The fundamental equation in Method 2 (Analytical Procedure) for determining the at any given height is:
: The numerical constant accounting for the standard mass density of air and necessary unit conversions. Kzcap K sub z : Velocity pressure exposure coefficient. Kztcap K sub z t end-sub : Topographic factor. Kdcap K sub d : Wind directionality factor. : Basic wind speed (miles per hour, mph). : Importance factor. Step-by-Step Parameter Selection
Urban and suburban areas, wooded areas, or other terrain with numerous closely spaced obstructions. wind load calculation as per asce 7-05
: Urban/suburban areas, wooded terrain, or closely spaced obstructions.
Open terrain with scattered obstructions (e.g., flat open country, grasslands). Exposure D: Flat, unobstructed areas and water surfaces. The formula for Kzcap K sub z The fundamental equation in Method 2 (Analytical Procedure)
Apply the required load combinations (ASCE 7-05, Chapter 2 and relevant code such as IBC) when combining wind with gravity, seismic, etc.
(Use actual ASCE tables for Kz, Cp and enclosure classification in real designs.) Kdcap K sub d : Wind directionality factor
Example: Roof panel in Zone 1, roof height 30 ft, ( q_h = 17.3 ) psf (previous), ( GC_p = -0.90 ), ( GC_pi = +0.18 ): [ p = 17.3(-0.90) - 17.3(0.18) = -15.57 - 3.11 = -18.68 \text psf (suction) ] If positive pressure needed: ( GC_p = +0.40 ) → ( p = 17.3(0.40) - 3.11 = 6.92 - 3.11 = +3.81 ) psf.
) is the 3-second gust speed measured at 33 feet (10 meters) above the ground in Exposure Category C. This value is obtained from the wind speed map provided in Figure 6-1 of ASCE 7-05. Unlike newer codes where wind speeds vary by risk category, ASCE 7-05 uses a single map for all structures, adjusting for risk via an importance factor. 2. Importance Factor (
ASCE 7-05 is a legacy standard (superseded by 7-10, 7-16, 7-22). Use it only if required by a specific existing project or building code. For new designs, use the current edition.
