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[Towertalk] Wind pressure calculations (2/3 factor)

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Subject: [Towertalk] Wind pressure calculations (2/3 factor)
From: (Michael Keane, K1MK)
Date: Wed, 27 Feb 2002 21:30:30 -0500
At 08:00 PM 2/27/02, Richard Karlquist wrote:

>One thing has become a least a little clear:
>you only use the 2/3 with the .004 wind pressure coefficient
>and you do NOT use the 2/3 with the .00256 wind pressure
>coefficient.  What you don't want to do is use
>the 2/3 with .00256 and get an optimistic number.

Another thing that may not be so obvious is that one should only be using 
the RS 222-C coefficients (2/3 & 0.004) with basic wind speeds read from a 
RS 222-C wind zone map, not with basic wind speed from more recent maps 
were revised along with coefficients (1.2 & 0.00256) in EIA 222-D (1986).

Many locations that were designated Zone A (86.6 mph) under RS 222-C were 
relabeled as 70 mph or 80 mph in EIA 222-D. If you plug a basic wind speed 
taken from EIA 222-D (or the current EIA 222-F) into the RS 222-C formula 
you would also get an optimistic number that under estimates the peak 

Mike K1MK

Michael Keane, K1MK

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