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

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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

	-----Original Message-----
	From:	Seaintonln(--nospam--at)aol.com [SMTP:Seaintonln(--nospam--at)aol.com]
	Sent:	Thursday, July 01, 1999 9:36 AM
	To:	seaint(--nospam--at)seaint.org
	Subject:	'97 UBC - R values for structures with Pendulums

	I understand the basics for using the lowest R in each direction
based upon 
	the resisting elements. However, I can't agree that the entire
structure 
	should be penalized when an block - isolated on three sides - is
designed 
	using embedded columns at the side opposite an adjacent block.

	Assume for the moment that the home was constructed with
conventional 
	Shearwalls of plywood. The R used in the design would be 5.5. 
	A Patio cover (tile or composition roof) was built on the structure
an the 
	pendulums were used to resist shear on the open side.  The R for
this would 
	be 2.2
	The code requires the entire structure in the direction of force
resisted by 
	the columns, to be designed using the lower R value or 2.2.
	I don't accept that, with the exception of the common wall between
the patio 
	and the residence (assuming that the roof diapragm is framed
separately) that 
	any other shearwalls will be substantially influenced by the
stiffness of the 
	columns at the patio?

	Therefore,  how do convince not only the building official to accept
my 
	judgment when I can not prove it by rational analysis?

	Dennis Wish PE