AS1170!4!2007 Structural Design Actions Part 4 Earthquake Actions in Australia

AS 1170.4—2007 1170.4—2007

A S 1 1 7 0 . 4 — 2 0 0 7

Australian Standard

®

Structural design actions Part 4: Earthquake actions in Australia Australia

This Australian Standard® Standard® was prepared by Committee BD-006, BD-006, General Design Requirements and Loading on Structures. It was approved on behalf of the Council of Standards Australia on 22 May 2007. This Standard was published on 9 October October 2007.

The following are represented represented on Committee Committee BD-006: • • • • • • • • • • • • • • • • • • •

Association of Consulting Engineers Engineers Australia Australian Building Codes Board Board Australian Steel Institute Cement Concrete and Aggregates Australia Concrete Masonry Association of Australia Department of Building and Housing (New Zealand) Engineers Australia Housing Industry Association Institution of Professional Engineers New Zealand James Cook University Master Builders Australia New Zealand Heavy Engineering Research Association Property Council of Australia Steel Reinforcement Institute of Australia Swinburne University of Technology Timber Development Development Association (NSW) University of Canterbury New Zealand University of Melbourne University of Newcastle

Additional Interests: • • • • • • • • • • •

Australian Defence Defence Force Academy Australia Earthquake Earthquake Engineering Society Australian Seismological Seismological Centre Building Research Association of New Zealand Environmental Systems and Services Geoscience Australia Institute of Geological and Nuclear Science New Zealand National Society for Earthquake Engineering Primary Industries and Resources South Australia Seismology Seismology Research Centre, Australia University of Adelaide

This Standard was issued in draft form for comment comment as DR 04303. Standards Australia wishes to acknowledge the participation of the expert individuals that contributed to the development of this Standard through their representation on the Committee and through the public comment period.

Australian Standards® are are living documents documents that reflect progress in science, technology and and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments that may have been published since the Standard was published. Detailed information about Australian Standards, drafts, amendments and new projects can be found by visiting Standards Australia welcomes suggestions for improvements, and encourages readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at , or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.

This Australian Standard® Standard® was prepared by Committee BD-006, BD-006, General Design Requirements and Loading on Structures. It was approved on behalf of the Council of Standards Australia on 22 May 2007. This Standard was published on 9 October October 2007.

The following are represented represented on Committee Committee BD-006: • • • • • • • • • • • • • • • • • • •

Association of Consulting Engineers Engineers Australia Australian Building Codes Board Board Australian Steel Institute Cement Concrete and Aggregates Australia Concrete Masonry Association of Australia Department of Building and Housing (New Zealand) Engineers Australia Housing Industry Association Institution of Professional Engineers New Zealand James Cook University Master Builders Australia New Zealand Heavy Engineering Research Association Property Council of Australia Steel Reinforcement Institute of Australia Swinburne University of Technology Timber Development Development Association (NSW) University of Canterbury New Zealand University of Melbourne University of Newcastle

Additional Interests: • • • • • • • • • • •

Australian Defence Defence Force Academy Australia Earthquake Earthquake Engineering Society Australian Seismological Seismological Centre Building Research Association of New Zealand Environmental Systems and Services Geoscience Australia Institute of Geological and Nuclear Science New Zealand National Society for Earthquake Engineering Primary Industries and Resources South Australia Seismology Seismology Research Centre, Australia University of Adelaide

This Standard was issued in draft form for comment comment as DR 04303. Standards Australia wishes to acknowledge the participation of the expert individuals that contributed to the development of this Standard through their representation on the Committee and through the public comment period.

Australian Standards® are are living documents documents that reflect progress in science, technology and and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments that may have been published since the Standard was published. Detailed information about Australian Standards, drafts, amendments and new projects can be found by visiting Standards Australia welcomes suggestions for improvements, and encourages readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at , or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.

AS 1170.4—2007 1170.4—2007

Australian Standard

®

Structural design actions Part 4: Earthquake actions in Australia Australia

Originated as AS 2121—1979. Revised and redesignated as AS 1170.4—1993. Second edition 2007.

COPYRIGHT

© Standards Australia All rig hts are res erv ed. No par t o f t his wor k m ay be rep rod uce d o r c opie d i n a ny for m o r b y any means, electronic or mechanical, including photocopying, without the written permission of the publisher. Published by Standards Australia GPO Box 476, Sydney, NSW 2001, Australia ISBN 0 7337 8349 X

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PREFACE This Standard was prepared by the Joint Standards Australia/Standards New Zealand Committee BD-006, General Design Requirements and Loading on Structures, to supersede AS 1170.4—1993, Mini 1170.4—1993, Mini mum desig n loads l oads on structur stru ctures es,, Part 4: Earthq Ear thquake uake loads loa ds.. After consultation with stakeholders in both countries, Standards Australia and Standards New Zealand Zeal and decided deci ded to develo dev elop p this Stand ard as an Austral Aus tralian ian Standard Stan dard rather rath er than tha n an Australian/New Zealand Standard. The objective of this Standard is to provide designers of structures with earthquake actions and general detailing requirements for use in the design of structures subject to earthquakes. This Standard is Part 4 of the 1170 series Structural design actions, actions , which comprises the following parts, each of which has an accompanying Commentary* published as a Supplement: AS 1170 1170.4

Structural design actions Part 4: Earthquake actions (this Standard)

AS/NZS 1170.0 1170.1 1170.2 1170.3

Part Part Part Part

NZS NZ S 1170.5

Part 5:

0: 1: 2: 3:

General principles Permanent, imposed and other actions Wind actions Snow and ice actions Earthquake actions—New Zealand

This edition differs from AS 1170.4—1993 as follows: (a)

Importance factors have been been replaced with the annual probability of exceedance, to enable design to be set by the use of a single performance parameter. Values of hazard are determined using the return period factor determined from the annual probability of exceedance and the hazard factor for the site.

(b)

Combinations of actions actions are now given in the BCA and AS/NZS 1170.0. 1170.0.

(c)

Clauses on domestic domestic structures have been simplified and moved to an Appendix.

(d)

Soil profile descriptors have been replaced with five (5) new site sub-soil classes. classes.

(e)

Site factors and the effect of sub-soil conditions have been been replaced replaced with with spectral spectral shape factors in the form of response spectra that vary depending on the fundamental natural period of the structure.

(f)

The five (5) earthquake design categories categories have been simplified to three three (3) new categories simply described as follows:

(g)

(i)

I—a minimum static check.

(ii)

II—static analysis.

(iii)

III—dynamic analysis.

The option option to to allow no analysis analysis or detailing for some structures has been been removed (except for importance level 1 structures).

* The Commentary to this Standard, when published, will be AS 1170.4 Supp 1, Structural design actions — Ear thqu ake act ions — ions — Commentary C ommentary (Supplement to AS 1170.4—2007).

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(h)

All requirements requirements for the earthquake design categories categories are are collected collected together in in a single section (Section 5), with reference to the Sections on static and dynamic analysis.

(i)

The 50 m height limitation on ordinary moment-resisting frames has been removed but dynamic analysis is required above 50 m.

(j)

Due to to new new site site sub-soil spectra, spectra, adjustments were needed to simple design rules throughout the Standard. The basic static and dynamic methods have not changed in this respect.

(k)

The equation for base shear has been aligned with international methods.

(l)

Structural response factor has has been been replaced replaced by the combination combination of of structural structural performance factor and structural ductility factor (1/ R (1/ R f to S p/µ ) and values modified for some structure types.

(m)

A new method has been introduced for the calculation calculation of the fundamental fundamental natural period of the structure.

(n)

The clause on torsion effects has been simplified.

(o)

The clause on stability effects has been removed.

(p)

The requirement to design design some structures for vertical vertical components components of earthquake earthquake action has been removed.

(q)

Scaling of results has been removed from the dynamic analysis.

(r)

The Section on structural alterations has been removed.

(s)

The clauses on parts and components have been simplified.

(t)

The ‘informative’ Appendices have been removed.

The Standard has been drafted to be applicable to the design of structures constructed of any material or combination thereof. Designers will need to refer to the appropriate material Standard(s) for guidance on detailing requirements additional to those contained in this Standard. This Standard is not equivalent to ISO 3010:2001, Basis Basi s for design desi gn of structur stru ctures es — Seismic Seismic actions on structures , but is based on equivalent principles. ISO 3010 gives guidance on a general format and on detail for the drafting of national Standards on seismic actions. The principles of ISO 3010 have been adopted, including some of the detail, with modifications for the low s eismicity in Australia. The most significant points are as f ollows*: (i)

ISO 3010 is drafted as a guide for committees preparing Standards on seismic actions.

(ii)

Method and notation notation for presenting the mapped earthquake hazard data data has not been adopted.

(iii)

Some notation notation and definitions definitions have not been been adopted.

(iv)

Details of the equivalent static method have have been been aligned.

(v)

Principles of the dynamic method have been aligned.

Particular acknowledgment should be given to those organizations listed as ‘additional interests’ for their contributions to the drafting of this Standard. The terms ‘normative’ and ‘informative’ have been used in this Standard to define the application of the appendix to which they apply. A ‘normative’ appendix is an integral part of a Standard, whereas an ‘informative’ appendix is only for information and guidance.

* When published, the Commentary to this Standard will include additional information on the relationship of this Standard to ISO 3010:2001.

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Statements expressed in mandatory terms in notes to tables and figures are deemed to be an integral part of this Standard. Notes to the text contain information and guidance . They are not an integral part of the Standard.

