Below is a compact, practical guide you can use on a blog or for quick design checks. I cite the code and explanatory notes so you can check the clauses.
Check Below for Free Pdf Download of Wind Load Calculation & Nominal Payable Calculation Excel Spread Sheet
Wind load Calculation
Design wind speed at height z is calculated as
Vz = Vb × k1 × k2 × k3 × k4,
where
- Vb = basic wind speed from the IS-map (50-yr return).
- k1 = probability (risk) factor (depends on life/importance).
- k2 = terrain, height & structure-size factor (from Table 2).
- k3 = topography factor (hills, escarpments — usually 1.0 for flat).
- k4 = cyclonic importance factor (applies in cyclonic areas per clause).
Design wind pressure at height z:
pz = 0.6 × Vz² (units: N/m²).
Wind force on an element (wall/roof panel):
F = pz × A × (Cpe − Cpi) × Kd,
where Cpe = external pressure coefficient, Cpi = internal pressure coefficient, A = projected area, and Kd = wind directionality factor (typical Kd = 0.9 for frames; for local cladding pressures sometimes Kd = 1.0).
Wind Data:
Basic Wind Speed Vb = 50.00 m/s
(As per DBR)
Risk coefficient K1 = 1.00
(for General Buildings as per DBR)
Terrain, height and structure size factor K2 = 1.05
(from Table2 of IS:875 III, for Terrain category 2 & Class B)
Topography factor K3 = 1.00
( As per DBR)
Importance Factor for cyclonic region K4 = 1.15
Design Wind Speed Vz = Vbk1k2k3k4 = 60.38 m/s
Design Wind Pressure Pz = 0.6 Vz2 = 2187.1 N/m2
Pz = 2.19 kN/m2
Wind directional factor, kd = 1.00
Combination factor, Kc = 1.00
For open framed structure kc = 1
For closed framed structure kc = 0.9
Area averaging Factor, Ka = 0.80
Pd = kdkakc*Pz Pd = 1.7497
Load on open structure
Wind force on member, F=CfxAexPd
| Cf – Net force coefficient | 0.8 | Table 24 IS875-part3 | ||
| Level | Height above ground “m” | Pd (kN/m²) | Cf * Pd (kN/m²) | |
| Level-1 | 0.00 – | 5.00 | 1.587 | 1.27 |
| Level-2 | 5.00 – | 10.00 | 1.587 | 1.27 |
| Level-3 | 10.00 | 15.00 | 1.750 | 1.40 |
| Transverse Wind Force due to Pipe: | ||||||
| Tributary Area: Ae = (D + W tan10) x Bent Spacing(m) | ||||||
| where, D is maximum pipe diameter at respective level & W is Width of Pipe Rack | ||||||
| z, (m) | Dia. of Pipe – D (m) | Usuable Width of PR,(m) | Length | Af, (m2) | F=CfxAexPd, (kN | Remarks |
| 5.00 | 0.762 | 6.0 | 6.00 | 11.05 | 14.032 | 30″ dia pipe |
| 7.50 | 0.762 | 6.0 | 6.00 | 11.05 | 14.032 | |
| 12.50 | 0.762 | 6.0 | 6.00 | 11.05 | 15.473 | |
| Transverse Wind Force due to Cable Tray: | ||||||
| Tributary Area: Ae = (D + W tan10) x Bent Spacing(m) | ||||||
| No. of Trays = 3 no’s | ||||||
| z, (m) | cable tray height (m) | Usuable Width of PR,(m) | Length | Af, (m2) | F=CfxAexPd, (kN | Moment kNm (0.9m ht) |
| 10.00 | 0.150 | 6.0 | 6.00 | 22.14 | 28.11 | 25.30 |
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