2006 Structural Seismic Design Manual 1

Volume 3

2009 IBC

®

SEAOC STRUCTURAL/SEISMIC DESIGN MANUAL BUILDING DESIGN EXAMPLES FOR STEEL AND CONCRETE

Copyright Copyright © 2012 Structural Engineers Association of California. All rights reserved. This publication or any part thereof must not be reproduced in any form without the written permission of the Structural Engineers Association of California.

Publisher Structural Engineers Association of California (SEAOC) 1400 K Street, Suite 212 Sacramento, CA 95814 Telephone: (916) 447-1198; Fax: (916) 444-1501 E-mail: [email protected]; Web address: www.seaoc.org The Structural Engineers Association of California (SEAOC) is a professional association of four regional member organizations (Southern California, Northern California, San Diego, and Central California). SEAOC represents the structural engineering community in California. This document is published in keeping with SEAOC's stated mission: “to advance the structural engineering profession; to provide the public with structures of dependable performance through the application of state-of-the-art structural engineering principles; to assist the public in obtaining professional structural engineering services; to promote natural hazard mitigation; to provide continuing education and encourage research; to provide structural engineers with the most current information and tools to improve their practice; and to maintain the honor and dignity of the profession.”

Editor International Code Council

Disclaimer Practice documents produced by the Structural Engineers Association of California (SEAOC) and/or its member organizations are published as part of our association's educational program. While the information presented in this document is believed to be correct, neither SEAOC nor its member organizations, committees, writers, editors, or individuals who have contributed to this publication make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions, or recommendations included in this publication. The material presented in this publication should not be used for any specific application without competent examination and verification of its accuracy, suitability, and applicability by qualified professionals. Users of information from this publication assume all liability arising from such use. First Printing: September 2012

Table of Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi Suggestions for Improvement/Errata Notification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix How to Use This Document. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Notation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxii References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxi Design Example 1: Steel Concentrically Braced Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1A

Special Concentrically Braced Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1B

Chevron and Zipper Configurations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

1C

Cross-Bracing and Single-Diagonal Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

1D

Buckling-Restrained Braced Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

1E

Ordinary Concentrically Braced Frame. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

Design Example 2 Eccentrically Braced Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Design Example 3 Special Moment Frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 Design Example 4 Special Plate Shear Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 Design Example 5 Reinforced Concrete Wall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 Design Example 6 Reinforced Concrete Wall with Coupling Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245 Design Example 7 Reinforced Concrete Special Moment-Resisting Frame . . . . . . . . . . . . . . . . . . . . . . . . . . 289

2009 IBC Structural/Seismic Design Manual, Vol. 3

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Preface

This document is the third volume in the three-volume 2009 IBC Structural/Seismic Design Manual. It has been developed by the Structural Engineers Association of California (SEAOC) with funding provided by SEAOC. Its purpose is to provide guidance on the interpretation and use of the seismic requirements in the 2009 International Building Code (IBC), published by the International Code Council, Inc., and SEAOC’s 2005 Recommended Lateral Force Requirements and Commentary (also called the Blue Book). The 2009 IBC Structural/Seismic Design Manual was developed to fill a void that exists between the recommendations of the Blue Book, which explains the basis for the code provisions, and everyday structural engineering design practice. The 2009 IBC Structural/Seismic Design Manual illustrates how the provisions of the code are used. Volume I: Code Application Examples, provides step-by-step examples for using individual code provisions, such as computing base shear or building period. Volumes II and III: Building Design Examples, furnish examples of seismic design of common types of buildings. In Volumes II and III, important aspects of whole buildings are designed to show, calculation-by-calculation, how the various seismic requirements of the code are implemented in a realistic design. The examples in the 2009 IBC Structural/Seismic Design Manual do not necessarily illustrate the only appropriate methods of design and analysis. Proper engineering judgment should always be exercised when applying these examples to real projects. The 2009 IBC Structural/Seismic Design Manual is not meant to establish a minimum standard of care but, instead, presents reasonable approaches to solving problems typically encountered in structural/seismic design. The example problem numbers used in the prior manual—2006 IBC Structural/Seismic Design Manual—have been retained herein to provide easy reference to compare revised code requirements. SEAOC and ICC intend to update the IBC Structural/Seismic Design Manual with each edition of the building code. Jon P. Kiland and Rafael Sabelli Project Managers


v

Acknowledgments

Authors The 2009 IBC Structural/Seismic Design Manual was written by a group of highly qualified structural engineers. They were selected by a steering committee set up by the SEAOC Board of Directors and were chosen for their knowledge and experience with structural engineering practice and seismic design. The consultants for Volumes I, II, and III are: Jon P. Kiland, Co-Project Manager Rafael Sabelli, Co-Project Manager Matt Eatherton Stephen Kerr John W. Lawson

Joe Maffei Kevin Moore Karl Telleen Douglas S. Thompson Dan Wendowatz

Reviewers A number of SEAOC members and other structural engineers helped check the examples in this volume. During its development, drafts of the examples were sent to these individuals. Their help was sought in review of code interpretations, as well as detailed checking of the numerical computations.

