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RE: ASD vLRFD

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Title: RE: ASD vLRFD

You can avoid tracking two sets of load factors if you use the alternate load and strength reduction factors in Appendix C of ACI 318-99.

-- Joel

-------------------------
Joel Adair, EIT
Halff Associates, Inc.
E-mail: jadair(--nospam--at)halff.com
-------------------------


-----Original Message-----
From: HAWNENG(--nospam--at)aol.com [mailto:HAWNENG(--nospam--at)aol.com]
Sent: Wednesday, December 19, 2001 11:38 PM
To: Seaint(--nospam--at)seaint.org
Subject: RE: ASD vLRFD


Having not posted anything to the list server in many months, I could not
help but "weigh-in" on this discussion (pun intended).  Our office uses
nothing but "allowable stress design" and has since 1981.  We find that many
times, our design is governed by deflection, not stress.   We check
deflection at two stages, immediately after the mud is poured and then for
total deflection.  For "mud load" deflection, we try to limit the deflection
to 1/2".  Often times, rather than camber a steel member, we will increase
the member size by a few pounds to limit the deflection.  In the discussion
to date, I haven't read how deflection and floor vibrations play a role in
sizing the steel members.  We also design and detail all our steel
connections on the structural drawings then review the shop drawings to help
ensure the contractor is interpreting the drawings as intended by our design.

Not that this is necessarily the best way to design, but ASD gets my vote. 
Also, when it comes to the foundation design, you have to track two sets of
different load factors.  Yes, we do design concrete by ultimate stress
design.  We are definitely middle-aged engineers, but not real old-timers,
yet.

Greg Showerman, S.E.
Modesto, California
 

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