I have just finished getting Bonneville County, Idaho approval for a
building permit to install a US Tower HDX-572 . That approval required that
I have a Professional Engineer review and certify the stress analysis
document for the HDX-572 prepared for me by US Tower.
Bonneville County will not accept a document 'wet stamped' by any P.E
structural engineer who is not licensed by the State of Idaho. I would
expect that might be the case with many other municipalities. Further, it is
my understanding that in 2006 Idaho adopted the IBC-2006 and all new towers
or replacement towers or revisions to towers require that one update the
installation being affected to meet the 2006 code.
This code is SIGNIFICANTLY different from the 1997 code that had existed
previously. The wind force calculations are much more demanding as far as I
can tell. For example, the US Tower marketing documents for the HDX-572
[which are derived from the old code] state that the tower can handle 18
square feet of antenna at 70 mph at a height of 73 feet. [includes 1 foot of
mast]. When transformed to IBC-2006 with a Bonneville County wind speed of
75 mph <exposure C> the stress analysis document states 11 square feet of
antenna at 75 mph at 73 feet.
If you want to use 18 square feet of antenna and meet IBC-2006 you will need
to lower the antennas by about 10 feet or so.
The firm that I used is licensed in WA, OR, UT, MT, ID and WY. Since I have
paid the 'learning curve fee' for doing such certification I thought I would
mention it here and I will make available [by direct email, not on the
reflector] the name of the firm and the engineer at that firm should someone
else need a source of such certification.
Tod, KØTO
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