Seismology Committee Close collaboration with the SEAOC Seismology Committee was maintained during the development of the document. The Seismology Committee has reviewed the document and provided many helpful comments and suggestions. Their assistance is gratefully acknowledged.

Production and Art International Code Council

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Suggestions for Improvement

In keeping with SEAOC’s Mission Statement: “to advance the structural engineering profession” and “to provide structural engineers with the most current information and tools to improve their practice,” SEAOC plans to update this document as structural/seismic requirements change and new research and better understanding of building performance in earthquakes becomes available. Comments and suggestions for improvements are welcome and should be sent to the following: Structural Engineers Association of California (SEAOC) Attention: Executive Director 1020 12th Street, Suite 303 Sacramento, California 95814 Telephone: (916) 447-1198; Fax: (916) 444-1501 E-mail: [email protected]; Web address: www.seaoc.org

Errata Notification

SEAOC has made a substantial effort to ensure that the information in this document is accurate. In the event that corrections or clarifications are needed, these will be posted on the SEAOC web site at http://www.seaoc.org or on the ICC web site at http://www.iccsafe.org. SEAOC, at its sole discretion, may or may not issue written errata.


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Introduction

The 2009 IBC Structural/Seismic Design Manual is intended to help the reader understand and correctly use the IBC structural/seismic provisions and to provide clear, concise, and graphic guidance on the application of specific provisions of the code. It primarily addresses the major structural/seismic provisions of the IBC, with interpretation of specific provisions and examples highlighting their proper application. The 2009 IBC has had structural provisions removed from its text and has referenced several national standards documents for structural design provisions. The primary referenced document is ASCE/SEI 7-05, which contains the “Minimum Design Loads for Buildings and Other Structures.” ASCE/SEI 7-05 is referenced for load and deformation design demands on structural elements, national material design standards (such as ACI, AISC, MSJC and NDS) are then referenced to take the structural load demands from ASCE/SEI 7-05 and perform specific material designs. The complete 2009 IBC Structural/Seismic Design Manual has three volumes. Volume 1 illustrates the application of specific provisions of ASCE 7 and the IBC.Volumes 2 and 3 provide a series of structural/seismic design examples for buildings illustrating the seismic design of key parts of common building types such as a large three-story wood frame building, a tilt-up warehouse, a braced steel frame building, and a concrete shear wall building. While the 2009 IBC Structural/Seismic Design Manual is based on the 2009 IBC, there are some provisions of SEAOC’s Recommended Lateral Force Provisions and Commentary (Blue Book) that are applicable. When differences between the IBC and Blue Book are significant, they are brought to the attention of the reader. The 2009 IBC Structural/Seismic Design Manual is intended for use by practicing structural engineers and structural designers, building departments, other plan review agencies, and structural engineering students.


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How to Use This Document

The 2009 IBC Structural/Seismic Design Manual—Volume 3 is based on the 2009 IBC, unless otherwise indicated. Such indication is to be found in the “Code Reference” column at page right. ASCE/SEI 7-05 notation is generally used throughout the document. Code references to the 2009 IBC are enclosed in parentheses. Occasional references to other codes and standards are specifically identified as such (e.g., ACI 318-08, AISC-360-05, etc.) Abbreviations used in the “Code Reference” column are: § – Section

T – Table

F – Figure

Eq – Equation

Generally, each design example is presented in the following format. First, there is an “Overview” of the example: a description of the building to be designed. This is followed by an “Outline” indicating the tasks or steps to be illustrated in each example. Next, “Given Information” provides the basic design information, including plans and sketches given as the starting point for the design. This is followed by “Calculations and Discussion,” which provides the solution to the example. Some examples have a subsequent section designated “Commentary” that is intended to provide a better understanding of aspects of the example and/ or to offer guidance to the reader on use of the information generated in the example. Finally, references and suggested reading are given under “References.” Some examples also have a “Foreword” and/or “Factors Influencing Design” section that contains remarks on salient points about the design.


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Notation

The following notation is used in this document. These are generally consistent with those used in ASCE/SEI 7-05 and other standards such as ACI and AISC. Some new notations have been added. The reader is cautioned that the same notation may be used more than once and may carry entirely different meanings in different situations. For example, E can mean the tabulated elastic modulus under the AISC definition (steel) or it can mean the earthquake load under §12.4.2 of ASCE/SEI 7-05. A

=

total cross-sectional area of member

Ab

=

cross-sectional area of a horizontal boundary element (HBE)

Ac

=

cross-sectional area of a vertical boundary element (VBE)

Ach

=

cross-sectional area of a structural member measured out-to-out of transverse reinforcement

Acv

=

gross area of concrete section bounded by web thickness and length of section in the direction of shear force considered

