AS 1170.

4:2024

This Australian Standard ® was prepared by BD-006, General Design Requirements and
Loading on Structures. It was approved on behalf of Standards Australia’s Standards
Development and Accreditation Committee on 04 June 2024.
This Standard was published on 21 June 2024.

The following are represented on Committee BD-006:

Australasian Wind Engineering Society
Australian Building Codes Board
Australian Steel Institute
Bureau of Steel Manufacturers of Australia
Cement Concrete & Aggregates Australia
Concrete Institute of Australia
Concrete Masonry Association of Australia
Engineers Australia
Forest and Wood Products Australia
Housing Industry Association
Insurance Council of Australia
James Cook University
Property Council of Australia
Steel Reinforcement Institute of Australia
Swinburne University of Technology
The University of Melbourne
University of Newcastle

This Standard was issued in draft form for comment as DR AS 1170.4:2023.

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ISBN 978 1 76139 690 8

Originated as AS 2121—1979.
Revised and redesignated as AS1170.4—1993.
Previous edition 2007.
Third edition 2024.

© Standards Australia Limited 2024

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, unless otherwise permitted under the Copyright
Act 1968 (Cth).
AS 1170.4:2024 ii

Preface
This document was prepared by the Australian members of Joint Standards Australia/Standards New
Zealand Committee BD-006, General Design Requirements and Loading on Structures, to supersede
AS 1170.4:2007.
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 with a primary focus
on life safety.
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) on detailing
requirements additional to those contained in this Standard.
This Standard is based on equivalent principles to ISO 3010:2017, Basis for design of structures—
Seismic actions on structures. 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

are as follows:
(a) ISO 3010 is drafted as a guide for committees preparing Standards on seismic actions.
(b) Method and notation for presenting the mapped earthquake hazard data has not been adopted.

appendices to which they apply. A “normative” appendix is an integral part of a Standard, whereas an
“informative” appendix is only for information and guidance.

of this document. Notes that appear in the main text of this document provide information only.

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 iii AS 1170.4:2024

Contents
Preface ............................................................................................................................................................................................................................................... ii
Section 1 Scope and general.................................................................................................................................................................................. 1
.................................................................................................................................................................................................................... 1
............................................................................................................................................................................ 1
............................................................................................................................................................................ 2
.................................................................................................................................................................................... 4
......................................................................................................................... 6
Section 2 Design procedure ................................................................................................................................................................................10
............................................................................................................................................................................................................. 10
................................................................................................................................................................................... 10
Section 3 Site hazard ..................................................................................................................................................................................................13
) and probability factor ( p) .............................................................. 13
) ................................................................................................................................................................... 13
p ....................................................................................................................................................................................... 14
Section 4 Site sub-soil class.................................................................................................................................................................................22
....................................................................................................................................... 22
...................................................................................................................................................................................... 22
...................................................................................................................................... 22
.......................................................................................................... 22
............................................................................................................................................................................. 23
................................................................................................................................................................................. 23
e — Strong rock ............................................................................................................................................... 23
e — Rock ................................................................................................................................................................ 23
e — Shallow soil site .................................................................................................................................... 24
e— Deep or soft soil site .......................................................................................................................... 24
e — Very soft soil site.................................................................................................................................. 24
Section 5 Earthquake design .............................................................................................................................................................................25
............................................................................................................................................................................................................. 25
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Section 6 Equivalent static analysis ...........................................................................................................................................................30
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AS 1170.4:2024 iv

......................................................................................................................................... 30
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........................................................................................................................................................................... 31
........................................................................................................................... 31
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h( )) ....................................................................................................................................................... 32
) And structural performance factor ( p) ....................... 34
....................................................................................................................................................................................... 35
-delta effects .............................................................................................................................. 35
...................................................................................................................................................................................... 35
....................................................................................................................................... 35
-delta effects ..................................................................................................................................................................... 36
Section 7 Dynamic analysis .................................................................................................................................................................................37
............................................................................................................................................................................................................. 37
............................................................................................................................................................................... 37
............................................................................................................................................................................ 38
........................................................................................................................................................................................... 38
...................................................................................................................................................................................... 38
............................................................................................................................................................ 38
............................................................................................................................................................ 38
...................................................................................................................................................................................... 38
-delta effects .............................................................................................................................. 39
Section 8 Design of parts and components......................................................................................................................................... 40
......................................................................................................................................................................... 40
...................................................................................................................................................................................... 40
........................................................................................................................................................ 40
................................................................................................................................................ 40
................................................................................................................................................. 40
......................................................................................................................................... 42
.......................................................................................................................................................................................... 43
Appendix A (normative) Domestic structures (housing) ............................................................................................................44
Appendix B (informative) Structural ductility factor and structural performance factor for
......................................................................................................................................................46
Appendix C (informative) Displacement clearances between parts and components ..................................47
Bibliography ............................................................................................................................................................................................................................. 48
 1 AS 1170.4:2024

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

Section 1 Scope and general

This document 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:

(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.

