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Re: diaphragm does a structure make?

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Da,

Fp (from UBC Section 1632) would be used if your steel structure was on top of or part of another structure.  If your steel structure is a stand alone structure with its own lateral resisting system and own foundation then it would be a "non-building structure" and governed by UBC section 1634.  If your non-building structure has a lateral force resisting system that is "similar" to a building then you would use V from UBC Section 1629 (reference UBC Section 1634.2).  If your non-building structure does not have a lateral force resisting system that is similar to a building then you would use one of the applicable V formulas from UBC Sections 1634.3 through 1634.5.  Whether your structure has a solid diaphragm or not has little to do with it, however, you still need to make sure your structure has a complete load path from top to bottom.

Thomas Hunt, S.E.
ABS Consulting



"da" <dadie(--nospam--at)sbcglobal.net>

05/20/2004 06:04 PM

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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'?
 
tia,
da