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
Michael Keane, K1MK