFORCED MASONRY. 706.3.1 General. In addition to the requirements of Sections 706.1 and 706.2, the design of reinforced masonry structures by the working stress design method or the strength design method shall comply with the requirements of this section. 706.3.2 Plain bars. The use of plain bars larger than 6.4 mm in diameter is not permitted. 706.3.3 Spacing of longitudinal reinforcement. The clear distance between parallel bars, except in columns, shall not be less than the nominal diameter of the bars or 25 mm, except that bars in a splice may be in contact. This clear distance requirement applies to the clear distance between a contact splice and adjacent splices or bars. The clear distaftce between the surface of a bar and any surface of a masonry unit shall not be less than 6.4 mm for fine grout and 12.7 mm for coarse grout. Cross webs of hollow units may be used as support for horizontal reinforcement.

The shear is not over one half that permitted, including allowance for shear reinforcement where provided. Additional shear reinforcement in excess of that required is provided each way from the cutoff a distance equal to the depth of the beam. The shear reinforcement spacing shall not exceed dl8rb. The continuing bars provide double the area required for flexure at that point or double the perimeter required for reinforcing bond.

At least one third of the total reinforcement provided for negative moment at the support shall be extended beyond the extreme position of the point of inflection a distance sufficient to develop one half the allowable stress in the bar, not less than 1/16 of the clear span, or the depth d of the member, whichever is greater. Tensile reinforcement for negative moment in any span of a continuous restrained or cantilever beam, or in any member of a rigid frame, shall be adequately anchored by reinforcement bond, hooks or mechanical anchors in or through the supporting member. At least one third of the required positive moment reinforcement in simple beams or at the freely supported end of continuous beams shall extend along the same face of the beam into the support at least 152 mm. At least one fourth of the required positive moment reinforcement at the continuous end of continuous beams shall extend along the same face ofthe beam into the support at least 152 mm. Compression reinforcement in flexural members shall be anchored by ties or stirrups not less than 6.4mm in diameter, spaced not~farther apart than 16 bar diameters or 48 tie diameters, whichever is less. Such ties or stirrups shall be used throughout the distance where compression reinforcement is required.



706.3.5 Anchorage of shear reinforcement. Single, separate bars used as shear reinforcement shall be anchored each end by one of the following methods: Hooking tightly around the reinforcement through 180 degrees.

longitudinal

Embedment above or below the mid-depth of the beam on the compression side a distance sufficient to develop the stress in the bar for plain or deformed bars. By a standard hook, as defined in Section 707.2.2.5, considered as developing 52 MPa, plus embedment sufficient to develop the remainder of the stress to which the bar is subjected. The effective embedded length shall not be assumed to exceed the distance between the mid-depth of the beam and the tangent of the hook. The ends of bars forming a single U or multiple U stirrup shall be anchored by one of the methods set forth in Items 1 through 3 above or shall be bent through an angle of at least 90 degrees tightly around a longitudinal reinforcing bar not less in diameter than the stirrup bar, and shall project beyond the bend at least 12 stirrup diameters.

7-17

provided the total cross-sectional area of such smaller ties crossing a longitudinal plane is equal to that of the larger ties at their required spacing. 706.3.7 Column ancbor bolt ties. Additional ties shall be provided around anchor bolts which are set in the top of columns. Such ties shall engage at least four bolts or, alternately, at least four vertical column bars or a combination of bolts and bars totaling at least four. Such ties shall be located within the top 127 rom of the column and shall provide a total of 260 rom 2 or more in cross sectional area. The uppermost tie shall be within 51 mm of the top of the column. 706.3.8 Effective width b of compression area. In computing flexural stresses in walls where reinforcement occurs, the effective width assumed for running bond masonry shall not exceed six times the nominal wall thickness or the. center-to-center distance between reinforcement. Where stack bond is used, the effective width shall not exceed three times the nominal wall thickness or the center-to-center distance between reinforcement or the length of one unit, unless solid grouted open-end units are used.

The loops or closed ends of simple U or multiple U stirrups shall be anchored by bending around the longitudinal reinforcement through an angle of at least 90 degrees and project beyond the end of the bend at least 12 stirrup diameters. 706.3.6 Lateral ties. All longitudinal bars for columns shall be enclosed by lateral ties. Lateral support shall be provided to the longitudinal bars by the corner of a complete tie having an included angle of not more than 135 degrees or by a standard hook at the end of a tie. The corner bars shall have such support provided by a complete tie enclosing the longitudinal bars. Alternate longitudinal bars shall have such lateral support provided by ties and no bar shall be farther than 152 mm from such laterally supported bar. Lateral ties and longitudinal bars shall be placed not less than 38 mm and not more than 127 rom from the surface of the column. Lateral ties may be placed against the longitudinal bars or placed in the horizontal bed joints where the requirements of Section 706.1.8 are met. Spacing of ties shall not exceed 16 longitudinal bar diameters, 48 tie diameters or the least dimension of the column but not more than 457 mm. Ties shall be at least 6.4 mm in diameter for 20 rom or smaller longitudinal bars and at least 10 rom for longitudinal bars larger than 20 mm. Ties smaller than 10 mm may be used for longitudinal bars larger than 20 mm,

National structJP'81 Code of the Philippines, Volume 1

1-18

MASONRY

SECTION 707 - WORKING STRESS DESIGN OF MASONRY

strain distribution assumptions with all stresses elastic range as follows:

lfi

the

1.

Plane sections before bending remain plane after bending.

2.

Stress is proportional to strain.

3.

Masonry elements combine to form a homogenous member.

707.1 GENERAL. 707.1.1 Scope. The design of masonry structures using working stress design shall comply with the provisions of Section 706 and this section. Stresses in clay or concrete masonry under service loads shall not exceed the values given in this section.

707.1.5 Embedded anchor bolts. When quality 707.1.2 Allowable masonry stresses. assurance provisions do not include requirements for special inspection as prescribed in Section 701, the allowable stresses for masonry in Section 707 shall be reduced by one half. When one half allowable masonry stresses are used in Seismic Zone 4, the value ofI'm from Table 705-1 shall be limited to a maximum of 10 MPa for concrete masonry and 18 MPa for clay masonry unless the value ofI'm is verified b¥ tests in accordance with Section 705.3.4, Items 1 and 4 or 6. A letter of certification is not required. When one half allowable masonry stresses are used for design in Seismic Zones 4, the value ofj'm shall be limited to 10 MPa for concrete masonry and 18 MPa for clay masonry for Section 705.3.2, Item 3, and Section 705.3.3, Item 5, unless the value of I'm is verified during construction by the testing requirements of Section 705.3 .2, Item 2. A letter of certification is not required. 707.1.3 Minimum dimensions for masonry structures located in Seismic Zones 2 and 4. Elements of masonry structures located in Seismic Zones 2 and 4 shall be in accordance with this section. 707.1.3.1 Bearing waUs. The nominal· thickness of reinforced masonry bearing walls shall not be less than 152mm except that nominal 102 mm load-bearing reinforced hollow-clay unit masonry walls may be used, provided net area unit strength exceeds 55 MPa, units are laid in running bond, bar sizes do not exceed 12.7 mm with no more than two bars or one splice in a cel~ and joints are flush cut, concave or a protruding V section.

707.1.5.1 General. Allowable loads for plate anchor bolts, headed anchor bolts and bent bar anchor bolts shall be determined in accordance with this section. 707.1.5.2 Tension. Allowable loads in tension shall be the lesser value selected from Table 707-1 and 707-2 or shall be determined from the lesser of formula (707-1) or Formula (707-2).

B,

For SI :

0.5Ap

B,

707.1.4 Design assumptions. The working stress design procedure is based on working stresses and linear stress-

(707-1)

= 0.042Ap~

B, = 0.2A,fy

(707-2)

The area Ap shall be the lesser of Formula (707-3) or Formula (707-4) and where the projected areas of adjacent anchor bolts everlap, Ap of each anchor bolt shall be reduced by one half of the overlapping area. (707-3) (707-4)

707.1.5.3 Shear. Allowable loads in shear shall be the value selected from Table 707-3 or shall be determined from the lesser of Formula (707-5) or Formula (707-6).

Bv = 350 707.1.3.2 Columns. The least nominal dimension of a reinforced masonry column shall be 305 mm except that, for working stress design, if the allowable stresses are reduced by one halt: the minimum nominal dimension shall be 203 mm.

~

For SI:

Bv

Bv

=

4

~ fmAb

1070

.J

(707-5)

~ fm Ab

0.12 A,fy


(707-6)

WORKING STRESS DESIGN OF MASONRY

Where the anchor bolt edge distance he in the direction of load is less than 12 bolt diameters, the value of Bv in Formula (707~5) shall be reduced by linear interpolation to zero at an lbe distance of 38 mm. Where adjacent anchors are spaced closer than 8db, the allowable shear of the adjacent anchors determined by Formula (707~5) shall be reduced by linear interpolation to 0.75 times the allowable shear value at a center~to-center spacing of four bolt diameters. 707.1.5.4 Combined shear and tension. Anchor bolts subjected to combined shear and tension shall be designed in accordance with:

B

"

~

1.0

(707-7)

707.1.5 Compression in walls and columns. 707.1.6.1 Walls, axial loads. Stresses due to compressive forces applied at the centroid of wall may be computed, assuming uniform distribution over the effective area, by

fa

=

P/A e

(707-8)

707.1.6.2 Columns, axial loads. Stresses due to compressive forces applied at the centroid of columns may be computed by Formula (707-8) assuming uniform distribution over the effective area. 707.1.6.3 Columns, bending or combined bending and axial loads. Stresses in columns due to combined bending and axial loads shall satisfy the requirements of Section 707.2.7 wherefaffa is replaced by P;Pa. Columns subjected to bending shall meet all applicable requirements for flexural design. 707.1.7 Shear waDs, design loads. When calculating shear or diagonal tension stresses, shear walls which resist seismic forces in Seismic Zone 4 shall be designed to resist 1.5 times the forces required by Section 208.5. 707.1.8 Design, composite construction. 707.1.8.1 General. The requirements of this section govern multiwythe masonry in which at least one wythe has strength or composition characteristics different from the other wythe or wythes and is adequately bonded to act as a single structural element The following assumptions shall apply to the design of composite masonry : 1,

2.

7-19

The maximum computed stress in any portion of composite nlasonry shall not exceed the allowable stress for the material of that portion.

707.1.8.2 Determination of moduli of elasticity. The modulus of elasticity of each type of masonry in composite construction shall be measured by tests if the modular ratio of the respective types of masonry exceeds 2 to 1 as determined by Section 706,2.12, 707.1.8.3 Structural continuity. 707.1.8.3.1 Bonding of wythes. All wythes of composite masonry elements shall be tied together as specified in Section 706,1.5.2 as a minimum requirement. Additional ties or 'the combination of grout and metal ties shall be provided to transfer the calculated stress, The effect of 707.1.8.3.2 Material properties. dimensional changes of the various materials and different boundary conditions of various wythes shall be included in the design, 707.1.8.4 Design procedure, transformed sections. In the design of transformed sections, one material is chosen as the reference material, and the other materials are transformed to an equivalent area of the reference material by multiplying the areas of the other materials by the respective ratios of the moduli of elasticity of the other materials to that of the reference materiaL Thickness of the transformed area and its distance perpendiCUlar to a given bending axis remain unchanged, Effective height or length of the element remains unchanged. • 707.1.9 Reuse of masonry units. The allowable working stresses for reused masonry units shall not exceed 50 percent of those pennitted for new masonry units of the same properties,

707.2 DESIGN OF REINFORCED MASONRY. 707.2.1 SCOPE. The requirements of this section are in addition to the requirements of Sections 706 and 707,1, and govern masonry in which reinforcement is used to resist forces. Walls with openings used to resist lateral loads whose pier and beam elements are within the dimensional limits of Section 708,2,6,1.2 may be designed in accordance with Section 708.2.6. Walls used to resist lateral loads not meeting the dimensional limits of Section 708,2.6.1.2 may be designed as walls in accordance with this section or Section 708.2.5,

Analysis shall be based on elastic transformed section of the net area.


