[TowerTalk] Rohn HDBR48 and International Building Code

Alan C. Zack k7acz at cox.net
Wed Mar 17 17:41:02 EST 2004

Hi Jerry,
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.

Jerry wrote:
> 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.
> _______________________________________________
                                     Alan Zack
                     Amateur Radio Station K7ACZ
                         Las Vegas, Nevada, USA
          Quality Engineer, The Boeing Company, Retired
  Aviation Chief Warrant Officer, U.S. Coast Guard, Retired
        U.S. Coast Guard, Always Ready, Always There
Every hour, Every day, Around the Clock and Around the World
                               SEMPER PARATUS

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