Acw

=

area of concrete section of an individual pier, horizontal wall segment, or coupling beam resisting shear

Ae

=

effective net area

A f

=

flange area

Ag

=

gross area of member

Ag

=

gross area of concrete section. For a hollow section, Ag is the area of the concrete only and does not include the area of the void(s)

An

=

net area of member

Ant

=

net area subject to tension

Anv

=

net area subject to shear

As

=

area of nonprestressed longitudinal tension reinforcement

Asc

=

area of the yielding segment of steel core

Ash

=

total cross-sectional area of transverse reinforcement (including crossties) within spacing s and perpendicular to dimension bc

As, min

=

minimum area of flexural reinforcement

Ast

=

area of link stiffener


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xiv

At

=

area of one leg of a closed stirrup resisting torsion within spacing s

Atr

=

total cross-sectional area of all transverse reinforcement within spacing s that crosses the potential plane of splitting through the reinforcement being developed

Avf

=

area of shear-friction reinforcement

Aw

=

link web area (excluding flange depth)

Aw

=

web area, the overall depth times the web thickness, dt w

Aw

=

effective area of the weld

B

=

overall width of rectangular HSS member, measured 90 degrees to the plane of the connection

B1, B2

=

factors used in determining M u for combined bending and axial forces when first-order analysis is employed

C a

=

ratio of required strength to available strength

C b

=

lateral-torsional buckling modification factor for nonuniform moment diagrams when both ends of the unsupported segment are braced

C d

=

coefficient relating relative brace stiffness and curvature

C d

=

deflection amplification factor

C m

=

coefficient assuming no lateral translation of the frame

C pr

=

factor to account for peak connection strength, including strain hardening, local restraint, additional reinforcement, and other connection conditions

C r

=

parameter used for determining the approximate fundamental period

C v

=

web shear coefficient

D

=

outside diameter of round HSS member

D

=

dead load due to the weight of the structural elements and permanent features on the building

E

=

earthquake load

E

=

modulus of elasticity of steel, E = 29,000 ksi (200,000 Mpa)

F cr

=

critical stress

F e

=

elastic critical buckling stress

F ex

=

elastic flexural buckling stress about the major axis 2009 IBC Structural/Seismic Design Manual, Vol. 3

F EXX

=

electrode classification number

F u

=

specified minimum tensile strength

F w

=

nominal strength of the weld metal per unit area

F y

=

specified minimum yield stress of the type of steel to be used, ksi (MPa). As used in the Specification, “yield stress” denotes either the minimum specified yield point (for those steels that have a yield point) or the specified yield strength (for those steels that do not have a yield point)

F yb

=

F y of a beam

F yc

=

F y of a column

F ysc

=

specified minimum yield stress of the steel core, or actual yield stress of the steel core as determined from a coupon test

H

=

height of story, which may be taken as the distance between the centerline of floor framing at each of the levels above and below, or the distance between the top of floor slabs at each of the levels above and below

I

=

moment of inertia

I c

=

moment of inertia of a vertical boundary element (VBE) taken perpendicular to the direction of the web plate line

K

=

effective length factor for prismatic member

K tr

=

transverse reinforcement index

L

=

live load due to occupancy and moveable equipment

L

=

distance between VBE centerlines

L

=

story height, inches

L

=

length of the member

L′

=

distance between plastic hinges

Lb

=

length between points that are either braced against lateral displacement of compression flange or braced against twist of the cross section

Lcf

=

clear distance between VBE flanges

L p

=

limiting laterally unbraced length for full plastic flexural strength, uniform moment case

Lr

=

limiting laterally unbraced length for the limit state of inelastic lateraltorsional buckling


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M f

=

maximum moment expected at face of column

M lt

=

first-order moment under LRFD or ASD load combinations caused by lateral translation of the frame only

M max

=

absolute value of maximum moment in the unbraced segment

M n

=

nominal flexural strength

M nt

=

first-order moment using LRFD or ASD load combinations assuming there is no lateral translation of the frame

M p

=

plastic bending moment

M pa

=

nominal plastic flexural strength modified by axial load

M pe

=

plastic moment of beam based on expected yield stress

M pr

=

probable maximum moment at plastic hinge (steel)

M pr

=

probable flexural strength of members, with or without axial load, determined using the properties of the member at the joint faces assuming a tensile stress in the longitudinal bars of at least 1.25 f y and a strength reduction factor, φ, (concrete)

M u

=

required flexural strength

M 1

=

smaller moment, calculated from a first-order analysis, at the ends of that portion of the member unbraced in the plane of bending under consideration

M 2

=

larger moment, calculated from a first-order analysis, at the ends of that portion of the member unbraced in the plane of bending under consideration

N

=

length of bearing (not less than k for end beam reactions)

Pb

=

required strength of lateral brace at ends of the link

Pbr

=

required brace strength

Pe1, Pe2 =

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elastic critical buckling load for braced and unbraced frame, respectively