7-20

MASONRY

707.2.2 REINFORCEMENT.

and ties shall not be less than that set forth in Table 707-4.

707.2.2.1 Maximum reinforcement size. The maximum Maximum size of reinforcement shall be 32 mm. reinforcement area in cells shall be 6 percent of the cell area without splices and 12 percent of the cell area with splices. 707.2.2.2 Cover. All reinforcing bars, except joint reinforcement, shall be completely embedded in mortar or grout and have a minimum cover, including the masonry unit, of at least 19 mm, 38 mm of cover when the masonry' is exposed to weather and 50 mm of cover when the masonry is exposed to soil. 707.2.2.3 Development length. The required development length ld for deformed bars or deformed wire shall be calculated by : ld = 0.29 db.ls for bars in tension ld 0.22 db.ls for bars in compression

(707-10)

707.2.2.4 Reinforcement bond stress. Bond stress u in reinforcing,bars shall not exceed the following:

Hooks shall not be assumed to carry a load which would produce a tensile stress in the bar greater than 52MPa.

6.

Hooks shall not be considered effective in adding to the compressive resistance of bars.

7.

Any mechanical device capable of developing the strength of the bar without damage to the masonry may be used in lieu of a hook. Data must be presented to show the adequacy of such devices.

707.2.2.6 Splices. The amount of lap of lapped splices shall be sufficient to transfer the allowable stress of the reinforcement as specified in Sections 706.3.4, 707.2.2.3 and 707.212. In no case shall the length of the lapped splice be less than 30 bar diameters for compression or 40 bar diameters for tension. Welded or mechanical connections shall develop 125 percent of the specified yield strength of the bar in tension.

I

EXCEPTION:

I

kPa 1378 kPa

689 kPa For compression bars in columns that are not part of the seismic-resisting system and are not subject tof/exlIre, only the compressive strength need be developed

The term "standard hook" shall mean one of the following: 1.1 A 180-degree tum plus extension of at least 4 bar diameters, but not less than 63mm at free end of bar. 1.2 A 90-degree tum plus extension of at least 12 bar diameters at free end of bar. 1.3 For stirrup and tie anchorage only, either a 90 degree or a US-degree tum, plus an extension of at least six bar diameters, but not less than 63 mm at the free end ofthe bar.

2.

5.

I 413

707.2.2.5 Hooks. 1.

Hooks shall not be permitted in the tension portion of any beam, except at the ends of simple or cantilever beams or at the freely supported end of continuous or restrained beams.

(707-9)

Development length for smooth bars shall be twice the length determined by Formula (707-9).

• Plain Bars Deformed Bars Deformed Bars without S'pecial Inspection

4.

Inside diameter of bend of the bars, other than for stirrups and ties, shall not be less than that set forth in Table 707-4 Inside diameter of bend for 16 mm or smaller stirrups and ties shall not be less than four bar diameter. Inside diameter of bend for 16mm or larger stirrups

When adjacent splices in grouted masonry are separated by 76 mm or less, the required lap length shall be increased 30 percent.

EX(''EPTION: Where lap splices are .\1aggered at least 2-1 bars diameters, no increase in lap length is required

See Section 707.2.12 for lap splice increases. 707.2.3 Design assumptions. The following assumptions are in addition to those stated in Section 707.].4: L

Masonry carries no tensile stress.

2.

Reinforcement is completely surrounded by and bonded to masonry material so that they work together as a homogenous material within the range of allowable working stresses.



707.2.4 Nonrectangular flexural elements. Flexural elements of nonrectangular cross section shall be designed in accordance with the assumptions given in Sectiol!S 707.1.4 and 707.2.3. ' 707.2.5 Allowable axial compressive stress and force. For members other than reinforced masonry columns, the allowable axial compressive stress Fa shall be determined as follows.

7-21

707.2.8 Allowable shear stress in flexural members. Where no shear reinforcement is provided, the allowable shear stress F .. in flexural members is :

Fv = 0.083

w.-:

345 kPa maximum

(707-17)

EXCEPTION: For a distance of 1116 the clear span beyond the point of inflection, the maximum stress shall be 140 kPa.

(707-11) Where shear reinforcement designed to take entire shear force is provided, the allowable shear stress, F" in flexural members is:

for h'l r:5. 99 70r Fa := 0.25) 111 ( h'

J2

for h 'Ir> 99

For SI:

For reinforced masonry columns, the allowable axial compressive force P a shall be determined as follows:

Pa

Fv = 3.0 ~ 150

(707-12)

[0.25}mAe + 0.65As Fscl for h'/r:5. 99

Fv= O.2SW;:: 1.0

psi maximum MPamaximum

707.2.9 Allowable shear stress in shear walls. Where inplane flexural reinforcement is provided and masonry is used to resist all shear, the allowable shear stress Fv in shear wall is:

MJ Vd

(707-13)

M"")maximum "'-~0-4S I}m 'l ;;J (707-19)

For SI:

Fv

1112

W. ' 240 kPa maximum

•

(707-20)

for h'/r> 99

(707-14)

707.2.6 Allowable flexural compressive stress. allowable flexural compressive stress Fh is : Fb =: 0.33/'m

, 13.8 MPa maximum

The

(707-15)

707.2.7 Combined compressive stresses, unity formula. Elements subjected to combined axial and flexural stresses shall be designed in accordance with accepted principles of mechanics or in accordance with Formula (707-16) :

fa

Jb

Where shear reinforcement designed to take all the shear is provided, the allowable shear stress F.." in shear walls is:

ForA1/Vd < 1,

F.~ 1!24G - ~J £

:J

maximum (707-21)

MlVd;? 1, FV7 0.12#,"520 kPa maximum "

(707-16)

[120 -45

"

(707-22)

707.2.10 Allowable bearing stress. When a member bears on the full area of a masonry element, the allowable bearing stress F br is : Fbr =

0.26}m


(707-23)

l

I

MASONRY

7·22

When a member bears on one third or less of a masonry element, the allowable bearing stress Fbr is:

Fbr = 0.38 Pm

(70'/-24)

Formula (707-24) applies only when the least dimension between the edges of the loaded and unloaded areas is a minimum of one fourth of the parallel side dimension of the loaded area. The allowable bearing stress on a reasonably concentric area greater than one third but less than the full area shall be interpolated between the values of Formulas (707-23) and (707-24). 707.2.11 AUowable stresses in reinforcement. The allowable stresses in reinforcement shall be as follows' 1.

Tensile stress.

1.1

Deformed bars,

(707-25)

Wire reinforcement,

Fs = 0.5fy , 207 MPa maximum (707-26)

1.3

Ties, anchors and smooth bars,

p, =

O.4/;, , 138 MPa maximum (707-27)

2. 2.1

Compressive stress. Deformed bars in columns,

Fsc = OA/;. ,165 MPa maximum (707-28) 2.2 Deformed bars in flexural members, f~ =

0.5 h

50 percent of the minimum required length. Other equivalent means of stress transfer to accomplish the same 59 percent increase may be used. 707.2.13 Reinforcement for columns. Columns shall be provided with reinforcement as specified in this section. 707.2.13.1 Vertical reinforcement. The area of vertical reinforcement shall not be less than 0.005 Ae and not more than 0.04 Ae. At least four 10 mm bars shall be provided. The minimum clear distance between parallel bars in columns shall be two and one halftimes the bar diameter. 707.2.14 Compression in walls and columns. 707.2.14.1 General. Stresses due to compressive forces in walls and columns shall be calculated in accordance with Section 707.2.5.

F, = 0.5.h ' 165 MPa maximum 1.2

Fa, the lap length of splices shall be increased not less than

707.2.14.2 Walls, bending or combined bending and axial loads. Stresses in walls due to combined bending and axial loads shall satisfy the requirements of Section 707,2,7 where ,fa is given by Formula (707-8). Walls subjected to bending with or without axial loads shall meet all applicable requirements for flexural design. The design of walls with an h '/t ratio larger than 30 shalJ be based on forces and moments determined from an analysis of the structure. Such analysis shall consider the influence of axial loads and variable moment of inertia on member stiffness and fixed-end moments, effect of deflections on moments and forces and the effects of duration of loads. 707.2.15 Flexural design, rectangular flexural elements. Rectangular elements shall be designed in accordance with the following formulas or other methods based on the assumptions given in Sections 707.1.4, 707.2.3 and this section.

1.

Compressive stress in the masonry :

. 165 MPa maximum

Ji

(707-29) 2.3

Deformed bars in shear walls which are confined by lateral ties throughout the distance where compression reinforcement is required and where such lateral ties are not less than 6.4 mm in diameter and spaced not farther apart than 16 bar diameters or 48 tie diameters,

Fsc

0.4.("

2.

;

[j~J

(707-31)

Tensile stress in the longitudinal reinforcement: M (707-32)

AJd

3.

. 165 MPa maximum

~

Design coefficients:

(707-30) 707.2.12 Lap splice increases. In regions of moment where the design tensile stresses in the reinforcement are greater than 80 percent of the allowable steel tensile stress

k

J(n p/

+2np -np

or

Association of Structural Engineers-of the-PhiJippines

(707-33)

.,


forces and are in addition to the requirements of Sections 706 and 707.1.

1

k

7-23

is

1 + nfi

(70;-34)

707.3.2 ADowable axial compressive stress. allowable axial compressive stress Fa is :

k j

1 3

(707-35)

707.2.16 Bond of flexural reinforcement. In flexural members in which tensile reinforcement is parallel to the compressive face, the bond stress shall be computed by the formula:

F = 0.25 f'm a

F = 0.25f'm a

~ - [~II for h ~ 99 '/r

~

[

(707-39)

140d.J

70r]2for h'lr> 99

h'

(707-40)

707.3.3 ADowable flexural compressive stress. allowable flexural compressive stress Fb is :

v u

The

The

(707-36) 707.2.17 Shear in flexural members and sbear walls. The shear stress in flexural members and shear walls shall be computed by :

(707-37) For members of T or I section, b' shall be substituted for b. Where Iv as computed by Formula (707-37) exceeds the allowable shear stress in masonry, F", web reinforcement shall be provided and designed to carry the total shear force. Both vertical and horizontal shear stresses shall be considered. The area required for shear reinforcement placed perpendicular to the longitudinal reinforcement shall be computed by :

Fb = 0.33f'm,

13.8 MPa maximum

(707-41)

707.3.4 Combined compressive stresses, unity formula. Elements subjected to combined axial and flexural stresses shall be designed in accordance with accepted principles of mechanics or in accordance with the Formula (707-42) :

(707-42)

707.3.5 ADowable tensile stress. Resultant tensile stress due to combined bending and axial load shall not exceed the allowable flexural tensile stress, Ft. The allowable tensile stress for walls in flexure without tensile reinforcement using portland cement and hydrated lime, or using mortar cement Type M or S mortar, shall not exceed the values in Table 707-5.

sV (707-38) Where web reinforcement is required, it shall be so spaced that every 45-degree line extending from a point at d/2 of the beam to the longitudinal tension bars shall be crossed by at least one line of web reinforcement.

