At 11:24 AM 9/5/96 -0400, you wrote:
>
>
>I want to calculate the effective wind area of
>a 2" diameter mast that is 72" long.
>
>Therefore 72" X 2" = 144 sq.in = 1 sq.ft.
>
>The calculation above would be accurate if the
>mast were square. But because it's round
>isn't there a constant I neet to multiply the
>result by.
>
>If anyone know this constant please let me know
>and also tell me its source such as EIA-222, etc.
>
>Thanks.
>
>Gene
>WD8OZL
>
>
George,
The shape factor is the number that you are looking for. For round member
shape factor is 1.0. For a flat surface the shape factor is 1.6.
This all factors into the equation: Load in Lbs. = 0.00256 x (V mph)**2 x
Shape Factor x Projected Area.
This is from Section 25 of the National Electrical Safety Code, ANSI
C2-1997. (The bible of electric utilities)
This section has its roots in the UBC regarding wind loads.
It also contains some nifty parts about calculating the wind load on a
lattice work tower and some caveats regarding the use of extreme wind loading.
Hope this helps.
Gary K7FR
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