z007:2'0L14 SZNISV AS/NZS 1170.2:2002 (Amendment No. 1 attached) Australian/New Zealand Standard™ Structural design actions Part 2: Wind actions STANDARDS AUSTRALIA(07 Sep 2007 Accessed by IRWINCONSULT PTY LTD ASINZS 1170.2:2002 ‘This Joint Australian/New Zealand Standard was prepared by Joint Technical Committee BD-006, General Design Requirements and Loading on Structures. It was approved on behalf of the Council of Standards Australia on 29 March 2002 and on behalf of the Council of Standards New Zealand on 28 March 2002. ‘This Standard was published on 4 June 2002. The following are represented on Committee BD-006: Association of Consulting Engineers Australia Australian Building Codes Board Austratian Institute of Steel Construetion Building Research Association of New Zealand ‘Coment and Concrete Association of Australia CSIRO Building, Construction and Engineering Cyclone Testing Station—James Cook University Electricity Supply Association of Australia Housing Industry Association Institution of Engineers Australia Institution of Professional Engineers New Zeatand Master Builders Australia ‘New Zealand Heavy Engineering Research Association Steel Reinforcement Institute of Australia University of Canterbury New Zealand University of Melbourne University of Newcastle Additional Interests: Bureau of Meteorology Curtin University of Technology Monash University National Institute of Water and Atmospheric Research, NZ University of Queensland Keeping Standards up-to-date Standards are living documents which 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 Standards may also be withdrawn.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 @ current Standard, which should include any amendments which may have been published since the Standard was purchased. Detailed information about joint Australian/New Zealand Standards can be found by visiting the Standards Web Shop at www.standards.com.au or Standards New Zealand web site at www.standards.co.nz and looking up the relevant Standard in the on-line catalogue. Alternatively. both organizations publish an annual printed Catalogue with full details of all current Standards. For more frequent listings or notification of revisions, amendments and withdrawals, Standards Australia and Standards New Zealand offer a number of update options, For information about these services, users should contact their respective national Standards organization, We also welcome suggestions for improvement in our Standards, and especially encourage readers to notify us immediately of any apparent ‘inaccuracies or ambiguities. Please address your comments to the Chief Executive of either Standards Australia or Standards New Zealand at the address shown on the back cover. This Standard was issued in draft form for comment as DR 99419,Accessed by IRWINCONSULT PTY LID on 97 Sep 2007" ASINZS 1170.2:2002 (Amendment No. 4 attached) Australian/New Zealand Standard™ Structural design actions Part 2: Wind actions Originated in Australia as part of AS CA1—1933, Originated in New Zealand as part of NZS 1900:1964, Previous Australian edition AS 1170.2—-1988. Previous New Zealand ection NZS 4203: 1982. ‘AS 1170.2—1989 and NZS 4203:1992 jointly revised, amalgamated and redesignated In part as ASINZS 1170.2:2002. Reissuee with Amendment No. 1 attached (April 2005), ‘COPYRIGHT © Standards Australia/Standards New Zealand Al 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 Jointly published by Standerds Australia, GPO Box $420, Sydney, NSW 2001 and Stencards New Zealand, Private Bag 2438, Wellington 6020 ISBN 0 7337 44737Accessed by IRWINCONSULT PTY LTD on 07 Sep 2007 ASINZS 1170.2:2002 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 1170.2—1989, Minimum design loads on structures, Part 2: Wind loads, and in part Part 5 of NZS 4203:1992, Code of practice for general structural design and design loading for buildings. This Standard is published as a joint Standard (as are also AS/NZS 1170.0 and AS/NZS 1170.1) and it is intended that it is suitable for use in New Zealand as well as Australia, However, NZS 4203. General structural design and design loadings for buildings remains current in New Zealand until the publication of all parts (including Part 4: Earthquake action) and for a transition period afterwards. ‘This Standard will be referenced in the Building Code of Australia by way of BCA Amendment 11 to be Published on I July 2002, thereby superseding the previous edition, AS 1170.2—1989, which will be withdrawn 12 months from the date of publication of this Edition, The objective of this Standard is to provide designers of structures with wind actions for use in the design of structures subject to wind action, It provides a detailed procedure for the determination of wind actions on structures, varying from those less sensitive to wind action to those for which dynamic response must be taken into consideration. This Standard is Part2 of the AS/NZS 1170 series Structural design actions, which comprises the following parts, each of which will have an accompanying Commentary published as a Supplement: Part 0: General principles Part I: Permanent, imposed and other Part 2: Wind actions Part 3: Snow and ice actions Part 4: Earthquake action ‘The Commentary to this Standard is AS/NZS 1170.2 Supp 1, Structural design actions— Wind actions—Commentary (Supplement to AS/NZS 1170.2:2002). ‘The wind speeds provided are based on existing data. At the time of drafting, it was considered that there was insufficient evidence to indicate any trend in wind speeds due to climatic change. This Standard is based on ISO 