707.3 DESIGN MASONRY.

OF

Values in Table 707-5 for tension normal to head joints are for running bond; no tension is allowed across head joints in stack bond masonry. These values shall not be used for horizontal flexural members. 707.3.6 Allowable shear stress in flexural members. The allowable shear stress F" in flexural members is :

UNREINFORCED Fv

707.3.1 General. The requirements of this section govern masonry in which reinforcement is not used to resist design

For SI :

=

1.0

F

50 psi maximum

(707-43)

F l , = 0.083.JF: ,345 kPa maximum

National Structural Code of the Philippines, VoIIane:'

MASONRY

7-24

EXCEPTION: th

For a distance of 1116 the clear span beyond the point qf inflection, the maximum stress shall be 138 kPa.

707.3.12 Shear in flexural members and shear walls. Shear calculations for flexural members and shear walls shall be based on Formula (707 -48). (707-48)

707.3.7 Allowable shear stress in shear walls. allowable shear stress Fv in shear walls is as follows: I.

Clay units, Fv (707-44)

For SI: 2.

3. 4.

Fv

=

0.025

0.3

F

F- '

The

80 psi maximum

551 kPa maximum

Concrete units with Type M or S mortar, Fv =234 kPa maximum.

Concrete units with Type N mortar, F" 158 kPa maximum. The allowable shear stress in unreinforced masonry may be increased by 0.2 imd.

707.3.13 Corbels. The slope of corbelling (angle measured from the horizontal to the face of the corbelled surface) or unreinforced masonry shaH not be less than 60 degrees.

The maximum horizontal projection of corbelling from the plane of the wall shaH be such that allowable stresses are not exceeded. 707.3.14 Stack bond. Masonry units laid in stack bond shall have longitudinal reinforcement of at least 0.00027 times the vertical cross-sectional area of the wall placed horizontally in the bed joints or in bond beams spaced vertically not more than 1219 mm apart.

707.3.8 Allowable bearing stress. When a member bears on the full area of a masonry element, the allowable bearing • Fbr shall be: stress Fbr =

0.26j'm

(707-45)

When a member bears on one-third or less of a masonry element, the allowable bearing stress Fbr shall be . (707-46)

Formula (707-46) applies only when the least dimension between the edges of the loaded and unloaded areas is a minimum of one fourth of the parallel side dimension of the loaded area. The allowable bearing stress on a reasonably concentric area greater than one third but less than the full area shall be interpolated between the values of Formulas (707-45) and (707-46)., 707.3.9 Combined bending and axial loads, compressive stresses. Compressive stresses due to combined bending and axial loads shall satisfy the requirements of Section 707.3.4. 707.3.10 Compression in walls and columns. Stresses due to compressive forces in walls and columns shall be calculated in accordance with Section 707.2.5. 707.3.11 Flexural design. Stresses due to flexure shall not exceed the values given in Sections 707.1.2, 707.3.3 and 707.3.5, where: (707-47)


STRENGTH DESIGN OF MASONRY

SECTION 708 - STRENGTH DESIGN OF MASONRY 708.1

. 708.1.4.3

7-25

Wall design for in-plane loads.

708.1.4.3.1 Axial load. Axial load and axial load with flexure: = 0.65.

GeneraL

708.1.1 General Provisions. The design of hollow-unit clay and concrete masonry structures using strength design shall comply with the provisions of Section 706 and this section.

For walls with symmetrical reinforcement in which};. does not exceed 413 MPa, the value of may be increased linearly to 0.85 as the value of Pn decreases from 0.10 fill Ae or 0.25 Pb to zero. For solid grouted walls, the value of Ph may be calculated by Formula (708-2)

EXCEPTION:

Two-wythe solid-unit masonry may be used under Sections

708.2.1 and 708.2.4.

(708-2) Where:

708.1.2 Quality assurance provisions. Special inspection during construction shall be provided as set forth in Section 1701.5, Item 7 ofUBC.

(708-3) 708.1.4.3.2 Shear. Shear:

708.1.3 Required strength. The required strength shall be determined in accordance with the factored load combinati::ms of Section 203.3. . 708.1.4 Design strength. Design strength is the nominal strength, multiplied by the strength-reduction factor, <1>, as specified in this section. Masonry members shall be proportioned such that the design strength exceeds the required strength. 708.1.4.1 Beams, piers and columns. 708.1.4.1.1 Flexure. Flexure with or without axial load, the value of shall be determined from Formula (708-1): Pu

and 0.60 s;; 1j> s;; 0.80 708.1.4.1.2 Shear. Shear:

= 0.60.

The value of may be 0.80 for any shear wall when its nominal shear strength exceeds the shear corresponding to development of its nominal flexural streng.rh tor the factored-load combination. 708.1.4.4 Moment-resisting wall frames. 708.1.4.4.1 Flexure with or without axial load. The value of shall be as determined from formula (708-4); however, the value of 1j> shall not be less than 0.65 nor greater than 0.85. •

¢ (708-1)

PU 0.85 -2 [ Anf'm

J

(708-4)

708.1.4.4.2 Shear. Shear: = 0.80. 708.1.4.5 Anchor. Anchor bolts: = 0.80.

0.60

708.1.4.6 Reinforcement.

708.1.4.2 Wall design for out-of-plane loads.

708.1.4.6.1 Development. Development:

708.1.4.2.1 Walls with factored axial load ofO.04Fm or less. Flexure: = 0.80.

708.1.4.6.2 Splices. Splices:

708.1.4.2.2 Walls with factored axial load greater than 0.04 F".. Axial load and axial load with flexure: 0.80. Shear: = 0.60.

0.80.

= 0.80.

708.1.5 Anchor bolts. 708.1.5.1 Required strength. The required strength of embedded anchor bolts shall be determined from factored loads as specified in Section 708.1.3.


MASONRY

7·26

708.1.5.2 Nominal anchor bolt strength. The nominal strength of anchor bolts times the strength-reduction factor shall equal or exceed the required strength. The nominal tensile capacity of anchor bolts shall be determined from the lesser of Formula (708-5) or (708-6).

708.2 REINFORCED MASONRY. 708.2.1 General. 708.2.1.1 Scope. The requirements of this section are in addition to the requirements of Sections 706 and 708.1 and govern masonry in which reinforcement is used to resist forces.

(708-5)

708.2.1.2 Design assnmptions. The following assumptions apply:

Bm =OAAify

(708-6)

The area Ap shall be the lesser of Formula (708-7) or (708-8) and where the projected areas of adjacent anchor bolts overlap, the value of Ap of each anchor bolt shall be reduced by one half of the overlapping area. (708-7) (708-8) The nominal shear capacity of anchor bolts shall be determined from the lesser of Formula (708-9) or (708-10).

Bsn

2750

J}

m

Ab

(708-9)

(708-10)

Bm 0.25A,fy

Where the anchor bolt edge distance, [be, in the direction of load is less than 12 bolt diameters, the value of Brn in formula (808-9) shall be reduced by linear interpolation to zero at an he distance of 38 mm. Where adjacent anchor bolts are spaced closer than 8db , the nominal shear strength of the adjacent anchors determined by Formula (708-9) shall be reduced by linear interpolation to 0.75 times the nominal shear strength at a center-to-center spacing of four bolt diameters. Anchor bolts subjected to combined shear and tension shall be designed in accordance with Formula (708-11). btu

+ tPBtn

Masonry carries no tensile stress greater than the modulus ofrupture. Reinforcement is completely surrounded by and bonded to masonry material so that they work together as a homogeneous material. Nominal strength of singly reinforced masonry wall cross sections for combined flexure and axial load shall be based on applicable conditions of equilibrium and compatibility of strains. Strain in reinforcement and masonry walls shall be assumed to be directly proportional to the distance from the neutral axis. Maximum usable strain, compression fiber shall:

e",."

at the extreme masonry

1.

be 0.003 for the design of beams, piers, columns and walls.

2.

not exceed 0.003 for moment-resisting wall frames, unless lateral reinforcement as defined in Section 708.2.6.2.6 is utilized.

Strain in reinforcement and masonry shall be assumed to be directly proportional to the distance from the neutral axis. Stress in reinforcement below specified yield strengthh for grade of reinforcement used shall be taken as Es times steel strain. For strains greater than that corresponding to h, stress in reinforcement shall be considered independent of strain and equal to/;,.

bSll ~

tPBsn

1.0

(708-11)

708.1.5.3 Anchor bolt placement. Anchor bolts shall be placed so as t~ meet the edge distance, embedment depth and spacing requirements of Sections 706.2 .14.2, 706.2.14.3 and 706.2.14.4.

Tensile strength of masonry walls shall be neglected in flexural calculation of strength, except when computing 'requirements for deUection. Relationship between masonry compressive stress and masonry strain may be assumed to be rectangular as defined by the following: Masonry stress of 0.85 1'm shall be assumed uniformly distributed over an equivalent compression zone bounded by edges of the cross section and a straight line located


..~

STRENGTH DESIGN OF MASONRY

parallel to the neutral axis at a distance a = 0.8Sc from the fiber of maximum compressive strain. Distance c from fiber of maximum strain to the neutral llxis shall he measured in a direction perpendicular to that axis.

7-27

Where: ForSI: 1.8d/h

708.2.2 Reinforcement requirements aDd details.

(708-13)

708.2.2.1 Maximum reinforcement. The maximum size of reinforcement shall be 28 mm. The diameter of a bar shall not exceed one fourth the least dimension of a cell. No more than two bars shall be placed in a cell of a wall or a wall frame. 708.2.2.2 Placement. The placement of reinforcement shall comply with the following: In columns and piers, the clear distance between vertical reinforcing bars shall not be less than one and one-half times the nominal bar diameter, nor less than 38mm. 708.2.2.3 Cover. All reinforcing bars shall be completely embedded in mortar or grout and shall have a cover of not less than 38 mm nor less than 2.S db. 708.2.2.4 Standard books. A standard hook shall be one of the following:

1.

K shall not exceed 3db• The minimum embedment length of reinforcement shall be 305 mm. 708.2.2.7 Splices. Reinforcement splices shall comply with one of the following: 1.

(708-14) Bars spliced by non-contact lap splices shall be spaced transversely a distance not greater than one fifth the required length oflap or more than 203mm.

2.

A welded splice shall have the bars butted and welded to develop in tension 125 percent ofthe yield strength of the bar,};..

3.

Mechanical splices shall have the bars connected to develop in tension or compression, as required, at least 125 percent ofthe yield strength of the bar,Y;.

A 180-degree tum plus an extension of at least four bar diameters, but not less than 63mm at the free end of the bar.

2.

A 13S-degree tum plus an extension of at least six bar diameters at the free end of the bar.

3.

A 90-degree tum plus an extension of at least 12 bar diameters at the free end of the bar.

708.2.2.5 Minimum bend diameter for reinforcing bars. Diameter of bend measured on the inside of a bar other than for stirrups and ties in sizes 10 mm through 16 m~ shall not be less than the values in Table 707-4 Inside diameter of bends for stirrups and ties shall not be less than 4db for 16 mm bars and smaller For bars larger than No.5, diameter of bend shall be in accordance with Tahle 707-4 708.2.2.6 Development. The calculated tension or compression reinforcement shall be developed 10 accordance with the follmving provisions: The embedment length of reinforcement determined by Formula (708-] 2).

shall

be

(708-12)

The minimum length oflap for bars shall be 305 mm or the length determined by Formula (708-14).

708.2.3 Design of beams. piers and columns. 708.2.3.1 General. The requirements of this section are for the design of masonry beams, piers and columns. The value off'", shall not be less than lO.3 MPa. For computational purposes, the value of 1'111 shall not exceed 21.6MPa. 708.2.3.2 Design assumptions. Member design forces shall be based on an analysis which considers the relative stiffuess of structural members. The calculation of lateral stiffness shall include the contribution of all beams, piers and columns. The effects of cracking on member stiffness shall be considered. The drift ratio of piers and columns shaiI satisfy the limits specitied in Chapter 2.


