Wind Load Calculator
Beta — preliminary loads only. This tool computes along-wind MWFRS pressures/forces on the windward and leeward walls of a simple rectangular building. It does not cover roof or side-wall pressures, frictional forces, or components-and-cladding (local) pressures, and has not been independently reviewed by a licensed engineer. Verify all results against the full code and your National Annex before use.
Peak Velocity Pressure
qp(h)
1187.2Pa
External-only reference pressure at the top of the building.
Along-Wind MWFRS Force
Fw (this case)
937.89kN
Windward + leeward walls only. For a simple box this total is essentially independent of the internal-pressure sign (it cancels for equal opposing wall areas) — it is the NET pressures per face, used below, that differ by case.
External Windward Pressure
we = qp(ze).cpe
949.8Pa
at ze
20.0 mPa
External Leeward Pressure
we = qp(h).cpe
-613.4Pa
| Face | ze (m) | qp/qz (Pa) | cpe | we (Pa) | wi (Pa) | wnet (Pa) | Governs |
|---|---|---|---|---|---|---|---|
| Windward strip 1 (0.0-20.0m) | 20.0 | 1187.2 | 0.80 | 949.8 | 237.4 | 712.3 | |
| Leeward (whole wall) | 20.0 | 1187.2 | -0.52 | -613.4 | 237.4 | -850.8 | GOVERNS |
| Along-wind MWFRS force, this case | 937.89 kN | ||||||
cscd = 1.0 is a simplified allowance conventionally limited to buildings of modest height/slenderness (commonly cited threshold: ~15 m in several National Annexes, e.g. the UK NA to BS EN 1991-1-4). This building is at or above that threshold — cscd should be calculated per EN 1991-1-4 Annex B/C or provided by a wind specialist for dynamically sensitive structures. Verify against your National Annex.
This tool computes the along-wind Main Wind Force Resisting System (MWFRS) force on the windward and leeward walls only. Side-wall and roof pressures, frictional forces (§5.3(3)/§7.5), and components-and-cladding (local, small-tributary-area) pressures are not covered.
Velocity & Peak Pressure [EN 1991-1-4 §4]▼
Velocity & Pressure
EN 1991-1-4 §4.2(2)Basic wind velocity
vb = cdir x cseason x vb,0
vb = 1.00 x 1.00 x 26.0
vb = 26.00 m/s
EN 1991-1-4 §4.3.2 / §4.4(1) / §4.5(1)Peak velocity pressure at reference height h (used for leeward/side walls, and internal pressure)
qp(z) = [1 + 7 Iv(z)] x 0.5 x rho x vm(z)^2, vm(z) = cr(z).c0.vb, Iv(z) = 1/(c0.ln(z/z0))
z = h = 20.0 m, z0 = 0.050 m, kr = 0.190
qp(h) = 1187.2 Pa
Windward Reference Heights [EN 1991-1-4 §7.2.2]▼
Reference Heights
EN 1991-1-4 §7.2.2, Fig. 7.4Windward-wall reference-height partition
h <= b: one part, ze = h
h = 20.0 m, b = 30.0 m
1 strip(s): ze=20.0m
External Pressures [EN 1991-1-4 §5.2, Table 7.1]▼
External Pressures
EN 1991-1-4 Table 7.1External pressure coefficients (h/d = 1.33)
cpe,10: zone D (windward) = +0.8 (const.); zone E (leeward) by h/d
cpe,D = 0.80, cpe,E = -0.52
EN 1991-1-4 §5.2, eq. (5.1)External pressures we = qp(ze) x cpe
we = qp(ze) x cpe
ze=20.0m: we=949.8Pa
leeward (ze=h): we = -613.4 Pa
Internal Pressure Cases [EN 1991-1-4 §7.2.9]▼
Internal Pressure
EN 1991-1-4 §7.2.9Internal pressure — each case applied to ALL internal surfaces uniformly (never mixed sign between faces in one case)
wi = qp(h) x cpi
cpi = +0.20: wi=237.4Pa; cpi = -0.30: wi=-356.2Pa
2 coherent load case(s)
Net Pressures & Forces [EN 1991-1-4 §5.3]▼
Net Pressures & Forces
EN 1991-1-4 §5.2(3) / §5.3(4)Net pressures and along-wind MWFRS force — case "cpi = +0.20"
wnet = we - wi; Fw = cscd x [Sum(wnet,windward x A) - wnet,leeward x A,leeward]
windward wnet: 712.3 Pa; leeward wnet: -850.8 Pa
Fw = 937.89 kN
EN 1991-1-4 §5.2(3) / §5.3(4)Net pressures and along-wind MWFRS force — case "cpi = -0.30"
wnet = we - wi; Fw = cscd x [Sum(wnet,windward x A) - wnet,leeward x A,leeward]
windward wnet: 1305.9 Pa; leeward wnet: -257.2 Pa
Fw = 937.89 kN