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AS 1170.4-2007 STRUCTURAL DESIGN ACTIONS - EARTHQUAKE ACTIONS IN AUSTRALIA

AS 1170.4-2007 STRUCTURAL DESIGN ACTIONS - EARTHQUAKE ACTIONS IN AUSTRALIA

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This Australian Standard® was prepared by Committee 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 2007.



The following are represented on Committee BD-006:









































Association of Consulting Engineers Australia

Australian Building Codes 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 Association (NSW)

University of Canterbury New Zealand

University of Melbourne

University of Newcastle



Additional Interests:



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



























Australian Defence Force Academy

Australia Earthquake Engineering Society

Australian 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 Research Centre, Australia

University of Adelaide



This Standard was issued in draft form for 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.



Keeping Standards up-to-date

Australian Standards® are living documents that reflect progress in science, technology 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Standards may also be withdrawn.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 www.standards.org.au

Standards Australia welcomes suggestions for improvements, and encourages readers to

notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at

mail@standards.org.au, or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.



AS 1170.4—2007



Australian Standard®

Structural design actions



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



Part 4: Earthquake actions in Australia



Originated as AS 2121—1979.

Revised and redesignated as AS 1170.4—1993.

Second edition 2007.



COPYRIGHT

© Standards Australia

All rights are reserved. No part of this work may be reproduced or copied in any form or by

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



AS 1170.4—2007



2



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, Minimum design loads on structures, Part 4: Earthquake loads.

After consultation with stakeholders in both countries, Standards Australia and Standards

New Zealand decided to develop this Standard as an Australian Standard rather than 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, 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 0:

Part 1:

Part 2:

Part 3:



General principles

Permanent, imposed and other actions

Wind actions

Snow and ice actions



NZS

1170.5



Part 5:



Earthquake actions—New Zealand



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



This edition differs from AS 1170.4—1993 as follows:

(a)



Importance factors have 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 are now given in the BCA and AS/NZS 1170.0.



(c)



Clauses on 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.



(e)



Site factors and the effect of sub-soil conditions have been replaced with 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 have been simplified to three (3) new

categories simply described as follows:

(i)



I—a minimum static check.



(ii)



II—static analysis.



(iii) III—dynamic analysis.

(g)



The option to allow no analysis or detailing for some structures has 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—

Earthquake actions—Commentary (Supplement to AS 1170.4—2007).



3



AS 1170.4—2007



(h)



All requirements for the earthquake design categories are collected together 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 new site sub-soil 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 been replaced by the combination of structural

performance factor and structural ductility factor (1/R f to S p/μ) and values modified

for some structure types.



(m)



A new method has been introduced for the calculation of the 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 some structures for vertical components of 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.



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



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 for design of structures—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 seismicity in Australia. The most significant points are as follows*:

(i)



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



(ii)



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

adopted.



(iii) Some notation and definitions have not been adopted.

(iv)



Details of the equivalent static method have 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.



AS 1170.4—2007



4



Statements expressed in mandatory terms in notes to tables and figures are deemed to be an

integral part of this Standard.



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



Notes to the text contain information and guidance. They are not an integral part of the

Standard.



5



AS 1170.4—2007



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 (kp)............................................................................................................. 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



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



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 (Ch(T)) ..................................................................... 37

6.5 DETERMINATION OF STRUCTURAL DUCTILITY (μ) AND

STRUCTURAL PERFORMANCE FACTOR (Sp) .................................................... 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



AS 1170.4—2007



6



STANDARDS AUSTRALIA

Australian Standard

Structural design actions

Part 4: Earthquake actions in Australia



SECT ION



1



SCOPE



AND



GENERA 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.



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



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.

NOTES:

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.

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



7



AS 1170.4—2007



1664



Aluminium structures (all parts)



BCA



Building Code of Australia



NASH



Standard Residential and low-rise steel framing, Part 1—2005, Design 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).



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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.



www.standards.org.au



© Standards Australia



AS 1170.4—2007



8



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 the 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



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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: Storey i is the storey below the ith 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 assessment of the ability of a structure to sustain cyclic displacements 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).



© Standards Australia



www.standards.org.au



9



AS 1170.4—2007



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).



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



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(T1 )



= 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 (T1 )



= 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 half

of the elastic site hazard spectrum for horizontal 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



di



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



d ie



= deflection at level ‘i’ determined by an elastic analysis



d st



= design storey drift



E



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



Eu



= 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



Fc



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



Fi



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



Fj



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



Fn



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

kilonewtons



Fr



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

kilonewtons



g



= acceleration due to gravity (9.8 m/s2)



G



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



Gi



= 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



www.standards.org.au



© Standards Australia



AS 1170.4—2007



10



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



Ic



= component importance factor



i, j



= levels of the structure under consideration



Ks



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



k



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



kc



= factor for determining height amplification factor (a x )



k F,i



= seismic force distribution factor for the ith level



kp



= probability factor appropriate for the limit state under consideration



kt



= factor for determining building period



mi



= seismic mass at each level



Accessed by SWINBURNE UNIVERSITY OF TECHNOLOGY on 19 Nov 2007



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



Qi



= imposed action for each occupancy class on the ith level



Rc



= component ductility factor



Sp



= structural performance factor



T



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

considered



T1



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

mode natural period)



Tv



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



V



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



Vi



= horizontal equivalent static shear force at the ith level



W



= sum of the seismic weight of the building (G + ψc Q) at the level where

bracing is to be determined and above this level, in kilonewtons



Wc



= seismic weight of the part or component, in kilonewtons



Wi



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



Wj



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



Wn



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

kilonewtons



Wt



= total seismic weight of the building, in kilonewtons



© Standards Australia



www.standards.org.au



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