(h) Transmission line towers.

This document does not consider the effect on a structure of related earthquake phenomena such as
settlement, slides, subsidence, liquefaction or faulting.

The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document.

AS 1684, Residential timber-framed construction (all parts)

AS 1720.1, Timber structures, Part 1: Design methods
AS 3600, Concrete structures
AS 3700, Masonry structures
AS 4100, Steel structures
AS/NZS 1170.0, Structural design actions, Part 0: General principles

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AS 1170.4:2024 2

AS/NZS 1170.1, Structural design actions, Part 1: Permanent, imposed and other actions
AS/NZS 1170.3, Structural design actions, Part 3: Snow and ice actions
AS/NZS 1664, Aluminium structures (all parts)
AS/NZS 4600, Cold formed steel structures

1.3.1
base, structural
level that earthquake motions are imparted to the structure, or level that structure as a dynamic
vibrator is supported (see )
1.3.2
bearing wall system
structural system in which loadbearing walls provide support for vertical loads while shear walls or
braced frames provide horizontal earthquake resistance
1.3.3
braced frame
two-dimensional structural system composed of a vertical truss (or equivalent) whose members are
subject to axial forces when resisting earthquake actions
1.3.3.1
braced frame, concentric
braced frame in which bracing members are connected at the column-beam joints (see Table 6.5)
1.3.3.2
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 6.5)
1.3.4
connection
mechanical means that provide a load path for actions between structural elements, non-structural
elements and structural and non-structural elements
1.3.5
design storey drift
dst
di) at the top and bottom of the storey under consideration
(see Clause 6.7.2)
1.3.6
diaphragm
structural system that transmits earthquake actions to the seismic-force-resisting system
1.3.7
domestic structure
single dwelling or one or more attached dwellings (single occupancy units) conforming to Class 1a or 1b

1.3.8
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

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1.3.9
earthquake actions
inertia-induced actions arising from the response to earthquake of the structure
1.3.10
engineering bedrock
horizon at which the shear wave velocity is greater than 600 m/s and below which it continuously
increases with depth (for sites with hard rock outcrops underlain by soft soils, the upper hard rock
outcrop should not be taken as the engineering bedrock)
1.3.11
moment-resisting frame

axial resistance of its members and connections

1.3.11.1
moment-resisting frame, intermediate
concrete or steel moment-resisting frame designed and detailed to achieve moderate structural
ductility (see Table 6.5)
1.3.11.2
moment-resisting frame, ordinary

standard (see Table 6.5)

1.3.11.3
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 6.5)
1.3.12
partition

1.3.13
parts and components
elements that are —
(a) structural or non-structural elements attached to and supported by the structure but are not
part of the seismic-force-resisting system; or
(b) structural 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
1.3.14
P-delta effect
additional induced structural forces caused by gravity loads being displaced horizontally
1.3.15
seismic-force-resisting system
part of the structural system that provides resistance to the earthquake forces and effects
1.3.16
shear wall
wall designed to resist horizontal earthquake forces acting in the plane of the wall
1.3.17
space frame
three-dimensional structural system composed of interconnected members (other than loadbearing
walls) able to support vertical loads and may provide horizontal resistance to earthquake forces

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AS 1170.4:2024 4

1.3.18
storey
space between levels including the space between the structural base and the level above (storey i is
the storey below the ith level)
1.3.19
structural performance factor
Sp
numerical assessment of the additional ability of the total building to survive earthquake motion
1.3.20
structural ductility factor

numerical assessment of a structure’s ability to sustain cyclic displacements in the inelastic range,
ductility value depends on structural form, ductility of materials and structural damping characteristics
1.3.21
top (of a structure)
level of the uppermost principal seismic weight (see Clause 1.5)

newtons (kg, m, s, Pa, N). Unless stated otherwise, the notation used in this Standard shall have the
following meanings:

ac =

a =

ax = 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(T1) = value of the elastic site hazard spectrum for the fundamental natural period of the
structure

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

Cd(T1) =
for the fundamental natural period of the structure)

C h(T) = spectral shape factor as a function of period (T

C h(T1) = value of the spectral shape factor for the fundamental natural period of the structure

Cv(Tv) = elastic site hazard spectrum for vertical loading, which may be taken as half of the
elastic site hazard spectrum for horizontal loading (C(T))

Cvd(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 = i’

die = i’ determined by an elastic analysis

dst = design storey drift (see Clause 6.7.2)

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 5 AS 1170.4:2024

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 Fi 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

g = acceleration due to gravity (9.8 m/s2)

G =

Gi = i, in kilonewtons

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

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

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

k = exponent, dependent on the fundamental natural period of the structure (T1)

kc = ax)

k = 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

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 =

Q = imposed action for each occupancy class, in kilonewtons

Qi = imposed action for each occupancy class on the ith level

Rc = component ductility factor

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AS 1170.4:2024 6

Sp = structural performance factor

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

T1 =
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 i th level

W = sum of the seismic weight of the building (G + cQ) 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

Z =
annual probability of exceedance of 1/500

= structural ductility factor ( = mu)

c = earthquake imposed action combination factor

a =

the levels of the structure (see ).

