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AS 1170.4—2007

Australian Standard®

Structural design actions

Part 4: Earthquake actions in Australia

A S 1 1 7 0 .4 —2 0 0 7

A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



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:

• 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Standards may also be withdrawn.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 tonotify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at

[email protected], or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.




AS 1170.4—2007

Australian Standard®



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 byany 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 A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



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:

AS1170 Structural design actions

1170.4 Part 4: Earthquake actions (this Standard)

AS/NZS

1170.0 Part 0: General principles

1170.1 Part 1: Permanent, imposed and other actions

1170.2 Part 2: Wind actions

1170.3 Part 3: Snow and ice actions

NZS

1170.5 Part 5: Earthquake actions—New Zealand

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 act ions — Commentary (Supplement to AS 1170.4—2007). A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



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/ Rf 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.

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 beenadopted.

(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. A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



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.

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 HAZARD3.1 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 ........................................................................................... 406.7 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 A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



AS 1170.4—2007 6

© Standards Australia www.standards.org.au

STANDARDS AUSTRALIA

Australian Standard



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.

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 Timber structures

1720.1 Part 1: Design methods

3600 Concrete structures

3700 Masonry structures

4100 Steel structures

AS/NZS

1170 Structural design actions

1170.0 Part 0: General principles

1170.1 Part 1: Permanent, imposed and other actions

1170.3 Part 3: Snow and ice actions A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



7 AS 1170.4—2007

www.standards.org.au © Standards Australia

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).

1.3.6 Connection

Mechanical means that provide a load path for actions between structural elements, non-

structural 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.




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 relevantmaterial 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-force-

resisting 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

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 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 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).




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).

Unless stated otherwise, the notation used in this Standard shall have the following

meanings:ac = component amplification factor

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

ax = height amplification factor at height hx 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 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

d i = 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)

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/s2)

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 A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



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)

hsi = 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 thestructure, 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

Rc = 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




11 AS 1170.4—2007


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 more

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 (hn) 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.




AS 1170.4—2007 12


Storey n

Storey i + 1

Storey i + 1

Storey i

Storey i

Storey 1

Force F n

Force F n - 1

Force F i + 1

Force F i - 1

Force F i

Force F i

Level n

Level n - 1

Level i + 1

Level i - 1

Level i + 1

Level i

Level i - 1

Level i

Level 1

Base

h n

h

h si

Uppermost seismic mass

W i

W ih si

2

h si

2

FIGURE 1.5(A) ILLUSTRATION OF LEVEL, STOREY, WEIGHT AND FORCE




13 AS 1170.4—2007


Storey n - 1

Storey n

W n

Top

Base

hn

PlantCentre ofgravity of W n

FIGURE 1.5(B) EXAMPLE OF DETERMINATION OF THE TOP OF THE STRUCTURE




AS 1170.4—2007 14


Building height, h n Building height, h n

(a) Base shear react ionat ground level

(b) Base shear react ionbelow ground level

Building height, h n Building height, h n

(c) Base shear react iontaken as at lowest level

(d) Base shear react ionat 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




15 AS 1170.4—2007


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 orelement, 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) given 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 definitiongiven 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: During an earthquake, motion wil l be imposed on all parts of any construction. Therefore,

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: Structures (including housing) that are constructed on a site with a hazard 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: Structures , where the structural ductil ity factor (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 remain serviceable for immediate use following

the design event for importance level 2 structures.




AS 1170.4—2007 16


TABLE 2.1

SELECTION OF EARTHQUAKE DESIGN CATEGORIES

(k p Z ) for site sub-soil classImportance

level, type of

structure(see

Clause 2.2)

Ee or D e Ce Be Ae

Structure

height,hn (m)

Earthquake

designcategory

1 — —

Not required to

be designed for

earthquake

actions

Top of

roof

≤8.5

Refer to

Appendix A Domestic

structure

(housing)

— Top of

roof

>8.5

Design as

importance

level 2

≤0.05 ≤0.08 ≤0.11 ≤0.14

≤12

>12, <50

≥50

I

II

III

>0.05 to ≤0.08 >0.08 to ≤0.12 >0.11 to ≤0.17 >0.14 to ≤0.21<50

≥50

II

III

2

>0.08 >0.12 >0.17 >0.21<25

≥25

II

III

≤0.08 ≤0.12 ≤0.17 ≤0.21<50

≥50

II

III3

>0.08 >0.12 >0.17 >0.21<25

≥25

II

III

4 — <12

≥12

II

III

NOTES: 1 Values for k p and Z are given in Section 3. Site sub-soil class are given in Section 4.

