Design Wind Speed to AS/NZS 1170.2

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Verified by the CalcTree engineering team on October 24, 2024
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This calculator determines the design wind speed and base wind pressures for the four cardinal directions, providing wind (base) loads for ULS and SLS design.
All calculations are performed in accordance with AS1170.2:2021.
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Results SummarySummary_inputs﻿
Input
Selection
Country
Australia
Wind region
A5
Importance level
2
Design working life
50 years
Average height of building
{"mathjs": "Unit", "value": 10, "unit": "m", "fixPrefix": false}
Terrain category
TC4
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Summary_outputs﻿
Output
Value
VR, ULS
{"mathjs": "Unit", "value": 44.976473752688804, "unit": "m / s", "fixPrefix": false}
V_R, SLS
{"mathjs": "Unit", "value": 37.28403378921448, "unit": "m / s", "fixPrefix": false}
Mc
1
Mz,cat
0.75
Ms
0.8360827634879544
Mt
1
Summary_results﻿
θ
Vdes,θ (m/s)
Wu (kPa)
Ws (kPa)
N
26.8
0.43
0.36
E
25.4
0.39
0.32
S
26.8
0.43
0.36
W
28.2
0.48
0.4
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CalculationTechnical notes
1. Properties1.1 Location
﻿﻿ Wind_region
:A2​
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﻿﻿Country
:Australia​
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﻿﻿cyclonic
:Non-cyclonic​
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Figure 3.1(A) & 3.2(B)
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1.2 Importance 
﻿﻿ Importance_level
:2​
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﻿﻿Design_life
:50 years​
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Section 3, Appendix F AS/NZS 1170.0
﻿﻿Annual probability of exceedance (ULS)
:1/500​
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﻿﻿R (ULS)
:500​
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Table 3.3, Table F2 AS/NZS 1170.0
﻿﻿Annual probability of exceedance (SLS)
:1/25​
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﻿﻿R (SLS)
:25​
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Table 3.3, Appendix C AS/NZS 1170.0
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1.2 Regional wind speed, ﻿VR​
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﻿﻿V_R (ULS)
:45.0 m / s​
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﻿﻿V_R (SLS)
:37.3 m / s​
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﻿﻿ratio
:0.83​
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﻿﻿VR​=⎩⎨⎧​26 to 6923 to 9931 to 57​for Region A (0 to 5) & B (1 to 2)for Region C & Dfor Region NZ (1 to 4)​
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Cl 3.2
1.3 Wind direction multiplier,  ﻿Md​
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M_d﻿
N
0.95
NE
0.8
E
0.8
SE
0.9
S
0.95
SW
0.95
W
1
NW
0.95
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﻿﻿Md​=⎩⎨⎧​0.75 to 1.00.75 to 0.950.90.75 to 1.0​for Region A (0 to 5)for Region B1for Region B2, C & Dfor Region NZ (1 to 4)​
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Cl 3.3
1.4 Climate change multiplier, ﻿Mc​
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﻿﻿M_c
:1.00​
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﻿﻿Ms​={1.01.05​for Region A(0 to 5), B1 & NZ (1 to 4)for Region B2, C & D​
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Cl 3.4
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2. Site Exposure Multipliers2.1 Average roof height, ﻿h
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﻿﻿h
:10.0 m​
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Figure 2.1
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2.2 Terrain/height multiplier, ﻿Mz,cat​
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﻿﻿TC
:3​
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Terrain category
Cl 4.2.1
﻿﻿Mz_cat
:1​
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﻿﻿Mz,cat​=⎩⎨⎧​0.97 to 1.390.91 to 1.290.87 to 1.270.83 to 1.240.75 to 1.16​for TC1for TC2for TC2.5for TC3for TC4​
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Table 4.1
2.3 Shielding multiplier, ﻿Ms​
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﻿﻿ns
:2​
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Number of upwind shielding buildings
Cl 4.3.3
﻿﻿hs
:5.0 m​
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Average roof height of shielding buildings
Cl 4.3.3
﻿﻿bs
:4.0 m​
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Average breadth of shielding buildings
Cl 4.3.3
﻿﻿ls
:100.0​
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﻿﻿ls​=h(10/ns​+5)
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Cl 4.3.3
﻿﻿s
:22.36​
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﻿﻿s=hs​bs​​ls​​
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Cl 4.3.3
﻿﻿M_s
:1.00​
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﻿﻿Ms​={1.00.7 to 1.0​for h>25mfor h≤25 m​
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Table 4.2
2.4 Topographic multiplier, ﻿Mt​
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﻿﻿M_h
:1.00​
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Hill shape multiplier
Cl 4.4.2
﻿﻿M_lee
:1.00​
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Lee effect multiplier
Cl 4.4.3
﻿﻿E
:700 m​
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Site elevation above mean sea level
Cl 4.4.1
﻿﻿M_t
:1.00​
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﻿﻿Mt​=⎩⎨⎧​0.5+0.5Mh​Mh​Mlee​(1+0.00015E)max(Mh​, Mlee​)​for Region A0for Region A4 & NZ1-4 where E>500melsewhere​
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Cl 4.4.1
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3. Wind Speeds3.1 Site wind speed, ﻿Vsit,β​
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V_sit﻿
Wind dir
Md
VR*Md*Mc (m/s)
Vsit,β (m/s)
NE
0.8
36
22.6
E
0.8
36
22.6
SE
0.9
40.5
25.4
S
0.95
42.7
26.8
SW
0.95
42.7
26.8
W
1
45
28.2
NW
0.95
42.7
26.8
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﻿﻿Vsit,β​=VR​Mc​Md​(Mz,cat​Ms​Mt​)
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Cl 2.2
3.2 Design wind speed, ﻿Vdes,θ​
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V_des﻿
Wind dir
Md
VR*Md*Mc (m/s)
Vsit,β (m/s)
NE
0.8
36
22.6
E
0.8
36
22.6
SE
0.9
40.5
25.4
S
0.95
42.7
26.8
SW
0.95
42.7
26.8
W
1
45
28.2
NW
0.95
42.7
26.8
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﻿﻿Vdes,θ​=maxiumum of Vsit,β​ in the range θ±45°
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Cl 2.3
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4. Wind Pressure4.1 Wind base pressure, ﻿pbase​
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W_base﻿
θ
Vdes,θ (m/s)
Wu (kPa)
Ws (kPa)
N
35.5
0.76
0.52
E
29.9
0.54
0.37
S
35.5
0.76
0.52
W
37.3
0.83
0.57
﻿﻿pbase​=(0.5ρair​)[Vdes,θ​]2={Wu​Ws​​using VR​ for ULSusing VR​ for SLS​
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Cl 2.4.1
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Design Wind Speed to AS/NZS 1170.2