1

,,

MASONRY

7·28

708.2.3.3 Balanced reinforcement ratio for compression limit state. Calculation of the balanced reinforcement ratio, Pb, shall be based on the following assumptions: The distribution of strain across the section shall be assumed to vary linearly from the maximum usable strain, emit, at the extreme compression fiber of the element, to a yield strain of fiE. at the extreme tension fiber of the element.

1.

2.

Compression forces shall be in equilibrium with the sum of tension forces in the reinforcement and the maximum axial load associated with a loading combination 1.0D + 1.0L + (1.4E or 1.3W).

3.

4.

The reinforcement shall be assumed to be uniformly distributed over the depth of the element and the balanced reinforcement ratio shall be calculated as the area of this reinforcement divided by the net area of the element.

All longitudinal reinforcement shaH be included in calculating the balanced reinforcement ratio except that the contribution of compression reinforcement to • resistance of compressive loads shall not be considered.

708.2.3.4 Required strength. Except as required by through 708.2.3.12, the required Sections 708.2.3.6 strength shall be determined in accordance with Section 708.1.3. 708.2.3.5 Design strength. Design strength provided by beam, pier or column cross sections in terms of axial force, shear and moment shall be computed as the nominal strength multiplied by the applicable strength-reduction factor, 4>, specified in Section 708.1.4.

Where :

ForSI:

and (708-18) L

The nominal shear strength shall not exceed the value given in Table 708-1.

2.

The value of Vm shall be assumed to be zero within any region subjected to net tension factored loads.

3.

The value of v,,, shall be assumed to be 172 kPa where M" is greater than 0.7 Mn. The required moment, M", for seismic design for comparison with the 07 Mn value of this section shall be based on an R", of 3.

708.2.3.7 Reinforcement. 1.

Where transverse reinforcement is required, the maximum spacing shall not exceed one half the depth of the member nor 1219 mm.

2.

Flexural reinforcement shall be uniformly distributed throughout the depth of the element.

3.

Flexural elements subjected to load reversals shall be symmetrically reinforced.

4.

The nominal moment strength at any section along a member shall not be less than one fourth of the maximum moment strength.

5.

The flexural reinforcement ratio, P, shall not exceed 0.5 Ph.

6.

Lap splices shall comply with the provisions of Section 708.2.2.7.

7.

Welded splices and mechanical splices which develop at least 125 percent of the specified yield strength . of a bar may be used for splicing the reinforcement. Not more than two longitudinal bars shall be spliced at a section. The distance between splices of adjacent bars shall be at least 762 mm along the longitudinal axis.

8.

Specified yield strength of reinforcement shall not exceed 413 MPa. The actual yield strength based on mill tests shall not exceed 1.3 times the specified yield strength.

708.2.3.6 Nominal strength. 708.2.3.6.1 Nominal axial and flexural strength. The nominal axial strength, Pn , and the nominal flexural strength, M", of a cross section shall be determined in the design assumptions of accordance with Section 708.2.1.2 and 108.2.3 .2. The maximum nominal axial compressive strength shall be determined in accordance with Formula (708-15).

(708-15) 708.2.3.6.2 Nominal shear strength. The nominal shear strength shall be

(708-16)


1 STRENGTH DESIGN OF MASONRY

708.2.3.8 Seismic design provisions. The lateral seismic load resistance in any line or story level shall be provided by shear walls or wall frames, or a combination of shear walls and wall frames. Shear walls and wall frames shall provide at least 80 percent of the lateral stiffness in any line or story level.

EXCEPTION: Where seismic loads are determined ba'Oed on Rw not greater than three and where all joints satisfy the provisions of Section 708.2.6.2.9, the piers may be used to provide seismic load resistance. 708.2.3.9 Dimensional limits. accordance with the following :

1.

Dimensions shall be in

7-29

3. Columns.

3. I

The nominal width of a column shall not be less than 305 mm. 3.2 The distance between lateral supports of a column shall not exceed 30 times the nominal width of the column. 3.3 The nominal leni,rth of a column shall not be less than 305 mm and not greater than three times the nominal width of the column. 708.2.3.10 Beams.

708.2.3.10.1 Scope. Members designed primarily to resist flexure shall comply with the requirements of this section The factored axial compressive force on a beam shall not exceed 0.05 Aej'",.

Beams. 708.2.3.10.2 Longitudinal reinforcement.

1.1

The nominal width of a beam shall not be less than 153 mm. 1.2 The clear distance between locations of lateral bracing of the compression side of the beam shall not exceed 32 times the least width of the compression area. 1.3 The nominal depth of a beam shall not be less than 203 mm.

2.

Piers.

2.1

The nominal width of a pier shall not be less than 153 mm and shall not exceed 406 mm.

1.

The variation in the longitudinal reinforcing bars shall not be greater than one bar size. Not more than two bar sizes shall be used in a beam.

2.

The nominal flexural strength of a beam shall not be less than 1.3 times the nominal cracking moment strength of the beam. The modulus ofrupture,j,., for this calculation shall be assumed to be 1.6 MPa.

708.2.3.10.3 Transverse reinforcement.

2.2 The distance between lateral supports of a pier shall not exceed 30 times the nominal width of the piers except as provided for in Section 708.2.3.9, Item 2.3.

Transverse reinforcement shall be provided where V, exceeds Vm • Required shear, Vu, shall include the effects of the drift. The value of Vu shall be based on LiM, When transverse shear reinforcement is required, the following provisions shall apply:

2.3

1.

Shear reinforcement shall be a single bar with 180 degree hook at each end.

2.

Shear reinforcement shall be hooked around the longitudinal reinforcement.

3.

The min. transverse shear reinforcement ratio shall be 0.0007.

4.

The first transverse bar shall not be more than one fourth of the beam depth from the end of the beam.

When the distance between lateral supports of a pier exceeds 30 times the nominal width of the pier, the provisions of Section 708.2.4 shall be used for design.

2.4 The nominal length of a pier shall not be less than three times the nominal width of the pier. The nominal length of a pier shall not be greater than six times the nominal width of the pier. The clear height of a pier shall not exceed five times the nominal length of the pier.

708.2.3.10.4 Construction. Beams shall be so!id grouted.

EXCEPTION: 708.2.3.11 Piers.

The length of a pier may be equal to the width of the pier when the axial force at the location ofmaximum moment is less than 0.04 j'mAg

National Structural Code of

708.2.3.11.1 Scope. Piers proportioned to resist flexure and shear in conjunction with axial load shall comply with

the


MASONRY

7-30

the requirements of this section. The factored axial compression on the piers shall not exceed 0.3 A,f'm.

708.2.4.1 ~neral. The requirements of this section ar<: for the design of walls for out-of-plane loads.

708.2.3.11.2 Longitudinal reinforcement. A pier subjected to in-plane stress reversals shall be longitudinally reinforced symmetrically on both sides of the neutral axis of the pier.

708.2.4.2 Maximum reinforcement. The reinforcement ratio shall not exceed 0.5 Pb.

L

One bar shall be provided in the end cells.

2.

The minimum longitudinal reinforcement ratio shall be 0.0007.

708.2.3.11.3 Transverse reinforcement. Transverse reinforcement shall be provided where V;, exceeds Vm. Required shear, Vu , shall include the effects of drift. The value of Vu shall be based on 41. When transverse shear reinforcement is required, the following provisions shall apply: 1.

2.

708.2.4.3 Moment and deflection calculations. All moment and deflection calculations in Section 708.2.4 are based on simple support conditions top and bottom. Other support and fixity conditions, moments and deflections shall be calculated using established principles of mechanics. 708.2.4.4 Walls with axial load of 0.04 f'm or less. The procedures set forth in this section, which consider the slenderness of walls by representing effects of axial forces and deflection in calculation of moments, shall be used when the vertical load stress at the location of maximum moment does not exceed 0.04/,,,, as computed by Formula (708-19). The value off'", shall not exceed 41.3 MPa.

Shear reinforcement shall be hooked around the extreme longitudinal bars with a 180-degree hook. Alternatively, at wall intersections, transverse reinforcement with a 90-degree standard hook around a vertical bar in the intersecting wall shall be permitted. The minimum transverse reinforcement ratio shall be 0.0015.

708.2.3.12 Columns. 708.2.3.12.1 Scope. Columns shall comply with the requirements of this section.

----:::; 0.04}11I (708-19) Walls shall have a minimum thickness of 153 mm. Required moment and axial force shall be determined at the midheight of the wall and shall be used for design The factored moment, M", at the midheight of the wall shall be determined by Formula (708-20).

h1 e Al,,= - - + P"r - + PIlLl/l 2 8 11'1/

708.2.3.12.2 Longitudinal reinforcement. Longitudinal reinforcement shall be a minimum of four bars, one in each corner of the column. 1.

Maximum reinforcement area shall be 0.03 A".

2.

Minimum reinforcement area shall be 0.005 A".

(708-20)

Where:

Au = deflection at midheight of wall due to factored loads (708-21)

708.2.3.12.3 Lateral ties. 1.

Lateral ties shall be provided Section 706.3.6.

2.

Minimum lateral reinforcement area shall be 0.0018 Ag .

708.2.3.12.4 grouted.

Construction.

In

accordance with

The design strength for out-of-plane wall loading shall be determined by Formula (708-22). (708-22)

Where:

Columns shall be solid

M" Asefy (d - 02)

708.2.4 WaD design for out-of-plane loads.

AS
p,J /'/;"

effective area of steel


(708-23)

(708-24)

7-31 STRENGTH DESIGN OF MASONRY

a = (Pu -rAsfy) O.85/'1II b,depthofstressblock due to factored loads

J,. = 0.3~1.6 MFa maximum

(708-31)

(708-25)

2. For partially grouted hollow-unit masomy, 708.2.4.5 Wan with axial load greater than 0.04fm' The procedures set forth in this section shall be used for the design of masonry walls when the vertical load stresses at the location of maximum moment exceed 0.04 1'm but are less than 0.2 1'm and the slenderness ratio h 'It does not exceed 30.'

Design strength provided by the wall cross section in terms of axial force, shear and moment shall be computed as the nominal strenbrth multiplied by the applicable strength reduction factor, 1\>, specified in Section 708.1.4. Walls shall be proportioned such that the design strength exceeds the required strength. The nominal shear strength shall be determined by Formula (808-26).

w::

(708-26)

V.,=0.166A mv

J,. = 0.21

As = 0.007 h

fr = 0.166 ~, 861 kPa maximum

The value of1'm shall not be less than 10.3 MPa nor greater than 27.6 MPa. 708.2.5.2 Reinforcement Reinforcement shall be in accordance with the following :

2.

3.

4. (708-28)

5 Mer h 2

As= 48 Em 19

5(Mser Mcr)h2

(708-33)

708.2.5.1 General. The requirements of this section are for the design of walls for in-plane loads.

P.6. effects shall be included in deflection calculation. The

for Mser ::;: Mer

(708~32)

708.2.5 Wall design ror in-plane loads.

(708-27)

midheight deflection shall be computed with the following formula:

861 kPa maximum

3. For two-wythe brick masomy,

1.

The midheight 708.2.4.6 Deflection design. deflection, .6.., under service lateral and vertical loads (without load factors) shall be limited by the relation:

F

Minimum reinforcement shall be provided in accordance with Section 706.1.12.4, Item 2.3, for all seismic areas using this method of analysis. When the shear wall failure mode is in flexure, the nominal flexural strength ofthe shear wall shall be at least 1.8 times the cracking moment strength of a fully grouted wall or 3.0 times the cracking moment strength of a partially grouted wall from Formula (708-30). ~ The amount of vertical reinforcement shall not·· be less than one half the horizontal reinforcement. , Spacing of horizontal reinforcement within thi' region defined in Section 708.2.5.5, Item 3, shall not exceed three times the nominal wall thickness nor 61Omm.

