[TowerTalk] wind loading

[Chanel1096@aol.com]

In a message dated 4/7/00 10:19:53 AM Eastern Daylight Time, K7LXC@aol.com 
writes:

> In a message dated 04/06/2000 9:32:42 PM Pacific Daylight Time, 
>  alwilliams@olywa.net writes:
>  
>  > My local area regulations require meeting 80 mph winds.  Is there a 
simple
>  >  derating factor for ratings for 70mph to 80mph?

The conversion of wind speed (mph) to pressure (psf) is  

    pressure = .00256*V^2

So it is a parabolic function.  Keep in mind however that is purely a 
conversion formula and is modified by quite a few factors to determine the 
actual pressure used, including and not limited to exposure factors, gust 
modifiers, terrain modifiers, shape factors, and the boundary layer equation. 
 Also keep in mind that a derating factor, if applicable, would work for self 
supporting or monpole structures.  Guy towers do not follow the rules, 
increasing the wind load does NOT result in a uniform increase in stress on 
the tower members.  Guy towers are extremely fickle and sensitive to load 
location.  

-Bill 

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