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RE: Antenna towers IBC wind load requirement

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As we were developing the seismic regulations, we intended to divert all design and analysis to the TIA/EIA/222-***. There were elements in the process that offered amendments such as requiring a nonlinear dynamic analysis, etc. for guyed telecommunication towers. We rejected their arguments as nonpersuasive. It looks like they were more successful in the IBC process. As you can tell, the requirement you are speaking of only lasted one cycle.

I would just use the 222 without the added IBC stuff. The 222 was intended as a stand alone document. The wind loads, earthquake loads, and ice loads are derived in a unique fashion and not per IBC, ASCE 7, or anything else. For the IBC to pick and choose requirements and arbitrary amplifications is inviting disaster. The IBC requirements are to vague to enforce. The authors of the amendments were well intentioned, but not well informed when it comes to telecommunication towers.

I do not have the latest final version of the 222-G (mine is a draft), but it does have limit state design.

Regards,
Harold Sprague


From: "Haan, Scott M." <HaanSM(--nospam--at)ci.anchorage.ak.us>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: Antenna towers IBC wind load requirement
Date: Fri, 30 Jul 2004 12:50:02 -0800

Anyone:

2000 International Building Code section 3108.4.2 indicates that
"Adequate foundations and anchorages shall be provided to resist two
times the calculated wind load."  I don't have a structural IBC
commentary but heard that there is something written about this.

Is the intent of this section for overturning stability only?  Should
footings  be designed for [1.7*[2*wind]+1.4*D]*75 or [1.7*W+1.4*D]*.75?
Should anchor rods be designed for .9*D+1.3*[2*wind] or .9*D+1.3*D?

Thanks.

Scott M. Haan P.E.
Deputy Building Official


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