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

3 Height (hn) 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.




17 AS 1170.4—2007


1 Det er mi ne

2 Look up

3 Det er mi ne

4 Apply EDC I

5 D es ig n p ar ts

and components

Structure location and importance level

Annual probability of exceedance (from AS/NZS 1170.0 or BCA)

k p, Z value (Section 3)

Soil c lass, A, B, C, D or E (Section 4)

EDC (Table 2.1)

Does the structure comply with the definit ion of

domestic structures (Housing) and is h n 8. 5

EDC II EDC I II

U se C la us e 5 .2

Clause 5.3

Simple static check

U se C la us e 5 .2

Clause 5.4

Static analysis

(Section 6)

U se C la us e 5 .2

Clause 5.5

Dynamic analysis

(Section 7)

EDC I

(Clause 5.3)

EDC II

(Section 8)

EDC III

(Section 8)

No

Appendix A

Y

FIGURE 2.2 FLOW DIAGRAM—DESIGN PROCEDURE




AS 1170.4—2007 18


S E C T I O N 3 S I T E H A Z A R D

3.1 ANNUAL PROBABILITY OF EXCEEDANCE ( P ) AND PROBABILITY

FACTOR (k p)

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 probability o f exceedance Probability factor

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 annual probabil ity of exceedance in Table 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).




19 AS 1170.4—2007


TABLE 3.2

HAZARD FACTOR ( Z ) FOR SPECIFIC AUSTRALIAN LOCATIONS

Location Z Location Z Location Z

Adelaide

AlbanyAlbury/Wodonga

0.10

0.080.09

Geraldton

GladstoneGold Coast

0.09

0.090.05

Port Augusta

Port LincolnPort Hedland

0.11

0.100.12

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

CamdenCanberra

Carnarvon

0.090.08

0.09

LismoreLorne

Mackay

0.050.10

0.07

Toowoomba Townsville

Tweed Heads

0.060.07

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

Newcastl 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

Northam

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

Norfolk Island

0.06

0.60

0.08




AS 1170.4—2007 20


Hazard (z)1 in 500 years annual

probabi l i ty of exceedance

FIGURE 3.2(A) HAZARD FACTOR (Z ) FOR NEW SOUTH WALES, VICTORIA

AND TASMANIA




21 AS 1170.4—2007



probability of exceedance

FIGURE 3.2(B) HAZARD FACTOR (Z ) FOR SOUTH AUSTRALIA




AS 1170.4—2007 22


FIGURE 3.2(C) HAZARD FACTOR (Z) FOR WESTERN AUSTRALIA




23 AS 1170.4—2007



probability of exceedance

FIGURE 3.2(D) HAZARD FACTOR (Z ) FOR SOUTH-WEST OF WESTERN AUSTRALIA




AS 1170.4—2007 24



probabil i ty of exceedance

FIGURE 3.2(E) HAZARD FACTOR (Z ) FOR NORTHERN TERRITORY




25 AS 1170.4—2007



probabil i ty of exceedance

FIGURE 3.2(F) HAZARD FACTOR (Z ) FOR QUEENSLAND




AS 1170.4—2007 26


H a z a r d

( z )

1

i n

5 0 0

y e a r s

a n n u a l

p r o b a b i l i t y

o f e x c e e d a n c e

F I G U R E

3 . 2 ( G

)

H A Z A R D F

A C T O R (

Z )




27 AS 1170.4—2007


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 DETERMINATION 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 Ae to Ee as

follows:

(a) Class Ae —Strong rock.

(b) Class Be —Rock.

(c) Class Ce —Shallow soil.

(d) Class De —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.




AS 1170.4—2007 28


TABLE 4.1

MAXIMUM DEPTH LIMITS FOR SITE SUB-SOIL CLASS C

Soil type and description PropertyMaximum

depth of soil

Representative undrainedshear strengths

RepresentativeSPT N -values

(kPa) (Number) (m)

Very soft <12.5 — 0

Soft 12.5 – 25 — 20

Firm 25 – 50 — 25

Stiff 50 – 100 — 40

Cohesive soils

Very stiff or hard 100 – 200 — 60

Very loose — <6 0

Loose dry — 6 – 10 40Medium dense — 10 – 30 45

Dense — 30 – 50 55

Very dense — >50 60

Cohesionless soils

Gravels — >30 100

4.2 CLASS DEFINITIONS

4.2.1 Class Ae —Strong rock

Site sub-soil Class Ae is defined as strong to extremely strong rock satisfying the following

conditions:(a) Unconfined compressive strength greater than 50 MPa or an average shear-wave

velocity over the top 30 m greater 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 Be —Rock

Site sub-soil Class Be 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 anaverage 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 present.