The seismic weight at a level is determined by summing the weights that would act at that level,

to the level above and half way to the level below and adding the factored imposed actions on that level.

any beams).

of the combined mass (see

weight exists above the ceiling level that contributes more than 1/3 of Wn, it shall be treated as the top
seismic weight and Wn and W recalculated.
The building height (hn) is taken as the height of the centre of mass of Wn above the base.
illustrates the structural base for various situations.

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Figure 1.5(A) — Illustration of level, storey, weight and force

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AS 1170.4:2024 8

Figure 1.5(B) — Example of determination of the top of the structure

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 9 AS 1170.4:2024

transmitted to the structure

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AS 1170.4:2024 10

Section 2 Design procedure

E) shall be appropriate for the type of structure or element, its

intended use, design working life and exposure to earthquake shaking. The earthquake actions (Eu)
determined in accordance with this document shall be deemed to conform to this provision.

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

(b) determine the probability factor (kp) and the hazard design factor (Z) (see Section 3);

given in Appendix A and whether it complies with the requirements therein;

(d) determine the site sub-soil class (see Section 4);
Table 2.1;
Section 5;
and
(g) design parts and components in accordance with the requirements set out in Section 8.
Importance level 1 structures are not required to be designed to this Standard, (i.e. for earthquake
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.

structure (including non-loadbearing walls, etc.) should be designed for lateral earthquake forces such as out-of-
plane forces.

Table 2.1
Appendix A shall be designed as importance
level 2 structures.
Z of 0.3 or
greater should be designed in accordance with NZS 1170.5 (see Macquarie Islands, Table 3.2).

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.
) assumed in design is greater than 3, should be
designed in accordance with NZS 1170.5 and associated New Zealand Standards.

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 demonstrate
that they will remain operational for immediate use following the design event associated with
importance level 2 structures.

functionality. Case-by-case assessment is essential.

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 11 AS 1170.4:2024

Importance (kpZ) for site sub-soil class

Structure
level, type of
height, hn
structure (see e or De Ce Be Ae category
(m)
Clause 2.2)
Not required to
1 — — be designed for
earthquake actions
Top of
Domestic See Appendix A
structure —
(housing) Top of Design as
roof > 8.5 importance level 2
I
0.08 0.08 > 12, < 50 II
III
2 > 0.08 > 0.11 > 0.14 < 50 II
0.08
III
< 25 II
> 0.08 > 0.12 > 0.17 > 0.21
III
< 50 II
0.08
III
3
< 25 II
> 0.08 > 0.12 > 0.17 > 0.21
III
< 25 II
4 —
III
kp and Z are given in Section 3. Site sub-soil class are given in Section 4.

hn Clause 1.5 Appendix A.

that they will remain operational for immediate use following the design event for importance level 2 structures.

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AS 1170.4:2024 12

Figure 2.2 — Flow diagram—design procedure

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 13 AS 1170.4:2024

Section 3 Site hazard

) and probability factor ( p)

The probability factor (kp) for the annual probability of exceedance, appropriate for the limit state
under consideration, shall be obtained from Table 3.1.

kp)
Annual probability of exceedance Probability factor
P kp
1/2500 1.8
1/2000 1.7
1/1500 1.5
1/1000 1.3
1/800 1.25
1/500 1.0
1/250 0.75
1/200 0.7
1/100 0.5

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

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AS 1170.4:2024 14

Z
Z Z Z
Adelaide 0.10 Gladstone 0.09 Port Augusta 0.11
0.09 Gippsland 0.10 0.12
Bendigo 0.09 Gosford 0.09 Port Lincoln 0.10
Brisbane 0.08 Goulburn 0.09 Port Pirie 0.10
Broome 0.12 0.08 Robe 0.10
Bundaberg 0.11 Karratha 0.12 Shepparton 0.09
Camden 0.09 Katoomba 0.09 Sydney 0.08
Canberra 0.08 Latrobe Valley 0.10 Tennant Creek 0.13
Carnarvon 0.09 Lorne 0.10 0.09
Dampier 0.12 Maitland 0.10 0.09
Darwin 0.09 Melbourne 0.08 0.09
Derby 0.09 Mittagong 0.09 0.09
0.09 Morisset 0.10 0.09
Geelong 0.10 Newcastle 0.11 0.10
Geraldton 0.09 Perth 0.09
Meckering region Islands
Ballidu 0.15 Meckering 0.20 Christmas Island 0.15
Corrigin 0.14 Northam 0.14
Cunderdin 0.22 0.15 0.10
Dowerin 0.20 0.15
Goomalling 0.16 York 0.14 Macquarie Island 0.60
Kellerberrin 0.14

The minimum value of the product kpZ shall be in accordance with Table 3.3.

kpZ values for Australia

Annual probability
Minimum value of kpZ
of exceedance
1/500 0.08
1/1000 0.10
1/1500 0.12
1/2000 0.14
1/2500 0.15

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AS 1170.4:2024 16

Z) for South Australia

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Z) for Queensland

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Z)

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AS 1170.4:2024 22

Section 4 Site sub-soil class

The site shall be assessed and assigned to the site sub-soil class it most closely resembles.
Clause 4.2, that is, Classes Ae e as follows:

(a) Class Ae — Strong rock.

