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Re: '97 UBC - R values for structures with Pendulums

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Thanks Ben, but the fly in the ointment is the term "Flexible Diapragm". I 
can't think of an instance in a two story single family home where the 
diaprhagm will calculate as flexible. With closely spaced shearwalls and an 
aspect ratio approaching 1, the diaphragm automatically will calculate much 
stiffer than twice the story drift - even if the blocked deflection is 
calculated and multiplied by APA's suggested 2.5. 
This, this, becomes extremely limited in where it can be applied (for 
example, a trellis without a plywood diaphragm). 

Am I missing something or is there still a "Catch-22" attached to this 2000 
IBC exception?

Dennis

In a message dated 7/1/99 10:09:38 AM Pacific Daylight Time, 
Ben.Yousefi(--nospam--at)ci.sj.ca.us writes:

<< Dennis 
 
 I agree with your rationale, especially in regard to lightframed buildings.
 It may be of some solace to you that a code change proposal was approved in
 the hearing to the final draft of the 2000 IBC that specifically dealt with
 this issue. An exception was inserted to the section under combination along
 the same axis (1617.6.2), that for light frame "flexible diaphragm"
 buildings of two stories or less in height you may use the appropriate R
 value for the each line of resistance.  The proposal was "Approved as
 Modified". I can't recall what the modification was but you may want to
 contact ICBO to get the whole scoop on that. The code change number was
 S93-99 and was proposed by Dennis Richardson (currently the building
 official in Sacramento) on behalf of the ICBO Structural Review Committee.
 
 Regards,
 Ben Yousefi >>