AS 1170.4-2007 Structural design actions - Earthquake actions in Australia

AS 1170.4—2007 AS 1170.4—2007Australian Standard®Structural design actionsPart 4: Earthquake actions in AustraliaThis 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 NewcastleAdditional 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 AdelaideThis 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-dateAustralian 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 Between editions, amendments may be issued.Standards may also be withdrawn.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 w w .auStandards Australia welcomes suggestions for improvements, and encourages readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at mail@.au, or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.AS 1170.4—2007Australian Standard ®Structural design actionsPart 4: Earthquake actions in AustraliaOriginated as AS 2121—1979.Revised and redesignated as AS 1170.4—1993.Second edition 2007.COPYRIGHT© Standards AustraliaAll rights are reserved. No part of this work may be reproduced or copied in any form or byany means, electron i c or mechan i cal, i nclud i ng photocopy i ng, w i thout the wr i ttenpermission of the publisher.Published by Standards Australia GPO Box 476, Sydney, NSW 2001, AustraliaISBN 0 7337 8349 XAS 1170.4—2007 2PREFACEThis 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 actions1170.4 Part 4: Earthquake actions (this Standard)AS/NZS1170.0 Part 0: General principles1170.1 Part 1: Permanent, imposed and other actions1170.2 Part 2: Wind actions1170.3 Part 3: Snow and ice actionsNZS1170.5 Part 5: Earthquake actions—New ZealandThis edition differs from AS 1170.4—1993 as follows:(a) Importance factors have been replaced with the annual probability of exceedance, toenable design to be set by the use of a single performance parameter. Values ofhazard are determined using the return period factor determined from the annualprobability 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 spectralshape factors in the form of response spectra that vary depending on the fundamentalnatural period of the structure.(f) The five (5) earthquake design categories have been simplified to three (3) newcategories 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 Co mmentary to this Standard, when published, will be AS 1170.4 Supp 1, Structural design actions—Earthquake actions—Commentary (Supplement to AS 1170.4—2007).3AS 1170.4—2007(h) All requirements for the earthquake design categories are collected together in asingle section (Section 5), with reference to the Sections on static and dynamicanalysis.(i) The 50 m height limitation on ordinary moment-resisting frames has been removedbut 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 inthis respect.(k) The equation for base shear has been aligned with international methods.(l) Structural response factor has been replaced by the combination of structural performance factor and structural ductility factor (1/R f to S p/μ) and values modifiedfor 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 ofany material or combination thereof. Designers will need to refer to the appropriate materialStandard(s) for guidance on detailing requirements additional to those contained in thisStandard.This Standard is not equivalent to ISO 3010:2001, Basis for design of structures—Seismicactions on structures, but is based on equivalent principles. ISO 3010 gives guidance on ageneral format and on detail for the drafting of national Standards on seismic actions. Theprinciples of ISO 3010 have been adopted, including some of the detail, with modificationsfor the low seismicity in Australia. The most significant points are as follows*:(i) ISO 3010 is drafted as a guide for committees preparing Standards on seismic actions.(ii) Method and notation for presenting the mapped earthquake hazard data has not been adopted.(iii) Some notation and definitions have not been adopted.(iv) Details of the equivalent static method have been aligned.