4354, Wind actions on structures. ISO 4354 gives general format and guidance on detail for the drafting of national Standards on wind actions. This edition differs from the previous editions as follow: (a) The format of ISO 4354 has been adopted except that the effects of exposure are applied to the wind speed to give directional site wind speeds before conversion to pressure (see Note to Clause 2.4) (b) Importance factors have been replaced with variable annual probability of exceedance, to enable reliability-based design. Values of wind speed are determined using the annual probability of exceedance (see AS/NZS 1170.0). (©) It isa joint Standard intended for use in Austratia and New Zealand. (@) Average roof height is used to calculate wind pressures for rectangular enclosed buildings.Accessed by IRWINCONSULT PTY LTD on 07 Sep 2007 3 ASINZS 1170.2:2002 (©) Actions determined from wind tunnel tests or other methods are not covered through the ‘deemed-to-comply’ solution given in this Standard, but must be separately established (by a special study; see AS/NZS 1170.0). () Asimplified procedure is not included. (g) Wind speeds for permissible stress design are not included (see the Commentary, ASINZS 1170.2 Supp 1). (h) Directional wind speed multipliers have been revised and extended beyond the capital cities in Australia. (i) Generally, the clauses have been updated to incorporate the latest research and to improve useability. The following new information has been included: (i) Elevation effect for Tasmania, (ii) Separation zone for crests of steeper slopes. (iii) Combination factor for major structural members (iv) Parapet reduction factor. (v) Hyperbolic paraboloid roofs. (vi) Methods for open lattice structures and lattice towers (including ancillaries). (vii) Flags and spheres. () The calculation of dynamic wind response has been simplified and the use of an hourly mean wind speed for dynamic analysis has been replaced with the 3s gust. ‘When dynamic response is to be determined, a single additional factor is determined ‘The Joint Commitice has considered exhaustive research and testing information from Australian, New Zealand and overseas sources in the preparation of this Standard. The design wind actions prescribed in this Standard are the minimum for the general cases described. Particular acknowledgment should be given to Monash University, University of Queensland, James Cook University, Curtin University of Technology, Building Research Association of New Zealand, Bureau of Meteorology (Aust) and National institute of Water and Atmospheric Research (NZ) 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. 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 and are not considered to be an integral part of the StandardINCONSULT PTY LTD on 07 Sep 20¢ Accessed by IRI AS/NZS 1170.2:2002 4 CONTENTS, Page SECTION | GENERAL 1.1 SCOPE APPLICATION voce REFERENCED DOCUMENTS. DETERMINATION OF WIND ACTIONS UNITS ., fe DEFINITIONS. ann NOTATION cccsccsrsrnreresenesn 1 1 le 1 1 1 Sab ROD SECTION 2. CALCULATION OF WIND ACTIONS, GENERAL oo SITE WIND SPEED DESIGN WIND SPEED. DESIGN WIND PRESSURE AND DISTRIBUTED FORCES WIND ACTIONS pl SECTION 3. REGIONAL WIND SPEEDS 3.1 GENERAL .. 3.2. REGIONAL WIND SPEEDS (Vs). 3.3. WIND DIRECTION MULTIPLIER (Mj)... 3.4 FACTORS FOR REGIONS C AND D (Fe, Fs) ECTION 4 SITE EXPOSURE MULTIPLIERS 4.1 GENERAL vaseoson 4.2. TERRAIN/HEIGHT MULTIPLIER (Ma). 4.3. SHIELDING MULTIPLIER (M,). 4.4 TOPOGRAPHIC MULTIPLIER (4). SECTION § AERODYNAMIC SHAPE FACTOR GENERAL... 5.1 | 52. EVALUATION OF AERODYNAMIC SHAPE FACTOR 5.3 INTERNAL PRESSURE FOR ENCLOSED RECTANGULAR BUILDINGS. 3.4 EXTERNAL PRESSURES FOR ENCLOSED RECTANGULAR BUILDINGS ......29 5.5 FRICTIONAL DRAG FORCES FOR ENCLOSED BUILDINGS 36 SECTION 6 DYNAMIC RESPONSE FACTOR 6.1 EVALUATION OF DYNAMIC RESPONSE FACTOR... 62 ALONG-WIND RESPONSE OF TALL BUILDINGS AND TOWERS... 6.3 CROSSWIND RESPONSE .. 64 COMBINATION OF ALONG-WIND AND CROSSWIND RESPONSEAccessed by IRWINCONSULT PTY LTD on 07 Sep 2007 ASINZS 1170.2:2002 Page APPENDICES A DEFINITIONS... ea : : 46 Bo NOTATION .sstne nae senmensnenees SO C ADDITIONAL PRESSURE COEFFICIENTS FOR ENCLOSED BUILDINGS...... 56 D FREESTANDING WALLS, HOARDINGS AND CANOPIES... senesenee 62 E AERODYNAMIC SHAPE FACTORS FOR EXPOSED STRUCTURAL MEMBERS, FRAMES AND LATTICE TOWERS. n F FLAGS AND CIRCULAR SHAPES... 85 G ACCELERATIONS FOR WIND SENSITIVE STRUCTURES .. 87ASINZS 1170.2:2002 6 STANDARDS AUSTRALIA/STANDARDS NEW ZEALAND Australian/New Zealand Standard Structural design actions Part 2: Wind actions SECTION 1 GENERAL 1.1 SCOPE ‘This Standard sets out procedures for determining wind speeds and resulting wind actions to be used in the structural design of structures subjected to wind actions other than those caused by tornadoes. ‘The Standard covers structures the following criteria: (a) Buildings tess than 200 m high (b) Structures with roof spans less than 100 m. (c) Structures other than offshore structures, bridges and transmission towers. NOTES: 1 This Standard is a stand-alone document for structures within the above criteria. It may be used, in general, for all structures but other information may be necessary, Guidance on wind tunnel testing, reliable references and altemative data is given in AS/NZS 1170.2 Supp 1, Structural design —actions—Wind —actions—Commentary (Supplement to ASINZS 1170.2:2002), Where structures have natural frequencies less than 1 Hz, Section 6 requires dynamic analysis to be carried out (see Section 6), 1.2 APPLICATION ‘This Standard shall be read in conjunction with AS/NZS 1170.0. This Standard may