(b) Class Be — Rock.
(c) Class Ce — Shallow soil.
(d) Class De — Deep or soft soil.

e — Very soft soil.

to least preferred:
(a) Site periods based on four times the shear-wave travel-time through material from the surface
to underlying rock.

properties.
(c) Borehole logs, including measurements of geotechnical properties, used in conjunction with
surface geology and estimates of the depth to underlying rock.

site.

preferred method shall be used.

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.

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 23 AS 1170.4:2024

Property Maximum
Soil type and description Representative undrained depth of soil
shear strengths (kPa) N-values (Number) (m)
Cohesive soils Very soft < 12.5 — 0
Soft 12.5 – 25 — 20
25 – 50 — 25
Stiff 50 – 100 — 40
Very stiff or hard 100 – 200 — 60
Cohesionless Very loose — <6 0
soils Loose dry — 6 – 10 40
Medium dense — 10 – 30 45
Dense — 30 – 50 55
Very dense — > 50 60
Gravels — > 30 100

provided Clauses 4.2.1 to 4.2.5. The low-amplitude natural site period may be estimated from —
(a) four times the shear-wave travel time from the surface to engineering bedrock;
(b) measured site period, such as Nakamura ratios;
(c) recorded earthquake motions at the site; or
(d) evaluated in accordance with Clause 4.1.3 for sites with layered sub-soil.

Clause 4.1.2 shall be adopted.

e — Strong rock

Site sub-soil Class Ae

over the top 30 m greater than 1 500 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.

e — Rock

Site sub-soil Class Be

with rock satisfying the following conditions:
(a) A compressive strength between 1 MPa and 50 MPa inclusive or an average shear-wave
velocity, over the top 30 m, greater than 760 m/s.
(b) Not underlain by materials having a compressive strength less than 0.8 MPa or an average
shear wave velocity less than 300 m/s.

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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.

e — Shallow soil site

Site sub-soil Class Ce e, Class Be e 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.

e— Deep or soft soil site

Site sub-soil Class De

that is —
(a) not Class Ae, Class Be e 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.

e
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 described in Items (a), (b) and (c).

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Section 5 Earthquake design

Structures required by Section 2 to be designed for earthquake actions shall be designed in accordance
with the general principles of Clause 5.2. Structures shall also be designed in accordance with
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.

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.

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.

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. In the absence of
appropriate advanced analysis, the horizontal tie force for footings shall be taken as 5 % of the ultimate
limit state vertical load.

adequate horizontal capacity to prevent a buckling mechanism occurring from horizontal movement
of the footing. In the absence of appropriate advanced analysis, the footing shall be designed for a
horizontal load taken as 5 % of the ultimate limit state vertical load.

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

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 forces determined for each limit state.

(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.

which they are not tied.

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AS 1170.4:2024 26

designed in accordance with Section 8.

Diaphragms are a critical element in the design of any structures for seismic actions as they tie the
structure and lateral load resisting elements together.

attached element to maintain its structural integrity and continue to support the prescribed forces.

All structures shall be designed, detailed and proportioned to ensure the system ductility assumed

based on the ductility assumptions.

This Clause shall not apply to structures of height (hn) over 12 m. All structures subject to earthquake
Clause 5.2 and the requirements of this
Clause. Parts and components shall be designed in accordance with Section 8.
The structure shall be designed for the following equivalent static forces applied laterally to the
centres of mass of the levels of the structure (see ), in combination with gravity loads (see
combination [G, Eu cQ] in AS/NZS 1170.0):

. 5.3

where:

Wi = seismic weight of the structure at level i as given in Clause 6.2.2

If the building is not detailed in accordance with the relevant Australian material Standard to achieve
a ductility factor greater than or equal to 1.25, the design actions at each level of the structure shall be
increased to F i = 0.2Wi.

plan dimensions for each major axis of the building exceeds 40 m, the building shall be —
(a) separately assessed for Fi in each major axis of the building with 0.3 Fi simultaneously applied
in the perpendicular direction; and
(b) the building shall be assessed for torsional effects in accordance with Clause 6.6.

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 27 AS 1170.4:2024

Figure 5.2 — Illustration of earthquake design category I

Clause 5.2 and Clauses 5.4.2 to 5.4.6.

