Design Wind Speed:

It is the wind speed for which the structure is to be designed. The basic wind speed, Vb, for any site is modified to include the effect of risk level, terrain roughness, height and size of the structure and local topography. It may be mathematically expressed as:

V_Z = (k₁ k₂ k₃) V_b

where, V_Z = design wind speed at any height z (in m /sec),

k₁ = risk coefficient,

k₂ = terrain, height and structure size factor, and

k₃ = topography factor.