708.2.5.3 Design strength. Design strength provided by the shear wall cross section in terms of axial force, shear and moment shall be computed as the nominal strength multiplied by the applicable strength-reduction factor, 1\>, specified in Section 708.1.4.3.

+---- 48EJer

for Mer < Mser <: U,

(708-29)

The cracking moment strength of the wall shall be determined from the formula:

708.2.5.4 Axial strength. The nominal axial strength of the shear wall supporting axial loads only shall be calculated by Formula (708-34). (708-34)

(708-30)

The modulus of rupture,J,., shall be as follows:

Axial design strength pr.!?vided by the shear wall cross section shall satisfy FormiJia (708-35).

For fully grouted hollow-unit masonry,


7-32

MASONRY

Pu s 0.80 ell Po 708.2.5.5 follows: 1.

2.

(708-35)

Shear strength.

Shear strength shall be as

The nominal shear strength shall be determined using either Item 2 or 3 below. Maximum nominal shear strength values are determined from Table 708-1. The nominal shear strength of the shear wall shall be determined from Formula (708-36), except as provided in Item 3 below (708-36)

Where:

Vm 0.083 C d"lmv

W.

(708-37)

n08-38)

3. For a shear wall whose nominal shear strength exceeds the shear corresponding to development of its nominal flexural strength, two shear regions exist. For all cross sections within the region defined by the base of the shear wall and a plane at a distance L", above the base of the shear wall, the nominal shear strength shall be determined from Formula (708-39).

v"

Amv p,fy

(708-39)

The required shear strength for this region shall be calculated at a distance Lj2 above the base of the shear wall, but not to exceed one half story height. For the other region, the nominal shear strength of the shear wall shall be determined from Formula (708-36). 708.2.5.6 Boundary members shall be as follows:

2.

Lateral reinforcement shall be provided for the boundary elements. The lateral reinforcement shall be a minimum of No. 3 bars at a maximum of 203mm spacing within the grouted core or equivalent confinement which can develop an ultimate compressive masonry strain of at least 0.006.

708.2.6 Design of moment-resisting wall frames. 708.2.6.1 General requirements. 708.2.6.1.1 Scope. The requirements of this section are for the design of fully grouted moment-resisting waIl frames constructed of reinforced open-end hollow-unit concrete or hollow-unit clay masonry. 708.2.6.1.2 Dimensional limits. Dimensions shall be in accordance with the following: Beams. Clear span for the beam shall not be less than two times its depth.

and

1.

3.

members.

Boundary

Boundary members shall be provided at the boundaries of shear walls when the compressive strains in the wall exceed 0.0015. The strain shall be determined using factored forces and R", equal to 1.5. The minimum length of the boundary member shall be three times the thickness of the wall, but shall include all areas where the compressive strain per Section 2108.2.6.2.7 is greater than 0.0015.

The nominal depth of the beam shall not be less than two units or 406mm, whichever is greater. The nominal beam depth to nominal beam width ratio shall not exceed 6. The nominal width of the beam shall be the greater of 203mm or 1/26 ofthe clear span between pier faces. Piers. The nominal depth of piers shall not exceed 2438mm. Nominal depth shall not be less than two full units or 813mm, whichever is greater. The nominal width of piers shall not be less than the nominal width of the beam, nor less than 203mm or 1114 of the clear height between beam faces, whichever is greater. The clear height-to-depth ratio of pier shall not exceed 5. 708.2.6.1.3 Analysis. Member design forces shall be the based on an analysis which considers the relative stiffness of pier and beam member, including the stiffening influence ofjoints. The calculation of beam moment capacity for the determination of pier design shall include any contribution offloor slab reinforcement. The out-of-plane drift ratio of all piers shall satisfY the drift ratio limits specified in Section 2-47. 708.2.6.2 Design procedure. 708.2.6.2.1 Required strength. Except as required by the Sections 708.2.6.7 and 708.2.6.2.8, the required strength shall be determined in accordance with Section 708.1.3


STRENGTH DESIGN DF MASONRY

708.2.6.2.2 Design strength. Design strength provided by frame member cross sections in terms of axial force, shear and moment shall be computed as the nominal strength multiplied by the applicable strength-reduction factor. 4> , specified in Section 708.1.4.4 Members shall be proportioned such that the design strength exceeds the required strength.

Minimum reinforcement ratio calculated over the gross cross section shall be 0.002. Maximum reinforcement ratio calculated over the gross cross section shall be 0.15 f'm / /y 2.

708.2.6.2.3 Design assumption for nominal strength. The nominal strength of member cross sections shall be based on assumptions prescribed in Section 70S.2.I.2.

708.2.6.2.4 Reinforcement. The nominal moment strength at any section along a member shall not be less than one fourth of the higher moment strength provided at the two ends of the member.

The maximum spacing of transverse reinforcement shall not exceed one half the nominal depth of the beam.

Lap splices shall be as defined in Section 70S.2.2.7. The center of the lap splice shall be the center of the member clear length.

Reinforcement shall not have a specified yield strength greater than 413 MFa. The actual yield strength based on mill tests shall not exceed the specified yield strength times

Minimum reinforcement ratio shall be 0.0015 The first transverse bar shall not be more than 102 rom from the face ofthe pier.

708.2.6.2.6 flexure.

708.2.6.2.5 Flexural members (beam). Requirements of this section apply to beams proportioned primarily to resist flexure as follows. The axial compressive force on beams due to factored loads shall not exceed 0.10 Anl'm.

1.

Longitudinal reinforcement. A minimum of four longitudinal bars shall be provided at all sections of every pier. Flexural reinforcement shall be distributed across the member depth. Variation in reinforcement area between reinforced cells shall not exceed 50 percent. Minimum reinforcement ratio calculated over the 0.002 gross cross section shall be

Longitudinal reinforcement. At any section of a beam, each masonry unit through the beam depth shall contain longitudinal reinforcement. The variation in the longitudinal reinforcement area between units at any section shall not be greater than 50 percent, except multiple No.4 bars shall not be greater than 100 percent of the minimum area of longitudinal reinforcement contained by anyone unit, except where splices occur.

Members subjected to axial force and

The requirements set forth in this subsection apply to piers proportioned to resist flexure in conjunction with axial loads. • 1.

1.3.

Transverse reinforcement. Transverse reinforcement shall be hooked around top and bottom longitudinal bars with a standard ISO-degree hook, as defined in Section 708.2.2.4, and shall be single pieces. Within an end region extending one beam depth from pier faces and at any region at which beam flexural yielding may occur during seismic or wind of transverse loading, maximum spacing reinforcement shall not exceed one fourth the nominal depth of the beam.

The value ofI'm shall not be less than 10.3 MFa or greater than 27.6 MFa.

Welded splices and mechanical connection conforming to Section 412.14.3. Item 1 through 4 of UBC, may be used for splicing the reinforcement at any section provided not more than alternate longitudinal bars are spliced at section, and the distance between splices of alternate bars is at least 6IOmm along the longitudinal axis.

7-33

Maximum reinforcement ratio calculated over the gross cross section shall be 0.15 f'/1/ / fr Maximum bar diameter shall be one eight nominal width of the pier. 2.

Transverse reinforcement. Transverse reinforcement shall be hooked around the extreme longitudinal bars with standard 180-degree hook as defined in Section 70S.2.2.4.


MASONRY

7-34

Within an end region extending one pier depth from the end of the beam, and at any region at which flexural yielding may 'occur during seismic or wind loading, the maximum spacing of transverse reinforcement shall not exceed one fourth the nominal depth ofthe pier. The maximum spacing of transverse reinforcement shall not exceed one half the nominal depth of the pier. The minimum transverse reinforcement ratio shall be 0.0015.

Lateral reinforcement. Lateral reinforcement shall be provided to confine the grouted core when compressive strains due to a.xial and bending forces exceed 0.0015. corresponding to factored forces with Rw equal to 1.5. The unconfined portion of the cross section with strain exceeding 0.0015 shall be neglected in computing the nominal strent"rth of the section. The total cross-sectional area of rectangular tie feinforcement for the confined core shall not be less than: (708-40) Alternatively, equivalent confinement which can develop an ultimate compressive strain of at least 0.006 may be substituted for rectangular tie reinforcement.

708.2.6.2. i Pier design forces. Pier nominal moment strength shall not be less than 1.6 times the pier moment corresponding to the development of the beam plastic hinges, except at the foundation leve1.

Pier axial load based on the development of beam plastic bing.:s in accordance with the paragraph above and illcluding tactored dead and live loads shall not exceed 0.15 A,J'/II'

The drift ratio 0f piers shall sati:;fy the limits specified in Chapter 2. The effects of cracking on member stiffness shall be considered. The base plastic hinge of the pier must form immediately adjacent to the level of lateral support provided at the base ,)f toundation.

708.1.6.2.8 Shear design. 1.

General. Beam and pier nominal shear strength shall not be less than 1.4 times the shears corresponding to the development of the flexural yielding.

It shall be assumed in the calculation of member shear force that moments of opposite sign act at the joint faces and that the member is loaded with the tributary gravity load along its span.

2.

Vertical member shear strength. The nominal shear strength shall be determined from Formula (708-41). (708-41)

Where: (708-42) and (708-43) The value of f:" shall be zero within an end region extending one pier depth from beam laces and at any region where pier flexural yielding may occur during seismic loading, and at piers subjected to net tension factored loads. The nominal pier shear strength, l'~, shall not exceed the value determined from Table 708-1.

3

Beam shear strength. The nominal shear strength shall be determined from Formula (708-44). V~1l

(808-44)

0.01 Amv

The value of JI:" shall be zero within an end region extending one beam depth from pier faces and to any region at which beam flexure yielding may occur during seismic loading. The nominal beam shear strength, Vn , shall be determined from Formula (708-45).

1:,

:s; 0.33

Amv

V.

(708-45)

708.2.6.2.9 Juints. I.

General Requirements. Where reinforcing bars extend through a joint, the joint dimensions shall be proportioned such that


STRENGTH DESIGN OF MASONRY & EMPIRICAL DESIGN OF MASONRY

(708-46)

and

7-35

SECTION 709. EMPIRICAL DESIGN OF MASONRY

(708-47)

709.1 HEIGHT. The grout strength shall not exceed 34,4 MPa for the purposes of Formula (708-46) and (708-47).

Building relying on masonry walls for lateral load resistance shall not exceed 10.668 m in height.

Joint shear farces shall be calculated on the assumption that the stress in all flexural tension reinforcement of the beams at that pier faces is 1.4.1;,.

709.2 LATERAL STABILITY.

Strength of joint shall be governed by the appropriate strength reduction factors specified in Section 708.1.4.4. Beam longitudinal reinforcement terminating in a pier shall be extended to the far face of the pier and anchored by a standard 90 or 180 degree hook., as defined in Section 708.2.2.4, bent back to the beam. Pier longitudinal reinforcement terminating in a beam shall be extended to the far face of the beam and anchored by a standard 90 or 180 degree hook., as defined in Section 708.2.2.4, bent back to the beam. 2.