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CONTENTS Page SECTION 1 SCOPE AND GENERAL 1.1 SCOPE ........................................................................................................................ 6 1.2 NORMATIVE REFERENCES.................................................................................... 6 1.3 DEFINITIONS ............................................................................................................ 7 1.4 NOTATION AND UNITS........................................................................................... 9 1.5 LEVELS, WEIGHTS AND FORCES OF THE STRUCTURE.................................. 11 SECTION 2 DESIGN PROCEDURE 2.1 GENERAL ................................................................................................................ 15 2.2 DESIGN PROCEDURE ............................................................................................ 15 SECTION 3 SITE HAZARD 3.1 ANNUAL PROBABILITY OF EXCEEDANCE ( P) AND PROBABILITY FACTOR (k p)............................................................................................................. 18 3.2 HAZARD FACTOR (Z ) ............................................................................................ 18 SECTION 4 SITE SUB-SOIL CLASS 4.1 DETERMINATION OF SITE SUB-SOIL CLASS.................................................... 27 4.2 CLASS DEFINITIONS ............................................................................................. 28 SECTION 5 EARTHQUAKE DESIGN 5.1 GENERAL ................................................................................................................ 30 5.2 BASIC DESIGN PRINCIPLES ................................................................................. 30 5.3 EARTHQUAKE DESIGN CATEGORY I (EDC I)................................................... 31 5.4 EARTHQUAKE DESIGN CATEGORY II (EDC II) ................................................ 31 5.5 EARTHQUAKE DESIGN CATEGORY III (EDC III).............................................. 34 SECTION 6 EQUIVALENT STATIC ANALYSIS 6.1 GENERAL ................................................................................................................ 35 6.2 HORIZONTAL EQUIVALENT STATIC FORCES.................................................. 35 6.3 VERTICAL DISTRIBUTION OF HORIZONTAL FORCES.................................... 36 6.4 SPECTRAL SHAPE FACTOR (C h(T )) ..................................................................... 37 6.5 DETERMINATION OF STRUCTURAL DUCTILITY (µ ) AND STRUCTURAL PERFORMANCE FACTOR (S p) .................................................... 38 6.6 TORSIONAL EFFECTS ........................................................................................... 40 6.7 DRIFT DETERMINATION AND P-DELTA EFFECTS .......................................... 40 SECTION 7 DYNAMIC ANALYSIS 7.1 GENERAL ................................................................................................................ 42 7.2 EARTHQUAKE ACTIONS ...................................................................................... 42 7.3 MATHEMATICAL MODEL .................................................................................... 42 7.4 MODAL ANALYSIS ................................................................................................ 43 7.5 DRIFT DETERMINATION AND P-DELTA EFFECTS .......................................... 43 SECTION 8 DESIGN OF PARTS AND COMPONENTS 8.1 GENERAL REQUIREMENTS ................................................................................. 44 8.2 METHOD USING DESIGN ACCELERATIONS ..................................................... 46 8.3 SIMPLE METHOD ................................................................................................... 46 APPENDIX A

DOMESTIC STRUCTURES (HOUSING).......................................... 48

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STANDARDS AUSTRALIA

Australian Standard Structural design actions Part 4: Earthquake actions in Australia

S E C T I O N

1

S C O P E

A N D

G E N E R A L

1.1 SCOPE

This Standard sets out procedures for determining earthquake actions and detailing requirements for structures and components to be used in the design of structures. It also includes requirements for domestic structures. Importance level 1 structures are not required to be designed for earthquake actions. The following structures are outside the scope of this Standard: (a)

High-risk structures.

(b)

Bridges.

(c)

Tanks containing liquids.

(d)

Civil structures including dams and bunds.

(e)

Offshore structures that are partly or fully immersed.

(f)

Soil-retaining structures.

(g)

Structures with first mode periods greater than 5 s.

This Standard does not consider the effect on a structure of related earthquake phenomena such as settlement, slides, subsidence, liquefaction or faulting. NOTE S: 1

For structures in New Zealand, see NZS 1170.5.

2

For earth-retaining structures, see AS 4678.

1.2 NORMATIVE REFERENCES

The following referenced documents are indispensable to the application of this Standard.

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AS 1684

Residential timber-framed construction (all parts)

1720 1720.1

Timber structures Part 1: Design methods

3600

Concrete structures

3700

Masonry structures

4100

Steel structures

AS/NZS 1170 1170.0 1170.1 1170.3

Structural design actions Part 0: General principles Part 1: Permanent, imposed and other actions Part 3: Snow and ice actions

Standards Australia

www.standards.org.au

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AS 1 170. 4—20 07

1664

Aluminium structures (all parts)

BCA

Building Code of Australia

NASH

Standard Residential and low-rise steel framing, Part 1—2005, Desig n criteria

1.3 DEFINITIONS

For the purpose of this Standard, the definitions given in AS/NZS 1170.0 and those below apply. Where the definitions in this Standard differ from those given in AS/NZS 1170.0, for the purpose of this Standard, those below apply. 1.3.1 Base, structural

Level at which earthquake motions are considered to be imparted to the structure, or the level at which the structure as a dynamic vibrator is supported (see Figure 1.5(C)). 1.3.2 Bearing wall system

Structural system in which loadbearing walls provide support for all or most of the vertical loads while shear walls or braced frames provide the horizontal earthquake resistance. 1.3.3 Braced frame

Two-dimensional structural system composed of an essentially vertical truss (or its equivalent) where the members are subject primarily to axial forces when resisting earthquake actions. 1.3.4 Braced frame, concentric

Braced frame in which bracing members are connected at the column-beam joints (see Table 6.2). 1.3.5 Braced frame, eccentric

Braced frame where at least one end of each brace intersects a beam at a location away from the column-beam joint (see Table 6.2). 1.3.6 Connection

Mechanical means that provide a load path for actions between structural elements, nonstructural elements and structural and non-structural elements. 1.3.7 Diaphragm

Structural system (usually horizontal) that acts to transmit earthquake actions to the seismic-force-resisting system. 1.3.8 Domestic structure

Single dwelling or one or more attached dwellings (single occupancy units) complying with Class 1a or 1b as defined in the Building Code of Australia. 1.3.9 Ductility (of a structure)

Ability of a structure to sustain its load-carrying capacity and dissipate energy when responding to cyclic displacements in the inelastic range during an earthquake. 1.3.10 Earthquake actions

Inertia-induced actions arising from the response to earthquake of the structure. 1.3.11 Moment-resisting frame

Essentially complete space frame that supports the vertical and horizontal actions by both flexural and axial resistance of its members and connections.

ww w.s tan dard s.o rg. au

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1.3.12 Moment-resisting frame, intermediate

Concrete or steel moment-resisting frame designed and detailed to achieve moderate structural ductility (see Table 6.2). 1.3.13 Moment-resisting frame, ordinary

Moment-resisting frame with no particular earthquake detailing, specified in the relevant material standard (see Table 6.2). 1.3.14 Moment-resisting frame, special

Concrete or steel moment-resisting frame designed and detailed to achieve high structural ductility and where plastic deformation is planned under ultimate actions (see Table 6.2). 1.3.15 Partition

Permanent or relocatable internal dividing wall between floor spaces. 1.3.16 Parts and components

Elements that are— (a)

attached to and supported by the structure but are not part of the seismic-forceresisting system; or

(b)

elements of the seismic-force-resisting system, which can be loaded by an earthquake in a direction not usually considered in t he design of that element.

1.3.17

P - delta

effect

Additional induced structural forces that develop as a consequence of the gravity loads being displaced horizontally. 1.3.18 Seismic-force-resisting system

Part of the structural system that provides resistance to the earthquake forces and effects. 1.3.19 Shear wall

Wall (either loadbearing or non -loadbearing) designed to resist horizontal earthquake forces acting in the plane of the wall. 1.3.20 Space frame

A three-dimensional structural system composed of interconnected members (other than loadbearing walls) that is capable of supporting vertical loads, which may also provide horizontal resistance to earthquake forces. 1.3.21 Storey

Space between levels including the space between the structural base and the level above. NOTE : Store y i is the storey below the i th level.

1.3.22 Structural performance factor ( S p)

Numerical assessment of the additional ability of the total building (structure and other parts) to survive earthquake motion. 1.3.23 Structural ductility factor (µ )

Numerical asses sment of the ability of a structure to sustain cyclic displacem ents in the inelastic range. Its value depends upon the structural form, the ductility of the materials and structural damping characteristics. 1.3.24 Top (of a structure)

Level of the uppermost principal seismic weight (see Clause 1.5).

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AS 1 170. 4—20 07

1.4 NOTATION AND UNITS

Except where specifically noted, this Standard uses SI units of kilograms, metres, seconds, pascals and newtons (kg, m, s, Pa, N). Unless stated otherwise, the notation used in this Standard shall have the following meanings: ac

= component amplification factor

a floor

= effective floor acceleration at the height of the component centre of mass

ax

= height amplification factor at height h x of the component centre of mass

b

= plan dimension of the structure at right angles to the direction of the action, in metres

C (T )

= elastic site hazard spectrum for horizontal loading as a function of period ( T )

C (T 1)

= value of the elastic site hazard spectrum for the fundamental natural period of the structure

C d(T )

= horizontal design response spectrum as a function of period (T )

C d(T 1)

= horizontal design action coefficient (value of the horizontal design response spectrum for the fundamental natural period of the structure)

C h(T )

= spectral shape factor as a function of period (T ) (dimensionless coefficient)

C h(T 1)

= value of the spectral shape factor for the fundamental natural period of the structure

C v (T v )

= elastic site hazard spectrum for vertical loading, which may be taken as hal of the elastic site hazard spectrum for h orizontal loading ( C ( T ))

C vd (T )

= vertical design response spectrum as a function of period (T )

C h(0)

= bracketed value of the spectral shape factor for the period of zero seconds

d i

= horizontal deflection of the centre of mass at level ‘i’

d ie

= deflection at level ‘i’ determined by a n elastic analysis

d st

= design storey drift

E

= earthquake actions (see Clause 1.3 and AS/NZS 1170.0)

E u

= earthquake actions for ultimate limit state = represented by a set of equivalent static forces F i at each level ( i) or by resultant action effects determined using a dynamic analysis

F c

= horizontal design earthquake force on the part or component, in kilonewtons

F i

= horizontal equivalent static design force at the ith level, in kilonewtons

F j

= horizontal equivalent static design force at the jth level, in kilonewtons

F n

= horizontal equivalent static design force at the uppermost seismic mass, in kilonewtons