(v) Principles of the dynamic method have been aligned.Particular acknowledgment should be given to those organizations listed as ‘additionalinterests’ for their contributions to the drafting of this Standard.The terms ‘normative’ and ‘informative’ have been used in this Standard to define theapplication of the appendix to which they apply. A ‘normative’ appendix is an integral partof 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 ofthis Standard to ISO 3010:2001.AS 1170.4—2007 4 Statements expressed in mandatory terms in notes to tables and figures are deemed to be an integral part of this Standard.Notes to the text contain information and guidance. They are not an integral part of the Standard.5AS 1170.4—2007CONTENTSPage SECTION 1 SCOPE AND GENERAL1.1 SCOPE (6)1.2 NORM ATIVE 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 PROCEDURE2.1 GENERAL (15)2.2 DESIGN PROCEDURE (15)SECTION 3 SITE HAZARD3.1 ANNUAL PROBABILITY OF EXCEEDANCE (P) AND PROBABILITYFACTOR (k p) (18)3.2 HAZARD FACTOR (Z) (18)SECTION 4 SITE SUB-SOIL CLASS4.1 DETERMINATION OF SITE SUB-SOIL CLASS (27)4.2 CLASS DEFINITIONS (28)SECTION 5 EARTHQUAKE DESIGN5.1 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 ANALYSIS6.1 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) ANDSTRUCTURAL PERFORMANCE FACTOR (S p) (38)6.6 TORSIONAL EFFECTS (40)6.7 DRIFT DETERMINATION AND P-DELTA EFFECTS (40)SECTION 7 DYNAMIC ANALYSIS7.1 GENERAL (42)7.2 EARTHQUAKE ACTIONS (42)7.3 M ATHEM ATICAL M ODEL (42)7.4 M ODAL ANALYSIS (43)7.5 DRIFT DETERMINATION AND P-DELTA EFFECTS (43)SECTION 8 DESIGN OF PARTS AND COMPONENTS8.1 GENERAL REQUIREM ENTS (44)8.2 METHOD USING DESIGN ACCELERATIONS (46)8.3 SIM PLE M ETHOD (46)APPENDIX A DOMESTIC STRUCTURES (HOUSING) (48)AS 1170.4—2007 6© Standards Australia.au STANDARDS AUSTRALIAAustralian Standard Structural design actions Part 4: Earthquake actions in AustraliaS E C T I O N 1 S C O P E A N D G E N E R A L1.1 SCOPEThis Standard sets out procedures for determining earthquake actions and detailingrequirements for structures and components to be used in the design of structures. It alsoincludes 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 phenomenasuch as settlement, slides, subsidence, liquefaction or faulting.NOTES:1For structures in New Zealand, see NZS 1170.5. 2For earth-retaining structures, see AS 4678.1.2 NORMATIVE REFERENCESThe following referenced documents are indispensable to the application of this Standard.AS1684 Residential timber-framed construction (all parts)1720 Timber structures1720.1 Part 1: Design methods3600 Concrete structures3700 M asonry structures4100 Steel structuresAS/NZS1170Structural design actions 1170.0Part 0: General principles 1170.1Part 1: Permanent, imposed and other actions 1170.3 Part 3: Snow and ice actions7 AS 1170.4—2007.au © Standards Australia 1664Aluminium structures (all parts) BCABuilding Code of Australia NASH Standard Residential and low-rise steel framing, Part 1—2005, Design criteria1.3 DEFINITIONSFor the purpose of this Standard, the definitions given in AS/NZS 1170.0 and those belowapply. Where the definitions in this Standard differ from those given in AS/NZS 1170.0, forthe purpose of this Standard, those below apply.1.3.1 Base, structuralLevel at which earthquake motions are considered to be imparted to the structure, or thelevel at which the structure as a dynamic vibrator is supported (see Figure 1.5(C)).1.3.2 Bearing wall systemStructural system in which loadbearing walls provide support for all or most of the verticalloads while shear walls or braced frames provide the horizontal earthquake resistance.1.3.3 Braced frameTwo-dimensional structural system composed of an essentially vertical truss (or itsequivalent) where the members are subject primarily to axial forces when resistingearthquake actions.1.3.4 Braced frame, concentricBraced frame in which bracing members are connected at the column-beam joints (seeTable 6.2).1.3.5 Braced frame, eccentricBraced frame where at least one end of each brace intersects a beam at a location awayfrom the column-beam joint (see Table 6.2).1.3.6 ConnectionM echanical means that provide a load path for actions between structural elements, non-structural elements and structural and non-structural elements.1.3.7 DiaphragmStructural system (usually horizontal) that acts to transmit earthquake actions to theseismic-force-resisting system.1.3.8 Domestic structureSingle dwelling or one or more attached dwellings (single occupancy units) complying withClass 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 whenresponding to cyclic displacements in the inelastic range during an earthquake.1.3.10 