be used as a means for demonstrating compliance with the Requ of Part BI of the Building Code of Australia, 1.3 REFERENCED DOCUMENTS ‘The following documents are referred to in this Standard: AS 4040 Methods of testing sheet roof and wall cladding 4040.3. Part 3: Resistance to wind pressures for cyclone regions AS/NZS 1170 Structural design actions 1170.0 Part 0: General principles Iso 2394 General principles on reliability for structures 4354 Wind actions on structures Accessed by IRWINCONSULT PTY LTD on 07 Sep 2007 Australian Building Codes Board Building Code of Australia COPYRIGHT2S 1170.2:2002 1.4 DETERMINATION OF WIND ACTIONS, Values of wind actions (IF) for use in design shall be established that are appropriate for the type of structure or structural element, its intended use, design working life and exposure to wind action. This Clause shall be deemed to be satisfied when wind actions are determined in accordance with the procedures detailed in Section 2, using the values given in this Standard. 15 UNITS Except where specifically noted, this Standard uses the SI units of kilograms, metres, seconds, pascals, newtons and hertz (kg, m, s, Pa, N, Hz). 1.6 DEFINITIONS Definitions of the terms used in this Standard are given in Appendix A. 1.7 NOTATION The notation used in this Standard is given in Appendix B. INCONSULT PTY LTD on 07 Sep 2007 Accessed by IRI COPYRIGHTAccossed by IRWINCONSULT PTY LTD on 07 Sep 2007 ASINZS 1170.2:2002 8 SECTION 2. CALCULATION OF WIND ACTIONS 2.1 GENERAL The procedure for determining wind actions (JP) on structures and elements of structures or buildings shall be as follows: (a) Determine site wind speeds (see Clause 2.2). (b) Determine design wind speed from the site wind speeds (see Clause 2.3) (6) Determine design wind pressures and distributed forces (see Clause 2.4). (d) Calculate wind actions (see Clause 2.5). 2.2 SITE WIND SPEED The site wind speeds (Vsi,g) defined for the 8 cardinal directions (/9) at the reference height (z) above ground (see Figure 2.1) shall be as follows: Vang = Vx Mg (M,.ca Me Mi) where Vg = regional 3 s gust wind speed, in metres per second, for annual probability of exceedance of 1/R, as given in Section 3 Mz = wind directional multipliers for the 8 ci jal directions (B) as given in Section 3 Mca = terrain/height multiplier, as given in Section 4 M, = shielding multiplier, as given in Section 4 M, = topographic multiplier, as given in Section 4 Generally, the wind speed is determined at the average roof height (). In some cases this varies, as given in the appropriate sections, according to the structure. ‘Where the orientation of a building is not known, the regional wind speed shall be assumed to act from any cardinal direction (i.e. My = 1.0 for all directions). 2.3. DESIGN WIND SPEED. ‘The building orthogonal design wind speeds (Vig,s) shall be taken as the maximum cardinal direction site wind speed (V,p) linearly interpolated between cardinal points within a sector £45 degrees to the orthogonal direction being considered (see Figures 2.2 and 2.3). NOTE: That is, Vise equals the maximum value of site wind speed (Vuus) in the range [B= 0 £43 degrees} where fis the cardinal direction clockwise from true North and @is the angle to the building orthogonal axes In cases such as walls and hoardings and lattice towers, where an angle of 45° is considered, Vc. shall be the value of Vg in a sector £22.5° from the 45° direction being considered. For ultimate limit states design, Vig. shall not be less than 30 m/s. NOTE: A conservative approach is to design the structure using the wind velocity and multipliers for the worst direction. For example, for a building on an escarpment, it may be easily checked whether the Ve Ms (Mzox MM, Mj) on the exposed face (towards the escarpment) is the worst case. To simplify design, this value could then be used as the design wind speed for all directions on the building. ‘COPYRIGHTAccessed by IRWINCONSULT PTY LTD on 07 Sep 2007 Average root / height oR L REFERENCE HEIGHT OF STRUCTURES. COPYRIGHT ASINZS 1170.2:2002ASINZS 1170.2:2002 go NW ‘Cardinal VC ion w—— 8=270° Building orthogonal axes—~ / ig ~ * g [A sw FIGURE 2.2 RELATIONSHIP OF WIND DIRECTIONS AND BUILDING ORTHOGONAL AXES. 45° 90° 180° 270° NE E s w N CARDINAL DIRECTION, 6 wind speed X. NOTE: The value of Figg ithe maximum of Vay in the range 045 degrees, which, in the case shown her, 5 the FIGURE 2.3 EXAMPLE OF Vsz5 CONVERSION TO Véose coPyRIGHTn ASINZS 1170.2:2002 2.4 DESIGN WIND PRESSURE AND DISTRIBUTED FORCES 2.441 Design wind pressures The design wind pressures (p) in pascals, shall be determined for structures and parts of structures as follows: P= (05 psi) Peasol” Cris Casn 2.401) where design wind pressure acting normal to a surface, in paseals = Pep or p, where the sign is given by the C, values used to evaluate Chg NOTE: Pressures are taken as positive, indicating pressures above ambient and negative, indicating pressures below ambient Por = density of air, which shall be taken as 1.2 kg/m* “sex ~ building orthogonal design wind speeds (usually, @= 0°, 90°, 180°, and 270°), as given in Clause 2.3 NOTE: For some applications, V4e,9 may be a single value or may be expressed as a function of height (2) e.g., windward walls of tall buildings (25m), Chg = aerodynamic shape factor, as given in Section 5 Cayn dynamic response factor, as given in Section 6 (the value is 1.0 except where the structure is wind sensitive, see Section 6) 2.4.2 Design wind distributed forces The design wind frictional drag force per u structures and parts of structures as follows: f= (05 par) Wiesel Cag Cayn 2.4(2) area (f) in pascals, shall be taken for 2.5 WIND ACTIONS 2.5.1 General Wind actions (WW) for use in AS/NZS 1170.0 shall be determined as given in Clauses 2.5.2 to 2.5.5 and accelerations as given in Clause 2.5.6. 