Transverse reinforcement. Special horizontal joint shear reinforcement crossing a potential comer to comer diagonal joint shear crack., and anchored by standard hooks, as defined in Section 708.2.2.4, around the extreme pier reinforcing bars shall be provided such that

0.5 Yfh I h

(708-48)

Vertical shear forces may be considered to be carried by a combination of masonry shear resisting mechanisms and truss mechanism involving intermediate pier reinforcing bars. 3, Shear strength. The nominal horizontal shear strength ofthe joint shall not exceed: 0.58

fm

2.4 MPa, whichever is less.

Where the structure depends on masonry walls for lateral stability, shear walls shall be provided parallel to the direction ofthe lateral forces resisted. Minimum nominal thickness on masonry shear walls shall be203b mm. In each direction in which shear walls are required for lateral stability, the minimum cumulative length of shear walls provided shall be 0.4 times the dimension of the building. The cumulative length of shear walls shall not include openings, The maximum spacing of shear walls shall not exceed the ratio listed in Table 709-1.

709.3 COMPRESSIVE STRESSES. 709.3.1 General. Compressive stresses in masonry due to vertical dead loads plus live loads, excluding wind q{ seismic loads, shall be determined in accordance with Section 709.4.3. Dead and live loads shall be in accordance with this code with permitted live load reductions. 709.3.2 AUowable stresses. The compressive stresses in masonry shall not exceed the values set forth in Table 709-2. The allowable stresses given in Table 709-2 for the weakest combination of the units and mortar used in any load wythe shall be used for all loaded wythes of muItiwythe walls. 709.3.3 Stress calculations. Stresses shall be calculated based on specified rather than nominal dimensions. Calculated compressive stresses shall be determined by dividing the design load by the gross cross-sectional area of the member. The area of openings, chases or recesses in walls shall not be included in the gross cross-sectional area ofthe wall. 709.3.4 Anchor bolts. Bolt values shall not exceed those set forth in Table 709-3.


MASONRY

7-36

709.4 LATERAL SUPPORT. Masonry walls shall be laterally supported in either the horizontal or vertical direction not exceeding the intervals set forth in Table 709-4. Lateral support shall be provided by cross walls, pilasters, buttresses or structural framing members horizontally or by floors, roof or structural framing members vertically. Except for parapet walls, the ratio of height to nominal thickness for cantilever walls shall not exceed 6 for solid masonry or 4 for hollow masonry.

In computing the ratio for cavity walls, the value of thickness shall be the sums of the nominal thickness of the inner and outer wythes of the masonry. In walls composed of different classes of units and mortars, the ratio of height or length to thickness shall not exceed that allowed for the weakest of the combinations of units and mortar of which the member is composed.

709.5.5 Foundation walls. Mortar used in masonry foundation walls shall be either Type M or S. Where the height of unbalanced fill (height of finished grade above basement floor or inside grade) and the height of the wall between lateral support does not exceed 2438 mm, and when the equivalent fluid weight of unbalanced fill does not exceed 480 kg/m2, the minimum thickness of foundation walls shall be as set forth in Table 709-5. Maximum depths of unbalanced fill permitted in Table 709-5 may be increased with the approval of the building official when local soil conditions warrant such an increase. Where the height of unbalanced fill, height between lateral supports or equivalent fluid weight of unbalanced fill exceeds that set forth above, foundation walls shall be designed in accordance with Chapter 3.

709.6 BOND. 709.6.1 General. The facing and backing of multiwythe masonry walls shall be bonded in accordance with this section.

709.5 MINIMUM TmCKNESS•

•

709.5.1 General. The nominal thickness of masonry bearing walls in buildings more than one story in height shall not be less than 200 mm. Solid masonry walls in one storey buildings may be of 152 mm nominal 'thickness when not over 2745 mm in height, provided that when gable construction is used, an additional 1830 mm is permitted to the peak ofthe gable. EXCEPTION: The thickness of unreinforced grouted brick masonry walls may be 50mm less than required by this section, but in no case less than J50 mm.

709.5.2 Variation in tbickness. Where a change in thickness due to minimum thickness occurs between floor levels, the greater thickness shall be carried up to the higher floor level. 709.5.3 Decrease in thickness. Where walls of masonry of hollow units or masonry-bonded hollow walls are decrease in thickness, a course or courses of solid masonry shall be constructed between the walls below and the thinner wall above, or special units or construction shall be used to transmit the loads from face shells or wythes to the walls below. 709.5.4 Parapets. Parapet walls shall be at least 200 mm in thickness and their height shall not exceed three times their thickness. The parapet wall shall not be thinner than the wall below.

709.6.2 Masonry headers. Where the facing and backing of solid masonry construction are bonded by masonry headers, not less than 4 percent of the wall surface of each face shall be composed of headers extending not less than 76 mm into the backing. The distance between adjacent full-length headers shall not exceed 610 mm either vertically or horizontally. In walls in which a single header does not extend through the wall, headers from opposite sides shall overlap at least 76 mm, or headers from opposite sides shall be covered with another header course overlapping the header below at least 76 mm. Where two or more hollow units are used to make up the thickness of the wall, the stretcher courses shall be bonded at vertical intervals not exceeding 864 mm by lapping at least 76 mm over the unit below, or by lapping at vertical intervals not exceeding 432 mm with units which are at least 50 percent greater in thickness than the units below.

709.6.3 Wall ties. Where the facing and backing of masonry walls are bonded with 4.8 mm diameter wall ties or metal ties of equivalent stiffness embedded in the horizontal mortar joints, there shall be at least one metal tie for each 0.42 m2, of wall area. Ties in alternate courses shall be staggered, the maximum vertical distance between ties shall not exceed 610 mm, and the maximum horizontal distance shall not exceed 914 mm. Rods bent to rectangular shape shall be used with hollow-masonry units laid with the cells vertical. In other walls, the ends of ties shall be bent to 90-degree angles to provide hooks not less than 50 mm long. Additional ties shall be provided at all openings,


EMPIRICAL DESIGN OF MASONRY

spaced not more than 914 mm apart around the perimeter and within 305 mm of the opening. The facing and backing of masonry walls may be bonded with prefabricated joint reinforcement. There shall be at least one cross wire serving as a tie for each 0.25 m2 of wall area. The vertical spacing of the joint reinforcement shall not exceed 406 mm. Cross wires of prefabricated joint reinforcement shall be at least No. 9 gage wire. The longitudinal wire shall be embedded in mortar.

1.

Wood floor joists bearing on masonry walls shall be anchored to the -\!tall by approved metal strap anchors at intervals not exceeding 1829 mm. Joists parallel to the wall shall be anchored with metal straps spaced not more than 1829 mm on center extending over and under and secured to at least three joists. Blocking shall be provided between joists at each strap anchor.

2.

Steel floor joists shall be anchored to masonry walls with No.3 bars, or their equivalent, spaced not more than 1829 mm on center. Where joists are parallel to the wall, anchors shall be located at joists cross bridging.

3.

Roof structures shall be anchored to masonry walls with 12.7 mm bolts at 1829 mm on center or their equivalent. Bolts shall extend and be embedded at least 381 mm into the masonry, or be hooked or welded to not less than 129 mm2 of bond beam reinforcement placed not less than 152 mm from the top of the wall.

709.6.4 Longitudinal bond. In each wythe of masonry, head joints in successive courses shall be offset at least one fourth of the unit length or the walls shall be reinforced longitudinally as required in Section 706.1.12.3, Item 4.

709.7 ANCHORAGE. 709.7.1 Intersecting walls. Masonry walls depending on one another for lateral support shall be anchored or bonded at locations where they meet or intersect by one of the following methods: 1.

Fifty percent of the units at the intersection shall be laid in an overlapping pattern, with alternating units having a bearing of not less than 76 mm on the unit below.

2.

Walls shall be anchored by steel connectors having a minimum section of 6.4 mm by 38 mm with ends bent up at least 51 mm, or with cross pins to form anchorage. Such anchors shall be at least 610 mm long and the maximum spacing shall be 1219 mm vertically.

3.

Walls shall be anchored by joint reinforcement spaced at a maximum distance of 203 mm vertically. Longitudinal rods of such reinforcement shall be at least NO.9 gage and shall extend at least 762 mm in each direction at the intersection.

4.

Interior nonbearing walls may be anchored at their intersection, at vertical spacing of not more than 406 mm with joint reinforcement or 6.4 mm mesh galvanized hardware cloth.

7-37

709.7.3 Walls adjoining structural framing. Where walls are dependent on the structural frame for lateral support, they shall be anchored to the structural members with metal anchors or keyed to the structural members. Metal anchors shall consist of 12.7 mm bolts spaced at a maximum of 1219 mm on center and embedded at least 102 mm into the masonry, or their equivalent area.

709.8 UNBURNED CLAY MASONRY. 709.8.1 General. Masonry of stabilized clay unburned units shall not be used in any building more than one story in height. The unsupported height of every wall of unburned clay units shall not be more than 10 times the thickness of such walls. Bearing walls shall in no case be less than 406 mm in thickness. All footing walls which support masonry of unburned clay units shall extend to an elevation not less than 152 mm aQove the adjacent ground at all points. 709.8.2 Bolts. Bolt values shall not exceed those set forth in Table 709-6.

709.9 STONE MASONRY. Other metal ties, joint reinforcement or anchors may be used, provided they are spaced to provide equivalCJlt area of anchorage to that required by this section.

709.9.1 General. Stone masonry is that form of construction made with natural or cast stone in which the units are laid and set in mortar with all joints filled.

709.7.2 Floor and roof anchorage. Floor and roof diaphragms providing lateral support to masonry walls shall be connected to the masonry walls by one of the following methods:

709.9.2 Construction. In ashlar masonry, bond stones uniformly distributed shall be provided to the extent of not less than 10 percent of the area of exposed facets. Rubble stone masonrv 610 mm Or less in thickness shall have bond

5.


1 I

MASONRY

7-38

stones with a maximum spacing of 914 mm vertically and 914 mm horizontally and, if the masonry is of greater thickness than 610 mm, shall have one bond stone for each 0.56 m2 of wall surface on both sides.•

709.9.3 Minimum thickness. The thickness of stone masonry bearing walls shall not be less than 406 mm.

SECTION 710 - GLASS MASONRY 710.1 GENERAL. Masonry of glass blocks may be used in non-load-bearing exterior or interior walls and in openings which might otherwise be filled with windows, either isolated or in continuous bands, provided the glass block panels have a minimum thickness of 76 mm at the mortar joint and the mortared surfaces of the blocks are treated for mortar bonding. Glass block may be solid or hollow and may I;ontain inserts.

710.5 SIZE OF PANELS.

Glass block panels for exterior walls shall not exceed

13.4m2 of unsupported wall surface or 4572 mm in any

dimension. For interior walls, glass block panels shall not

exceed 23.2 m2 of unsupported area or 7620 mm in any

dimension.

710.6 EXPANSION JOINTS.

Glass block shall be provided with expansion joints along

the sides and top, and these joints shall have sufficient

thickness to accommodate displacements of the supporting

structure, but not less than 9.5 mm. Expansion joints shall

be entirely free of mortar and shall be filled with resilient

material.

710.7 REUSE OF UNITS.

Glass block units shall not be reused after being removed

from an existing panel.

710.2 MORTAR JOINTS. Glass block shall be laid in Type S or N mortar. Both vertical and horizontal mortar joints shall be at least 6 mm and not more than 9.5 mm thick and shall be completely filled. All mortar contact surfaces shall be treated to ensure adhesion between mortar and glass. 710.3 LATERAL SUPPORT. Glass panels shall be laterally supported along each end of the paneL Lateral support shall be provided by panel anchors spaced not more than 406 mm on center or by channels. The lateral support shall be capable of resisting the horizontal design forces determined in Chapter 2 or a minimum of 2920 Newtons per linear meter of wall, whichever is greater. The connection shall accommodate movement requirements of Set.:tion 710.6.