Pn

=

nominal axial strength

Pu

=

required axial strength

P y

=

nominal axial yield strength of a member, equal to F y Ag

P ysc

=

axial yield strength of steel core

Qb

=

maximum unbalanced vertical load effect applied to a beam by the braces


Q1

=

axial forces and moments generated by at least 1.25 times the expected nominal shear strength of the link

R

=

seismic response modification coefficient

Rn

=

nominal strength

Rt

=

ratio of the expected tensile strength to the specific minimum tensile strength F u, as related to overstrength in material yield stress R y

Ru

=

required strength

Rv

=

panel zone nominal shear strength

R y

=

ratio of the expected yield stress to the specified minimum yield strength, F y

R yb

=

ratio of expected yield stress to specified minimum yield stress F y, for a beam

R ye

=

ratio of expected yield stress to specified minimum yield stress F y, for a column

S

=

snow load

S h

=

distance from the face of a column to a plastic hinge, in

U

=

required strength to resist factored loads or related internal moments and forces, ACI-318

U

=

shear lag factor

U bs

=

reduction coefficient, used in calculating block shear rupture

V c

=

nominal shear strength provided by concrete, ACI-318

V e

=

design shear force corresponding to the development of the probable moment strength of the member

V gravity

=

beam shear force resulting from 1.2 D + f 1 L + 0.2S , IBC

V n

=

nominal shear strength of a member

V p

=

nominal shear strength of a link

V pa

=

nominal shear strength of a link modified by the axial load magnitude

V RBS

=

larger of the two values of shear force at the center of the reduced beam section at each end of a beam

V RBS ′

=

smaller of the two values of shear force at the center of the reduced beam section at each end of a beam


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V s

=

nominal shear strength provided by shear reinforcement, ACI-318

V u

=

required shear strength

Z

=

plastic section modulus of a member

Z b

=

plastic section modulus of the beam

Z c

=

plastic section modulus of the column

Z e

=

effective plastic modulus of a section (or connection) at the location of a plastic hinge, Z RBS

Z x

=

plastic section modulus x -axis

Z RBS

=

minimum plastic section modulus at the reduced beam section

a

=

horizontal distance between a column flange and the start of an RBS cut,

b

=

width of compression element as defined in the AISC Specification

b

=

length of an RBS cut

bbf

=

width of beam flange

c

=

depth of cut at the center of the reduced beam section

d

=

nominal fastener diameter

d

=

overall member depth

d z

=

overall panel zone depth between continuity plates

e

=

EBF link length

f e′

=

specified compressive strength of concrete

f y

=

specified yield strength of reinforcement, ACI-318

f 1

=

load factor determined by the applicable building code for live loads but not less than 0.5

h

=

clear distance between flanges less the fillet or corner radius for rolled shapes

h

=

distance between horizontal boundary elements’ centerlines

ho

=

distance between flange centroids

k c

=

distance from outer face of a column flange to web toe of fillet (design value) or fillet weld


l

=

unbraced length of compression or bracing member

n

=

length of clear span measured face-to-face of supports, ACI-318

u

=

unsupported length of compression member, ACI-318

w

=

length of entire wall or length of segment of wall considered in direction of shear force, ACI-318

n

=

number of items; such as strength tests, bars, wires, monostrand anchorage devices, anchors, or shearhead arms, ACI-318

r

=

governing radius of gyration

r y

=

radius of gyration about y-axis

s

=

center-to-center spacing of items; such as longitudinal reinforcement, transverse reinforcement, prestressing tendons, wires, or anchors, ACI-318

t

=

thickness of element

t bf

=

thickness of beam flange

t bw

=

thickness of beam web

t cf

=

thickness of column flange

t cw

=

thickness of column web

t f

=

thickness of flange

t p

=

thickness of plate or panel zone including doubler plates

t w

=

thickness of web

w

=

uniform beam gravity load

w z

=

width of panel zone between column flanges

x

=

parameter used for determining the approximate fundamental period

x

=

connection eccentricity

∆

=

first-order interstory drift due to the design loads

∆b

=

deformation quantity used to control loading of test specimen (total brace end rotation for the subassemblage test specimen; total brace axial deformation for the brace test specimen)

∆bm

=

value of deformation quantity, ∆b, corresponding to the design story drift

∆by

=

value of deformation quantity, ∆b, at first significant yield of test specimen


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xx

∆ H

=

first-order interstory drift due to lateral forces

Ωo

=

system overstrength factor

α

=

angle defining the orientation of reinforcement, ACI-318

α

=

angle of web yielding in radians, as measured relative to the vertical

αc

=

coefficient defining the relative contribution of concrete strength to nominal wall shear strength, ACI-318

β

=

compression strength adjustment factor

β1

=

factor relating depth of equivalent rectangular compressive stress block to neutral axis depth, ACI-318

