Wind Pressure Asce7simplified Calculator
Plan your structural engineering project with our free wind pressure asce7simplified calculator. Get precise measurements, material lists, and budgets.
Reviewed by Abdullah, Technical Content Specialist
Formula
qz = 0.613 * Kz * Kzt * Kd * V^2 (Pa) | p = qz * G * Cp
The velocity pressure qz equals 0.613 times the product of the exposure coefficient Kz, topographic factor Kzt, directionality factor Kd, and the square of the basic wind speed in m/s. The design wind pressure p equals the velocity pressure times the gust effect factor G (0.85 for rigid buildings) times the external pressure coefficient Cp for each surface.
Worked Examples
Example 1: Office Building Wind Pressure
Problem:Calculate wind pressure at 12m height for a 150 km/h wind speed, Exposure C, enclosed building, Importance Factor 1.0.
Solution:V = 150 km/h = 41.67 m/s\nKz = 2.01 * (39.37/900)^(2/9.5) = 0.849\nqz = 0.613 * 0.849 * 1.0 * 0.85 * 1.0 * 41.67^2 / 1000 = 0.768 kPa\nWindward = 0.768 * 0.85 * 0.8 = 0.522 kPa
Result:qz = 0.768 kPa, net wall pressure = 0.848 kPa
Example 2: Coastal Warehouse
Problem:Wind pressure for a 10m tall warehouse, V = 200 km/h, Exposure D, partially enclosed.
Solution:V = 200 km/h = 55.56 m/s\nKz for Exp D at 10m = higher due to open terrain\nqz significantly higher due to V^2 relationship\nGCpi = 0.55 for partially enclosed -> much higher net pressure
Result:Design pressures will be significantly higher requiring robust structural connections
Frequently Asked Questions
What is the ASCE 7 simplified wind pressure method?
The ASCE 7 simplified method (Chapter 28) provides a straightforward approach to calculate wind pressures on enclosed low-rise buildings. It uses tabulated pressure coefficients that combine the effects of external and internal pressure into a single net design pressure. The simplified method is limited to regular-shaped buildings with a mean roof height of 18 meters or less, though the full analytical method from Chapter 27 can be used for any building.
What does the velocity pressure exposure coefficient Kz represent?
Kz accounts for the variation in wind speed with height above ground and the terrain roughness. Wind speed increases with height due to reduced friction from surface obstacles. In Exposure B (urban areas), the wind profile increases slowly because buildings and trees slow the wind near the surface. In Exposure D (flat open terrain near water), wind speeds are higher at low elevations because there is little surface friction. Kz equals 1.0 at a reference height that varies by exposure category.
How does building enclosure classification affect wind pressure?
The enclosure classification determines the internal pressure coefficient GCpi. Enclosed buildings have GCpi of plus or minus 0.18, partially enclosed buildings have plus or minus 0.55, and open buildings have zero internal pressure. Partially enclosed buildings experience much higher net pressures because wind entering through an opening pressurizes the interior while suction acts on the exterior, creating an additive effect that can double the net wall pressure compared to an enclosed building.
What basic wind speed should I use for my location?
The basic wind speed is determined from ASCE 7 wind speed maps based on the risk category of the building. Risk Category II buildings (most residential and commercial) use the standard map, while Risk Category III and IV structures use higher wind speeds. In the continental US, basic wind speeds range from about 160 km/h in the interior to over 250 km/h along the hurricane-prone Gulf and Atlantic coastlines. Your local building department or the ASCE 7 Hazard Tool can provide the exact value.
References
Reviewed by Abdullah, Technical Content Specialist · Editorial policy