2.5.2 Directions to be considered Wind actions shall be derived by considering wind from no fewer than four orthogonal directions aligned to the structure. 2.5.3 Forces on surfaces or structural elements, 2.5.3.1 Forces derived from wind pressure To determine wind actions, the forces () in newtons, on surfaces or structural elements, such as a wall or a roof, shall be the vector sum of the forces calculated from the pressures applicable to the assumed areas (4), as follows: F= Lp. Ad 2.5(1) where Pp: = design wind pressure, in pascals (normal to the surface), at height z, calculated in Clause 2.4.1 NOTE: The sign convention for pressures leads to forces towards the surface for positive pressures and forces away from the surface for negative pressures. A, = areference area, in square metres, at height z, upon which the pressure at that height (p,) acts COPYRIGHTAccessed by IRWINCONSULT PTY LTD an 07 Sep 2007 ASINZS 1170.2:2002 PR For enclosed buildings, internal pressures shall be taken to act simultaneously with external pressures including the effects of local pressure factors (K,). The most severe combinations of internal and external pressures shalll be selected for design Where variations in the surface pressure with height are considered, the area shall be subdivided so that the specified pressures are taken over appropriate areas (see Clause 4.2 for variation of wind speed with height). 2.5.3.2 Forces derived from frictional drag To determine wind actions, the forces (F) in newtons, on a building element, such as a wall ‘ot a roof, shall be the vector sum of the forces calculated from distributed frictional pressures applicable to the assumed areas, as follows: F= 3h Ad) 2.5(2) where f. = the design frictional distributed foree parallel to the surface, calculated in Clause 2.4.2 at height z, in pascals 2.5.3.3 Forces derived from force coefficients Appendices E and F cover structures for which shape factors are given in the form of force coefficients rather than pressure coefficients. In these cases, to determine wind actions, the forces (F) in newtons, shall be determined as follows’ F=(0.5 pai) Vaal” Crig Cyn Ares 2.53) where Aree = as defined in Appendix F, for flags = Ixb for other structures or elements of structures covered in Appendices E and F 2.5.4 Forces and moments on complete structures To determine wind actions, the total resultant forces and overturning moments on complete structures shall be taken to be the summation of the effects of the external pressures on all surfaces of the building, For rectangular enclosed buildings where the ratio d/h or dib (see Clause 5.4) is greater than 4, the total resultant force on a complete structure shall include the frictional drag calculated in accordance with Clause 5.5. For dynamic effects, the combination of along-wind and crosswind responses shall be calculated in accordance with Section 6. 2.5.5. Performance of fatigue-sensitive elements In regions C and D, cladding, its connections and immediate supporting members shall demonstrate performance under the pressure sequences defined in AS 4040.3, based on the ultimate limit state wind pressure on external and internal surfaces, as determined in accordance with this Standard, 2.5.6. Serviceability of wind-sensitive structures For the purpose of calculating wind actions for serviceability of wind-sensitive chimneys, masts and poles of circular cross-section (as defined in Clause 6.1), deflections shall be calculated in accordance with Section 6. NOTE: Information on peak acceleration of other wind-sensitive structures is given in Appendix G COPYRIGHTees yee eee eae B ASINZS 1170.2:2002 SECTION 3. REGIONAL WIND SPEEDS 3.1. GENERAL This Section shall be used to calculate gust wind speeds appropriate to the region in which a structure is to be constructed, including wind direction effects. 3.2. REGIONAL WIND SPEEDS (Va) Regional wind speeds (Vg) for all directions based on 3 second gust wind data shall be as given in Table 3.1 for the regions shown in Figure 3.1 where R (average recurrence interval) is the inverse of the annual probability of exceedance of the wind speed. Refer to AS/NZS 1170.0 for information on values of annual probability of exceedance appropriate for the design of structures. TABLE 3.1 REGIONAL WIND SPEEDS oe Region satya Now-eyelonle Grete Age | Ww B € > 2 9 28 ms iss 3 a 33 Feil Fa aT 48 38 Fels FSi 38 a FB FO 41 48 Fe 56 Fos 1 ® 2 esi Fo? 45 3 3 76 Foto Fin 46 3 6 Fe1 Fas Vaso 48 3a a Pet P90 Fa (see Notey [67-41 K°! | 104— 70K | 106-92 Re! | Fe (122-404 RN) | Fy (156-1421) NOTE: The calculated value shall be rounded to the nearest 1 m/s. 3.3. WIND DIRECTION MULTIPLIER (My) 3.3.1 Regions A and W The wind direction multiplier (44) for regions A and W shall be as given in Table 3 3.3.2. Regions B, C and D ‘The wind direction multiplier (Mj) for all directions in regions B, C and D shall be as follows: (a) 0.95 for determining the resultant forces and overturning moments on complete buildings and wind actions on major structural elements (members resisting collapse of the whole structure) (b) 1.0 for all other cases (including cladding), COPYRIGHTa ASINZS 1170.2:2002 rm 3.4. FACTORS FOR REGIONS C AND D (Fe, Fo) ‘The wind speeds given in Table 3.1 for regions C and D include additional factors (Fe and Fp) which shall be as follows: (a) For ultimate limit states wind speeds, Fy = 1.1 (b) For ultimate limit states wind speeds, Fe = 1.05 (c) For serviceability limit states wind speeds, Fc and Pp = 1.0. NOTE: The frequency of Category 5 cyclone crossings in Region D in the years 1998 to 2002 is, much greater than predicted from the historic data on which the wind speeds in this Standard are based. The factors in this Clause have been introduced to allow for uncertainties in the prediction of ultimate design wind speeds in Regions C and D (tropical cyclones regions) when they are based on recorded wind speeds. The values of these factors may be revised in the future followi simulations based on recorded cyclone tracks. Such an analysis would naturally include eyelone activity throughout the northern coast of Australia (i.e., in regions © and D). The effects of long- term climate change may also be included. TABLE 3.2 WIND DIRECTION MULTIPLIER (Ma) Cardinal | Region | Region | Region | Region | Region | Region | Region | Region directions |__AL AD a3 Ad S| AG AT w N 0.90 oso | 085 0.90 1.00 0.85, 090 | 10 NE 0.80 oso | 0.80 085 os 095 90 | 09s E 0.80 oso | 0.80 090 080 | 10 080 | 080 SE 0.80 09s | 080 0.90 030 | 098 090 | 090 s 08s 090 | 0.80 0.95 0.88 0.85 090 | 10 sw 0.95 oss | oss 095 | 0.90 0.95 a9 | 10 Ww 1.00 1.00 | 090 09s | 1.00 10 10 0.90 NW 093 095 | 1.00 0.90 0.95 0.95 10 0.95 Any ato | O 10 10 Lo | 10 10 10 Lo COPYRIGHTASINZS 1170.2:2002 urls; OOH PAO SNOIDSY NIM (edu!) Fe SYNOIs 8 eyesisny (2) 1s800 \uso8{pe yeqor —— <7 8V wojBoy 109 _-suoi90 pore euneaion 10 o1eg 1883, pal wy OL Faeane ee al se. y uo8ey exewoom. ty wowou punoe og 7 8 vee 7, 91004 -equoomoo vy voIsey “yon sBUIED sounds’ eony oH Hod umoienine Zpueios0w 180M a SK ost ~u oot wy 08 9 wojBoy 9 vojtoy spuels) $0005 ~ we I g voldey [dwo Asoyss04 veyeaisayy Sg uojsey purisi Seunsinig 1g voy one des #0. U0 CIT Ald LINSNOS COPYRIGHT-TH on 07 Sep 2007 Accessed by IRWINCONSULT PTY ASINZS 1170.2:2002 16 REGION A6 Gisborne New Plymouth: wangahat Palmerston Novthe \Walpukurau ‘upper Hutt ee Gion a7 Westport Harner Springs REGION W REGION AT}. Hokitike LEE MULTIPLIER, Mioe North-west wind f 44° | [J shedow zone : 0-12 km witors Sound mary Outer zone : 12-30 km Dunedin South-east wind Shadow zone : 0-12 km Q& 7 Outer zone : 12-30 km Distances measured In the down wind direction of the wind from the initiating ridge. (b) New Zealand FIGURE 3.1 (in part) WIND REGIONS CoPyRIGHTAccessed by IRWINCONSULT PTY LTD on 07 Sep 2007 ” AS/NZS 1170.2:2002 SECTION 4 SITE EXPOSURE MULTIPLIERS 4.1 GENERAL This Section shall be used to calculate the exposure multipliers relating to site conditions related to terrain/height (M,,.a). shielding (M4,) and topography (M). The design shall take account of known future changes to terrain roughness when assessing terrain category and to buildings providing shielding when assessing shielding. 4.2. TERRAIN/HEIGHT MULTIPLIER (Mics 4.2.1, Terrain category definitions Terrain, over which the approach wind flo basis of the following category descriptio vs towards a structure, shall be assessed on the (a) Category I—Exposed open terrain with few or no obstructions and water surfaces at serviceability wind speeds. (b) Category 2—Water surfaces, open terrain, grassland with few, well-scattered obstructions having heights generally from 1.5 m to 10m. (ec) Category 3—Terrain with numerous closely spaced obstructions 3 m to 5 m high such as areas of suburban housing. (@) Category 4—Terrain with numerous large, high (10 m to 30m high) and closely spaced obstructions such as large city centres and well-developed industrial complexes. Selection of terrain category shall be made with due regard to the permanence of the obsiructions that constitute the surface roughness. In particular, vegetation in tropical cyclonic regions shall not be relied upon to maintain surface roughness during wind events. 4.2.2. Determination of terrain/height multiplier (Mya) ‘The variation with height (z) of the effect of terrain roughness on wind speed (terrain and structure height multiplier, Mf, <2) shall be taken from the values for fully developed profiles given in Tables 4.1(A) and 4.1(B). For intermediate values of height and terrain category, use linear interpolation, COPYRIGHTAS/NZS 1170.2:2002 18 TABLE 4.1(A) TERRAIN/HEIGHT MULTIPLIERS FOR GUST WIND SPEEDS IN FULLY DEVELOPED TERRAINS—SERVICEABILITY LIMIT STATE DESIGN—ALL REGIONS AND ULTIMATE LIMIT STATE—REGIONS Ai TO A7, W AND B Terrain/height multiplier (fsa Height (z) * per ¢ 7 Terrain Terrain Terrain | Terrain category 1 | category? | eategory3_| category 4 3 099 oo 083 os 5 10s 031 083 0.5 10 ua | 100 083 os 5 16 os 049 ons 20 Lis 0g oot 078 30 iz ur 1.00 0.80 40 we | 16 04 os 30 135 ie 107 0.90 78 in ia Le 098 100 129 Las 16 103 150 131 a7 var) 200 1 129 124 nie 250 138 131 um | 120 300 138 32 a9 1 600 137 135 132 18 500 138 137 13s Last NOTE: For intermediate values of height z and terrain category, use linear interpolation. TABLE 4.1(B) TERRAIN/HEIGHT MULTIPLIERS FOR GUST WIND SPEEDS IN FULLY DEVELOPED TERRAINS—ULTIMATE LIMIT STATE DESIGN—REGIONS C AND D ONLY Height (2) Multiplier (Mz eu) |___Multiplier (fra) m Terrain categories Land 2 | Terrain eategories 3 and 4 3 0.90 | 0.80 5 0.95 o.80 10 1.00 0.89 15 1.07 0.95 20 1B 1.05 30 120 1s 40 125 1.25 50 129 129 B 135 135 2100 1.40 140 NOTE: For intermediate values of height z and terrain category, use linear interpolation, 4.2.3 Changes in terrain eategory When considering a direction where the wind approaches across ground with changes in terrain category that lie within the averaging distances given in Table 4.2(A) for structure height, the