[TowerTalk] Fwd: Comment on twr derating

[UpTheTower]

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Date: Fri, 16 Jan 1998 10:38:22 +0000
From: Hank Lonberg <hank.lonberg@harrisgrp.com>
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To: k7lxc@contesting.com
Subject: Comment on twr derating
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Steve:

I was browsing thru tower talk archives, I'm not subscribed and ran
across the attached message concerning derating a crank-up tower. To
properly derate the tower an engineer needs to look at this case.
Consider the following per the 1994 UBC

the basic stagnation wind pressure formula is   Q= 0.00256 * V*V
where Q is in psf and V is in mph.

This is the basic wind pressure that is modifiec for height, exposure,
gust, importance and
geometric coefficients.

Basically if increase from 50 mph to 80 mph then the increase is:

(80/50)(80/50) = 2.56  due to the fact that it is a function of the
velocity squared.

Hope this helps this gentleman and others.

KR7X / Hank Lonberg P.E. (structural engineer and ARRL VCE)



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