[TowerTalk] windload

[Pete Brunet]

Hi, I didn't get a response on my last note about wind load.  Maybe I am
getting into an unknown area.  Here is a summary of those questions.  These
questions are related to Rohn 45.

Since Rohn's wind loads are substantially higher for a house bracketed 70'
tower (at 56' and 28') (32 sq. ft. at 70 mph) than a tower with their two
recommended guys at 35' and 65' (9.5 sq. ft. at 70 mph assuming tower has 8 sq.
ft. for sidearms and 6 transmission lines coming up the sides), how much extra
wind load, if any, would be gained by using 3 guys at 23' increments?

Concerning subtracting 8 sq. ft. for the side arms, is that 8 sq. ft. a round
member spec or a flat member spec?

The Rohn notes say that the tower design includes a 1/2" and 7/8" transmission
line on each of the three faces.  Ours will only have two (probably .5 inch) so
it appears that I can also subtract the surface area of the missing 4 lines (1
1/2" line and 3 7/8" lines), i.e. ( 70' * (1/2 + 3 * 7/8) / 12 ) * .6 ) = 10.9
sq.ft.   But that assumes that wind load of the coax along the side is the same
as the wind load for an antenna at the top, which probably isn't equivalent.
Does anyone know how much is the right amount, if any, to subtract for the
unused coax?

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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