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Re: Competing Codes

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> From: "Randy Russ" <rruss(--nospam--at)eatel.net>

> Paragraph 1606.1.1 of the Standard Build Code states, "Wind forces on =
> every building or structure shall be determined by the provisions of =
> ASCE 7." Five exceptions to this are then listed. Nowhere in the =
> exceptions are telecommunication towers, water towers or metal =
> buildings. I suspect other building codes are similar to SBC in this =
> regard.
> 
> Telecommunications towers are routinely designed for EIA/TIA-222-F. =
> Water towers use a code put out by AWWA. Metal building manufacturers =
> design to an MBMA code.
> 
> My question is this. By what legal authority are these other codes =
> allowed? I am somewhat familiar with EIA/TIA. In the first paragraph =
> they state that "....these standards are not intended to replace or =
> supersede applicable codes." If the EIA/TIA code is used without =
> checking against ASCE 7, isn't that superseding?

MBMA (Metal Building Manufacturers Association) produces an industry
practices manual - Low Rise Building Systems Manual - which is not a
"code" and has no specific legal capacity. It is a set of guidelines,
commentary and information for the application of loads and model
concepts to low-rise metal buildings. It does not cover occupancy
classifications (e.g. SBC) or structural analysis methods (e.g. AISC).
It should be superseded by locally applicable design standards and codes
where appropriate. That said, most aspects described in the MBMA manual
are generally within the practices of model building codes.

As Greg Effland pointed out, where no explicit building code exists,
MBMA is the typical default used by the manufacturer. However, the
conservative practices described for Butler and some other manufacturers
are not necessarily adopted by all manufacturers.

If you are EOR on a project and accept a building qualified to MBMA, you
should have a copy of the manual in your hands. In fact, I believe that
it is a requirement, in some codes, that the manufacturer provide this
with their design submittal (in practice, only provided if requested).

I don't have my copy of SBC at hand but you may want to check for
specific inclusions, rather than exclusions, for the towers. Ditto
ASCE7, including references and commentary. 

-- 
Paul Ransom, P. Eng.
Civil/Structural/Project/International
Burlington, Ontario, Canada
<mailto:ad026(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>

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