710.4 REINFORCEMENT. Glass block panels shall have joint reinforcement spaced not more than 406 mm on center and located in the mortar bed joint extending the entire length of the panel. A lapping oflongitudinal wires for a minimum of 152 mm is required for joint reinforcement splices. Joint reinforcement shall also be placed in the bed joint immediately below and above openings in the panel. Joint reinforcement shall conform to ASTM A 385 and A 641. Joint reinforcement in exterior panels shall be hot-dip galvanized in accordance with ASTM A 385 and A 641.


7-39

TABLE 703-1- MORTAR PROPORTIONS FOR UNIT MASONRY

PROPORTIONSBYVOLUME(CEMENTnnOUSMA~~

MORTAR Cement -Lime

TYPE M S N

0 Mortr.r cement

M M S S N M M S S N

Masonry cement

I

Portland Cement or Blended Cement I I I 1 I

- v.,-

-

-

-

I

-

-

1

It,

-

0

Masonry Cement M S N

-

-

-

-

-

-

-

-

I

-

Masonry cement confomung to the reqmrements ofUBe Standard 21-11. cement confonning to the requirements ofUBe Standard 21-14.

I

I

1 I

Mortar Cement • S N M

I

-

-

-

-

-

-

-

-

I

-

-

1

-

I

-

-

I

-

-

-

-

-

-

-

-

-

Jlydrated Lime or Lime PuttY. y. over Y. to It, over It, to I Y. over 1 Y. to 2 V.

AGGREGATE MEASURED IN A DAMP, LOOSE CONDITION

Not less than 2 Y. and not more than 3 times the smn of the separate volmnes of cementitious materials.

-

-

2 Mortar

TABLE 703-2 - GROUT PROPORTIONS BY VOLUME 1 PARTS BY VOLUME OF PORTLAND CEMENT OR BLENDED CEMENT

..-.....,

AGGREGATE MEASURED IN A DAMP, LOOSE CONDITION Fine Coarse I Fine 1 2 Y. to 3 times the smn of the volmnes ofthe cementitious materials gr<>ut oto lito 2 y. to 3 times the smn of the volmnes 11 to 2 times the sum of the volumes Coarse I grout of the cementitious materials of the cementitious materials .. Grout shall attam a nnmmum CompressIve strength at 28 days of 13.8 MPa. The building official may requrre a compresslve field strength test ot grout ~ made in accordance with DEC Standard 21-18.

I TYPE

PARTS BY VOLUME OF HYDRATED LIME OR LIME PUTTY oto 110

1

-.-J

.

TABLE 704-1~ GROUTING LIMITATIONS

, GROUT TYPE

GROUT POUR MAXIMUM HEIGHT (feet}l x 304.8 for mm I

I

MINIMUM DIMENSIONS OF THE TOfAL CLEAR AREAS WITHIN GROUT SPACES AND CELLSlJ X 15.4 formm Multiwythe Masonry HaUow-unit Masonry I It,x2 % lit, I It, x 2 IY., 1\1, x2 1\1, l'hx3 3x3 2 I \1, I \1,x3 2 \1,x3 2 2 3x3 2\1, 3x3 3x4 3

Fine 5 Fine 8 Fine 12 Fine 24 Fine I Coarse 5 Coarse 8 Coarse 12 Coarse 24 Coarse I I See also Sectton 2104.6. 2 The actual grout space or grout cell dimensions must be larger than the smn of the following items (I) The required minimmn dimensions of total clear areas in Table 704-1; (2) The width of any mortar projections within the space; and (3) The horizontal projections of the diameters of the horizontal reinforcing bars within a cross section of the grout spaoe or cell. ) The minimmn dimensions ofthe total clear areas shall be made up of one or more open areas with at least one area being 19 rom or greater in width.

~

National Structural Code of the Philippines,' Volume 1

7-40

TABLE 705-1 - SPECIFIED COMPRESSIVE STRENGTH OF MASONRY,fm (psi) BASED ON SPECIFYING THE COMPRESSIVE STRENGTH OF MASONRY UNITS I

COMPRESSIVE STRENGTH OF CLAY MASONRY UNITS 1,2

I

(psi)

SPECIFIED COMPRESSIVE STRENGTH OF MASONRY f'm Type M or S Mortar 3 Type N Mortar' (psi)

I

14,000 or more 12,000 10,000 8,000 6,000 4,000

(psi)

x 6.89 for kPa 5,300 4,700 4,000

4,400 3,800 3,300 2,700 2,200 1,600

3,350 2,700 2,000

SPECIFIED COMPRESSIVE STRENGTH OF MASONRY, rift Type N Mortarl I

COMPRESSIVE STRENGTH OF CONCRETE MASONRYUNITS1.4

Type M or S Mortar~

(psi)

I

(psi)

(psi)

x 6.89 for kPa

i

3,000 4,800 or more 2,800

3750

2,500 2,350

2,800

2,000 1,850

1,350 1,500 1,900

1,000 950 1250 . . COIhpreSSlve strength of sohd clay masonry UnIts IS based on gross area. Compressrve strength of hollow clay masonry UnIts IS based on IIllIll1llUnI net area . YaIues may be interpolated. When hollow clay masonry units are grouted, the grout shall confOlm to the proportion in Table 703-2. 1 Assumed assemblage. The specified compressive strength of masonry /' m is based on gross area strength when uSmg solid units or solid grouted masonry and net area strength when using ungrouted hollow units. 3 Mortar for unit masonry, proportion specification, as specified in Table 703-1. These values apply to portland cement - lime mortars without added air - entraining materials. 4y,lues may be interpolated. In grouted concrete masonry, the compressive strength of grout shall be equal to or greater than the compressive strength ofthe concrete masonry units.

TABLE 707-1- ALLOWABLE TENSION, B" FOR EMBEDDED ANCHOR

BOLTS FOR CLAY AND CONCRETE MASONRY, pounds1,2,3

EMBEDMENT LENGTH, lin or EDGE DISTANCE, 1M (inches)

I'm' (psi) : X i

2

3

4

240 270 280 310 340 400 440 480

550 600 630 710 770 890 1,000 1,090

970 1,070 1,120 1260 1,380 1,590 1,780 1950

6.89 for kPa

1,500 1,800 2,000 2,500 3,000 4,000 5,000 6000

-

5 x25.4formm x 4.45 forN 1,520 1,670 ' 1,760 1,960 2,150 i 2,480 2,780 3040

!

: !

6

8

10

2,190 2,400 2,520 2,830 3,100 3580 4,000 4,380

3,890 4,260 4,500 5030 5,510 6,360 7,110 7,790'

6,080 6,660 7,020 7850 8,600 9,930 11,100 12,200

The allowable tension values m Table 707 1 are based on compresslVl;l strength of masonry assemblages. Where Yield strength ofanchor bolt steel governs, the allowable tension in pounds is given in Table 707-2. l Yalues are for bolts of at least A 307 quality. Bolts shall be those specified in Section 706.2.4.1 lYalues shown are for work with or without special inspection.,


7-41

TABLE 707-2 - ALLOW ABLE TENSION, B" FOR EMBEDDED ANCHOR BOLTS FOR CLAY AND CONCRETE MASONRY, pounds 1,2 ANCHOR BOLT DIAMETER (inchesl x25.4formm %

350

I I

%

790

I I

~

1410

I

%

I

%

x 4.45 CorN 2210 I 3180

l

I

'Va

I

1

I

1%

I

4330

I

5650

I

7160

I

I Values

are for bolts of at least A 307 quality. Bolts sball be those specdied In Sechon 706.2.14.1

2 Values

shown are for work with or without special inspection.

TABLE 707-3- ALLOWABLE SHEAR, B", FOR EMBEDDED ANCHOR

BOLTS FOR CLAY AND CONCRETE MASONRY, pounds 1,2

I'm

(psi)

I

1,500 1,800 2,000 2,500 3,000 4,000 5000 6000

I

I

I

I

%

480 480 480 480 480 480 480 480

I

!

Yz 850 850 850 850 850 850 850 850

ANCHOR BOLT DIAMETER (inches) x 25.4 for mm % % 'Va 1,330 1,780 1,920 1,860 2,101 1,330 1,330 1,900 2,060 1330 1,900 2,180 1,330 1,900 2,280 1,330 1900 2,450 1330 1900 2,590 1330 1,900 2600

I

I

I

1

1%

2,050 2,150 2,200 2,330 2440 2,620 2,770 2,900

2,170 2280 2,340 2,470 2,590 2,780 2,940 3,080

Values are for bolts ofat least A 307 quality. Bolts sball be those specified In Sectl011706.2.14.1. shown are for work with or without special inspection.

2 Values

TABLE 707-4- MINIMUM DIAMETERS OF BEND BAR SIZE 10 mm through 25 mm 28 mm tbrou~ 36 mm

MINIMUM DIAMETER 6 bar diameters 8 bar diameters

TABLE 707-5- ALLOWABLE FLEXURAL TENSION (psi)

UNIT TYPE Normal to bed Joints

Solid

Hollow Normal to head joints . Solid

Ul!~

MORTAR TYPE Cement -lime and Mortar Cement Masonry Cement N Mol'S Mol'S I x 6.89 for kPa

40 25 80 50

I I

I

30 19

24 15

60 38

48 30

i

NationiJl Structural Code of the Philippines, Volume 1

N

15 9

I

30 18

7-42

TABLE 708-1- MAXIMUM NOMINAL SHEAR STRENGTH VALUES 1,2

MlVd :::;0.25

!

I 2':1.00 I

A1 is the maximum bending moment that occurs simultaneously WIth the shear load Vat the section under consideration. InteIpolation may be by straight line for AflVd values between 0.25 and 1.00. 2 Vn is in pounds (N), and j'm is in pounds per square inches (1cPa).

TABLE 708-2- NOMINAL SHEAR STRENGTH COEFFICIENT

:::;0.25

2.4

> l.00

1.2

Ai is the maximum bending moment that occurs simultaneously with the shear load Vat the section under consideration. InteIpolation

may be by straight line tOr AJ.Td ''alues between 0.25 and 1.00.

!

TABLE 709-1- SHEAR WALL SPACING REQUIREMENTS FOR EMPIRICAL DESIGN OF MASONRY

I

FLOOR OR ROOF CONSTRUCTION Cast-in-place concrete Precast Concrete i Metal deck with concrete fill Metal deck with no fill I Wood Diaphragm

MAXIMUM RATIO Shear Wall Spaciog to Shear Wall Leogth 5:1


4:1 3:1 2:1 2:1

7-43

TABLE 709-2- ALLOWABLE COMPRESSIVE STRESSES FOR EMPIRICAL DESIGN OF MASONRY I CONSTRUCTION: COMPRESSIVE STRENGTH OF UNIT, GROSS AREA X

ALLOWABLE COMPRESSIVE STRESSES} GROSS CROSS SECTIONAL AREA (psi) x 6.89 for kPa

t__

T~ M or S Morta:::..r__

6.89 for kPa

Solid masonry of brick and other solid units of clay or shale; Sand-lime or concrete brick: 8,000 plus, psi 4,500 psi 2,500 psi 1------'2-1,5=--::00 psi , Grouted masonry, of clay or shale; sand-lime or concrete: 4,500 plus, psi 2,500 psi 1,500 psi Solid masonry of solid concrete m=nry units 3,000 plus, psi 2,000 psi

,

I I

I 350 225 ' 160 _ _----=-11:.;,,5_ _ _ _- t - _ _

300 200 140 100

I , I,

275 215 175

I

200, 140

100

--225 200

160 140

115_ _ _---i_ _ _---=-1O-=-0'---_ _--i

1200 pSI.

Masonry of hollow load-bearing units: 2,000 plus, psi 1,500 psi 1,000 psi 700 psi Hollow walls (cavity or masonry bonded)k solid units:

2,500 plus, psi

,------1_,500 psi Hotlow units Stone ashlar masonry: Granite Limestone or marble Sandstone or cast stone Rubble stone masonry Coarse, rough or random Unburned clay masonry ..