The structural system shall be designed to resist the most critical action effect arising from the
application of the earthquake actions in any direction.

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.

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

Connections between components of the structure shall be capable of transmitting an internal ultimate
limit state horizontal action equal to the values calculated using this section but not less than 5 % of
the vertical reaction arising from the seismic weight or 5 % of the seismic weight of the component
whichever is the greater.

Section 6.
Section 7, may be used if desired (see Clause 2.2).

Vertical earthquake actions need not be considered.

Clause 8.1.3.

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AS 1170.4:2024 28

The design 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

capacity to accommodate the design storey drift (dst). Stairs required for emergency egress shall be
capable of accommodating a drift of 1.5 dst .

Structures shall be separated from adjacent structures or set back from a building boundary by a

seismic force-resisting elements are structural walls that extend to the base, or the setback from a
boundary or adjacent structure is more than 1 % of the structure height.

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

Clause 5.2 and Clauses 5.5.2 to 5.5.6.

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
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.

Section 7.

Vertical earthquake actions need not be considered.

Clause 8.1.3.

The design 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

capacity to accommodate the design storey drift (dst). Stairs required for emergency egress shall be
capable of accommodating a drift of 1.5dst .

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 29 AS 1170.4:2024

Structures shall be separated from adjacent structures or set back from a building boundary or adjacent

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.

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AS 1170.4:2024 30

Section 6 Equivalent static analysis

The procedure for equivalent static analysis is as follows:

(a) Decide on the form and material of the structure.
(b) Calculate kpZ using Section 3.
(c) Determine T1, C h(T1), , and other structural properties.

(e) Determine the seismic weight at each level (Wi).

(f) Calculate V using Clause 6.2.
(g) Calculate F i using Clause 6.3.
Clause 6.6.
(i) Take P Clause 6.7.

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
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:

6.2(1)

/ 6.2(2)

/ 6.2(3)

where:

Cd(T1) =
the fundamental natural period of the structure)

= C(T1)Sp 6.2(4)

C(T1) = 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

= kpZC h(T1) 6.2(5)

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 31 AS 1170.4:2024

C h(T1) = value of the spectral shape factor for the fundamental natural period of the structure, as
given in Clause 6.4

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

Sp = structural performance factor, as given in Clause 6.5

= structural ductility factor, as given in Clause 6.5

T1 = fundamental natural period of the structure, as given in Clause 6.2.3

The seismic weight (Wi) at each level shall be as given by the following equation:

6.2(6)

where

Gi and cQ i are summed between the mid-heights of adjacent storeys

Gi = i, including an allowance of 0.3 kPa for ice on
roofs in alpine regions as given in AS/NZS 1170.3
c = earthquake-imposed action combination factor
= 0.6 for storage applications
= 0.3 for all other applications
Qi = imposed action for each occupancy class on level i, except a minimum value of 1.5 kPa shall be adopted
Qi is determined from the reference value of imposed

Clause 3.4 of AS/NZS 1170.1, except a is taken as 1.0 for all storage and plant areas)

mi = Wi/g).

The fundamental period of the structure as a whole (T1, 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:
.
. 6.2(7)

where:

kt = 0.11 for moment-resisting steel frames

= 0.075 for moment-resisting concrete frames

= 0.06 for eccentrically-braced steel frames

= 0.05 for structural wall buildings and 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 (T1) determined by a rigorous
structural analysis shall be not less than 80 % of the base shear obtained with T1 calculated using the
above equation.

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AS 1170.4:2024 32

The horizontal equivalent static design force (Fi) at each level (i) shall be obtained as follows:

i ,i 6.3(1)

6.3(2)

where:

k = seismic distribution factor for the ith level

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

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

k = exponent, dependent on the fundamental natural period of the structure (T1), taken as—

1.0 when T1

2.0 when T1

linearly interpolated between 1.0 and 2.0 for 0.5 < T1 < 2.5

n = number of levels in a structure

The horizontal equivalent static earthquake shear force (Vi) at storey i is the sum of all the horizontal
forces at and above the ith level (Fi to Fn).

h( ))
The spectral shape factor (C h(T)) shall be as given in Table 6.4 (illustrated in ) for the
Section 4.

