[TowerTalk] wind load

[Pete Brunet]

I got a chance to look at a Rohn catalog.  In the 45G section there is one
windload chart that shows max wind loads of 32, 23.8, and 17 sq. ft. for 70,
80, and 90 mph.  Then later on separate charts for 70, 90, and 110 mph, for a
70' tower they show wind load figures of 15.9, 15.2, and 9.2 "allowable proj.
area (sq. ft.).  Is "proj. area" on these later three charts the same as an
"antenna area" on the first chart.  If so, why the apparent discrepancy?  We
are considering  20.1 sq. ft. of antenna (see next paragraph).

With a 15' chrome-moly mast with a TH11 (wind load 12.5) at the bottom and a
F12 Magnum 340 (wind load 7.6) at the top does the torque associated with the
force of the top antenna on the 15' mast need to be factored in?  I did not see
any mention of this in the Rohn catalog.

K7LXC reported that Williamson Co. is a 70 mph zone.  What does that figure
mean?  Is this the highest recorded speed over a 100 year period?  By the way
the station will be just South of Williamson Co. in Travis Co.  Is that also a
70 mph zone?

Thanks, Pete ws4g

=====
Pete Brunet -- IBM Special Needs Systems, 11400 Burnet Road, MS 9448, Austin,
TX  78758
(512) 838-4594 voice, (512) 838-9367 fax, brunet@us.ibm.com, ws4g

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