Earthquake actionsInertia-induced actions arising from the response to earthquake of the structure.1.3.11 Moment-resisting frameEssentially complete space frame that supports the vertical and horizontal actions by bothflexural and axial resistance of its members and connections.AS 1170.4—2007 81.3.12 Moment-resisting frame, intermediateConcrete or steel moment-resisting frame designed and detailed to achieve moderatestructural ductility (see Table 6.2).1.3.13 Moment-resisting frame, ordinaryM oment-resisting frame with no particular earthquake detailing, specified in the relevantmaterial standard (see Table 6.2).1.3.14 Moment-resisting frame, specialConcrete or steel moment-resisting frame designed and detailed to achieve high structuralductility and where plastic deformation is planned under ultimate actions (see Table 6.2).1.3.15 PartitionPermanent or relocatable internal dividing wall between floor spaces.1.3.16 Parts and componentsElements 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 earthquakein a direction not usually considered in the design of that element.1.3.17 P-delta effectAdditional induced structural forces that develop as a consequence of the gravity loadsbeing displaced horizontally.1.3.18 Seismic-force-resisting systemPart of the structural system that provides resistance to the earthquake forces and effects.1.3.19 Shear wallWall (either loadbearing or non-loadbearing) designed to resist horizontal earthquake forcesacting in the plane of the wall.1.3.20 Space frameA three-dimensional structural system composed of interconnected members (other thanloadbearing walls) that is capable of supporting vertical loads, which may also providehorizontal resistance to earthquake forces.1.3.21 StoreySpace 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 otherparts) to survive earthquake motion.1.3.23 Structural ductility factor (μ)Numerical assessment of the ability of a structure to sustain cyclic displacements in theinelastic range. Its value depends upon the structural form, the ductility of the materials andstructural damping characteristics.1.3.24 Top (of a structure)Level of the uppermost principal seismic weight (see Clause 1.5).© Standards Australia .au1.4 NOTATION AND UNITSExcept 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:a c= component amplification factora floor= effective floor acceleration at the height of the component centre of massa x= height amplification factor at height h x of the component centre of massb= plan dimension of the structure at right angles to the direction of the action, in metresC(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 ofthe structureC d(T)= horizontal design response spectrum as a function of period (T)C d(T1)= horizontal design action coefficient (value of the horizontal design responsespectrum for the fundamental natural period of the structure)C h(T)= spectral shape factor as a function of period (T) (dimensionless coefficient)C h(T1)= value of the spectral shape factor for the fundamental natural period of thestructureC v(T v)= elastic site hazard spectrum for vertical loading, which may be taken as halfof 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 secondsd i= horizontal deflection of the centre of mass at level ‘i’d ie= deflection at level ‘i’ determined by an elastic analysisd st= design storey driftE= 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 analysisF c= horizontal design earthquake force on the part or component, in kilonewtonsF i= horizontal equivalent static design force at the i th level, in kilonewtonsF j= horizontal equivalent static design force at the j th level, in kilonewtonsF n= horizontal equivalent static design force at the uppermost seismic mass, inkilonewtonsF r= horizontal design racking earthquake force on the part or component, inkilonewtonsg= acceleration due to gravity (9.8 m/s2)G= permanent action (self-weight or ‘dead load’), in kilonewtonsG i= permanent action (self-weight or ‘dead load’) at level i, in kilonewtonsh i= height of level i above the base of the structure, in metresh n= height from the base of the structure to the uppermost seismic weight or mass,in metres (see Clause 1.5)h si= inter-storey height of level i, measured from centre-line to centre-line of floor,in metresh x= height at which the component is attached