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AS/NZS 1170.2:2021


Structural design actions, Part 2: Wind actions

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. To be read in conjunction with AS/NZS 1170.0.
Published: 30/07/2021
Pages: 107
Table of contents
Cited references
Content history
Table of contents
About this publication
1 Scope and general
1.1 Scope
1.2 Application
1.3 Normative references
1.4 Terms and definitions
1.5 Notation
1.6 Determination of wind actions
1.7 Units
2 Calculation of wind actions
2.1 General
2.2 Site wind speed
2.3 Design wind speed
2.4 Design wind pressure and distributed forces
2.4.1 Design wind pressures
2.4.2 Design frictional drag force per unit area
2.5 Wind actions
2.5.1 General
2.5.2 Directions
2.5.3 Forces on surfaces or structural elements Forces derived from wind pressure Forces derived from frictional drag Forces derived from force coefficients
2.5.4 Forces and moments on complete structures
2.5.5 Number of stress exceedances produced by wind loading
2.5.6 Performance of cladding elements sensitive to low-cycle fatigue
2.5.7 Deflections of dynamically wind-sensitive structures
2.5.8 Impact loading from windborne debris
3 Regional wind speeds
3.1 General
3.2 Regional wind speeds (VR)
3.3 Wind direction multiplier (Md)
3.4 Climate change multiplier (Mc)
4 Site exposure multipliers
4.1 General
4.2 Terrain/height multiplier (Mz,cat)
4.2.1 Terrain category definitions
4.2.2 Determination of terrain/height multiplier (Mz,cat)
4.2.3 Averaging of terrain categories and terrain-height multipliers
4.3 Shielding multiplier (Ms)
4.3.1 General
4.3.2 Buildings providing shielding
4.3.3 Shielding parameter (s)
4.4 Topographic multiplier (Mt)
4.4.1 General
4.4.2 Hill-shape multiplier (Mh)
4.4.3 Lee multiplier (Mlee)
5 Aerodynamic shape factor
5.1 General
5.2 Evaluation of aerodynamic shape factor
5.3 Internal pressure for enclosed rectangular buildings
5.3.1 Internal pressure General Internal pressure coefficients for all cases, except ultimate limit states for parts of buildings below 25 m in Regions B2, C and D Internal pressure coefficients for ultimate limit states for parts of buildings below 25 m in Regions B2, C and D
5.3.2 Openings General Openings in buildings in Regions A (0 to 5), B1 and NZ (1 to 4), and parts of buildings at heights of 25 m or above in Regions B2, C and D Openings in buildings for ultimate limit states for parts of buildings below 25 m in Regions B2, C and D
5.3.3 Internal walls and ceilings
5.3.4 Open area/volume factor, Kv
5.4 External pressures for enclosed rectangular buildings
5.4.1 External pressure coefficients (Cp,e)
5.4.2 Area reduction factor (Ka) for roofs and walls
5.4.3 Action combination factor (Kc)
5.4.4 Local pressure factor (Kℓ) for cladding
5.4.5 Permeable cladding reduction factor (Kp) for roofs and side walls
5.5 Frictional drag forces for enclosed buildings
6 Dynamic response factor
6.1 Introduction
6.2 Structures for which Cdyn = 1.0
6.3 Other structures
6.4 Along-wind response
6.4.1 Dynamic response factor (Cdyn) for tall buildings and free-standing towers
6.4.2 Dynamic response factor for towers, poles and masts with head frames (Cdyn)
6.4.3 Dynamic response factor for horizontal slender structures (Cdyn)
6.5 Crosswind response
6.5.1 General
6.5.2 Crosswind response of tall enclosed buildings and towers of rectangular cross-section Equivalent static crosswind force Crosswind base overturning moment Crosswind force spectrum coefficient (Cfs)
6.5.3 Crosswind response of cantilevered chimneys, masts and poles of circular cross-section Crosswind tip deflection Equivalent static crosswind force
6.6 Combination of along-wind and crosswind response
6.6.1 Combination of base moments
6.6.2 Combination of load effects
Appendix A
A.1 Additional pressure coefficients
A.2 Multi-span buildings (α < 60°)
A.3 Buildings with curved roofs
A.4 Mansard roofs
A.5 Circular bins, silos and tanks
A.5.1 General
A.5.2 Isolated circular bins, silos and tanks
A.5.2.1 Walls
A.5.2.2 Roofs and lids
A.5.2.3 Internal pressures in bins, silos and tanks
Appendix B
B.1 General
B.1.1 Application
B.1.2 Area reduction factor (Ka)
B.1.3 Local net pressure factor (Kℓ)
B.1.4 Net porosity factor (Kp)
B.2 Freestanding hoardings and walls
B.2.1 Aerodynamic shape factor for normal net pressure on freestanding hoardings and walls
B.2.2 Aerodynamic shape factor for frictional drag
B.3 Free roofs and canopies
B.3.1 Aerodynamic shape factor for net pressure on free roofs
B.3.2 Aerodynamic shape factor for frictional drag and drag on exposed members for free roofs
B.3.3 Aerodynamic shape factor for net pressure on conical canopies
B.4 Attached canopies, awnings and carports (roofs)
B.4.1 Aerodynamic shape factor for net pressure on attached canopies
B.4.2 Aerodynamic shape factor for frictional drag and drag on exposed members of attached canopies
B.5 Cantilevered roofs
B.6 Solar panels
B.6.1 Panels mounted parallel to inclined roofs
B.6.2 Panels mounted on ground
B.6.3 Panels mounted on large, near-flat roofs
Appendix C
C.1 General
C.2 Aerodynamic shape factors for individual members and frames
C.2.1 Simple shapes and individual members
C.2.2 Single open frame
C.2.3 Multiple open frames
C.3 Force coefficients for structural members and simple sections
C.3.1 Rounded cylindrical shapes, sharp-edged prisms and structural sections
C.3.2 Rectangular prismatic sections
C.4 Lattice towers
C.4.1 General
C.4.2 Drag force coefficient
C.4.2.1 Tower sections without ancillaries
C.4.2.2 Tower sections with ancillaries
C.4.2.3 Correction factor for interference
Appendix D
D.1 General
D.2 Flags
D.3 Circular shapes
Appendix E
E.1 Acceleration for serviceability
E.2 Peak along-wind acceleration for serviceability
E.3 Crosswind acceleration for serviceability of tall buildings and towers of rectangular cross-section
E.3.1 General
E.3.2 Peak crosswind acceleration for serviceability
E.4 Rotational velocities
E.5 Peak torsional acceleration
E.6 Combined peak acceleration
Amendment control sheet
AS/NZS 1170:2021
Amendment No. 1 (2023)
Correction Amendment
Amendment No. 2 (2024)
Revised Text Amendment
Cited references in this standard
Methods of testing sheet roof and wall cladding, Method 3: Resistance to wind pressures for cyclone regions
Structural design actions, Part 0: General principles - Commentary (Supplement to AS/NZS 1170.0:2002)
Content history
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