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Re: diaphragm does a structure make?

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I would classify your condition as a non-building structure and use the provisions of section 1634.  The individual pipe support systems and attachments to the structure would be considered using section 1632.  The lack of a diaphragm is not really the determining factor.
There is an excellent discussion regarding non-building structures and design, including specific commentary on pipe-rack systems, in the Blue Book commentary.
----- Original Message -----
From: da
Sent: Thursday, May 20, 2004 6:04 PM
Subject: diaphragm does a structure make?

situation:  hss columns, hss beams, and light rod bracing.  in the longitudinal direction, the "structure" resists lateral forces by "moment frame action".  in the transverse direction, the "structure" resists lateral forces with the rod bracing.  the "structure" carries misc. piping. 
someone was given the task to look at seismic.  that person thought, "even though this isn't a classic building, it is made of steel components and resists lateral forces in a 'moment frame / braced frame' manner.  they then calculated the corresponding base shears, V."  someone else thinks "this isn't a classical building, it doesn't have a diaphragm, and should resist Fp forces".
questions:  which method is right?  should a non building structure V be used? or is there a different, better way?  if these frames look like bears, smell like bears, and eat like bears - are they bears?  shouldn't they follow the provisions for steel frames?  does the lack of a diaphragm automatically demote these components to a 'non building structure'?