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RE: Design of SMRF

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Sat

1-The requirement for SCWB only applies to members that are part of the
lateral force resisting system. So if you do not need to rely on the beam
and column for your lateral loads you do not have a code compliance issue. 

2-Also section 2213.7.5 of UBC has several exceptions for steel frames in
this regard that could possibly provide some guideline for following in your
case.

3-As far as stiffness and strength irregularity, if you are performing a
dynamic analysis and if you keep the strength of the lower level to at least
65% of the strong story (or Omega times the design force) you will be
satisfying the code requirements (see table 16-L of UBC) in this regard.

Ben Yousefi, SE
San Jose, CA

	-----Original Message-----
	From:	satd(--nospam--at)techie.com [SMTP:satd(--nospam--at)techie.com]
	Sent:	Thursday, February 24, 2000 9:02 PM
	To:	SEAOC
	Subject:	Design of SMRF

	I am resending this.  Sorry for any inconvenience that might have
caused.

	> 
	> Dear Sir/Madam:
	> 
	> The design of a 10 story SMRF demands a "very" strong beam at the
10th floor level due to a very heavy dead load (5 times as much compared to
other floors) at this level.  Rest of the floors carry usual dead + live.
If I am required to meet the SCWB criteria as per the ACI/UBC, then I need
to make the columns supporting the 10th floor and the 11th floor quite heavy
(strong).  However, since my lower floor beams are considerably lighter, I
can relax the strength of the lower floor columns to the extent that it
satisfies both the SCWB criteria at those levels and the strength criteria
from the load combo.  
	> 
	> Is it "PRACTICAL" to have a heavy (strong) column on an
intermediate floor (in order to satisfy the SCWB criteria on that level) and
then curtail the reinforcement on the bottom floors so that a reduced
strength is achieved as required?  I was thinking whether this would
introduce a possible weak story in the 9th floor level where I reduce the
strength by curtailing the reinforcements appropriately.
	> 
	> Thanks very much in advance for your thoughts.
	> 
	> Regards,
	> 
	> Sat
	> 
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