βbr

=

required brace stiffness

γ total

=

link rotation angle

δu

=

design displacement, ACI-318

εt

=

net tensile strain in extreme layer of longitudinal tension steel at nominal strength, excluding strains due to effective prestress, creep, shrinkage, and temperature, ACI-318

θ

=

interstory drift angle, radians

λ

=

modification factor related to unit weight of concrete, ACI-318

λ p

=

limiting slenderness parameter for compact element

λ p, λ ps

=

limiting slenderness parameter for compact element

Σ M * pb

=

moment at the intersection of the beam and column centerlines determined by projecting the beam maximum developed moments from the column face. Maximum developed moments shall be determined from test results

Σ M * pc

=

moment at beam and column centerline determined by projecting the sum of the nominal column plastic moment strength, reduced by the axial stress Puc / Ag, from the top and bottom of the beam

φ

=

resistance factor

φb

=

resistance factor for flexure

φc

=

resistance factor for compression

φd

=

resistance factor for ductile limit states

φn

=

resistance factor for non-ductile limit states


φt

=

resistance factor for tension

φv

=

resistance factor for shear

ψ e

=

factor used to modify development length based on reinforcement coating, ACI-318

ψ s

=

factor used to modify development length based on reinforcement size, ACI-318

ψ t

=

factor used to modify development length based on reinforcement location, ACI-318

ω

=

strain hardening adjustment factor


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Definitions

Adjusted Brace Strength. Strength of a brace in a buckling-restrained braced frame at deformations corresponding to 2.0 times the design story drift. Amplification Factor. Multiplier of the results of first-order analysis to reflect second-order effects. Amplified Seismic Load. Horizontal component of earthquake load E multiplied by Ωo’, where E and the horizontal component of E are specified in the applicable building code. Backing. Piece of metal or other material, placed at the weld root to facilitate placement of the root pass. Base. The level at which the horizontal seismic ground motions are considered to be imparted to the structure. Base Shear. Total design lateral force or shear at the base. Boundary Elements. Diaphragm and shear wall boundary members to which the diaphragm transfers forces. Boundary Members. Portions along wall and diaphragm edges strengthened by longitudinal and transverse reinforcement and/or structural steel members. Buckling-restrained Braced Frame (BRBF). Diagonally braced frame satisfying the requirements of Section 16 of AISC 341 in which all members of the bracing system are subjected primarily to axial forces and in which the limit state of compression buckling of braces is precluded at forces and deformations corresponding to 2.0 times the design story drift. Charpy V-Notch Impact Test. Standard dynamic test measuring notch toughness of a specimen. Complete-joint-penetration Groove Weld (CJP). Groove weld in which weld metal extends through the joint thickness, except as permitted for HSS connections. Concrete. Mixture of portland cement or any other hydraulic cement, fine aggregate, coarse aggregate, and water, with or without admixtures. Confined Region. The portion of a reinforced concrete component in which the concrete is confined by closely spaced special transverse reinforcement restraining the concrete in directions perpendicular to the applied stress. Continuity Plates. Column stiffeners at the top and bottom of the panel zone; also known as transverse stiffeners. Coupling Beam. A beam that is used to connect adjacent concrete wall piers to make them act together as a unit to resist lateral forces.

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Dead Loads. The weight of materials of construction incorporated into the building, including but not limited to wall, floors, roofs, ceilings, stairways, built-in partitions, finishes, cladding, and other similarly incorporated architectural and structural items, and fixed service equipment, incuding the weight of cranes. Design Story Drift. Amplified story drift (drift under the design earthquake, including the effects of inelastic action), determined as specified in the applicable building code. Design Strength. The product of the nominal strength and a resistance factor (or strength reduction factor). Design Wall Thickness. HSS wall thickness assumed in the determination of section properties. Development Length. Length of embedded reinforcement, including pretensioned strand, required to develop the design strength of reinforcement at a critical section. Doubler. Plate added to, and parallel with, a beam or column web to increase resistance to concentrated forces. Drift. Lateral deflection of structure. Ductile Limit State. Ductile limit states include member and connection yielding, bearing deformation at bolt holes, as well as buckling of members that conform to the width-thickness limitations of Table I-8-1 of the Seismic Provisions. Fracture of a member or of a connection, or buckling of a connection element, is not a ductile limit state. Effective Net Area. Net area modified to account for the effect of shear lag. Embedment Length. Length of embedded reinforcement provided beyond a critical section. Expected Yield Strength. Yield strength in tension of a member, equal to the expected yield stress multiplied by Ag. Expected Tensile Strength. Tensile strength of a member, equal to the specified minimum tensile strength, F u, multiplied by Rt . Expected Yield Stress. Yield stress of the material, equal to the specified minimum yield stress, F y, multiplied by R y. Factored Load. The product of a load factor and the nominal load. Filler Metal. Metal or alloy to be added in making a welded joint. Fillet Weld. Weld of generally triangular cross section made between intersecting surfaces of elements. Fillet Weld Reinforcement. Fillet welds added to groove welds. Flat Width. Nominal width of a rectangular HSS minus twice the outside corner radius. In absence of knowledge of the corner radius, the flat width may be taken as the total section width minus three times the thickness.


