How to Calculate Wind Load on a Large Flat Surface
- 1). Determine the surface area exposed to the wind. Assume there is a billboard that has the dimensions of 20 feet by 40 feet. The surface area is length multiplied by width or 20 times 40, which is 800 square feet.
- 2). Determine the wind speed or wind velocity measured in miles per hour. Assume a hurricane has sustained winds of 100 miles per hour (arbitrary value). Air has a density of 0.075 pounds per cubic foot.
- 3). Determine the force of the wind load on the billboard. This is done using the formula F = 1/2 rho x v^2 x A x C where F is the force of the wind load in pounds, rho is the air density, v is the wind velocity, A is the surface area of the billboard and C is a dimensionless drag coefficient (assumed to be 1.0). The calculation yields 1/2 x 0.075 x 100^2 x 800 x 1.0 or 300,000 pounds of force which is substantial.
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