F r

= horizontal design racking earthquake force on the part or component, in kilonewtons

g

= acceleration due to gravity (9.8 m/s 2)

G

= permanent action (self-weight or ‘dead load’), in kilonewtons

G i

= permanent action (self-weight or ‘dead load’) at level i, in kilonewtons

hi

= height of level i above the base of the structure, in metres


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hn

= height from the base of the structure to the uppermost seismic weight or mass, in metres (see Clause 1.5)

h si

= inter-storey height of level i, measured from centre-line to centre-line of floor, in metres

hx

= height at which the component is attached above the structural base of the structure, in metres

I c

= component importance factor

i, j

= levels of the structure under consideration

K s

= factor to account for height of a level in a structure

k

= exponent, dependent on the fundamental natural period of the structure ( T 1)

k c

= factor for determining height amplification factor (ax )

k F,i

= seismic force distribution factor for the ith level

k p

= probability factor appropriate for the limit state under consideration

k t

= factor for determining building period

mi

= seismic mass at each level

N -values = number of blows for standard penetration (Standard Penetration Test)

©

n

= number of levels in a structure

P

= annual probability of exceedance

P-delta

= second order effects due to amplication of axial loads

Q

= imposed action for each occupancy class, in kilonewtons

Q i

= imposed action for each occupancy class on the ith level

R c

= component ductility factor

S p

= structural performance factor

T

= period of vibration, which varies according to the mode of vibration being considered

T 1

= fundamental natural period of the structure as a whole (translational first mode natural period)

T v

= period of vibration appropriate to vertical mode of vibration of the structure

V

= horizontal equivalent static shear force acting at the base (base shear)

V i

= horizontal equivalent static shear force at the ith level

W

= sum of the seismic weight of the building ( G + ψ cQ ) at the level where bracing is to be determined and above this level, in kilonewtons

W c

= seismic weight of the part or component, in kilonewtons

W i

= seismic weight of the structure or component at the ith level, in kilonewtons

W j

= seismic weight of the structure or component at level j, in kilonewtons

W n

= seismic weight of the structure or component at the nth level (upper level), in kilonewtons

W t

= total seismic weight of the building, in kilonewtons

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AS 1 170. 4—20 07

Z

= earthquake hazard factor which is equivalent to an acceleration coefficient with an annual probability of exceedance in 1/500, (i.e., a 10% probability of exceedance in 50 years)

µ

= structural ductility factor (µ = mu)

θ

= stability coefficient

ψ c

= earthquake imposed action combination factor

1.5 LEVELS, WEIGHTS AND FORCES OF THE STRUCTURE

For the purposes of analysis, the masses of the structure, parts and components are taken as acting at the levels of the structure (see Figure 1.5(A)). The seismic weight at a level is determined by summing the weights that would act at that level, including the weight of the floor plus any items spanning from one level to the next, e.g., walls, half way to the level above and half way to the level below and adding the factored imposed actions on that level. This mass is then assumed to act at the height of the centre of the floor slab (excluding consideration of any beams). The centre of mass of the uppermost (top) weight (including roofing, structure and any additional parts and components above and down to half way to the floor below) shall be considered to act at the centre of the combined mass (see Figure 1.5(B)). For m ore complicated situations, the uppermost seismic weight shall be assessed depending on the effect on the distribution of forces. Where a concentrated weight exists above the ceiling level that contributes more than 1/3 of W n, it shall be treated as the top seismic weight and W n and W n − 1 recalculated. The building height (h n) is taken as the height of the centre of mass of W n above the base. Figure 1.5(C) illustrates the structural base for various situations.


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Uppermost seismic mass Force

F n

Storey

Level

n

n

Force

F n - 1

Level

n

- 1

Force

F i + 1

Level

i

+ 1

Level

i

Storey Force

i

+ 1

F i

Storey Force

i

Force

h si h

Level

F i - 1

h n

i

- 1

Level 1

F i

Storey 1 Base

Storey W i

h si

2 h si

2

FIGURE 1.5(A)

©

Standards Australia

i

Level

i

Level

i

Level

i

+ 1

+ 1

W i

Storey

i

- 1

ILLUSTRATION OF LEVEL, STOREY, WEIGHT AND FORCE


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Centre of gravity of

Plant

W n

Top W n

Storey

n

hn Storey

n

- 1

Base

FIGURE 1.5(B)


EXAMPLE OF DETERMINATION OF THE TOP OF THE STRUCTURE

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Building height,

h n

(a) Base shear reaction at ground level

Building height,

h n

Building height,

h n

(b) Base shear reaction below ground level

Building height,

(c) Base shear reaction taken as at lowest level

h n

(d) Base shear reaction at ground level

NOTE: Building height measured from top of slab at relevant level.

FIGURE 1.5(C) EXAMPLES OF DEFINITION OF BUILDING BASE WHERE EARTHQUAKE MOTIONS ARE CONSIDERED TO BE TRANSMITTED TO THE STRUCTURE

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S E C T I O N

2

D E S I G N

P R O C E D U R E

2.1 GENERAL

Earthquake actions for use in design ( E ) shall be appropriate for the type of structure or element, its intended use, design working life and exposure to earthquake shaking. The earthquake actions ( E u) determined in accordance with this Standard shall be deemed to comply with this provision. 2.2 DESIGN PROCEDURE

The design procedure (see Figure 2.2) to be adopted for the design of a structure subject to this Standard shall— (a)

determine the importance level for the structure (AS/NZS 1170.0 and BCA);

(b)

determine the probability factor (k p) and the hazard factor (Z ) (see Section 3);

(c)

determine if the structure complies with the definition for domestic structures (housing) g iven in Appendix A and whether it complies with the requirements therein;

(d)

determine the site sub-soil class (see Section 4);

(e)

determine the earthquake design category (EDC) from Table 2.1; and

(f)

design the structure in accordance with the requirements for the EDC as set out in Section 5.

Importance level 1 structures are not required to be designed to this Standard, (i.e., for earthquake actions), and domestic structures (housing) that comply with the definition given in Appendix A and with the provisions of Appendix A are deemed to satisfy this Standard. All other structures, including parts and components, are required to be designed for earthquake actions. NOTE : Du rin g a n earthqua ke, motion wil l b e i mposed on all part s o f a ny constr uction. Ther efor e, parts of a structure (including non-loadbearing walls, etc.) should be designed for lateral earthquake forces such as out-of-plane forces.

A higher level of analysis than that specified in Table 2.1 for a particular EDC may be used. Domestic structures that do not comply with the limits specified in Appendix A shall be designed as importance level 2 structures. NOTE : St ruct ures (includin g housing) tha t are cons tructed on a sit e wit h a haz ard factor Z of 0.3 or greater should be designed in accordance wi th NZS 1170.5 (see Macquarie Islands, Table 3.2).

For structures sited on sub-soil Class E (except houses in accordance with Appendix A), the design shall consider the effects of subsidence or differential settlement of the foundation material under the earthquake actions determined for the structure. NOTE : St ructures, whe re the struct ural ductil ity fac tor (µ ) assumed in design is greater than 3, should be designed in accordance with NZS 1170.5.

Serviceability limit states are deemed to be satisfied under earthquake actions for importance levels 1, 2 and 3 structures that are designed in accordance with this Standard and the appropriate materials design Standards. A special study shall be carried out for importance level 4 structures to ensure they re main serviceable for immediate use following the design event for importance level 2 structures.


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TABLE 2.1 SELECTION OF EARTHQUAKE DESIGN CATEGORIES Importance level, type of structure (see Clause 2.2)

(k p Z ) for site sub-soil class

E e or D e

Ce

1

A e

Earthquake design category

—

Not required to be designed for earthquake actions

Top of roof ≤ 8.5

Refer to Appendix A

Top of roof >8.5

Design as importance level 2

≤ 12

>12, <50 ≥ 50

I II III

<50 ≥ 50

II III

—

Domestic structure (housing)

—

≤ 0.05

2

Be

Structure height, hn (m)

≤ 0.08

≤ 0.11

≤ 0.14

>0.05 to ≤0.08 >0.08 to ≤0.12 >0.11 to ≤0.17 >0.14 to ≤0.21 >0.08

>0.12

>0.17

>0.21

<25 ≥ 25

II III

≤ 0.08

≤ 0.12

≤ 0.17

≤ 0.21

<50 ≥ 50

II III

>0.08

>0.12

>0.17

>0.21

<25 ≥ 25

II III

<12 ≥ 12

II III

3

4

—

NOT ES:

©

k p and Z are

1

Values for

2

A higher earthquake design category or procedure may be used in place of that specified.

3

Height ( h n ) is defined in Clause 1.5. For domestic structures refer to Appendix A.

4

In addition to the above, a special study is required for importance level 4 structures to demonstrate they remain serviceable for immediate use following the design event for importance level 2 structures.

Standards Australia

given in Section 3. Site sub-soil class are given in Section 4.


AS 1 170. 4—20 07

17

Structure location and importance level Annual probability of exceedance (from AS/NZS 1170.0 or BCA) 1

k p , Z value

Det er mi ne

(Section 3)

Does the structure comply with the definition of 2

domestic structures (Housing) and is

Look up

h n

Y

8. 5

Appendix A

No Soil class, A, B, C, D or E (Section 4)

3

Det er mi ne

4

Apply

EDC (Table 2.1)

EDC I

EDC II

EDC I II

U se C la us e 5 .2

U se C la us e 5 .2

U se C la us e 5 .2

Clause 5.3

Clause 5.4

Clause 5.5

Simple static check

5

Des ig n p ar ts and components

Dynamic analysis

(Section 6)

(Section 7)

EDC I

EDC II

EDC III

(Clause 5.3)

(Section 8)

(Section 8)

FIGURE 2.2


Static analysis

FLOW DIAGRAM—DESIGN PROCEDURE

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AS 1 170. 4—20 07

18

S E C T I O N 3.1 ANNUAL FACTOR (k p)

PROBABILITY

3 OF

S I T E

H A Z A R D

EXCEEDANCE

( P )

AND

PROBABILITY

The probability factor (k p) for the annual probability of exceedance, appropriate for the limit state under consideration, shall be obtained from Table 3.1. TABLE 3.1 PROBABILITY FACTOR (k p) Annual pro bab ility o f exceedance

Pro babili ty f act or

P

k p

1/2500 1/2000 1/1500

1.8 1.7 1.5

1/1000 1/800 1/500

1.3 1.25 1.0

1/250 1/200 1/100

0.75 0.7 0.5

1/50 1/25 1/20

0.35 0.25 0.20

NOTE: The annu al prob abil ity of exc eedanc e in Tab le 3.1 is taken from the BCA and AS/NZS 1170.0.