4.2.3 Class Ce —Shallow soil site

Site sub-soil Class Ce is defined as a site that is not Class A e, Class Be (i.e., not rock site),

or Class Ee 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; A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



29 AS 1170.4—2007


(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 De —Deep or soft soil site

Site sub-soil Class De is defined as a site that is—

(a) not Class Ae, Class Be (i.e., not rock site) or Class Ee site (i.e., very soft soil site); and

(b) underlain by less 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 Ee —Very soft soil site

Site sub-soil Class Ee 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 velocities 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.




AS 1170.4—2007 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 inaccordance 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 earthquake, 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 the structure, including structural

and other parts and components, 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 seismic-

force-resisting system, shall be designed to perform their required function while sustaining

the deformation of the structure resulting from the application of the earthquake forcesdetermined 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.




31 AS 1170.4—2007


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) shall 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 . . . 5.3where

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.

Base

Storey 1

Storey 2

Storey 3

W 3F 3

F 2

F 1

W 2

W 1

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) shall comply with the

requirements of Clause 5.2 and Clauses 5.4.2 to 5.4.6.




AS 1170.4—2007 32


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 horizontalearthquake 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 perpendicular direction.

Forces shall be applied at the centre of mass of each floor except where offset from the

centre of mass is required for the consideration of torsion effects (see Clause 6.6).

Connections between components of the structure shall be capable of transmitting aninternal 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 analysis, in accordance with Section 7, may be used if desired (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 shallbe 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




33 AS 1170.4—2007


TABLE 5.4

VALUES OF K s FOR STRUCTURES NOT EXCEEDING 15 m

K s factor

Storey under consideration

Total

number of

stories

Sub-soil

class 5th 4th 3rd 2nd 1st

5

A e

Be

Ce

De, 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

De, 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

Ce, D e, E e

—

—

—

—

—

—

3.1

3.9

5.5

2.0

2.6

3.6

1.0

1.3

1.8

2

A e

Be

Ce, D e, E e

—

—

—

—

—

—

—

—

—

3.1

3.9

4.9

1.6

1.9

2.5

1

A e

Be

Ce, D e, E e

—

—

—

—

—

—

—

—

—

—

—

—

2.3

3.0

3.6

5.4.3 Vertical earthquake actions

Vertical earthquake actions need not be considered.

NOTE: For parts and components, see Clauses 5.4.6 and 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.


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.




AS 1170.4—2007 34


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: For parts and components, 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 havesufficient 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.


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




35 AS 1170.4—2007


S E C T I O N 6 E Q U I V A L E N T S T A T I C

A N A L Y S I S

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 given in Clause 6.6 in combination with other actions as specified inAS/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 following 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 designresponse spectrum at the fundamental natural period of the structure)

= C (T 1)S p/μ . . . 6.2(4)

C (T 1) = 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 A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



AS 1170.4—2007 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: Seismic mass is the weight divided by acceleration due to gravity (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 thn0.75

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

hn = 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,iV . . . 6.3(1)

( )( ) t

p

1hpn

1 j

k j j

kii

W S

T ZC k

hW

hW ⎥⎦

⎤⎢⎣

⎡=

∑=

µ

. . . 6.3(2)

where

k F,i = seismic distribution factor for the ith level

W i = seismic weight of the structure at the ith level, in kilonewtons

hi = height of level i above the base of the structure, in metres A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



37 AS 1170.4—2007


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 6.4SPECTRAL SHAPE FACTOR (C h(T ))

Site sub-soil class

Period

(seconds)

Ae

Strong rock

Be

Rock

Ce

Shallow soil

De

Deep or soft soil

Ee

Very soft soil

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

0.384.0

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

Equations for spectra

0 < T ≤ 0.1

0.1 < T ≤ 1.5

T > 1.5

0.8 + 15.5T

0.704/T but ≤ 2.35

1.056/T 2

1.0 + 19.4T

0.88/T but ≤ 2.94

1.32/T 2

1.3 + 23.8T

1.25/T but ≤ 3.68

1.874/T 2

1.1 + 25.8T

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)




AS 1170.4—2007 38


0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Soil Ae

Soil Be

Soil Ce

Soil De

Soil Ee

PERIOD IN SECONDS (T )

S P E C T R A L

O R D I N A T E S (

C h ( T ) )

FIGURE 6.4 NORMALIZED RESPONSE SPECTRA FOR SITE SUB-SOIL CLASS

6.5 DETERMINATION 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 datais 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.

