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1997 AISC seismic - IBC seismic design category D - OBF brace co nnections - column strength

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Hello :


I don't think this went through so I am sending it one more time.  1997 AISC
Seismic Provisions Section 4.1 indicates orthogonal effects are not required
with special load combinations including OMEGAo*Qe.  

IBC 1620.3.5 always requires orthogonal effects to be considered for Seismic
Design Category D.  IBC 1617.1.2 does not say that orthogonal effects are
not required when considering the special load combinations in the IBC.
1997 UBC only required orthogonal effects for highly loaded columns at
intersecting lateral systems, non-parallel systems and torsional
irregularities and didn't say orthogonal effects did not need to be
considered with special load combinations for ASD steel design [it did for
LRFD].

It seems the intent of the IBC is to use the orthogonal effects with the
special load combinations in Seismic Design Category D.  Is this an
oversight in the conversion to the IBC from the UBC, that the AISC
provisions were not amended?  Should orthogonal effects be included in
special load combinations for columns, and brace connections in Seismic
Design Category D?  For tension only braces?


Thanks,



Scott M Haan P.E.
Plan Review Engineer
Building Safety Division http://www.muni.org/building
Development Services Department
Municipality of Anchorage
phone:907-343-8183  fax:907-249-7399
mailto:haansm(--nospam--at)ci.anchorage.ak.us



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