3.2 HAZARD FACTOR ( Z )

The hazard factor (Z ) shall be taken from Table 3.2 or, where the location is not listed, be determined from Figures 3.2(A) to 3.2(F). A general overview of the hazard factor ( Z ) for Australia is shown in Figure 3.2(G).

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Standards Australia


AS 1 170. 4—20 07

19

TABLE 3.2 HAZARD FACTOR ( Z ) FOR SPECIFIC AUSTRALIAN LOCATIONS Location

Z

Location

Z

Location

Z

Adelaide Albany Albury/Wodonga

0.10 0.08 0.09

Geraldton Gladstone Gold Coast

0.09 0.09 0.05

Port Augusta Port Lincoln Port Hedland

0.11 0.10 0.12

Alice Springs Ballarat Bathurst

0.08 0.08 0.08

Gosford Grafton Gippsland

0.09 0.05 0.10

Port Macquarie Port Pirie Robe

0.06 0.10 0.10

Bendigo Brisbane Broome

0.09 0.05 0.12

Goulburn Hobart Karratha

0.09 0.03 0.12

Rockhampton Shepparton Sydney

0.08 0.09 0.08

Bundaberg Burnie Cairns

0.11 0.07 0.06

Katoomba Latrobe Valley Launceston

0.09 0.10 0.04

Tamworth Taree Tennant Creek

0.07 0.08 0.13

Camden Canberra Carnarvon

0.09 0.08 0.09

Lismore Lorne Mackay

0.05 0.10 0.07

Toowoomba Townsville Tweed Heads

0.06 0.07 0.05

Coffs Harbour Cooma Dampier

0.05 0.08 0.12

Maitland Melbourne Mittagong

0.10 0.08 0.09

Uluru Wagga Wagga Wangaratta

0.08 0.09 0.09

Darwin Derby Dubbo

0.09 0.09 0.08

Morisset Newca stl e Noosa

0.10 0.11 0.08

Whyalla Wollongong Woomera

0.09 0.09 0.08

Esperance Geelong

0.09 0.10

Orange Perth

0.08 0.09

Wyndham Wyong

0.09 0.10

Meckering region

Islands

Ballidu Corrigin Cunderdin

0.15 0.14 0.22

Meckering Northa m Wongan Hills

0.20 0.14 0.15

Christmas Island Cocos Islands Heard Island

0.15 0.08 0.10

Dowerin Goomalling Kellerberrin

0.20 0.16 0.14

Wickepin York

0.15 0.14

Lord Howe Island Macquarie Island Nor fol k Island

0.06 0.60 0.08


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AS 1 170. 4—20 07

20

Hazard (z) 1 in 500 years annual probability of exceedance

FIGURE 3.2(A)

©

Standards Australia

HAZARD FACTOR ( Z ) FOR NEW SOUTH WALES, VICTORIA AND TAS MANIA


21

AS 1 170. 4—20 07


FIGURE 3.2(B)


HAZARD FACTOR ( Z ) FOR SOUTH AUSTRALIA

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AS 1 170. 4—20 07

23


FIGURE 3.2(D)


HAZARD FACTOR ( Z ) FOR SOUTH-WEST OF WESTERN AUSTRALIA

© Standards

Australia

AS 1 170. 4—20 07

24


FIGURE 3.2(E)

©

Standards Australia

HAZARD FACTOR ( Z ) FOR NORTHERN TERRITORY


AS 1 170. 4—20 07

25


FIGURE 3.2(F)


HAZARD FACTOR ( Z ) FOR QUEENSLAND

© Standards

Australia

©

A S 1 1 7 0 .4 — 2 0 0 7

S t a n d a r d s A u s t r a l i a

2 6

w w w . s t a n d a r d s . o r g . a u


FIGURE 3.2(G)

HAZARD FACTOR ( Z )

AS 1 170. 4—20 07

27

S E C T I O N

4

S I T E

S U B - S O I L

C L A S S

4.1 DETERMINATIO N OF SITE SUB-SOIL CLASS 4.1.1 General

The site shall be assessed and assigned to the site sub-soil class it most closely resembles. The site sub-soil classes shall be as defined in Clause 4.2, that is, Classes A e to E e as follows: (a)

Class A e —Strong rock.

(b)

Class B e —Rock.

(c)

Class C e —Shallow soil.

(d)

Class D e —Deep or soft soil.

(e)

Class Ee —Very soft soil.

4.1.2 Hierarchy for site classification methods

Site classification shall be determined using the methods in the following list, in order of most preferred to least preferred: (a)

Site periods based on four times the shear-wave travel-time through material from the surface to underlying rock.

(b)

Bore logs, including measurement of geotechnical properties.

(c)

Evaluation of site periods from Nakamura ratios or from recorded earthquake

AS 1 170. 4—20 07

27

S E C T I O N

4

S I T E

S U B - S O I L

C L A S S

4.1 DETERMINATIO N OF SITE SUB-SOIL CLASS 4.1.1 General

The site shall be assessed and assigned to the site sub-soil class it most closely resembles. The site sub-soil classes shall be as defined in Clause 4.2, that is, Classes A e to E e as follows: (a)

Class A e —Strong rock.

(b)

Class B e —Rock.

(c)

Class C e —Shallow soil.

(d)

Class D e —Deep or soft soil.

(e)

Class Ee —Very soft soil.

4.1.2 Hierarchy for site classification methods

Site classification shall be determined using the methods in the following list, in order of most preferred to least preferred: (a)

Site periods based on four times the shear-wave travel-time through material from the surface to underlying rock.

(b)

Bore logs, including measurement of geotechnical properties.

(c)

Evaluation of site periods from Nakamura ratios or from recorded earthquake motions.

(d)

Bore logs with descriptors but no geotechnical measurements.

(e)

Surface geology and estimates of the depth to underlying rock.

Where more than one method has been carried out, the site classification determined by the most preferred method shall be used. 4.1.3 Evaluation of periods for layered sites

For sites consisting of layers of several types of material, the low-amplitude natural period of the site may be estimated by summing the contributions to the natural period of each layer. The contribution of each layer may be estimated by determining the soil type of each layer, and multiplying the ratio of each layer’s thickness to the maximum depth of soil for that soil type (given in Table 4.1) by 0.6 s. In evaluating site periods, material above rock shall be included in the summation.


© Standards

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AS 1 170. 4—20 07

28

TABLE 4.1 MAXIMUM DEPTH LIMITS FOR SITE SUB-SOIL CLASS C Soil type and description

Cohesive soils

Very soft

Maximum depth of soil

Property Representative undrained shear strengths

Representative SPT N - values

(kPa)

(Number)

(m)

<12.5

—

0

Soft

12.5 – 25

—

20

Firm

25 – 50

—

25

AS 1 170. 4—20 07

28

TABLE 4.1 MAXIMUM DEPTH LIMITS FOR SITE SUB-SOIL CLASS C Soil type and description

Cohesive soils

Very soft

Representative undrained shear strengths

Representative SPT N - values

(kPa)

(Number)

(m)

<12.5

—

0

Soft

12.5 – 25

—

20

Firm

25 – 50

—

25

Stiff

50 – 100

—

40

100 – 200

—

60

Very loose

—

<6

0

Loose dry

—

6 – 10

40

Medium dense

—

10 – 30

45

Dense

—

30 – 50

55

Very dense

—

>50

60

Gravels

—

>30

100

Very stiff or hard Cohesionless soils

Maximum depth of soil

Property

4.2 CLASS DEFINITIONS 4.2.1 Class A e —Strong rock

Site sub-soil Class A e is defined as strong to extremely strong rock satisfying the following conditions: (a)

Unconfined compressive strength greater t han 50 MPa or an average shear-wave velocity over the top 30 m g reater than 1500 m/s.

(b)

Not underlain by materials having a compressive strength less than 18 MPa or an average shear wave velocity less than 600 m/s.

4.2.2 Class B e —Rock

Site sub-soil Class B e is defined as rock satisfying the following conditions: (a)

A compressive strength between 1 and 50 MPa inclusive or an average shear-wave velocity, over the top 30 m, greater than 360 m/s.

(b)

Not underlain by materials having a compressive strength less than 0.8 MPa or an average shear wave velocity less than 300 m/s.

A surface layer of no more than 3 m depth of highly weathered or completely weathered rock or soil (a material with a compressive strength less than 1 MPa) may be pr esent. 4.2.3 Class C e —Shallow soil site

Site sub-soil Class C e is defined as a site that is not Class A e , Class B e (i.e., not rock site), or Class E e site (i.e., not very soft soil site) and either— (a)

the low-amplitude natural site period is less than or equal to 0.6 s; or

(b)

the depths of soil do not exceed those listed in Table 4.1.

The low-amplitude natural site period may be estimated from—

©

(i)

four times the shear-wave travel time from the surface to rock;

(ii)

Nakamura ratios;

Standards Australia


AS 1 170. 4—20 07

29

(iii)

recorded earthquake motions; or

(iv)

evaluated in accordance with Clause 4.1.3 for sites with layered sub-soil.

