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RE: Tension Only Braces Seismic Zone 3
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: Tension Only Braces Seismic Zone 3
- From: Francois Rambau <Francois.Rambau(--nospam--at)StarBuildings.net>
- Date: Wed, 3 Oct 2001 13:58:47 -0500
tension only bracing is part of the ordinary brace frame (OBF) with an R of 5.6
and omega of 2.2.
provision of chapter 22 shall be applied as required for the steel provisions
(LRFD & ASD)
Are tension only braces allowed in Seismic Zone 3
anymore? I have a large one-story building (covers a swimming
pool) in design and the architect wants to have 100% windows on one
side. So far I'm losing the battle to get some wall piers. The
building is too large to assume that rotation of the wood diaphragm
distributes forces to end walls (cmu walls). The architect currently
will only except diagonal rods in front of the windows (and states that other
engineers, our competitors, wouldn't require anything along this wall - per
similar previous projects before 97 code), and is against tube steel
bracing (braced frame). I can't find anything that either allows
or prohibits this lateral system per the 97 UBC if we use R=2.8 and
Omega = 2.2. I know that the braced frame sections in the code
prohibit tension-only braces but can't find any information on design of rod
tension-only bracing. I also see many issues with
connections and transferring the loads from a glu-lam drag strut/collector
into the steel rods with the omega factor making the loads very high. I
don't like this current system and am looking for justification to
discuss alternate lateral options with the architect. This architect is
a big client of ours.
Thanks in advance for any tension-only input and
Peder Golberg, P.E., S.E.