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 33 AS 1170.4:2024

C h(T))
Site sub-soil class
Period Ae Be Ce De Ee
(seconds) Strong rock Rock Shallow soil Deep or soft soil
0.0 2.35 (0.8) 2.94 (1.0) 3.68 (1.3) 3.68 (1.1) 3.68 (1.1)
0.1 2.35 2.94 3.68 3.68 3.68
0.2 2.35 2.94 3.68 3.68 3.68
0.3 2.35 2.94 3.68 3.68 3.68
0.4 1.76 2.20 3.12 3.68 3.68
0.5 1.41 1.76 2.50 3.68 3.68
0.6 1.17 1.47 2.08 3.30 3.68
0.7 1.01 1.26 1.79 2.83 3.68
0.8 0.88 1.10 1.56 2.48 3.68
0.9 0.78 0.98 1.39 2.20 3.42
1.0 0.70 0.88 1.25 1.98 3.08
1.2 0.59 0.73 1.04 1.65 2.57
1.5 0.47 0.59 0.83 1.32 2.05
1.7 0.37 0.46 0.65 1.03 1.60
2.0 0.26 0.33 0.47 0.74 1.16
2.5 0.17 0.21 0.30 0.48 0.74
3.0 0.12 0.15 0.21 0.33 0.51
3.5 0.086 0.11 0.15 0.24 0.38
4.0 0.066 0.083 0.12 0.19 0.29
4.5 0.052 0.065 0.093 0.15 0.23
5.0 0.042 0.053 0.075 0.12 0.18
Equations for spectra
0<T 0.8 + 15.5T 1.0 + 19.4T 1.3 + 23.8T 1.1 + 25.8T 1.1 + 25.8T
0.1 < T 0.704/T 0.88/T 1.25/T 1.98/T 3.08/T

T > 1.5 1.056/T 2 1.32/T 2 1.874/T 2 2.97/T 2 4.62/T 2

the numerical integration time history methods and for use in the method of calculation of forces on parts and
components (see Section 8)

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AS 1170.4:2024 34

) And structural performance factor ( p)

The ductility of the structure ( ) and the structural performance factor (Sp) shall be determined, either
—
(a) in accordance with the appropriate material standard where the data are provided; or
(b) as given in Table 6.5 for the structure type and material where the data are not provided,

determine and Sp by using a nonlinear static pushover analysis. In such situations, the
combined p value used to calculate the equivalent static forces shall be taken as 0.8 times
the combined p value determined from the pushover analysis.

Alternatively, when undertaking a displacement-based approach, the seismic acceleration demand shall
be based on a response spectrum of KpZC h(T) and the seismic displacement demand shall be based on a
KpZC h(T).

then the values given in the last row for each material type in Table 6.5 should be used.

and Sp should be determined as set

out therein.

provided as a guide in Appendix B.

A lower
all cases, the structure shall be detailed to achieve the level of ductility assumed in the design, in
accordance with the applicable material design Standard.

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 35 AS 1170.4:2024

) and structural performance factor (Sp) — basic

structures
Description Sp Sp/ /Sp

4 0.67 0.17 6
Moderately ductile lateral load resisting systems 3 0.67 0.22 4.5
Limited ductile lateral load resisting systems 2 0.77 0.38 2.6
Low ductile lateral load resisting systems 1.5 0.77 0.51 2.0
Non-ductile lateral load resisting systems 1 0.77 0.77 1.3
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 eccentrically braced frames 3 0.67 0.22 4.5
Limited ductile concentrically braced frames 2 0.77 0.38 2.6
2 0.77 0.38 2.6
Light gauge steel structures in accordance with AS/NZS 4600 1.25 0.93 0.74 1.35

Shear walls 2 0.77 0.38 2.6

Braced frames (with ductile connections) 2 0.77 0.38 2.6
Moment-resisting frames (with ductile connections) 2 0.77 0.38 2.6
Other wood or gypsum based seismic-force-resisting systems not 1 0.77 0.77 1.3
listed above
Masonry structures
Close-spaced reinforced masonry (limited ductile) 2 0.77 0.38 2.6
1.5 0.77 0.5 2
Unreinforced masonry in accordance with AS 3700 1.25 0.77 0.62 1.6
Other unreinforced masonry structures not conforming to AS 3700 1.00 0.77 0.77 1.3
Clause 2.2)

Clause 6.3,
shall be applied at the position calculated as ± 0.1b from the nominal centre of mass, where b is the plan
dimension of the structure at right angles to the direction of the action.
This ± 0.1b eccentricity shall be applied in the same direction at all levels and orientated to produce the
most adverse torsion moment for the 100 % and 30 % loads.

-delta effects

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.

Storey drifts shall be assessed for the two major axes of a structure considering horizontal earthquake
forces acting independently, but not simultaneously, in each direction. The design storey drift (dst)

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AS 1170.4:2024 36

di) at the top and bottom of the storey under

consideration.
di) shall be determined from the following equation:

/ 6.7(1)

where

die = ith level determined by an elastic analysis, carried out using the horizontal
equivalent static earthquake forces (Fi Clause 6.3, applied to the structure in
accordance with Clause 6.6

dst) shall be increased to allow for the P-delta effects as given

in Clause 6.7.3.

-delta effects

) calculated for each level, design for P-delta effects shall be

as follows:
P-delta effects need not be considered.

P-delta effects shall be calculated as given in Clause 6.7.3.2:

/ 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 the

Values of the horizontal earthquake shear forces and moments, the resulting member forces and
moments. The storey drifts that include the P-delta effects shall be determined by—
)), which is greater
than or equal to 1; or
(b) using a second-order analysis.