Where more than one method is used, the value determined from the most preferred method given in Clause 4.1.2 shall be adopted. 4.2.4 Class D e —Deep or s oft soil site

Site sub-soil Class D e is defined as a site that is— (a)

not Class A e, Class B e (i.e., not rock site) or Class E e site (i.e., very soft soil site); and

(b)

underlain by l ess than 10 m of soil with an undrained shear-strength less than 12.5 kPa or soil with Standard penetration test (SPT) N -values less than 6; and either (i)

the low-amplitude natural site period is greater than 0.6 s; or

(ii)

the depths of soil exceed those listed in Table 4.1,

where the low-amplitude natural site period is estimated in accordance with Clause 4.2.3. 4.2.5 Class E e —Very soft soil site

Site sub-soil Class E e is defined as a site with any one of the following: (a)

More than 10 m of very soft soil with undrained shear-strength less than 12.5 kPa.

(b)

More than 10 m of soil with SPT N -values less than 6.

(c)

More than 10 m depth of soil with shear wave v elocities of 150 m/s or less.

(d)

More than 10 m combined depth of soils with properties as described in Items (a), (b) and (c) above.


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AS 1 170. 4—20 07

30

S E C T I O N

5

E A R T H Q U A K E

D E S I G N

5.1 GENERAL

Structures required by Section 2 to be designed for earthquake actions shall be designed in accordance with the general principles of Clause 5.2, the provisions of the appropriate earthquake design category (see Clauses 5.3, 5.4 or 5.5) and the requirements of the applicable material design Standards. 5.2 BASIC DESIGN PRINCIPLES 5.2.1 Seismic-force-resisting system

All structures shall be configured with a seismic-force-resisting system that has a clearly defined load path, or paths, that will transfer the earthquake actions (both horizontal and vertical) generated in an earth quak e, together with gravity loads, to the supporting foundation soil. 5.2.2 Tying structure together

All parts of the structure shall be tied together both in the horizontal and the vertical planes so that forces generated by an earthquake from all parts of t he structure, including structural and other parts and com ponents, are carried to the foundation. Footings supported on piles, or caissons, or spread footings that are located in or on soils with a maximum vertical ultimate bearing value of less than 250 kPa shall be restrained in any horizontal direction by ties or other means, to limit differential horizontal movement during an earthquake. 5.2.3 Performance under earthquake deformations

Stiff components (such as concrete, masonry, brick, precast concrete walls or panels or stair walls, stairs and ramps) shall be— (a)

considered to be part of the seismic-force-resisting system and designed accordingly; or

(b)

separated from all structural elements such that no interaction takes place as the structure undergoes deflections due to the earthquake effects determined in accordance with this Standard.

All components, including those deliberately designed to be independent of the seismicforce-resisting system, shall be designed to perform their required function while sustaining the deformation of the structure resulting from the application of the earthquake forces determined for each limit state. Floors shall be— (i)

continuous over a series of internal walls at right angles or near right angles; or

(ii)

tied to supporting walls at all supported edges.

Provision shall be made for floors to span without collapse if they become dislodged from edges to which they are not tied. 5.2.4 Walls

Walls shall be anchored to the roof and restrained at all floors that provide horizontal support for the wall. Walls shall be designed for in-plane and out-of-plane forces. Out-of-plane forces on walls shall be designed in accordance with Section 8.

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AS 1 170. 4—20 07

31

5.2.5 Diaphragms

The deflection in the plane of the diaphragm, as determined by analysis, 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 and continue to support the prescribed forces. 5.3 EARTHQUAKE DESIGN CATEGORY I (EDC I)

This Clause shall not apply to structures of height ( hn) over 12 m. All structures subject to earthquake design category I (EDC I) s hall comply with the requirements of Clause 5.2 and the requirements of this Clause. The structure and all parts and components shall be designed for the following equivalent static forces applied laterally to the centre of mass of the part or component being considered, or to the centres of mass of the levels of the structure (see Figure 5.2), in combination with gravity loads (see combination [ G , E u, ψ cQ ] in AS/NZS 1170.0): F i = 0.1W i

. . . 5.3

where W i = seismic weight of the structure or component at level i as given in Clause 6.2.2 Each of the major axes of the structure shall be considered separately. Vertical earthquake actions and pounding need not be considered, except where vertical actions apply to parts and components.

W 3

F 3

Storey 3 F 2

W 2

Storey 2 F 1

W 1

Storey 1 Base

FIGURE 5.2

ILLUSTRATION OF EARTHQUAKE DESIGN CATEGORY I

5.4 EARTHQUAKE DESIGN CATEGORY II (EDC II) 5.4.1 General

All structures subject to earthquake design category II ( EDC II) s hall comply with the requirements of Clause 5.2 and Clauses 5.4.2 to 5.4.6.


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AS 1 170. 4—20 07

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5.4.2 Strength and stability provisions 5.4.2.1 General

The structural system shall be designed to resist the most critical action effect arising from the application of the earthquake actions in any direction. Except for structure components and footings that participate in resisting horizontal earthquake forces in both major axes of the structure, this provision shall be deemed to be satisfied by applying the horizontal force in the direction of each of the major axes of the structure and considering the effect for each direction separately. For structure components and footings that participate in resisting horizontal earthquake forces in both major axes of the structure, the effects of the two directions determined separately shall be added by taking 100% of the horizontal earthquake forces for one direction and 30% in the p erpendicular direction. Forces shall be applied at the centre of mass of each floor except where offset from the centre of mass is r equired for the consideration of torsion effects (see Clause 6.6). Connections between components of the structure shall be capable of transmitting an internal ultimate limit state horizontal action equal to the values calculated using this section but not less than 5% of the vertical reaction arising from the seismic weight or 5% of the seismic weight of the component which ever is the greater. 5.4.2.2 Earthquake forces—Equivalent static method

Earthquake forces shall be calculated using the equivalent static method, in accordance with Section 6 except where covered by Clause 5.4.2.3. NOTE : Dynamic analys is, in acc ordance wit h S ect ion 7, may be used i f de sired ( see Clause 2.2) .

5.4.2.3 Simplified design for structures not exceeding 15 m

Structures not exceeding 15 m tall and structural components within those structures shall be deemed to meet the requirements of Clause 5.4.2.2 when they have been designed to resist at the ultimate limit state a minimum horizontal static force given by the following, applied simultaneously at each level for the given direction in combination with other actions as specified in AS/NZS 1170.0: F i = K s[k pZS p/µ ] W i

. . . 5.4

where k p and Z are as given in Section 3 and S p and µ are given in Clause 6.5 K s = factor to account for floor, as given in Table 5.4 W i = seismic weight of the structure or component at level i

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AS 1 170. 4—20 07

33

TABLE 5.4 VALUES OF K s FOR STRUCTURES NOT EXCEEDING 15 m K s factor

Total number of stories

Sub-soil class

Storey under consideration 5th

4th

3rd

2nd

1st

5

A e Be Ce D e, E e

2.5 3.1 4.4 6.1

1.9 2.5 3.5 4.9

1.4 1.8 2.6 3.6

1.0 1.2 1.7 2.5

0.5 0.6 0.9 1.2

4

A e Be Ce D e, E e

— — — —

2.7 3.5 4.9 5.8

2.0 2.6 3.6 4.4

1.4 1.7 2.5 3.0

0.6 0.9 1.2 1.4

3

A e Be C e, D e, E e

— — —

— — —

3.1 3.9 5.5

2.0 2.6 3.6

1.0 1.3 1.8

2


— — —

— — —

— — —

3.1 3.9 4.9

1.6 1.9 2.5

1


— — —

— — —

— — —

— — —

2.3 3.0 3.6

5.4.3 Vertical earthquake actions

Vertical earthquake actions need not be considered. NOTE : Fo r parts and compone nts , s ee Clause s 5.4.6 an d 8. 1.3.

5.4.4 Drift

The inter-storey drift at the ultimate limit state calculated from the forces determined in Clause 5.4.2 shall not exceed 1.5% of the storey height for each level (see Clause 6.7.2). Attachment of cladding and facade panels to the seismic-force-resisting system shall have sufficient deformation and rotational capacity to accommodate the design storey drift ( d st ). This Clause is deemed to be satisfied if the primary seismic force-resisting elements are structural walls that extend to the base. 5.4.5 Pounding

Structures over 15 m shall be separated from adjacent structures or set back from a building boundary by a distance sufficient to avoid damaging contact. This Clause is deemed to be satisfied if the primary seismic force-resisting elements are structural walls that extend to the base, or the setback from a boundary is more than 1% of the structure height. 5.4.6 Parts and components

Non-structural parts and components shall be designed in accordance with Section 8 except that for importance level 2 and 3 structures not exceeding 15 m, parts and components of non-brittle construction may be attached using connectors designed for horizontal capacity of 10% of the seismic weight of the part.


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5.5 EARTHQUAKE DESIGN CATEGORY III (EDC III) 5.5.1 General

All structures subject to earthquake design category III (EDC III) shall comply with the requirements of Clause 5.2 and Clauses 5.5.2 to 5.5.6. 5.5.2 Strength and stability provisions 5.5.2.1 General

The seismic-force-resisting system shall be designed to resist the most critical action effect arising from the application of the earthquake actions in any direction. The design shall consider the earthquake loading applied, as specified in Clause 5.4.2.1. Connections between elements of the structure shall be capable of transmitting an internal ultimate limit state horizontal action equal to the values calculated using the dynamic analysis but not less than 5% of the vertical reaction arising from the seismic weight or 5% of the seismic weight of the component, whichever is the greater. 5.5.2.2 Earthquake forces—Dynamic analysis

Earthquake forces shall be calculated using the dynamic analysis method given in Section 7. 5.5.3 Vertical earthquake actions

Vertical earthquake actions need not be considered. NOTE : Fo r parts and com pone nts , see Clause 8.1. 3.

5.5.4 Drift

The inter-storey drift at the ultimate limit state, calculated from the forces determined in Clause 5.5.2, shall not exceed 1.5% of the storey height for each level (see Clause 6.7.2). Attachment of cladding and facade panels to the seismic-force-resisting system shall have sufficient deformation and rotational capacity to accommodate the design storey drift ( d st ). 5.5.5 Pounding

Structures shall be separated from adjacent structures or set back from a building boundary by a distance sufficient to avoid damaging contact. This Clause is deemed to be satisfied when the setback from a boundary is more than 1% of the structure height. 5.5.6 Parts and components

Non-structural parts and compone nts shall be designed in accordance with Section 8.

