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RE: Commercial Construction Standards

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-----Original Message-----
From: Dennis Wish [mailto:wish(--nospam--at)]
Sent: Tuesday, July 28, 1998 10:17 PM
To: SEAOC Listservice
Subject: Commercial Construction Standards

b) Should I follow '94 code and distribute lateral according to an Rw of 6
or follow the '97 code and take the penalty for the pendulum condition?
Also, if I follow '97 UBC convention should I use the lateral component for
the entire building or just the embedded poles?

[Bill Allen]
The Rw=3 requirement for inverted pendulums appears in the 1996 Accumulative
Supplement to the 1994 UBC. So, you don't have to ponder this one. The only
debatable issue is the application of Rw=3 to all elements in the same
direction as your inverted pendulums. If you have significant lengths of
wood shear walls on three sides, this is a ridiculous requirement, IMO as
well as the opinions of several who attended SEAOSC's seminar on the 1997
Seismic Provisions. I believe LA City has adopted a much more practical
approach (Tim McCormick, are you still here?). I believe their approach is
something like this: you apply the Rw=6 to the distribution. When you design
your inverted pendulums, you multiply your force by 3Rw/8 and do not use the
1/3 increase in allowable stresses.

4. 3(b) leads to this question - Has the SEAOSC code committee taken a
position yet regarding embedded column lateral design. It was suggested in
their minutes that they intended to take the position that only the columns
be loaded with higher shear in order to compensate for story drift. Any
comments yet?

[Bill Allen]
Good question.


Any comments you might have would be greatly appreciated. At the least,
please let me know if you think I am on the right track.

Thanks in advance for all advice.
Dennis S. Wish PE

Bill Allen