Analysis & loading · Wind, snow & cyclone
Wind actions (AS/NZS 1170.2 simplified) calculator
Site wind speed, design pressure and net wall and roof pressures for an enclosed rectangular building.
Standard: AS/NZS 1170.2:2011 · VR, Mz,cat, Cpe, Cpi
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Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Region | A | |
| Return period R | 500 | yr |
| Average roof height | 8 | m |
| Terrain category | TC2 | |
| Direction multiplier Md | 1 | |
| Shielding Ms | 1 | |
| Topographic Mt | 1 | |
| Plan depth / breadth d/b | 1 | |
| Roof pitch | 5 | ° |
| Internal Cpi (+) | 0.2 | |
| Internal Cpi (−) | -0.3 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| VR (R = 500) | 45.0 | m/s |
| Mz,cat at 8 m (TC2) | 0.964 | |
| Site/design speed V | 43.4 | m/s |
| q = 0.5ρV² | 1.128 | kPa |
| Windward wall (Cpe 0.70) | 0.56 / 1.13 | kPa (Cpi +/−) |
| Leeward wall (Cpe -0.50) | -0.79 / -0.23 | kPa (Cpi +/−) |
| Side walls (Cpe -0.65) | -0.96 / -0.39 | kPa (Cpi +/−) |
| Roof (uplift, upwind) (Cpe -0.90) | -1.24 / -0.68 | kPa (Cpi +/−) |
| Roof (downwind) (Cpe -0.40) | -0.68 / -0.11 | kPa (Cpi +/−) |
- ✓ Height ≤ 50 m (table range)
Method, formulas and assumptions
- VR from the Table 3.1 formulae (e.g. region A: 67 − 41R^−0.1)
- Mz,cat interpolated from Table 4.1(B) (2011 edition values, check against the edition you design to)
- p = 0.5·ρ·V²·(Cpe·Ka·Kl − Cpi), ρ = 1.2 kg/m³, Ka = Kl = 1 (no area or local factors)
- Cpe: windward 0.7, leeward −0.5/−0.3/−0.2 by d/b, side −0.65, roof upwind −0.9 (reduced for steeper pitch)
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.