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Frame. Braced frame. An essentially vertical truss, or its equivalent, of the concentric or eccentric type that is provided in a building frame system or dual frame system to resist shear. Concentrically braced frame (CBF). A braced frame in which the members are subjected primarily to axial forces. Eccentrically braced frame (EBF). A diagonally braced steel frame meeting the requirements of Section 15 of AISC 341 that has at least one end of each bracing member connected to a beam a short distance from another beam-to-brace connection or a beamto-column connection. Ordinary concentrically braced frame (OCBF). A diagonally braced steel frame meeting the requirements of Section 14 of the Seismic Provisions in which all members of the bracing system are subjected primarily to axial forces. Members and connections are designed for moderate ductility. Special concentrically braced frame (SCBF). A diagonally braced frame meeting the requirements of Section 13 of the Seismic Provisions in which all members of the bracing system are subjected primarily to axial forces. Frame System. Building frame system. A structural system with an essentially complete space frame system providing support for vertical loads. Seismic force resistance is provided by shear walls or braced frames. Dual frame system. A structural system with an essentially complete space frame system providing support for vertical loads. Seismic force resistance is provided by a momentresisting frame and shear walls or braced frames. Space frame system. A structural system composed of interconnected members, other than bearing walls, that is capable of supporting vertical loads and that also may provide resistance to seismic forces. Fully Restrained Moment Connection. Connection capable of transferring moment with negligible rotation between connected members. Gouge. Relatively smooth surface groove or cavity resulting from plastic deformation or removal of material Gravity Frame. Portion of the framing system not included in the lateral load resisting system. Gravity Load (W ). The total dead load and applicable portions of other loads as defined in ASCE/ SEI 7-05, §§12.7.2 and 12.14.8.1. Gusset Plate. Plate element connecting truss members or a strut or brace to a beam or column. Importance Factor. A factor assigned to each structure according to its occupancy category as prescribed in ASCE/SEI 7-05, §11.5.1. Inelastic Analysis. Structural analysis that takes into account inelastic material behavior, including plastic analysis. Interstory Drift Angle. Interstory displacement divided by story height, radians. Joint (concrete). A portion of a column bounded by the highest and lowest surfaces of the other members framing into it. xxiv


k-area. The

region of the web that extends from the tangent point of the web and the flangeweb fillet (AISC “k ” dimension) a distance 11 /2 inches (38 mm) into the web beyond the “k ” dimension.

K-braced Frame. A

bracing configuration in which braces connect to a column at a location with no diaphragm or other out-of-plane support.

Limit State. A condition beyond which a structure or member becomes unfit for service and is judged to be no longer useful for its intended function (serviceability limit state) or to be unsafe (strength limit state). Link. In EBF, the segment of a beam that is located between the ends of two diagonal braces or between the end of a diagonal brace and a column. The length of the link is defined as the clear distance between the ends of two diagonal braces or between the diagonal brace and the column face. Link Intermediate Web Stiffeners. Vertical web stifffeners placed within the link in EBF. Link Rotation Angle. Inelastic angle between the link and the beam outside the link when the total story drift is equal to the design story drift. Link Shear Design Strength. Lesser of the available shear strength of the link developed from the moment or shear strength of the link. Live Loads. Those loads produced by the use and occupancy of the building or other structure and do not include construction or environmental loads such as wind load, snow load, rain load, earthquake load, flood load, or dead load. Live Loads (Roof). Those loads produced 1) during maintenance by workers, equipment, and materials; and 2) during the life of the structure by movable objects such as planters and by people. Load and Resistance Factor Design (LRFD). A method of proportioning structural members and their connections using load and resistance factors such that no applicable limit state is reached when the structure is subjected to appropriate load combinations. The term “LRFD” is used in the design of steel and wood structures. Load Factor. A factor that accounts for deviations of the actual load from the nominal load, for uncertainties in the analysis that transforms the load into a load effect, and for the probability that more than one extreme load will occur simultaneously. Loads. Forces or other actions that result from the weight of building materials, occupants and their possessions, environmental effect, differential movement, and restrained dimensional changes. Permanent loads are those loads in which variations over time are rare or of small magnitude. Other loads are variable loads (see also “Nominal loads”). Loads Effects. Forces and deformations produced in structural members by the applied loads. Local Buckling. Limit state of buckling of a compression element within a cross section. Local Crippling. Limit state of local failure of web plate in the immediate vicinity of a concentrated load or reaction.