~'N Mortar----J

140 115 75 60

120 100 70

I . I

160 115 75

140 100

I

70

I

-------+-------~~ I

I I

720 450 360

640 400 320

120 30

100

I

Linear mterpollltton may be used for detemllrung allowable stresses for masonry umts havmg. compressive strengths which are intermediate behveen those given in the table. ' 2 Where floor and floor loads are carned upon v\iythe, the gross cross-sectional area is that of the wythe under load. If both wythes are loaded, the gross cross-sectional area is that of the wall minus the the area of the cavity between the wythes. I

TABLE 709-3- ALLOWABLE SHEAR ON BOLTS FOR EMPIRICALLY

DESIGNED MASONRY EXCEPT UNBURNED CLAY UNITS

EMBEDMENT DIAMETER BOLT (inches) '" (inches) x 25.4 for mm ,..----'

, ..

Yz % % % I 1%

I i

4 4 5 6 7 8

.

GROUTED MASONRY SSOLID MASONRY I {shear in pounds} (shear: in pounds) I x 4.45 for N

.

350 500 750 1,000 1,250 1,500

I i

I I

550 750 1,100 1,500 1,8501 2,250":

I An addittonal2 fiches of embedment shall be proHded for anchor bolts located m the top of colurrms tor bUlldmgs located m Selsnnc Zones 2 and 4 . 2 Permitted only with not less than 2,500 pounds per square inch (l7.24l\..1Pa) units.

National Structural Code of the PhiHppines, Volume 1

I

I, I I I i

I

7-44

TABLE 709-4- WALL LATERAL SUPPORT REQUIREMENTS FOR EMPIRICAL DESIGN OF MASONRY MAXIMUM lit or hit

CONSTRUCTION Bearing walls Solid or solid grouted All other Nonbearing walls Exterior Interior

20 18 18 36

TABLE 709-5 - THICKNESS OF FOUNDATION WALLS FOR EMPIRICAL DESIGN OF MASONRY NONUNALTEUCKNESS x25.4formm

MAXIMUM DEPTH OF UNBALANCED FILL (feet) x 30·t8 for mm

8 10 12 8 10 12 8 10 12 8

4 5 6 5 6 7 7 8 8 7

(inches)

FOUNDATION WALL CONSTRUCTION

Masonry of hollow units, ungrouted

Masonry of solid units

•

Masonry of h.ollow or solid units, fuUy grouted

Masonry of hollow units reinforced vertically with. NO.4 bars and grout at 24" O.c. Bars located Not less than 4Y2 from pressure side of wall. I

!

I

Y2 % %

Va 1

Pis

I

I I !

I

TABLE 709-6 -ALLOWABLE SHEAR ON BOLTS FOR MASONRY OF UNBURNED CLAY UNITS DIAMETER OF BOLTS (iocbes)

!

EMBEDMENTS (iocbes) x 25.4 for mm

SHEAR (pooods)

-

-

12 15 18 21 24

200 300 400 500 600


7-45

TABLE 710-1- RADIUS OF GYRATION1 FOR CONCRETE MASONRY UNlTS2 NOMINAL WIDTH OF WALL (inches) x. 25.4 for mm

I

GROUT SPACING ~ (inches) a. 25.4 for mm Solid Grouted 16 I ! 24 32 : 40 i i 48 56 i i 64 I 72 No .Imlut I

C=..

1

4 1.04 1.16 1.21 1.24 1.26 1.27 1.28 1.29 1.30 1.32

I

~.--

.

,

6 1.62 1.79 1.87 1.91 1.94 1.96 1.98 1.99 2.00 2.08

10 2.77 3.04 3.17 3.25 3.30 3.33 3.36 3.38 3.40 3.55

8

2.19 2.43 2.53 2.59 2.63 2.66 2.68 2.70 2.71 2.84

I

12 3.34

3.6~---j

i

3.82 3.91 3.97 4.02 4.05 4.08 4.LO 4.29

------4

For smgle-v'y1:he masonry or for an mdlVldual wythe of a CRVlty walL

r=..J J/Ae 2 The

radius of gyration shall be based on the specified dimensions of the masonry units or shall be in accordance with the values shown which are based on the minimum dimensions ofhollow concrete masonry unit face shells and webs in accordance with UBC Standard 21-4 for two cell units.

TABLE 710-2- RADIDS OF GYRATION1 FOR CLAY MASONRY UNIT LENGTH, 16 INCHES2 NOMINAL WIDTH OF WALL (inches)~_ _ _ _ _ GROUT SPACING (inches) x25.4formm I Solid Grouted 16 I",. 24 32 i 40 I 48 56 64 72 rNowout l'

X

!

,

.

4 1.06 1.16 1.20 1.23 1.25 1.26 1.27 1.27 1.28 1.32

6 1.64 1.78 1.85 1.88 1.91 1.93 1.94 1.95 1.95 2.02

S 2.23 2.42 2.51 2.56 2.59 2.61 2.63 2.64 2.65 2.75

---j

=:::::J

25.4for mm

! I

I

i

10 2.81 3.03 3.13 3.19 3.23 3.26 3.28 3.30 3.31 3.42

I I

12 3.39 3.65 3.77 3.85 3.90 3.93 3.95 3.97 3.99 4.13

For single-wythe masonry or for an mdiVldual wythe of a CRVlty wall.

r=..J11Ae 2 The

radius of gyration shall be based on the specified dimensions of the masonry units or shall be in accordance with the values shown which are based on the minimum dimensions ofhollow clay concrete masonry face shells and webs in accordance with UBC Standard 21-1 for two cell units.


I

i i

I

7-46

l

TABLE 710-3- RADIUS OF GYRATION FOR CLAY MASONRY UNIT LENGTH, 12 INCHES2

•

GROUT SPACING (inches) x 25.4 (ormm Solid Grouted 12 18 24 30 36 42 48 54 60 66 72

No grout

I

NOMINAL WIDTH OF WALL (inches) x 25.4 (ormm

6

4 1.06 1.15 1.19 1.21 1.23 1.24 1.24 1.25 1.25 1.26 1.26 1.26 1.29

IFors'mgle-W)1.hemasomy or for an individual

1.65 1.77 1.82 1.85 1.87 1.88 1.89 1.90 1.90 1.91 1.91 1.91 1.95

8 2.24 2.40 2.47 2.51 2.53 2.55 2.56 2.57 2.58 2.59 2.59 2.59 2.65

10

2.82 3.00 3.08 3.12 3.15 3.17 3. ]9 3.20 3.21 3.21 3.22 3.22 3.28

12 3.41 3.61 3.71 3.76 3.80 3.82 3.84 3.85 3.86 3.87 3.88 3.88 3.95

e of a eavi . wall.

radius of gyration shall be based on the specified dimensions of the masomy units or shall be in accordance with the values shoVlu VI hich are based on the minimum dimensions of hollow clay concrete masomy lace shells and webs in accordance with UBC Standard 21-\ for two cell units.

2 The


CONVERSION FACTORS mUittDl,y b~

to

TO£ODvert

LENGTH 1 mile (U.S. statue) 1 yd 1ft

Ian rn m nnn

lin

mm

1 mile' (U.S. statue) 1 acre (U.S. survey)

km' ha m2 m2 m2 mm2

1.609.344 0.9144 0.3048 304.8 25.4

AREA

1 yd 2 1 ft2 2 1 in

2.589998 0.4046873 4046.873 0.8361274 0.092 903 04 645.16

VOLUME, MODULUS OF SECfION !'

1 acre ft 3 1 yd

100 board ft

1 ft3

1 in3 1 barrel (42 U.S. gallons)

m' 3 m m3 m3 L(dm~ mm3 mL(cm~ rn)

1233.489 0.7645549 0.2359737 0.02831685 28.3168 16387.06 16.3871 0.1589873

(FLUID) CAPACITY 1 gal (U.S. liquid)· 1 qt (lJ. S. liquid) 1 pt lUS. liquid) 1 fl oz (U.S) 1 gal (U. S. liquid) • 1 gallon (UK) approx. 1.2 gal (U.S.)

LU mL mL mL , mU 1 liter approx. 0.001 cubic meter

3.785412 946.3529 473.1765 29.5735 0.003785412

SECOND MOMENT OF AREA 1 in4

mrn4 m4

4162314 4162314 x 10'7

PLANE ANGLE 1° (degree) l' (minute) I" (second)

rad mrad urad urad

0.01745329 17.453.29 290.8882 4.848137

VELOCITY, SPEED 1 ftls 1 milelh

mls

kmIh mls

0.3048 1.609344 0.44704

VOLUME RATE OF FLOW 1 ft'/s 1 ft 3/min 1 gal/min 1 gal/min 1 gallh 1 million gal/d I acre ftls

m'/s Lis Lis m3/rnin mUs Lis m 3/s

0.02831685 0.471 9474 0.0630902 0.0038 l.051 50 43.8126 1233.49

TEMPERATURE INTERVAL 1"F

toF

°CorK

EQUIVALENT TEMPERATURE (t",-.=T.,...273.15) toe (ContinlWti)

National Structural Code of the Philippines, Volume 1 ~

-_._-----_._------_....-.:

0.555556 j/90C = 5/9K toF=9/j 1oc+32

•

CONVERSION FACTORS-(Continued) To convert

muJtiplybv

to

MASS 1 ton (short..··)

metric ton

Hb loz "·1 long ton (2,240 lb)

kg kg

~

0.907185 907.1847

0.4535924 28.34952 1016.047

MASS PER UNIT AREA kglm2 2

I Ib/ft' 2 10Z/Yd 1 ozlft2

'i/m

f4m2

4.882428 33.90575 305.1517

DENSITY (MASS PER UNIT VOLUME) kglm3 kglm3

1 Ib/ft'. Ilblyd3 1 tonlvd'

t/m3

16.01846 0.5932764 1.186553

FORCE 1 tonf (ton-force) 1 kip (1,000 Ibf) 1 Ibf(pound-force)

kN kN N

8.89644 4.44822 4.44822

MOMENT OF FORCE, TORQUE I1bf·ft 1 Ibf·in 1 {onMl: I kip-ft

N'm N·m kN·m kN·m

1.355818 0.1129848 2.711 64 1.35582

FORCE PER UNIT LENGTH I lbflft ! Ibffm I tonflft

NIm NIm

kNlm PRESSURE, STRESS, MODULUS OF ELASTICITY (FORCE PER UNIT AREA) (1

1 tonflin' 1 t011flft2 I kiplin2 IIbffm2 IlbflW Atmosphere 1 inch mercury I foot (water column at 32"F)

MFa kPa MFa

kPa Pa kPa

kPa kPa

14.5939 175.1268 29.1878 Pa = 1 N/m~) 13.7895 95.7605 6.894757 6.894757 47.8803 101.3250 3.37685 2.98898

WORK. ENERGY, HEAT (lJ = IN·m = lW "8)

!

1 kWh (550 ft·lbf/s) 1 Btu (Tnt.Table) 1 ft·lbf

MJ kJ J J

3.6 1.055056 1055.056 1.355818

COEFFICIENT OF HEAT TRANSFER

i

I Btu/(W.h."F)

W/(m'·K)

5.678263

THERMAL CONDUCTIVITY 1 Btu/eft·h·"F) . I ImIftz (footcandle)

W/(m·K)

1.730735

ILLUMINANCE Ix (lm()

10.763.91

LUMINANCE I cdlft' 1 foot lambert 1 lambert

cdinr' cdlm2

kcdlm2


10.7639 3.426259 3.183099

I

NSCP-2001.pdf

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