Calculate wind pressure

Jonathan Ochshorn

Directions: Enter values for wind speed (mph); exposure category (B, C, or D); roof height (feet); importance factor (1.0 for normal buildings); plan dimensions, L and B (units in feet; see Fig. 1); K_d, the wind directionality factor (equal to 0.85 when multiple load types are being considered simultaneously, otherwise, 1.0); and K_t, the topography factor (equal to 1.0 for normal conditions, but may be higher for buildings on hills or escarpments). Press "update" button.

More detailed explanations and examples can be found in my text.

Fig. 1. Plan dimensions "L" and "B"

Fig. 2. Windward and leeward wind pressure

Wind pressure is deployed on the "windward" and "leeward" sides of the building as shown in Fig. 2. Note that (a) the windward pressure varies along the height of the building, while the leeward pressure is assumed to be constant; and that (b) the leeward pressure is negative, i.e., pulling rather than pushing on the building. As the windward and leeward pressures act in the same direction, the combined value is found by subtracting the negative leeward values from the positive windward values. Magnitudes of these wind pressures are tabulated below. Works for "rigid" rectangular buildings with flat roofs.

Disclaimer: This calculator is not intended to be used for the design of actual structures, but only for schematic (preliminary) understanding of structural design principals. For the design of an actual structure, a competent professional should be consulted.

First posted July 14, 2009 | Last updated Feb. 15, 2010