ASCE 7-22 Wind Pressure
Velocity pressure and design wind pressure on a building surface using the ASCE 7-22 directional method.
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The engineering
The velocity pressure qz converts the basic wind speed into a stagnation pressure, modified for exposure/height (Kz), terrain (Kzt), wind direction (Kd), and site elevation (Ke). Design pressure on a surface is that qz scaled by the gust-effect factor G and the external pressure coefficient Cp, then combined with the internal pressure qi·GCpi. This card evaluates one surface at a time — run it per wall/roof zone with the appropriate Cp.
The 0.613 constant already bakes in ½·ρ_air at sea level for SI units (use 0.00256 for V in mph, qz in psf). Sign matters: positive Cp is pressure pushing in, negative is suction; internal pressure is applied in both directions, so always check the −GCpi and +GCpi combinations and take the worst for the member you're sizing.
Where this math comes from
American wind provisions grew out of the ASA A58.1 standard first issued in 1945, which turned scattered building-code wind maps into a national loading document. The velocity-pressure form q = 0.00256·V² has anchored U.S. practice for decades, with successive committees refining the exposure, gust, and pressure-coefficient factors as boundary-layer wind-tunnel data accumulated through the 1970s and 80s.
ASCE took over the standard as ASCE 7, and the 7-22 edition (published 2022) updated the wind hazard maps to a multiple-return-period, risk-category basis and added the Ke ground-elevation factor introduced in 7-16. The directional procedure this card follows lives in Chapters 26–27.
- 1945ASA (A58.1 committee)First national U.S. minimum-load standard including wind.
- 1972Alan DavenportBoundary-layer gust-factor approach shapes modern wind provisions.
- 1988ASCEStandard reissued as ASCE 7 with the directional procedure.
- 2016ASCE 7-16Adds the ground-elevation factor Ke to velocity pressure.
- 2022ASCE 7-22Revised wind maps and the qz = 0.613·Kz·Kzt·Kd·Ke·V² form this card evaluates.
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