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35

S E C T I O N

6

E Q U I V A L E N T A N A L Y S I S

S T A T I C

6.1 GENERAL

Equivalent static analysis, when used, shall be carried out in accordance with this Section. The procedure for equivalent static analysis is as follows: (a)

Decide on the form and material of the structure.

(b)

Calculate k pZ using Section 3.

(c)

Determine T 1, C h(T 1), µ , and other structural properties.

(d)

Determine the design action coefficients.

(e)

Determine the seismic weight at each level ( W i).

(f)

Calculate V using Clause 6.2.

(g)

Calculate F i using Clause 6.3.

(h)

Apply the forces to the structure at the eccentricities specified in Clause 6.6.

(i)

Take P-delta effects into account as specified in Clause 6.7.

6.2 HORIZONTAL EQUIVALENT STATIC FORCES 6.2.1 Earthquake base shear

The set of equivalent static forces in the direction being considered shall be assumed to act simultaneously at each level of the structure and shall be applied taking into account the torsion effects as giv en in Clause 6.6 in combination with other actions as specified in AS/NZS 1170.0. The horizontal equivalent static shear force ( V ) acting at the base of the structure (base shear) in the direction being considered shall be calculated from the f ollowing equations: V = C d(T 1)W t

. . . 6.2(1)

= [C (T 1)S p/µ ] W t

. . . 6.2(2)

= [k pZC h(T 1)S p/µ ] W t

. . . 6.2(3)

where C d(T 1) = horizontal design action coefficient (value of the horizontal design response spectrum at the fundamental natural period of the structure) = C (T 1)S p/µ C (T 1)

. . . 6.2(4)

= value of the elastic site hazard spectrum, determined from Clause 6.4 using k p appropriate for the structure, Z for the location and the fundamental natural period of the structure = k pZC h(T 1)

. . . 6.2(5)

C h(T 1) = value of the spectral shape factor for the fundamental natural period of the structure, as given in Clause 6.4 W t

= seismic weight of the structure taken as the sum of W i for all levels, as given in Clause 6.2.2

S p

= structural performance factor, as given in Clause 6.5

µ

= structural ductility factor, as given in Clause 6.5


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AS 1 170. 4—20 07

36

T 1

= fundamental natural period of the structure, as given in Clause 6.2.3

6.2.2 Gravity load

The seismic weight (W i ) at each level shall be as given by the following equation: W i = ∑G i + ∑ψ cQ i

. . . 6.2(6)

where G i and ψ cQ i are summed between the mid-heights of adjacent storeys G i = permanent action (self-weight or ‘dead load’) at level i, including an allowance of 0.3 kPa for ice on roofs in alpine regions as given in AS/NZS 1170.3 ψ c = earthquake-imposed action combination factor = 0.6 for storage applications = 0.3 for all other applications Q i = imposed action for each occupancy class on level i (see AS/NZS 1170.1) NOTE : Seis mic mas s is the wei ght div ided by acce leration due to gravit y ( mi = W i / g ).

6.2.3 Natural period of the structure

The fundamental period of the structure as a whole ( T 1, fundamental natural translational period of the structure) in seconds, including all the materials incorporated in the whole construction, may be determined by a rigorous structural analysis or from the following equation: T 1 = 1.25k thn

0.75

for the ultimate limit state

. . . 6.2(7)

where k t = 0.11

for moment-resisting steel frames

= 0.075

for moment-resisting concrete frames

= 0.06

for eccentrically-braced steel frames

= 0.05

for all other structures

h n = height from the base of the structure to the uppermost seismic weight or mass, in metres The base shear obtained using the fundamental structure period ( T 1) determined by a rigorous structural analysis shall be not less than 80% of the value obtained with T 1 calculated using the above equation. 6.3 VERTICAL DISTRIBUTION OF HORIZONTAL FORCES

The horizontal equivalent static design force ( F i) at each level (i) shall be obtained as follows: F i = k F,i V

. . . 6.3(1)

S p   ( ) k ZC T  p h 1  W t µ  k  (W h ) k

W i hi

=

n

∑

. . . 6.3(2)

j j

j 1 =

where k F,i = seismic distribution factor for the ith level W i = seismic weight of the structure at the ith level, in kilonewtons h i = height of level i above the base of the structure, in metres ©

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AS 1 170. 4—20 07

37

k = exponent, dependent on the fundamental natural period of the structure ( T 1), which is taken as— 1.0 when T 1 ≤ 0.5; 2.0 when T 1 ≥ 2.5; or linearly interpolated between 1.0 and 2.0 for 0.5 < T 1 < 2.5 n = number of levels in a structure The horizontal equivalent static earthquake shear force ( V i ) at storey i is the sum of all the horizontal forces at and above the ith level ( F i to F n). 6.4 SPECTRAL SHAPE FACTOR (C h(T ))

The spectral shape factor (C h(T )) shall be as given in Table 6.4 (illustrated in Figure 6.4) for the appropriate site sub-soil class defined in Section 4. TABLE 6.4 SPECTRAL SHAPE FACTOR (C h (T )) Site sub-soil class Period (seconds)

A e Strong rock

Be Rock

Ce Shallow soil

De Deep or soft soil

Ee Ver y soft soi l

0.0 0.1 0.2

2.35 (0.8)* 2.35 2.35

2.94 (1.0)* 2.94 2.94

3.68 (1.3)* 3.68 3.68

3.68 (1.1)* 3.68 3.68

3.68 (1.1)* 3.68 3.68

0.3 0.4 0.5

2.35 1.76 1.41

2.94 2.20 1.76

3.68 3.12 2.50

3.68 3.68 3.68

3.68 3.68 3.68

0.6 0.7 0.8

1.17 1.01 0.88

1.47 1.26 1.10

2.08 1.79 1.56

3.30 2.83 2.48

3.68 3.68 3.68

0.9 1.0 1.2

0.78 0.70 0.59

0.98 0.88 0.73

1.39 1.25 1.04

2.20 1.98 1.65

3.42 3.08 2.57

1.5 1.7 2.0

0.47 0.37 0.26

0.59 0.46 0.33

0.83 0.65 0.47

1.32 1.03 0.74

2.05 1.60 1.16

2.5 3.0 3.5

0.17 0.12 0.086

0.21 0.15 0.11

0.30 0.21 0.15

0.48 0.33 0.24

0.74 0.51 0.38

4.0 4.5 5.0

0.066 0.052 0.042

0.083 0.065 0.053

0.12 0.093 0.075

0.19 0.15 0.12

0.29 0.23 0.18

1.0 + 19.4T 0.88/T but ≤ 2.94 1.32/T 2

1.3 + 23.8 T 1.25/T but ≤ 3.68 1.874/ T 2

Equations for spectra 0< 0.1 <

T ≤ 0.1

0.8 + 15.5 T 0.704/T but ≤ 2.35 1.056/T 2 T > 1.5 T ≤ 1.5

1.1 + 25.8 T 1.98/T but ≤ 3.68 2.97/T 2

1.1 + 25.8T 3.08/T but ≤ 3.68 4.62/T 2

* Values in brackets correspond to values of spectral shape factor for the modal response spectrum and the numerical integration time history methods and for use in the method of calculation of forces on parts and components (see Section 8)


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38

4.00 ) )

T

(

3.50

h

C

(

S E T A N I D R O L A R T C E P S

3.00 2.50

Soil A e Soil B e

2.00

Soil C e Soil D e

1.50

Soil E e

1.00 0.50 0.00 0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

PERIOD IN SECONDS ( T ) FIGURE 6.4

NORMALIZED RESPONSE SPECTRA FOR SITE SUB-SOIL CLASS

6.5 DETERMINATIO N OF STRUCTURAL DUCTILITY (µ ) AND STRUCTURAL PERFORMANCE FACTOR ( S p)

The ductility of the structure ( µ ) and the structural performance factor ( S p) shall be determined either— (a)

in accordance with the appropriate material standard where the data is provided; or

(b)

as given in Table 6.5(A) or 6.5(B) for the structure type and material where the data is not provided,

except that, for a specific structure, it shall be permissible to determine µ and S p by using a non-linear static pushover analysis. NOTE S: 1

Where the design is carried out using other than recognized Australian material design Standards, then the values given in the last row for each material type in Table 6.5A should be used.

2

Where the desi gn is carried out in accordance with NZ S 1170.5, determined as set out therein.

µ

and S p should be

A lower µ value that is specified in this Clause or the relevant material standard may be used. In all cases, the structure shall be detailed to achieve the level of ductility assumed in the design, in accordance with the applicable material design Standard.