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Local Yielding. Yielding that occurs in a local area of an element. LRFD Load Combination. Load combination in the applicable building code intended for strength design (load and resistance factor design). Maximum Considered Earthquake. The most severe earthquake effects considered by this code. Moment Connection. Connection that transmits bending moment between connected members. Moment Frame. Framing system that provides resistance to lateral loads and provides stability to the structural system; members and joints are capable of resisting forces by flexure as well as along their axis. Net Area. Gross area reduced to account for removed material. Nominal Load. Magnitude of the load specified by the applicable building code (dead, live, soil, wind, snow, rain, flood, earthquake). Nominal Strength. Strength of a structure or component (without the resistance factor or safety factor applied) to resist the load effects. Notch Toughness. Energy absorbed at a specified temperature as measured in the Charpy V-Notch test. Occupancy Category. Classification assigned to a structure based on its use as specified by the applicable building code. Overstrength Factor,  o. Factored specified by the applicable building code in order to determine the amplified seismic load, where required by the Seismic Provisions. Panel Zone. Web area of beam-to-column connection delineated by the extension of beam and column flanges through the connection, transmitting moment through a shear panel. Partial-joint-penetration Groove Weld (PJP). Groove weld in which the penetration is intentionally less than the complete thickness of the connected element. Percent Elongation. Measure of ductility, determined in a tensile test as the maximum elongation of the gage length divided by the original gage length. P-Delta Effect. Effect

of loads acting on the displaced location of joints or nodes in a structure. In tiered building structures, this is the effect of loads acting on the laterally displaced location of floors and roofs.

P-

Effect. Effect of loads acting on the deflected shape of a member between joints or nodes.

Plastic Hinge. Yielded zone that forms in a structural member when the plastic moment is attained. The member is assumed to rotate further as if hinged, except that such rotation is restrained by the plastic moment. Plastic Hinge Location. Location in a beam column assembly where inelastic energy dissipation is assumed to occur through the development of plastic flexural straining.

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Plastic Moment. Theoretical resisting moment developed within a fully yielded cross section. Prequalified Connection. Connection that complies with the requirements of the Seismic Provisions or AISC 358. Probable Maximum Moment at Plastic Hinge. Expected moment developed at a plastic hinge location along a member, considering the probable (mean) value of the material strength for the specified steel and effects of strain hardening. Protected Zone. Area of members in which limitations apply to fabrication and attachments. See Section 7.4 of the Seismic Provisions. Prototype. The connection or brace design that is to be used in the building (SMF, IMF, EBF, and BRBF). Quality Assurance. System of shop and field activities and controls implemented by the owner or his/her designated representative to provide confidence to the owner and the building authority that quality requirements are implemented. Quality Assurance Plan. Written description of qualifications, procedures, quality inspections, resources, and records to be used to provide assurance that the structure complies with the engineer’s quality requirements, specifications, and contract documents. Quality Control. System of shop and field controls implemented by the fabricator and erector to ensure that contract and company fabrication and erection requirements are met. Reduced Beam Section. Reduction in cross section over a discrete length that promotes a zone of inelasticity in the member. Reinforcing Fillet. Fillet weld applied to a groove welded “tee joint” to obtain a contour to reduce stress concentrations associated with joint geometry. Required Strength. Forces, stresses, and deformations produced in a structural component, determined by either structural analysis, LRFD or ASD load combinations or by the Specification and Seismic Provisions. Resistance Factor. A factor that accounts for deviations of the actual strength from the nominal strength and the manner and consequences of failure (also called strength reduction factor). Root. Portion of a multi-pass weld deposited in the first pass of welding. Root of Joint. Portion of a joint to be welded where the members are closest to each other. Rotation Capacity. Incremental angular rotation that a given shape can accept prior to excessive load shedding, defined as the ratio of the inelastic rotation attained to the idealized elastic rotation at first yield. Second-order Analysis. Structural analysis in which equilibrium conditions are formulated on the deformed structure; second-order effects (both P-δ and P-∆, unless specified otherwise) are included.


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Seismic Design Category. A classification assigned to a structure based on its occupany category and the severity of the design earthquake ground motion at the site. Seismic-force-resisting System. The part of the structural system that has been considered in the design to provide the required resistance to the prescribed seismic forces. Seismic Forces. The assumed forces related to the response of the structure to earthquake motions, to be used in the design of the structure and its components. Seismic Load Resisting System (SLRS). Assembly of structural elements in the building that resists seismic loads, including struts, collectors, chords, diaphragms and trusses. Seismic Provisions. Refers to AISC Seismic Provisions for Structural Steel Buildings (ANSI/ AISC). Seismic Response Modification Coefficient, R. Factor that reduces seismic load effects to strength level as specified by the applicable building code. Seismic Response Coefficient. Coefficient C s, as determined from ASCE/SEI 7-05, §12.8. Shear Rupture. Limit state of rupture (fracture) due to shear. Shear Wall. Wall that provides resistance to lateral loads in the plane of the wall and provides stability for the structural system. Shear Wall-frame Interactive System. A structural system that uses combinations of shear walls and frames designed to resist lateral forces in proportion to their rigidities, considering interaction between shear walls and frames on all levels. Shear Yielding. Yielding that occurs due to shear. Simple Connection. Connection that transmits negligible bending moment between connected members. Site Class. A classification assigned to a site based on the types of soils present and their engineering properties as defined in ASCE/SEI 7-05, §11.4.2. Site Coefficients. The values of F a and F v indicated in ASCE/SEI 7-05, Tables 11.4-1 and 11.4-2, respectively. Special Plate Shear Wall (SPSW). Plate shear wall systems that meets the requirments of the Seismic Provisions. Special Reinforced Concrete Shear Wall. A cast-in-place wall complying with the requirements of ASCE/SEI 7-05 in addition to the requirements for ordinary reinforced concrete structural walls. Special Transverse Reinforcement. Reinforcement composed of spirals, closed stirrups or hoops, and supplementary cross-ties provided to restrain the concrete and qualify the portion of the component, where used, as a confined region. Specification. Refers to the AISC Specification for Structural Steel Buildings (ANSI/AISC 360). xxviii


