Section 26.1/Wind Load Parameters
ASCE 7-22 Chapter 26 establishes wind load design parameters including basic wind speed, exposure category, and topographic effects.
Wind load design requires determining several parameters before calculating pressures. The basic wind speed (V) is read from the wind speed maps in Chapter 26 for the applicable risk category. The exposure category (B, C, or D) is determined by the surrounding terrain roughness. The topographic factor (Kzt) accounts for wind speed-up over hills and escarpments. The wind directionality factor (Kd) accounts for the reduced probability that the worst wind comes from the critical direction. These parameters feed into the velocity pressure equation q = 0.00256 Kz Kzt Kd Ke V-squared.
Why this section exists
Wind loads are one of the primary lateral force systems that every building must resist. The design parameters translate the local wind climate and site conditions into the velocity pressure that acts on the building surfaces. An incorrect exposure category or wind speed can change the design wind pressure by 30% or more, directly affecting the structural member sizes and connections.
What plan reviewers look for
Plan reviewers check the structural general notes or wind load summary for the basic wind speed, risk category, exposure category, and all applicable factors. They verify the wind speed against the ASCE 7 maps for the project location. They check the exposure category against the site description and aerial imagery. They verify that topographic effects are considered if the site is on or near a hill.
Common violations
Related ASCE 7 requirements
Section 26.7 covers exposure categories in detail. Section 26.8 covers the topographic factor Kzt. Chapter 27 covers wind loads on the main wind force resisting system. Chapter 30 covers wind loads on components and cladding.