Results Summary

Calculation

Technical notes

1. Properties

1.1 Location

1.2 Importance

1.2 Regional wind speed,

$V_{R}$

1.3 Wind direction multiplier,

$M_{d}$

1.4 Climate change multiplier,

$M_{c}$

2. Site Exposure Multipliers

2.1 Average roof height,

$h$

2.2 Terrain/height multiplier,

$M_{z, c a t}$

2.3 Shielding multiplier,

$M_{s}$

2.4 Topographic multiplier,

$M_{t}$

3. Wind Speeds

3.1 Site wind speed,

$V_{sit, β}$

3.2 Design wind speed,

$V_{d es, θ}$

4. Wind Pressure

4.1 Wind base pressure,

$p_{base}$

Input	Selection
Country	Australia
Wind region	A5
Importance level	2
Design working life	50 years
Average height of building	{"mathjs": "Unit", "value": 10, "unit": "m", "fixPrefix": false}
Terrain category	TC4

Output	Value
VR, ULS	{"mathjs": "Unit", "value": 44.976473752688804, "unit": "m / s", "fixPrefix": false}
V_R, SLS	{"mathjs": "Unit", "value": 37.28403378921448, "unit": "m / s", "fixPrefix": false}
Mc	1
Mz,cat	0.75
Ms	0.8360827634879544
Mt	1

θ	Vdes,θ (m/s)	Wu (kPa)	Ws (kPa)
N	26.8	0.43	0.36
E	25.4	0.39	0.32
S	26.8	0.43	0.36
W	28.2	0.48	0.4

Wind dir	Md	VRMdMc (m/s)	Vsit,β (m/s)
NE	0.8	36	22.6
E	0.8	36	22.6
SE	0.9	40.5	25.4
S	0.95	42.7	26.8
SW	0.95	42.7	26.8
W	1	45	28.2
NW	0.95	42.7	26.8

Design Wind Speed to AS/NZS 1170.2

Results Summary

Calculation

Technical notes

1. Properties

1.1 Location

1.2 Importance

1.2 Regional wind speed, ﻿VR​﻿

1.3 Wind direction multiplier, ﻿Md​﻿

1.4 Climate change multiplier, ﻿Mc​﻿

2. Site Exposure Multipliers

2.1 Average roof height, ﻿h﻿

2.2 Terrain/height multiplier, ﻿Mz,cat​﻿

2.3 Shielding multiplier, ﻿Ms​﻿

2.4 Topographic multiplier, ﻿Mt​﻿

3. Wind Speeds

3.1 Site wind speed, ﻿Vsit,β​﻿

3.2 Design wind speed, ﻿Vdes,θ​﻿

4. Wind Pressure

4.1 Wind base pressure, ﻿pbase​﻿

1.2 Regional wind speed,

$V_{R}$

1.3 Wind direction multiplier,

$M_{d}$

1.4 Climate change multiplier,

$M_{c}$

2.1 Average roof height,

$h$

2.2 Terrain/height multiplier,

$M_{z, c a t}$

2.3 Shielding multiplier,

$M_{s}$

2.4 Topographic multiplier,

$M_{t}$

3.1 Site wind speed,

$V_{sit, β}$

3.2 Design wind speed,

$V_{d es, θ}$

4.1 Wind base pressure,

$p_{base}$