AS/NZS 1170.2:2011


Structural design actions, Part 2: Wind actions

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Provides requirements for determining wind actions for use in structural design. It includes revised sections on combination factors and cantilevered roofs and new provisions for torsion and windborne debris testing. It also provides for the treatment of doors as openings, and increased local pressure factors. Wind speeds and direction factors are given for regions in Australia and New Zealand. Factors are provided to cover the environment around the structure, the geometry of the structure and the dynamic interaction of the structure with the wind.
Published: 30/03/2011
Pages: 90
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Table of contents
Cited references
Content history
Table of contents
About this publication
1 General
1.1 Scope
1.2 Application
1.3 Normative references
1.4 Determination of wind actions
1.5 Units
1.6 Definitions
1.7 Notation
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 to be considered
2.5.3 Forces on surfaces or structural elements Forces derived from wind pressure Force derived from frictional drag Forces derived from force coefficients
2.5.4 Forces and moments on complete structures
2.5.5 Number of stress exceedences 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)
3.3.1 Regions A and W
3.3.2 Regions B, C and D
3.4 Factors for regions C and D (FC, FD)
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 C and D Internal pressure coefficients for ultimate limit states for parts of buildings below 25 m in Regions C and D
5.3.2 Openings General Openings in buildings for all cases, except ultimate limit states for parts of buildings below 25 m in Regions C and D Openings in buildings for ultimate limit states for parts of buildings below 25 m in Regions C and D
5.3.3 Text deleted
5.3.4 Internal walls and ceilings
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 side 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 Evaluation of dynamic response factor
6.2 Along-wind response of tall buildings and freestanding towers
6.2.1 General
6.2.2 Dynamic response factor (Cdyn)
6.3 Crosswind response
6.3.1 General
6.3.2 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)
6.3.3 Crosswind response of chimneys, masts and poles of circular cross-section Crosswind tip deflection Equivalent static crosswind force
6.4 Combination of along-wind and crosswind response
Appendix A
A1 Aerodynamic shape factor
A2 Annual probability of exceedence of the action
A3 Aspect ratio
A4 Awning
A5 Canopy
A6 Cladding
A7 Design wind speed
A8 Discharge coefficient
A9 Downdraft
A10 Drag
A11 Dynamic response factor
A12 Eccentricity
A13 Effective surface
A14 Elevated building
A15 Enclosed building
A16 Escarpment
A17 First mode shape
A18 First mode natural frequency
A19 Force coefficient
A20 Free roof
A21 Freestanding walls
A22 Frictional drag
A23 Gable roof
A24 Hill
A25 Hip roof
A26 Hoardings
A27 Immediate supports (cladding)
A28 Lag distance
A28a Large opening
A29 Lattice towers
A30 Lift
A31 Mansard roof
A32 Monoslope roof
A33 Obstructions
A34 Permeable
A35 Pitched roof
A36 Pressure
A37 Pressure coefficient
A38 Rectangular building
A39 Reynolds number
A40 Ridge (topographic feature)
A41 Roughness length
A42 Scruton number
A43 Shelter room
A44 Solidity (of cladding)
A45 Structural elements, major
A46 Structural elements, minor
A47 Terrain
A48 Topography
A49 Tornado
A50 Tributary area
A51 Tropical cyclone
A52 Troughed roof
A53 Turbulence intensity
Appendix B
Appendix C
C1 Additional pressure coefficients
C2 Multi-span buildings (α <60°)
C3 Buildings with curved roofs
C4 Mansard roofs
C5 Circular bins, silos and tanks
C5.1 General
C5.2 Isolated circular bins, silos and tanks
C5.2.1 Walls
C5.2.2 Roofs and lids
C5.2.3 Internal pressures in bins, silos and tanks
Appendix D
D1 General
D1.1 Application
D1.2 Area reduction factor (Ka)
D1.3 Local net pressure factor (Kℓ)
D1.4 Net porosity factor (Kp)
D2 Freestanding hoardings and walls
D2.1 Aerodynamic shape factor for normal net pressure on freestanding hoardings and walls
D2.2 Aerodynamic shape factor for frictional drag
D3 Free roofs and canopies
D3.1 Aerodynamic shape factor for net pressure on free roofs
D3.2 Aerodynamic shape factor for frictional drag and drag on exposed members for free roofs
D4 Attached canopies, awnings and carports (roofs)
D4.1 Aerodynamic shape factor for net pressure on attached canopies
D4.2 Aerodynamic shape factor for frictional drag and drag on exposed members of attached canopies
D5 Cantilevered roofs
D6 Solar panels
Appendix E
E1 General
E2 Aerodynamic shape factors for individual members and frames
E2.1 Simple shapes and individual members
E2.2 Single open frame
E2.3 Multiple open frames
E3 Drag factors for structural members and simple sections
E3.1 Rounded cylindrical shapes, sharp-edged prisms and structural sections
E3.2 Rectangular prismatic sections
E4 Lattice towers
E4.1 General
E4.2 Drag force coefficient
E4.2.1 Tower sections without ancillaries
E4.2.2 Tower sections with ancillaries
E4.2.3 Correction factor for interference
Appendix F
F1 General
F2 Flags
F3 Circular shapes
Appendix G
G1 Acceleration for serviceability
G2 Peak along-wind acceleration for serviceability
G3 Crosswind acceleration for serviceability of tall buildings and towers of rectangular cross-section
G3.1 General
G3.2 Peak crosswind acceleration for serviceability
Amendment control sheet
Cited references in this standard
Structural design actions, Part 0: General principles
Methods of testing sheet roof and wall cladding, Method 3: Resistance to wind pressures for cyclone regions