CHAPTER III. 

 WIND LOADS. 



Wind Pressure. The wind pressure (P) in pounds per square 

 foot on a flat surface normal to the direction of the wind for any given 

 velocity (F) in miles per hour is given quite accurately by the formula 



P = 0.004 F 2 (3) 



The following table gives the pressure per square foot on a flat 

 surface normal to the direction of the wind for different velocities as 

 calculated by formula (3). 



Vel. in miles Pressure, Ibs. per 

 per hour. square foot. 



10 0.4 Fresh breeze. 



20 1.6 



30 3.6 Strong wind. 



40 6.4 High wind. 



50 10 . o Storm. 



60 14.4 Violent storm. 



80 25.6 Hurricane. 



100 40.0 Violent hurricane. 



The pressure on other than flat surfaces may be taken in per cents 

 of that given by formula (3) as follows: 80 per cent on a rectangular 

 building; 60 per cent on the convex side of cylinders; 115 to 130 pet 



