Wind Load Calculator — Force on Structures
Wind Force
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Wind Pressure
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Overturning Moment
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Understanding Wind Loads on Structures
Wind load is the force exerted by wind on a structure. The basic formula is F = 0.5 x air density x velocity squared x drag coefficient x area. Wind pressure increases with the square of speed: doubling wind speed quadruples the force.
The drag coefficient (Cd) depends on shape: flat plates have Cd around 2.0, cylinders about 1.2, and spheres about 0.47. Streamlined shapes experience much less drag. Building codes use detailed methods accounting for gusts, terrain, and building height.
The overturning moment is the wind force times the height at which it acts, representing the tendency to topple a structure. This is critical for sign design, fence posts, towers, and tall structures. Foundation and anchoring must resist this moment.
Frequently Asked Questions
Why does doubling wind speed quadruple the force?
Wind force is proportional to velocity squared (F = 0.5 x rho x V squared x Cd x A). So doubling V means the force increases by 2 squared = 4 times. A 100 mph wind exerts 4 times the force of a 50 mph wind.
What wind speed can a house withstand?
Standard wood-frame houses are designed for 90-110 mph winds (ASCE 7 basic wind speed). Hurricane-resistant construction in coastal areas is designed for 120-180 mph. Tornado-resistant structures need special engineering.
How do building codes handle wind?
ASCE 7 (in the US) provides detailed wind load calculation methods considering risk category, exposure category (terrain), topographic effects, building height, and internal pressure. This calculator uses a simplified approach.