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Re: SEAOC Blue Book C805.3 Lateral Force Distribution

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In a message dated 8/17/99 9:43:09 PM Pacific Daylight Time, Byainc(--nospam--at)aol.com 
writes:

<< How would this have limited the excessive drift at the open 
 front of the garage which was the main cause of the collapse at Northridge 
 Meadows (there were no deformation compatibility requirements at the time 
 these buildings were designed, even if there was, there is much debate as to 
 how you apply that to a pin-pin one story steel column).  >>

Ben, this was my primary argument against the penalty for embedded columns. 
Seismology considered the stiffness of the lateral support elements in 
structures such as the Northridge Meadows as the cause of failure. I 
contended that it was not an example of a fixed based column but the total 
lack of lateral support (open front). I also heard this from Bob Kazanji who 
also studied the problem at UC Irvine (although is comments are his own and 
not those of his employer:>). 

I think Seismology backed off the position of penalizing the entire structure 
in the direction of the force when there was not adequate justification. The 
problem is that the commentary is worded poorly so as to leave too much room 
for interpretation and unresolved questions of intent. 
Seismology will not budge as they are in a hurry to get this into publication 
and will not authorize further drafts.

My interpretation is that they are allowing the engineer to make the judgment 
call and also to take the liability if it is disagreed by an opposing expert 
witness. The wording is everything.

Dennis