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RE: Diaphragm Calculations

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	Oops! I forgot to include the subject, so here it goes again:

	"Dennis, I know that you have frustrations with the changes related
to wood 
	frame designs, as do others.  But your response to Doug seems a bit
	Both Doug and Bill are not the authors of these code changes, these
	were proposed by SEAOC seismology and adopted by ICBO for inclusion
in the 
	1997 UBC.  Doug and Bill are the ones that were asked to develop
	showing how to implement these code changes and what would now be
involved to 
	satisfy these requirements.
	Michael Cochran"

What code change? 

I am still baffled by why so many people think this is a code change.  The
fact that this procedure was used in an example problem solved for a code
change seminar does not make it a code change. The criteria for distribution
of horizontal forces have not changed since the 88 UBC. 

Engineers have been designing wood framed buildings assuming the wood
diaphragm as flexible for the past 10 years (and many years before that)
since this was incorporated into the code. Numerous buildings designed and
built with this assumption have been tested in the past earthquakes (Loma
Prieta, Northridge, etc.).  As far as I know there has been no documentation
that this assumption led to any significant life safety or even
non-structural damage. John Rose of APA also previously attested this to in
an earlier posting on this subject. To the contrary there was substantial
documentation of damage to buildings that used diaphragm in rotation in
resisting lateral loads, which is down the path that the new line of
thinking is leading to.

Any way, please don't refer to this as a 97 UBC code change. 

Ben Yousefi, SE
San Jose, CA