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Re[4]: Big, heavy mast

To: <>
Subject: Re[4]: Big, heavy mast
From: (sawyers)
Date: Fri, 21 Jun 96 08:00:44 cst
A direct hit by a tornado is one of those "Acts of God" that you can't 
engineer against, like having a plane fly into your tower. We had a local 
occurence where a plane hit a guy wire on 700' tower. Sheared the wing off 
the single engine Cessna but the tower stayed up. Now if it had been a 
direct hit on the tower, it would have been a different story. Anyway, in a 
tornado, a bigger threat is the neighbor's garage roof blowing off in the 
gust front away from the tornado and taking out your tower.

I don't use the UBC, very much prefer and recommend Electronic Industries 
Association standard 222 rev E (EIA-222-E). They basically don't recognize 
anything other than Exposure C and have an extra factor based on height of 
the structure. They also do a better job of specifiying how to calculate 
the effective area of everything that is hanging in the breeze. They use it 
on everything up to 2000' so it gets a little hairy. 

There is an even more strigent international standard that is used in 

de n0vyv steve

______________________________ Reply Separator _________________________________
Subject: Re: Re[2]: Big, heavy mast
Author:  Gary Nieborsky <> at ccmgw1
To: <>
Date:    6/20/96 3:52 PM

       At 01:40 PM 6/20/96 cst, you wrote:
>>>>50 lbs. per sq. ft. wind gust
>My calcs show this as at the top of a 110 ft tower in a 110 MPH wind 
>district WOW! You must either live in Alaska, off the coast of NC, on in 
>Here in the upper midwest I figure 25 lbs. per sq. ft. wind gust for an 80 
>foot tower in an 80 MPH wind district. 
>Guess I didn't know how lucky I was! 
>de n0yvy steve

What's the gust factor for a tornado?

I based my tower on 90mph with an Exposure C gust factor.  Sometimes in the 
spring I kinda think maybe D would have been better......

Ain't the UBC fun?

73 Gary K7FR

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