NOTES:

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 design is carried out in accordance with NZS 1170.5, µ and S p should be

determined as set out therein.

A lower μ value that is specified in this Clause or the relevant material standard may beused. 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.




39 AS 1170.4—2007


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

Steel structures

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

Concrete structures

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 walls2 0.77 0.38 2.6

Other concrete structures not listed above 2 0.77 0.38 2.6

Timber structures

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 above2 0.77 0.38 2.6

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




AS 1170.4—2007 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 foundation3 1 3 0.33

Distributed mass cantilever structures, such as stacks, chimneys, silos

and skirt-supported vertical vessels3 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

Amusement 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 toproduce 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. Thedesign 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 ieμ /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.




41 AS 1170.4—2007


6.7.3 P -delta 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

i j

n

i j

jsi jst / F hW d μ θ . . . 6.7(2)

where

i = level of the structure under consideration

hsi = inter-storey height of level i, measured from centre-line to centre-line of thefloors

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.




AS 1170.4—2007 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. Theanalysis 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 andthe effects of the structural response as follows:

C d(T ) = C (T )S p/μ . . . 7.2(1)

= k pZC h(T )S p/μ . . . 7.2(2)

where values are as given 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 involves 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 ground-

motion 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. A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



43 AS 1170.4—2007


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 than5% of the fundamental natural period of the structure (<0.05T 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, modal 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 areused 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 torsion 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.




AS 1170.4—2007 44


S E C T I O N 8 D E S I G N O F P A R T S A N D

C O M P O N E N T S

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 vertical 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 thefollowing 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.


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 non-

loadbearing 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.




45 AS 1170.4—2007


(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 brackets, 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:

(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 m2 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.

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




AS 1170.4—2007 46


8.2 METHOD USING DESIGN ACCELERATIONS

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

afloor = 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 fundamental natural period of vibra 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

Rc = 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:

afloor = 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 attachments 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)]ax[ I cac/ Rc]W c but > 0.05W c . . . 8.3

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

k p = probability factor (see Section 3)

Z = hazard factor (see Section 3) A c c e s s e d b y C O N N E L L W A G N E R o n 2 9 A p r 2 0 0 8



47 AS 1170.4—2007


ax = height amplification factor at height hx at which the component is attached,

given as follows:

= (1 + k chx)

k c = 2/hn for hn ≥ 12 m

= 0.17 for hn < 12 m

hx = height at which the component is attached above the structural base o

the structure, in metres

hn = total height of the structure above the structural base, in metres




AS 1170.4—2007 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

resistanceMaterial type

Specific deemed

to satisfy limitsDesign required

As per the relevant

Standard

As per the relevant

Standard

No specif ic

earthquake design

required

Adobe, pressed earth

bricks, rammed earth

or other earth-wall

material not inaccordance with

AS 3700

None prov ided Use Paragraph A2

or design as for

importance

level 2 (seeSection 2)

≤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

Other materials ∗ None provided Use Paragraph A2

or design as for

importance

level 2 (see

Section 2)

>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

As per the relevant

Standard

As per the relevant

Standard

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 maximumspacing between walls of 9 m to resist the following forces:




49 AS 1170.4—2007


(i) For masonry veneer, reinforced masonry, timber, steel and concrete

structures—

F r = 1.4 k p Z W . . . A2(1)

(ii) 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 0.1W 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: See AS 3700 for detailing requirements for masonry structures.

FIGURE A1 SECTION GEOMETRY




AS 1170.4—2007 50


BIBLIOGRAPHY

AS

4678 Earth retaining structures

NZS1170 Structural design actions

1170.5 Part 5: Earthquake actions—New Zealand




51 AS 1170.4—2007

NOTES




AS 1170.4—2007 52

NOTES




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