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 37 AS 1170.4:2024

Section 7 Dynamic analysis

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

The earthquake ground motion shall be accounted for by using one of the following:
Cd(T)), including the site hazard spectrum and the
effects of the structural response, as follows:

/ 7.2(1)

/ 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

the rock spectra given in Clause 6.4.

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 calculates the response of a

time-history.

less than 70 % of the value obtained from an equivalent static analysis using Clause 6.2.1 and the
fundamental natural period as determined directly from .
If the design base shear is less than this value, the design actions and displacements obtained from
the dynamic model shall be scaled by k = 0.7Vs d, where Vs is the base shear from an equivalent
static analysis using and Vd
buildings taller than 50 m the threshold value decreases to 50 %.

directions shall be considered. The vertical design response spectrum shall be as follows:

7.2(3)

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AS 1170.4:2024 38

where

Cv(Tv) = elastic site hazard spectrum for vertical loading for the vertical period of vibration

A mathematical model of the physical structure shall represent the spatial distribution of the mass and

its dynamic response.

A dynamic analysis of a structure by the modal response spectrum method shall use the peak

Clause 7.4.2. Peak modal responses shall be calculated using the ordinates of the appropriate response
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.

90 % of the mass of the structure is participating for the direction under consideration. In three-

the mass of the structure is participating for the direction under consideration.

The peak member forces, displacements, horizontal earthquake shear forces and base reactions for

interaction effects shall be considered.

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

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.

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 39 AS 1170.4:2024

-delta effects
Storey drifts, member forces and moments due to P-delta effects shall be calculated in accordance with
Clause 6.7

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AS 1170.4:2024 40

Section 8 Design of parts and components

listed in Clause 8.1.4, shall:

Clauses 8.1.2 and
8.1.3; and,
(b) accommodate the design storey drift (see Clause 6.7.2).

prevent overturning.
A special study shall be carried out for importance level 4 facilities to demonstrate that the relevant
parts and components will remain serviceable and operational for immediate use following the design
event associated with importance level 2 structures.
Informative guidance on displacement clearances between parts and components is provided in
Appendix C.

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

(b) The forces determined by the general method given in Clause 8.2.
Clause 8.3.

I may alternatively be designed for a horizontal force equal to 10 % of the seismic weight of the part or
component. This exclusion does not apply to unreinforced masonry structures.

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, which need not be considered simultaneously with the horizontal force.
Connections (including fasteners) for parts and components shall be designed for earthquake actions

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

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 41 AS 1170.4:2024

(iii) Appendages, including parapets, gables, verandas, awnings, canopies, chimneys,

(iv) Partitions, operable walls and operable doors.

determined in accordance with Clause 6.2.2).

(vi) Ceilings.
(vii) Architectural equipment including free-standing storage racks and library shelves
with a height over 1.5 m or a height to thickness ratio greater than 3.
(viii) All other similar components.
(b) Mechanical, hydraulic and electrical components:
(i) Smoke control systems.

(iii) Battery storage systems or other energy storage systems.

(vi) Life safety systems and components.

(vii) Boilers, furnaces, incinerators, water heaters, and other equipment using

smokestacks, vents and pressure vessels.

(viii) Communication systems (such as cable systems motor control devices, pneumatic
systems, switchgear, transformers, and unit substations).
(ix) Reciprocating or rotating equipment (including all heating, ventilation and air
conditioning equipment).
(x) Utility and service interfaces.
(xi) Lift, machinery, controllers and hoist components including structural frames
providing support for guide rail brackets, guide rails and brackets, car and
counterweight members.

(xiii) Machinery (manufacturing and process).

(xvi) Conveyor systems (non-personnel).

(xvii) Mechanical ducts.
(xviii) Cabling distribution systems (including cable tray, busbar etc).
(xix) Piping distribution systems (including water, drainage, gas, etc).
(xx) All other similar components.

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AS 1170.4:2024 42

Mechanical, hydraulic and electrical components, except for those in Importance Level 4 facilities or
those required to remain operational immediately following an earthquake, are exempted as follows:

or less;

(C) Individually supported discrete components with an operating weight less than 10 kg;

Items (A) and (B), with an operating weight less than 10 kg per metre; or

Items (A) and (B), with an operating weight less than 30 kg per metre and vertical supports

actions from the accelerations determined using the design methods given in Sections 6 and 7, as

follows, based on the principles given in this Standard for design of the structure:

8.2(1)

where:

a =
earthquake actions determined for the structure using Sections 5, 6 and 7 divided by the
seismic weight, but not less than kpZC h(0), where the values of C(0) are the bracketed values
given in Table 6.4

determined by measurement.