terrain and structure height multiplier (M,,..) shall be taken as the weighted average value over the averaging distance upwind of the structure at height = above ground level (see Figure 4.1(a)) IRWINCONSULT PTY LTD on 07 Sep 2007, i i ‘COPYRIGHTAccessed by IRWINCONSULT PTY LTD on 07 Sep 20ur 19 ASINZS 1170.2:2002 The weighted average of M,cx shall be weighted by the length of each terrain upwind of the structure allowing for the lag distance at each terrain category change. An example is given in Figure 4.1(b), For evaluation at height z, a change in terrain incorporates a lag distance (x) given as follows: 42 where x; = distance downwind from the start of a new terrain roughness to the position where the developed height of the inner layer equals z (lag distance) Zoy = larger of the two roughness lengths at a boundary between roughnesses, as given in Table 4.2(B) z= reference height on the structure above the average local ground level ‘NOTE: Lag distance is not a significant effect for heights fess than 15 m. TABLE 4.2(A) AVERAGING DISTANCE FOR STRUCTURE HEIGHT Structure height ‘Averaging distance upwind of structure () (m) 50 1000 50h =100 2000 100 200 3000 2005h 4900 TABLE 4.2(B) ROUGHNESS LENGTHS FOR TERRAIN CATEGORIES. ‘Terrain category ninmianeie tee 1 0.002 2 0.02 3 02 4 20 ‘COPYRIGHTASINZS 1170.2:2002 20 Developed height Wind direction of inner layer — Upstream terrain category New terrain category Start of new 7 terrain roughness! lal Notation for changes in terrain category (a) Notation for changes in terrain category Wing , direction —7 Averaging distence | ag ; ma 2) -strvoture Laoged i response at height 2——~ t 1 {ty 1 2 Ey | 7 t A absiatetededyta [Tein cotessey [evr toner 8 Actual 4 Eo surfece Lag distance Lag distance (te3 to tea) {toa to teal Map X10 + Mya Xat Mya My gat eek 2312 or te case ilustrated ot Averaging distance (b) Example of changes in terrain category FIGURE 4.1 CHANGES IN TERRAIN CATEGORY 4.3. SHIELDING MULTIPLIER (M§,) 4.3.1 General The shielding multiplier (4) that is appropriate to a particular direction shall be as given in Table 4.3. The shielding multiplier shall be 1.0 where the average upwind ground gradient is greater than 0.2 or where the effects of shielding are not applicable for a particular wind direction or are ignored, COPYRIGHTE E 3 a ASINZS 1170.2:2002 TABLE 4.3 SHIELDING MULTIPLIER (,) Shielding parameter ©) Shielding multiplier NOTE: For intermediate values of 5, use tinear interpolation. 4.3.2 Buildings providing shielding Only buildings within a 45° sector of radius 20%, (symmetrically positioned about the directions being considered) and whose height is greater than or equal to /, shall be taken to provide shielding. 4.3.3, Shielding parameter (s) ‘The shielding parameter (s) in Table 4.3 shall be determined as follows: 43) 1, = average spacing of shielding buildings, given by: 10.) = 45) 43(2) Ame} hn, = average roof height of shielding buildings b, = average breadth of shielding buildings, normal to the wind stream h = average roof height, above ground, of the structure being shielded n, = number of upwind shielding buildings within a 45° sector of radius 20h and with hy 4.4 TOPOGRAPHIC MULTIPLIER (M) 44,1 General ‘The topographic multiplier (iM,) shall be taken as follows (a) For sites in New Zealand and Tasmania over 500 m above sea level: M,= My Mice (1+ 0.00015 E) 4.401) where ‘M, = hill shape multiplier Mi = lee (effect) multiplier (taken as 1.0, except in New Zealand lee zones, see Clause 4.4.3) E = site elevation above mean sea level in meters COPYRIGHTAccessed by IRWINCONSULT PTY LTD on 07 Sep 2007 ASINZS 1170.2:2002 2 (b) Elsewhere, the larger value of the following: @ M=M Gi) M= Mew 4.4.2. Hill-shape multiplier (1%) The hill shape multiplier (4,) shall be taken as 1.0 except that for the particular cardinal direction in the local topographic zones shown in Figures 4.2 to 4.4, the value shall be as follows: (a) For Hi(2L,) < 0.05, My = 1.0 (b) For 0.05 < Hi(2L,) <0.45, (see Figures 4.2 and 4.3) - |!) 4 a 4.42) (c) For Hi(2L,) > 0.45, (see Figure 4.4) (i) Within the separation zone (see Figure 4.4) a, ort 44 =14 bt a h L 3) Gi) Elsewhere within the local topographic zone (see Figures 4.2 and 4.3), My shall be as given in Equation 4.4(2) where HH = height of the hill, ridge or escarpment 1, = horizontal distance upwind from the crest of the hill, ridge or escarpment to a level half the height below the crest x = horizontal distance upwind or downwind of the structure to the crest of the hill, ridge or escarpment 1, = length scale, in metres, to determine the vertical variation of My, to be taken as the greater of 0.36 Ly or 0.4 H Ly = length scale, in metres, to determine the horizontal variation of My, to be taken as 4 Z; upwind for all types, and downwind for hills and ridges, or 10 Ly downwind for escarpments z = reference height on the structure above the average local ground level NOTE: Figures 4.2, 4.3 and 4.4 are cross-sections through the structure’s site for @ particular wind direction. For the case where x and z are zero, the value of M, is given in Table 4.4. Irrespective of the provisions of this Clause, the influence of any peak may be ignored, provided it is distant from the site of the structure by more than 10 times its elevation above sea level. COPYRIGHTE E z 5 Z Z 23 ASINZS 1170.2:2002 Local topographic zone Wind direction (whichever is greater) (whichever is greater! FIGURE 4.2 HILLS AND RIDGES Local topographic zone * i KKK U7 Gl Yi YH 4 ~ T _ PI STAD f ZA Ha t | Lg=tddly or 16H ly or a (whichever ie greater) [whichever is greater! NOTE: For