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RE: And you think you have plan check problems...

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Judging from the facts given in the article, it does appear that the project does not meet the limitation of the 2001 CBC, on height for concrete shear wall buildings (160 ft). So it appears that they are trying to justify a performance based approach on a non-defined system, rather than meeting the prescriptive requirements of the code. The firm Klemencic is known for pushing the envelope in structural design. One of the items that they pushed for during the ASCE-7 seismic provisions development was to remove any minimum base shear that a building would have to be checked for when considering drift. Imagine designing a high rise and running a site specific dynamic analysis one gets a very small base shear (may be even less than 1%) and that would be all the base shear that drift is checked for! It scares the hell out of me. (We were eventually able to get a minimum of 1% in there, thanks to a few wise engineers such as Dr. Ghosh on the committee)


City of San Francisco has traditionally relied on peer reviewers to basically tell them if a structure is good to go or not. While I believe peer review has a place in the plan check process, there ultimately has to be a knowledgeable person in the building department that considers all comments from the peer reviewers and their own in house (hopefully knowledgeable) plan check engineers and makes a the final decision when things need to be resolved. It appears that Hanson Tom, whom I know personally and respect as a good engineer, is putting his foot down on this. It would be interesting to see how it is resolved eventually.


Ben Yousefi, SE

Santa Monica, CA


From: Haan, Scott M POA [mailto:Scott.M.Haan(--nospam--at)]
Sent: Thursday, December 08, 2005 11:35 AM
To: seaint(--nospam--at)
Subject: RE: And you think you have plan check problems...


What response modification factor R do you use for a shear wall core with outriggers?  This may be a building department doing it’s job or being overzealous.  I am sure the designer kept story drift low enough so the curtain walls would not fall on people.  The outriggers are an integral part of the lateral system limiting drift and I don’t see an R, Cd or OMEGAo for the system in ASCE7 or the IBC.


From: Gerard Madden, SE [mailto:gmadden(--nospam--at)]
Sent: Thursday, December 08, 2005 9:19 AM
To: seaint(--nospam--at)
Subject: And you think you have plan check problems...


Sounds like someone got called on a “performance based design” to me. Pretty interesting article.