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39

TABLE 6.5(A) STRUCTURAL DUCTILITY FACTOR ( µ ) AND STRUCTURAL PERFORMANCE FACTOR ( S p)—BASIC STRUCTURES Structural system

Description

µ

S p

S p / µ

µ / S p

Special moment-resisting frames (fully ductile)*

4

0.67

0.17

6

Intermediate moment-resisting frames (moderately ductile)

3

0.67

0.22

4.5

Ordinary moment-resisting frames (limited ductile)

2

0.77

0.38

2.6

Moderately ductile concentrically braced frames

3

0.67

0.22

4.5

Limited ductile concentrically braced frames

2

0.77

0.38

2.6

Fully ductile eccentrically braced frames*

4

0.67

0.17

6

Other steel structures not defined above

2

0.77

0.38

2.6

Special moment-resisting frames (fully ductile)*

4

0.67

0.17

6

Intermediate moment-resisting frames (moderately ductile)

3

0.67

0.22

4.5

Ordinary moment-resisting frames

2

0.77

0.38

2.6

Ductile coupled walls (fully ductile)*

4

0.67

0.17

6

Ductile partially coupled walls*

4

0.67

0.17

6

Ductile shear walls

3

0.67

0.22

4.5

Limited ductile shear walls

2

0.77

0.38

2.6

Ordinary moment-resisting frames in combination with a limited ductile shear walls

2

0.77

0.38

2.6

Other concrete structures not listed above

2

0.77

0.38

2.6

Shear walls

3

0.67

0.22

4.5

Braced frames (with ductile connections)

2

0.77

0.38

2.6

Moment-resisting frames

2

0.77

0.38

2.6

Other wood or gypsum based seismic-force-resisting systems not listed above

2

0.77

0.38

2.6

Steel structures

Concrete structures

Timber structures

Masonry structures Close-spaced reinforced masonry†

2

0.77

0.38

2.6

Wide-spaced reinforced masonry†

1.5

0.77

0.5

2

Unreinforced masonry†

1.25

0.77

0.62

1.6

Other masonry structures not complying with AS 3700

1.00

0.77

0.77

1.3

* The design of structures with

µ >

3 is outside the scope of this Standard (see Clause 2.2)

† These values are taken from AS 3700


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40

TABLE

6.5(B)

STRUCTURAL DUCTILITY FACTOR ( µ ) AND STRUCTURAL PERFORMANCE FACTOR ( S p)—SPECIFIC STRUCTURE TYPES Type of structure

µ

S p

µ / S p

S p / µ

Tanks, vessels or pressurized spheres on braced or unbraced legs

2

1

2

0.5

Cast-in-place concrete silos and chimneys having walls continuous to the foundation

3

1

3

0.33

Distributed mass cantilever structures, such as stacks, chimneys, silos and skirt-supported vertical vessels

3

1

3

0.33

Trussed towers (freestanding or guyed), guyed stacks and chimneys

3

1

3

0.33

Inverted pendulum-type structures

2

1

2

0.5

Cooling towers

3

1

3

0.33

Bins and hoppers on braced or unbraced legs

3

1

3

0.33

Storage racking

3

1

3

0.33

Signs and billboards

3

1

3

0.33

Amuseme nt structures and monuments

2

1

2

0.5

All other self-supporting structures not otherwise covered

3

1

3

0.33

6.6 TORSIONAL EFFECTS

For each required direction of earthquake action, the earthquake actions, as determined in Clause 6.3, shall be applied at the position calculated as ±0.1b from the nominal centre of mass, where b is the plan dimension of the structure at right angles to the direction of the action. This ±0.1b eccentricity shall be applied in the same direction at all levels and orientated to produce the most adverse torsion moment for the 100% and 30% loads. 6.7 DRIFT DETERMINATION AND P -DELTA EFFECTS 6.7.1 General

Storey drifts, member forces and moments due to P-delta effects shall be determined in accordance with Clauses 6.7.2 and 6.7.3. 6.7.2 Storey drift determination

Storey drifts shall be assessed for the two major axes of a structure considering horizontal earthquake forces acting independently, but not simultaneously, in each direction. The design storey drift (d st ) shall be calculated as the difference of the deflections ( d i) at the top and bottom of the storey under consideration. The design deflections (d i) shall be determined from the following equations: d i = d ie µ /S p

. . . 6.7(1)

where d ie

= deflection at the ith level determined by an elastic analysis, carried out using the horizontal equivalent static earthquake forces ( F i) specified in Clause 6.3, applied to the structure in accordance with Clause 6.6

Where applicable, the design storey drift ( d st ) shall be increased to allow for the P-delta effects as given in Clause 6.7.3.

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41

6.7.3

P - delta

AS 1 170. 4—20 07

effects

6.7.3.1 Stability coefficient

For the inter-storey stability coefficient ( θ ) calculated for each level, design for P-delta effects shall be as follows: (a)

For θ ≤ 0.1, P-delta effects need not be considered.

(b)

For θ > 0.2, the structure is potentially unstable and shall be re-designed.

(c)

For 0.1 < θ ≤ 0.2, P-delta effects shall be calculated as given in Clause 6.7.3.2, n    θ = d st ∑ W j / hsi µ ∑ F j    j i j i   n

=

. . . 6.7(2)

=

where i

= level of the structure under consideration

h si = inter-storey height of level i, measured from centre-line to centre-line of the floors 6.7.3.2 Calculating P-delta effects

Values of the horizontal earthquake shear forces and moments, the resulting member forces and moments, and the storey drifts that include the P-delta effects shall be determined by— (a)

scaling the equivalent static forces and deflections by the factor (0.9/(1 – θ )), which is greater than or equal to 1; or

(b)

using a second-order analysis.


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42

S E C T I O N

7

D Y N A M I C

A N A L Y S I S

7.1 GENERAL

Dynamic analysis, when used, shall be carried out in accordance with this Section. The analysis shall be based on an appropriate ground-motion representation in accordance with Clause 7.2. The mathematical model used shall be in accordance with Clause 7.3. The analysis procedure may be either a modal-response-spectrum analysis in accordance with Clause 7.4 or a time-history analysis in accordance with Clause 7.2(c). Drift and P-delta effects shall be determined in accordance with Clause 7.5. 7.2 EARTHQUAKE ACTIONS

The earthquake ground motion shall be accounted for by using one of the following: (a)

Horizontal design response spectrum (C d(T )), including the site hazard spectrum and the effects of the structural response as follows: C d(T ) = C (T )S p/µ = k pZC h(T ) S p/µ

. . . 7.2(1) . . . 7.2(2)

where values are as giv en in Section 6, except that— T = period of vibration appropriate to the mode of vibration of the structure being considered (b)

Site-specific design response spectra developed for the specific site, which shall be based on analyses that consider the soil profile and apply a bedrock ground motion compatible with the rock spectra given in Clause 6.4.

(c)

Ground-motion time histories chosen for the specific site, which shall be representative of actual earthquake motions. Response spectra from these time histories, either individually or in combination, shall approximate the site design spectrum conforming to Item (a) or (b). A dynamic analysis of a structure by the time-history method inv olves calculating the response of a structure at each increment of time when the base is subjected to a specific ground-motion time-history. The analysis should be based on well-established principles of mechanics using groundmotion records compatible with the site-specific design response spectra.

Where design includes consideration of vertical earthquake actions, both upwards and downwards directions shall be considered and the vertical design response spectrum shall be as follows: C vd (T ) = C v (T v )S p

. . . 7.2(3)

= 0.5C (T v )S p = 0.5k pZC h(T v )S p where C v (T v ) = elastic site hazard spectrum for vertical loading for the vertical period of vibration 7.3 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 of the significant features of its dynamic response. ©

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AS 1 170. 4—20 07

7.4 MODAL ANALYSIS 7.4.1 General

A dynamic analysis of a structure by the modal response spectrum method shall use the peak response of all modes having a significant contribution to the total structural response as specified in Clause 7.4.2. Peak modal responses shall be calculated using the ordinates of the appropriate response spectrum curve specified in Clause 7.2(a) or 7.2(b) that corresponds to the modal periods. Maximum modal contributions shall be combined in accordance with Clause 7.4.3. 7.4.2 Number of modes

In two-dimensional analysis, sufficient modes shall be included in the analysis to ensure that at least 90% of the mass of the structure is participating for the direction under consideration. In three-dimensional analysis, where structures are modelled so that modes that are not those of the seismic-force-resisting system are considered, then all modes not part of the seismic-force-resisting system shall be ignored. Further, all modes with periods less than 5% of the f undamental natural period of the structure (<0.05 T 1) may be ignored. 7.4.3 Combining modes

The peak member forces, displacements, horizontal earthquake shear forces and base reactions for each mode shall be combined by a recognized method. When modal periods are closely spaced, m odal interaction effects shall be considered. 7.4.4 Torsion 7.4.4.1 Three-dimensional dynamic analysis

Three-dimensional dynamic analysis shall take account of torsional effects, including accidental torsional effects as described in Clause 6.6. Where three-dimensional models are used for analysis, the effects of accidental torsion shall be accounted for, either by appropriate adjustments in the model, such as adjustment of mass locations, or by equivalent static procedures, as described in Clause 6.6. 7.4.4.2 Two-dimensional dynamic analysis with static analysis for torsion

For static analysis for torsional effects, applied torsion at each level shall use either the actions calculated by the equivalent static method or the combined storey earthquake forces found in a two-dimensional modal response spectrum analysis for translation. The eccentricity used shall be as required in Clause 6.6. Action effects arising from t orsion shall be combined with the translational action effects by direct summation, with signs chosen to produce the most adverse combined effects in the resisting members. 7.5 DRIFT DETERMINATION AND P -DELTA EFFECTS

Storey drifts, member forces and moments due to P-delta effects shall be calculated in accordance with Clause 6.7, using the deflections, forces and moments calculated from the dynamic analysis.


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44

S E C T I O N

8

D E S I G N O F P A R T S C O M P O N E N T S

A N D

8.1 GENERAL REQUIREMENTS 8.1.1 General

Non-structural parts and components and their fastenings, as listed in Clause 8.1.4, shall be designed for horizontal and v ertical earthquake forces as defined in Clauses 8.1.2 and 8.1.3. Base isolation may be used to reduce the forces on a component. Where flexible mounting devices (such as spring mountings) are used, they shall be fitted with restraining devices to limit the horizontal and vertical motions, to inhibit the development of resonance in the flexible mounting system, and to prevent overturning. 8.1.2 Earthquake actions

Design of parts and components shall be carried out for earthquake actions by one of the following methods: (a)

Using established principles of structural dynamics.

(b)

Using the general method given in Clause 8.2.

(c)

Using the forces determined by the simplified method given in Clause 8.3.

8.1.3 Forces on components

The horizontal earthquake force on any component shall be applied at the centre of gravity of the component and shall be assumed to act in any horizontal direction. Vertical earthquake forces on mechanical and electrical components shall be taken as 50% of the horizontal earthquake force. Mechanical connectors from the following shall be designed for 1.5 times the design force for the supported element: (a)

Curtain walls.

(b)

External walls.