Ic = component importance factor

= 1.5 for all parts and components in importance level 4 structures

= 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, curtain walls, external walls, and walls enclosing
stairs, stair shafts, lifts and egress pathways

= 1.0 for all other components

ac =

=
dynamic analysis is used to justify lower values)

= 1.0 for all other mounting systems, and all other parts and components

Rc = component ductility factor

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 43 AS 1170.4:2024

= 1.0 for rigid components or non-ductile components

Wc = seismic weight of the component, in kilonewtons

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

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:

8.3

where

are as given in Clause 8.2; and:

kp = probability factor (see Section 3)

Z = hazard design factor (see Section 3)

C h(0) = the bracketed values given in Table 6.4

ax = hx at which the component is attached, given as

follows:

= (1 + kchx)

kc = 2/hn for hn

= 0.17 for hn < 12 m

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

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

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AS 1170.4:2024 44

Appendix A
(normative)

Domestic structures (housing)

in ) and shall be designed in accordance with Table A.1.

Domestic structures (housing) exceeding 8.5 m in height (see ), shall be designed in
accordance with Section 2 for Importance Level 2 structures, using the annual probability of exceedance

Provision for lateral

Material type deemed to Design required
the kp Z resistance
satisfy limits
As per the relevant As per the
detailed for lateral wind Standard relevant design required
forces in accordance with Standard
AS 1684, AS 3600, AS 3700, Adobe, pressed earth None provided Use Clause A.2 or design
AS 4100, AS/NZS 1664, bricks, rammed as for importance level 2
earth or other earth- (see Section 2)
Part 1—2005 wall material not
in accordance with
AS 3700
Other materials None provided Use Clause A.2 or design
as for importance level 2
(see Section 2)
> 0.11 As per the relevant As per the Use Clause A.2 or design
detailed for lateral wind Standard relevant as for importance level 2
forces in accordance with Standard (see Section 2)
AS 1684, AS 3600, AS 3700,
AS 4100, AS/NZS 1664,

Part 1—2005

masonry or hay bale construction

Domestic structures required to be designed in accordance with this clause shall conform to the
following requirements:

action, lateral bracing shall be provided in both orthogonal directions, distributed into at
least two walls in each orthogonal direction with a maximum spacing between walls of 9 m to
resist the following forces:

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 45 AS 1170.4:2024

.
where

Wi = seismic weight of the structure or component at level i as given in Clause 6.2.2

that provide horizontal in-plane and perpendicular to the plane of the wall support for the

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 0.1Wc, where Wc is the weight of the
component. Masonry veneer walls tied to framing in accordance with AS 3700 are deemed to
conform to this Item (c).

Figure A.1 — Section geometry

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AS 1170.4:2024 46

Appendix B
(informative)

Structural ductility factor and structural performance factor for

addressed in Clause 6.5 are listed in Table B.1 for guidance.

Sp)
structure types
Sp /Sp Sp/
Cast-in-place concrete silos and chimneys having walls continuous 3 1 3 0.33
to the foundation constructed using ductile materials
Distributed mass cantilever structures, such as stacks, chimneys, 3 1 3 0.33
silos and skirt-supported vertical vessels constructed using ductile
materials
Structural steel trussed towers (freestanding or guyed), guyed 3 1 3 0.33
stacks and chimneys
Cooling towers constructed using ductile materials 3 1 3 0.33
Signs and billboards constructed using ductile materials 3 1 3 0.33
Tanks, vessels, pressurized spheres, bins or hoppers on braced or 2 1 2 0.5
unbraced legs
Inverted pendulum-type structures 2 1 2 0.5
Amusement structures and monuments 2 1 2 0.5
Storage racking constructed using ductile materials 1.5 1 1.5 0.67
Standalone unreinforced masonry distributed mass cantilever 1.5 1 1.5 0.67
structures, such as stacks, chimneys, silos and skirt-supported
vertical vessels
All other self-supporting structures not otherwise covered 1.5 1 1.5 0.67

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 47 AS 1170.4:2024

Appendix C
(informative)

Displacement clearances between parts and components

horizontally and vertically, from other services and components to prevent collision between services
and components during the design earthquake.
In the absence of more accurate analysis, the minimum clearances given in Table C.1 may be used.
Clearances in other Australian Standards may override these values.

Condition being considered Minimum clearance

Unrestrained component to unrestrained component 150mm 25mm

Restrained component to unrestrained component 75mm 25mm
Restrained component to restrained component 25mm 25mm
nil nil

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AS 1170.4:2024 48

Bibliography

AS 4678, Earth retaining structures

AS 5100.2, Bridge design, Part 2: Design loads
NZS 1170.5, Structural design actions, Part 5: Earthquake actions—New Zealand
Australian Building Code Board (ABCB) NCC. National Construction Code
Commentary (www.aees.org.au)
NASH Standard—Residential and low-rise steel framing,
Part 1, Design criteria

© Standards Australia Limited 2024

Standards Australia

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For further information visit www.standards.org.au

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