escarpments, the average downwind slope, measured from the evest to a distance of the greater of 3.6 Ly or 4H shall not exesed 0.05. FIGURE 4.3 ESCARPMENTS Local topographic zone _-~ Separation zone starting at crest mir Y FIGURE 4.4 SEPARATION ZONE FOR SLOPES GREATER THAN 0.44 COPYRIGHTAccessed by IRWINCONSULT PTY LTD on 07 Sep 2007 ASINZS 1170.2:2002 uw TABLE 4.4 HILL-SHAPE MULTIPLIER AT CREST =0 (FOR GUST WIND SPEEDS) Upwind slope (Hi2Ly) 4.4.3 Lee multiplier (Mi..) The lee (effect) multiplier (M\..) shall be evaluated for New Zealand sites in the lee zones as shown in Figure 3.1(b). For all other sites, the lee multiplier shall be 1.0, Within the Jee zones, the lee multiplier shall apply only to wind from the cardinal directions nominated in Figure 3.1(b). Each lee zone shall be 30 km in width, measured from the leeward crest of the initiating range, downwind in the direction of the wind nominated. The lee zone comprises a ‘shadow lee zone’, which extends 12 km from the upwind boundary of the lee zone (crest of the initiating range), and an ‘outer lee zone’ over the remaining 18 km ‘The lee multiplier shall be 1.35 for sites within the shadow lee zone (i.e., within 12 km of the crest of the range). Within the outer lec zone, the lee multiplier shall be determined by linear interpolation with horizontal distance, from the shadow/outer zone boundary (where Migs = 1.35), to the downwind lee zone boundary (where Mie = 1.0). NOTE: No lee zones have been identified in Australia. COPYRIGHTAccessed by IRWINCONSULT PTY LED on 07 Sep e007 2s ASINZS 1170.2:2002 SECTION 5 AERODYNAMIC SHAPE FACTOR 5.1 GENERAL This Section shall be used to calculate the aerodynamic shape factor (Cpg) for structures or parts of structures. Values of Cg, shall be used in determining the pressures applied to cach surface. For calculating pressures, the sign of Cs, indicates the direction of the pressure on the surface or element (see Figure 5.1), positive values indicating pressure acting towards the surface and negative values pressure acting away from the surface (less than ambient pressure, i.c., suction). The wind action effects used for design shall be the sum of values determined for different pressure effects such as the combination of internal and external pressure on enclosed buildings Clauses 5.3, 5.4 and 5.5 provide values for enclosed rectangular buildings. For the purposes of this Standard, rectangular buildings includes buildings generally made up of rectangular shapes in plan. Methods for particular cases for buildings, free walls, free roofs, exposed members and other structures are given in the appropriate Appendices. Neve External pressures Interna pressures NOTE: Cig 18 used to give o pressure on one face of the surface under consideration. Positive value of Chip indicates pressure acting towards the surface, negative acting away {rom the surface la) Pressures normal to the surfaces of enclosed bulidings os / NOTE: Chg 1s used to give a frictional drag on external surfaces of the structuro only. Lead por anit area acts parallel to the surface. lb] Frictional drag on enclosed buildings FIGURE 5.1 (in part) SIGN CONVENTIONS FOR C;, COPYRIGHT: Ez § z i 2 ASINZS 1170.2:2002 6 NOTE: Ciig 1s used to give a net pressure normal NOTE: Cys is used to give frictional drag on both to the wall derived from face pressures on both sides of the wall, Load per unit area acts parallel upwind and downwind faces. The net pressure to both the surfaces of the wall falways acts normal to the longitudinal axis of the watt {oc} Pressure normal to the surfaces (d) Frictional drag on walls and hoardings of walls and hoardings NOTE: Cig is used vo give net pressure normal to NOTE: Cyg is used to give the total frictional the roof derived from face pressures on both upper drag forces derived from face frictional forces on and lower surfaces, The net pressure always acts both upper and lower surfaces. Load per unit arca normal to the surface and positive indicates acts parallel to both the surfaces of the roof downwards. (el Pressure normal to the surfaces (f} Frictional drag on freestanding roots freestanding roofs FIGURE 5.1 (in part) SIGN CONVENTIONS FOR Cig 5.2. EVALUATION OF AERODYNAMIC SHAPE FACTOR ‘The aerodynamic shape factor (Cj) shall be determined for specific surfaces or parts of surfaces as follows: (a) Enclosed buildings (see this Section 5 and Appendix C)— Cag ~ Coe Ku Ke Ke Ky, for external pressures + 5.2(1) Cap = Cy, Ke, for internal pressures = 5.22) Cry = Cr Ke, for frictional drag forces 203) COPYRIGHTAccessed by IRWINCONSULT PTY LTD on 0? Sep eu! 53.3. Dor 2 ASINZS 1170.2:2002 (b) Circular bins, silos and tanks—see Appendix C. (c) Freestanding walls, hoardings, canopies and roofs (see Appendix D)— Cig = Coa Ke Ke Kp, for pressure normal to surface -5.2(4) Cig = Ce for frictional drag forces + 5.25) (4) Exposed structural members, frames and lattice towers—see Appendix E. (e) Flags and cireular shapes—see Appendix F where Cye = external pressure coefficient K, = area reduction factor K, = combination factor K, = local pressure factor K, = porous cladding reduction factor Cy = internal pressure coefficient Cy = frictional drag force coefficient Cyn = net pressure coefficient acting normal to the surface for canopies, freestanding roofs, walls, and the like 5.3. INTERNAL PRESSURE FOR ENCLOSED RECTANGULAR BUILDINGS, 5.3.1 General Aerodynamic shape factors for internal pressure (C,;) shall be determined from Tables g shut and the wall permeability dominates. Table 5.1(B) shall be used for the design case where opel determined shall be the average roof height (hi). -1(A) and 5.1(B). Table 5.1(A) shall be used for the de: case where openings are ngs are assumed to be open. In all eases, the height at which the wind speed is Internal pressure is a function of the relative permeability of the external surfaces of the building. The permeability of @ surface shall be calculated by adding areas of opening to leakage on that surface of the building (e.g., vents, gaps in windows). 