Specified Minimum Tensile Strength. Lower limit of tensile strength specified for a material as defined by ASTM. Specified Minimum Yield Stress. Lower limit of yield stress specified for a material as defined by ASTM. Splice. Connection between two structural elements joined at their ends to form a single, longer element. Steel Core. Axial-force-resisting element of braces in BRBF. The steel core contains a yielding segment and connections to transfer its axial force to adjoining elements; it may also contain projectons beyond the casing and transition segments between the projections and yielding segment. Stiffener. Structural element, usually an angle or plate, attached to a member to distribute load, transfer shear or prevent buckling. Stiffness. Resistance to deformation of a member or structure, measured by the ratio of the applied force (or moment) to the corresponding displacement (or rotation). Story Drift Ratio. The story drift divided by the story height. Strength Design. A method of proportioning structural members such that the computed forces produced in the members by factored loads do not exceed the member design strength (also called load and resistance factor design.) The term “strength design” is used in the design of concrete and masonry structural elements. Strength, Nominal. The capacity of a structure or member to resist the effects of loads, as determined by computations using specified material strengths and dimensions and formulas derived from accepted principles of structural mechanics or by field tests or laboratory tests of scaled models, allowing for modeling effects and differences between laboratory and field conditions. Strength Required. Strength of a member, cross section, or connection required to resist factored loads or related internal moments and forces in such combinations as stipulated by these provisions. Structural Analysis. Determination of load effects on members and connections based on principles of structural mechanics. Tensile Rupture. Limit state of rupture (fracture) due to tension. Tensile Yielding. Yielding that occurs due to tension. Toe of Fillet. Junction of a fillet weld face and base metal. Tangent point of a rolled section fillet. Torsional Force Distribution. The distribution of horizontal seismic forces through a rigid diaphragm when the center of mass of the structure at the level under consideration does not coincide with the center of rigidity (sometimes referred to as a diaphragm rotation). Toughness. The ability of a material to absorb energy without losing significant strength.


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V-Braced Frame. Concentrically braced frame (SCBF, OCBF or BRBF) in which a pair of diagonal braces located either above or below a beam is connected to a single point within the clear beam span. Where the diagonal braces are below the beam, the system is also referred to as an inverted-V-braced frame. Wall, Load-bearing. Any wall meeting either of the following classifications: 1. Any metal or wood stud wall that supports more than 100 pounds per linear foot (1459 N/m) of vertical load in addition to its own weight. 2. Any masonry or concrete wall that supports more than 200 pounds per linear foot (2919 N/m) of vertical load in addition to its own weight. Wall, Nonload-bearing. Any wall that is not a load-bearing wall. Web Buckling. Limit state of lateral instability of a web. Web Compression Buckling. Limit state of out-of-plane compression buckling of the web due to a concentrated compression force. Weld Metal. Portion of a fusion weld that has been completely melted during welding. Weld metal has elements of filler metal and base metal melted in the weld thermal cycle. Weld Tab. Piece of metal affixed to the end of a welded joint to facilitate the initiation and termination of weld passes outside the structural joint. X-braced Frame. Concentrically braced frame (OCBF or SCBF) in which a pair of diagonal braces crosses near the mid-length of the braces. Yield Strength. Stress at which a material exhibits a specified limiting deviation from the proportionality of stress to strain as defined by ASTM.

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References

The following codes and standards are referenced in this document. Other reference documents are indicated at the end of each design example. ACI-318, American Concrete Institute, Building Code Regulations for Reinforced Concrete, Farmington Hills, Michigan, 2008. AISC-360, American Institute of Steel Construction, Specificaiton for Structural Steel Buildings, Chicago, Illinois, March 9, 2005. AISC-341, Seismic Provisions for Structural Steel Buildings, March 9, 2005. IBC, International Code Council, International Building Code. Washington, DC, 2009. SEAOC Blue Book, Recommended Lateral Force Requirements and Commentary . Structural Engineers Association of California, Sacramento, California, 1999.


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2006 Structural Seismic Design Manual 1

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