above the structural base of thestructure, in metresI c= component importance factori, j = levels of the structure under considerationK s= factor to account for height of a level in a structurek= exponent, dependent on the fundamental natural period of the structure (T1)k c= factor for determining height amplification factor (a x)k F,i= seismic force distribution factor for the i th levelk p= probability factor appropriate for the limit state under considerationk t= factor for determining building periodm i= seismic mass at each levelN-values= number of blows for standard penetration (Standard Penetration Test)n= number of levels in a structureP= annual probability of exceedanceP-delta= second order effects due to amplication of axial loadsQ= imposed action for each occupancy class, in kilonewtonsQ i= imposed action for each occupancy class on the i th levelR c= component ductility factorS p= structural performance factorT= period of vibration, which varies according to the mode of vibration being consideredT1= 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 i th levelW= sum of the seismic weight of the building (G + ψc Q) at the level where bracing is to be determined and above this level, in kilonewtonsW c= seismic weight of the part or component, in kilonewtonsW i= seismic weight of the structure or component at the i th level, in kilonewtons W j= seismic weight of the structure or component at level j, in kilonewtonsW n= seismic weight of the structure or component at the n th level (upper level), in kilonewtonsW t= total seismic weight of the building, in kilonewtonsZ= earthquake hazard factor which is equivalent to an acceleration coefficient with an annual probability of exceedance in 1/500, (i.e., a 10% probability ofexceedance in 50 years)μ= structural ductility factor (μ = mu)θ= stability coefficientψc= earthquake imposed action combination factor1.5 LEVELS, WEIGHTS AND FORCES OF THE STRUCTUREFor 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 (h n) is taken as the height of the centre of mass of W n above the base. Figure 1.5(C) illustrates the structural base for various situations.i+ 1ii- 1 W iFIGURE 1.5(A) ILLUSTRATION OF LEVEL, STOREY, WEIGHT AND FORCEFIGURE 1.5(B) EXAMPLE OF DETERMINATION OF THE TOP OF THE STRUCTUREh nh ntaken as at lowest level at ground levelNOTE: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 TRANSMITTEDTO THE STRUCTURES E C T I O N2D E S I G N P R O C E D U R E2.1 GENERALEarthquake actions for use in design (E) shall be appropriate for the type of structure or element, its intended use, design working life and exposure to earthquake shaking.The earthquake actions (E u) determined in accordance with this Standard shall be deemed to comply with this provision.2.2 DESIGN PROCEDUREThe 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 inSection 5.Importance level 1 structures are not required to be designed to this Standard, (i.e., for earthquake actions), and domestic structures (housing) that comply with the definition given in Appendix A and with the provisions of Appendix A are deemed to satisfy this Standard.All other structures, including parts and components, are required to be designed for earthquake actions.NOTE: During an earthquake, motion will be imposed on all parts of any construction. Therefore, parts o f a structure (including no n-lo adbearing walls, etc.) sho uld be designed fo r 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 with 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 ductility facto r (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.TABLE 2.1SELECTION OF EARTHQUAKE DESIGN CATEGORIES(k p Z ) for site sub-soil classImportance level, type of structure (see Clause 2.2)E e or D eC eB eA eStructure height, h n(m)Earthquake design category1 — — Not required to be designed forearthquakeactionsTop of roof ≤8.5 Refer to Appendix A Domestic structure (housing)—Top of roof >8.5Design 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 ≥50II III 2>0.08 >0.12 >0.17 >0.21<25≥25 II III ≤0.08≤0.12≤0.17≤0.21<50 ≥50II III 3>0.08 >0.12 >0.17 >0.21<25≥25II III 4 —<12≥12 II IIINOTES:1Values 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. 3Height (h n ) is defined in Clause 1.5. For domestic structures refer to Appendix A.4In 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.。