5.3.2, Openings Combinations of openings shall be assumed to give internal pressures, which together with external pressures give the most adverse wind actions. Potential openings include doors, windows and vents. In regions C and D, internal pressure resulting from the dominant opening shall be applied, unless the buil resisting impact loading equivalent to a 4 kg piece of timber of 100 mm x 50 mm cross- section, projected at 15 m/s at eny angle. 1g envelope (windows, doors and cladding) can be shown to be capable of inant openings A surface is considered to contain dominant openings if the sum of all openings in that surface exceeds the sum of openings in each of the other surfaces considered one at a time This does not include normal surface permeability. NOTE: A dominant opening does not need to be large and can occur as a result of a particular proposed scenario, such as an open air vent, while all other potential openings are shu. COPYRIGHTASINZS 1170.2:2002 28 TABLE §.1(A) INTERNAL PRESSURE COEFFICIENTS (C,,) FOR BUILDINGS WITH OPEN INTERIOR PLAN—CASES FOR PERMEABLE WALLS WITHOUT DOMINANT OPENINGS Examples showing openings, Con Ga ity and wind direction ‘One wall permeable, other walls impermeabie: (a) Windward wall permeable | 06 (>) Windward wall impermeable “03 Two oF tee walls equally permeable, other walls impermesdie (a) Windward wail permeable | 0.1, 0.2 (©) Windward wall impermeable “03 ‘Al walls equally permeable | =03 or 0.0 | whichever i the more severe for combined forces A building effectively sealed and heving ~02 or 60, . rnon-opening windows whichever is the more severe co for combined frees TABLE 5.1(B) INTERNAL PRESSURE COEFFICIENTS (C,,) FOR BUILDINGS WITH OPEN INTERIOR PLAN—DOMINANT OPENINGS ON ONE SURFACE, Tuo otdominaat ores] aocaeae | puma | pewaoa ‘otal aenaresncuding, | Domirant | Dominant | Dominant | bominaat permeability) of other wall pening Dee, Seal ‘opening on roof neatly of aker wall | yingward wall | iowa wal | va DS ores Taxon | 000 | 03,00 | -on00 1 -oio2 | -03,00 | -03.00 | -03,015 2 07Ge | 07Ge | 07% — | 07 Cpe 3 osc. | ass oss. | o8sey. 6 ormore Cy Gu Ge G. =! 1 => 1; => NOTE: C is the relevant external pressure coefficient at the location of the dominant opening. COPYRIGHT9 ASINZS 1170.2:2002 8.4 EXTERNAL PRESSURES FOR ENCLOSED RECTANGULAR BUILDINGS 5.4.1 External pressure coefficients (Cy) ‘The external pressure coefficients (C;,.) for surfaces of rectangular enclosed buildings shall be as given in Tables 5.2(A), 5.2(B) and 5.2(C) for walls and 5.3(A), 5.3(B) and 5.3(C) for roofs and for some special roofs in Appendix C. The parameters (e.g. dimensions) referred these Tables are set out in Figure 5.2. For windward wall, Wi, use V varying with height’ for buligings >25 m high Indicates wind tybetien LEGEND, W = Windward U = Upwing root slope S = Side R = Crossing roof slope L = Leeward D = Downwind roof slope h = Average roof heignt ACCESSEG DY TR INGUNSULT PEE RTM ONT SEP: FIGURE 5.2 PARAMETERS FOR RECTANGULAR ENCLOSED BUILDINGS COPYRIGHTASINZS 1170.2: 30 For leeward walls, side walls and roofs wind speed shal] be taken as the value at z= h. The reference height (#) shall be taken as the average height of the roof. Where two values are listed, roofs shall be designed for both values. In these cases, roof surfaces may be subjected to either value due to turbulence. Alternative combinations of external and internal pressures (see also Clause 5.3) shall be considered, to obtain the most severe conditions for design. For roofs, R, (see Figure 5.2) and for all @, the following cases shall be considered in determining the worst action effects using the values given in Tables 5.3(A) and 5.3(C) (a) The more negative value of the two given in the Table applied to both halves of the roof. (b) The more positive value of the two given in the Table applied to both halves of the roof. (c) The more negative value applied to one half, and the more positive value applied to the other half of the roof. For the underside of elevated buildings, C;,. shall be taken as 0.8 and ~0.6. For buildings with less elevation above ground than one-third of the height, use tinear interpolation between these values and 0.0, according to the ratio of clear unwalled height underneath first floor level to the total building height. For the calculation of underside external pressures, wind speed shall be taken as the value at h for all Under-eaves pressures shall be taken as equal to those applied to the adjacent wall surface below the surface under consideration. TABLE 5.2(A) WALLS—EXTERNAL PRESSURE COEFFICENTS (C,,-) FOR RECTANGULAR ENCLOSED BUILDINGS—WINDWARD WALL (W) h External pressure coefficients (Cy) 325.0 m (08 (wind speed varies with height) For buildings on ground— (0.8, when wind speed varies with height; or taken for A 625.0m taken at A) Ss TABLE 5.2(B) = WALLS—EXTERNAL PRESSURE COEFFICENTS (C,,.) FOR e RECTANGULAR ENCLOSED BUILDINGS—LFEWARD WALL (L) E ay degrees ao ____| External pressure coofietents e (see Note) (see Note) Coe) z st “05 = «10 2 -03 3 24 0.2 8 10 03 7 8 All values 03 4 ; 2 “0a : 21 “075 a 203 -03 2 NOTE: For intermediate valves of db and cy use linear inexpolation COPYRIGHT