The design wind pressures for buildings of all heights in lb/ft² is determined according to the following equation:

p = q G Cp - qi(GCpi)

(27.3-1)

The current implementation assumes that building is enclosed and sealed, so that internal pressures cancel each other. Therefore, the wind pressure equation becomes

p = q G Cp

where

G	=	Gust-effect factor (26.11). For rigid buildings, it is either 0.85 or it can be calculated according to Section 26.11.4. For flexible buildings, it is calculated according to Section 26.11.5. Methods given in both Sections are implemented.
Cp	=	External pressure coefficients (Figure 27.3-1). A value of 0.8 is used for Windward wall and an interpolated value is used for Leeward wall (Figure 27.3-1)

The velocity pressure, q (lb/ft²), is calculated as follows:

where

Kz	=	velocity pressure exposure coefficient (26.10.1) and it is determined based on exposure type (user input) and height above ground (see Table 26.10-1). Alternatively, it is allowed to use the following for Kz: $K_z=\{\begin{array}{cc}2.01 {\left(\frac{z}{z_g}\right)}^{\frac{2}{\alpha }}& 15 ft\le z\le z_g \\ 2.01 {\left(\frac{15}{z_g}\right)}^{\frac{2}{\alpha }}& z<15 ft\end{array}$ In which zg and α are defined in Table 26.11-1. The equations given above are used in this implementation.
Kzt	=	topographic factor (26.8.2). It can be a user input value or alternatively, it can be calculated from $K_{zt}={(1+K_1{K}_2{K}_3)}^2$ (26.8-1) in which K1, K2 and γ for K3 are user input values . If Kzt is provided directly, it is used for all heights. Otherwise, variation in Kzt is considered according to Equation 26.8-1.
Kd	=	wind directionality factor (26.6) (user input). It is determined from Table 26.6-1. For building type structures, Kd is given as 0.85. The value is hard-coded in the implementation (i.e., you are not allowed to enter a value for Kd).
Ke	=	ground elevation factor (26.9) (user input)
V	=	Basic wind speed (Section 26.5) (user input)