(c)

Walls enclosing stairs, stair shafts, lifts and required exit paths.

8.1.4 Parts and components

The following parts and components and their connections shall be designed in accordance with this Section: (a)

©

Architectural components: (i)

Walls that are not part of the seismic-force-resisting system.

(ii)

Appendages, including parapets, gables, verandas, awnings, canopies, chimneys, roofing components (tiles, metal panels) containers and miscellaneous components.

(iii)

Connections (fasteners) for wall attachments, curtain walls, exterior nonloadbearing walls.

(iv)

Partitions.

(v)

Floors (including access floor systems, where the weight of the floor system shall be determined in accordance with Clause 6.2.2).

(vi)

Ceilings.

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AS 1 170. 4—20 07

45

(vii) Architectural equipment including storage racks and library shelves with a height over 2.0 m. (b)

Mechanical and electrical components: (i)

Smoke control systems.

(ii)

Emergency electrical systems (including battery racks).

(iii)

Fire and smoke detection systems.

(iv)

Fire suppression systems (including sprinklers).

(v)

Life safety system components.

(vi)

Boilers, furnaces, incinerators, water heaters, and other equipment using combustible energy sources or high-temperature energy sources, chimneys, flues, smokestacks, vents and pressure vessels.

(vii) Communication systems (such as cable systems motor control devices, switchgear, transformers, and unit substations). (viii) Reciprocating or rotating equipment. (ix)

Utility and service interfaces.

(x)

Anchorage of lift machinery and controllers.

(xi)

Lift and hoist components including structural frames providing support for guide rail brackets, guide rails and br ackets, car and counterweight members.

(xii) Escalators. (xiii) Machinery (manufacturing and process). (xiv) Lighting fixtures. (xv) Electrical panel boards and dimmers. (xvi) Conveyor systems (non-personnel). (xvii) Ducts and piping distribution systems. (xviii) Supports for ducts and piping distribution systems, except supports in the following situations:

(c)

(A)

In structures classified as being in EDC I.

(B)

For gas piping less than 25 mm inside diameter.

(C)

For piping in boiler and mechanical rooms less than 32 mm inside diameter.

(D)

For all other piping less than 64 mm inside diameter.

(E)

For all electrical conduit less than 64 mm inside diameter.

(F)

For all rectangular air-handling ducts less than 0.4 m 2 in cross-sectional area.

(G)

For all round air-handling ducts less than 700 mm in diameter.

(H)

For all ducts and piping suspended by individual hangers 300 mm or less in length from the top of the pipe to the bottom of the support for the hanger.

All other components similar to those listed in Items (a) and (b).


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46

8.2 METHOD USING DESIGN ACCELERATION S

Architectural, mechanical and electrical components and their fixings shall be designed for earthquake actions from the accelerations determined using the design methods given in Sections 6 and 7, as appropriate for the particular structure in which the component or fixing is incorporated. The forces generated on the part or component in the specific structure being considered are given as follows, based on the principles given in this Standard for design of the structure: F c = afloor [ I cac/ Rc]W c ≤ 0.5W c

. . . 8.2(1)

where a floor = effective floor acceleration at the level where the component is situated, calculated from the earthquake actions determined for the structure using Sections 5, 6 and 7 divided by the seismic weight, but not less than k pZC h(0), where the values of C h(0) are the bracketed values given in Table 6.1 NOTE : The f undame ntal nat ural period o f v ibra tion of a completed structure may be determined by measurement.

I c

= component importance factor, taken as: = 1.5 for components critical for life safety, which includes parts and components required to function immediately following an earthquake, those critical to containment of hazardous materials, storage racks in public areas and all parts and components in importance level 4 structures = 1.0 for all other components

ac

= component amplification factor = 2.5 for flexible spring-type mounting systems for mechanical equipment (unless detailed dynamic analysis is used to justify lower values) = 1.0 for all other mounting systems

R c

= component ductility factor = 1.0 for rigid components with non-ductile or brittle materials or connections = 2.5 for all other components and parts

W c

= seismic weight of the component, in kilonewtons

For objects mounted on the ground, the acceleration should be taken as follows: a floor = k pZC h (0)

. . . 8.2(2)

where C h(0) = bracketed value of the spectral shape factor for the period of zero seconds, as given in Clause 6.4 8.3 SIMPLE METHOD

Non-structural parts or components and their attac hments shall be designed to resist the horizontal earthquake force determined as follows and applied to the component at its centre of mass in combination with the gravity load of the element: F c = [k pZC h(0)]a x[ I cac/ Rc]W c

but > 0.05W c

. . . 8.3

where I c, ac, R c, W c are as given in Clause 8.2; and

©

k p

= probability factor (see Section 3)

Z

= hazard factor (see Section 3)

Standards Australia


47

ax

AS 1 170. 4—20 07

= height amplification factor at height h x at which the component is attached, given as follows: = (1 + k ch x) k c = 2/h n for h n ≥ 12 m = 0.17 for h n < 12 m h x = height at which the component is attached above the structural base o the structure, in metres h n = total height of the structure above the structural base, in metres


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48

APPENDIX A

DOMESTIC STRUCTURES (HOUSING) (Normative) A1 GENERAL

For the purposes of this Appendix, a domestic structure (housing) is a single dwelling or one or more attached dwellings complying with Class 1a or 1b, as defined in the Building Code of Australia (as shown in Figure A1). Domestic structures (housing) exceeding 8.5 m in height (see Figure A1), shall be designed in accordance with Section 2 for Importance Level 2 structures, using the annual probability of exceedance specified for housing. TABLE A1 DESIGN OF DOMESTIC STRUCTURES OF HEIGHT LESS THAN OR EQUAL TO 8.5 METRES Hazard at the k p Z

Provision for lateral resistance

≤ 0.11

Housing designed and detailed for lateral wind forces in accordance with AS 1684, AS 3600, AS 3700, AS 4100, AS/NZS 1664, AS 1720.1 or NASH Standard Part 1—2005

> 0.11

∗

Housing designed and detailed for lateral wind forces in accordance with AS 1684, AS 3600, AS 3700, AS 4100, AS/NZS 1664, AS 1720.1 or NASH Standard Part 1—2005

Material type

Specific deemed to satisfy limits

Design required

As per the relevant Standard

As per the relevant No spe cif ic Standard earthquake design required

Adobe, pressed earth bricks, rammed earth or other earth-wall material not in accordance with AS 3700

None prov ided

Use Para graph A2 or design as for importance level 2 (see Section 2)

Other materials

None provided

Use Paragraph A2 or design as for importance level 2 (see Section 2)


Use Paragraph A2 or design as for importance level 2 (see Section 2)

∗


This includes any other materials that are not covered by accepted design Standards such as random stone masonry or hay bale construction

A2 DESIGN AND DETAILING

Domestic structures required to be designed in accordance with this Paragraph shall comply with the following requirements: (a)

©

Where the racking forces calculated in this item are greater than those calculated for wind action, lateral bracing shall be provided in both orthogonal directions, distributed into at least two walls in each orthogonal direction with a maximum spacing between walls of 9 m to resist the following forces:

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AS 1 170. 4—20 07

49

(i)

For masonry structures—

veneer,

reinforced

masonry,

timber,

steel

F r = 1.4 k p Z W (ii)

and

concrete . . . A2(1)

For unreinforced masonry and other structures— F r = 2.3 k p Z W

. . . A2(2)

where F r

= horizontal design racking earthquake force applied in each orthogonal direction on the part or component, in kilonewtons

W

= sum of the seismic weight of the building ( G + 0.3Q ) at the level where bracing is to be determined and above this level (see Figure 1.5(A))

k p

= probability factor appropriate for the limit state under consideration

Z

= earthquake hazard factor, which is equivalent to an acceleration coefficient with an annual probability of exceedance of 1/500 (i.e., a 10% probability of exceedance in 50 years)

(b)

Walls shall be tied to other walls that they abut and shall be anchored to the roof and all floors that provide horizontal in-plane and perpendicular to the plane of the wall support for the wall, with an anchorage capable of resisting 0.5 kN/m. Walls shall be checked for stability under out-of-plane lateral loads of Z times the weight of the wall.

(c)

Non-ductile components, such as unreinforced masonry gable ends, chimneys and parapets shall be restrained to resist a minimum force of 0.1 W c , where W c is the weight of the component. Masonry veneer walls tied to framing in accordance with AS 3700 are deemed to comply with this Item (c). NOTE : S ee AS 3700 for deta ili ng require men ts for mas onry struct ures.

FIGURE A1


SECTION GEOMETRY

© Standards

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AS 1 170. 4—20 07

50

BIBLIOGRAPHY

©

AS 4678

Earth retaining structures

NZS 1170 1170.5

Structural design actions Part 5: Earthquake actions—New Zealand

Standards Australia


51

NOT ES

AS 1 170. 4—20 07

AS 1 170. 4—20 07

52

NOT ES

Standards Australia develops Australian Standards® and other documents of public benefit and national interest. These Standards are developed through an open process of consultation and consensus, in which all interested parties are invited to participate. Through a Memorandum of Understanding with the Commonwealth Government, Standards Australia is recognized as Australia’s peak non-government national standards body. Standards Australia also supports excellence in design and innovation through the Australian Design Awards. For further information visit

Committees of experts from industry, governments, consumers and other relevant sectors prepare Australian Standards. The requirements or recommendations contained in published Standards are a consensus of the views of representative interests and also take account of comments received from other sources. They reflect the latest scientific and industry experience. Australian Standards are kept under continuous review after publication and are updated regularly to take account of changing technology.

Standards Australia is responsible for ensuring the Australian viewpoint is considered in the formulation of International Standards and that the latest international experience is incorporated in national Standards. This role is vital in assisting local industry to compete in international markets. Standards Australia represents Australia at both the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).

Australian Standards®, Handbooks and other documents developed by Standards Australia are printed and distributed under license by SAI Global Limited.

AS1170!4!2007 Structural Design Actions Part 4 Earthquake Actions in Australia

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