[TowerTalk] Rohn HDBR48 and International Building Code
Alan C. Zack
k7acz at cox.net
Wed Mar 17 17:41:02 EST 2004
I'm sure someone will have a more accurate or more technical answer to
your question. I'd just like to pass on my personal experiences
similar to yours.
When I moved to this QTH I thought it would be a relative easy matter
to put up a U.S. Towers MA-40 tubular tower. I got the base
foundation drawing from the U.S. Towers (UST) web site. I took it to
my bldg dept and the inspector said the drawing was fine, all I needed
was a Nevada PE wet stamp placed on the drawing. But as I got up from
his desk to leave, he mentioned, by the way, we also need 90 MPH wind
calcs. Those few words have turned into a nightmare. Seems the
industry standard is 50 and 70 MPH wind calcs under the code UBC-97
that most tower companies use. UST told me they were unable to
provide me with 90 MPH wind calcs and I should check back with my bldg
dept as 50 and 70 MPH were standards. I called my bldg dept and they
informed me 70 MPH was the standard under code UBC-97 but most cities
have now gone to 90 MPH wind calcs under code IBC-2000. So I am now
stuck trying to get 90 MPH wind calcs that tower manufactures are
unable to provide. I really want to get this little tower up but it
is like a brick wall. UST sales people tell me they don't have a PE
on staff, they contract PE work out to an outside engineer. I have
been trying to get 90 MPH wind calcs for months and all I get is the
PE haven't gotten back to them (UST sales) yet. I have told them if I
can't get wind calcs for the MA-40 then what about their TMM-541SS or
TX-438 or HDX-538. No answer.
If you have a used tower and have to hire your own PE to do the wind
calcs and provide a base foundation drawing for you from scratch it
may turn out to be an expensive experience. I hope not but be
prepared for the worse.
Hope you have better luck than me.
> Greetings -
> I have a Rohn HDBX48 tower that I wish to install. The City
> Engineer has come across a set of numbers in the International Building
> Codes for our area in Virginia for wind load(?) 90/40. Someone has told
> me that they stand for 90 mph gust and 40 mph with .5 inch of ice. The
> only wind load numbers I can seem to get on this tower is 70mph at 18 sq
> ft antenna. Can anyone help me with the conversion of these numbers.
> Without an answer to this question, I won't be able to get a permit.
> Best regards,
> Jerry K.
> jfk at cablenet-va.com - Please respond to this e-mail.
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