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RE: 94 UBC and Rigid Plywood Diaphragms??????

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This language is exactly as it appeared in section 1628.5 of 1994 UBC.

	-----Original Message-----
	From:	Cain, William [SMTP:bcain(--nospam--at)]
	Sent:	Monday, May 03, 1999 10:52 AM
	To:	'seaint(--nospam--at)'
	Subject:	RE: 94 UBC and Rigid Plywood Diaphragms??????

	The pertinent section of the 1997 UBC reads:

	"Section 1930.6 Horizontal Distribution of Shear.  The design story
	Vx, in any story is the sum of the forces Ft and Fx above that
story.  Vx
	shall be distributed to the various elements of the vertical
	lateral-force-resisting system in proportion to their rigidities,
	considering the rigidity of the diaphragm.  Se Section 1633.2 for
	elements that are not intended to be part of the

	Where diaphragms are not flexible, the mass at each level shall be
	to be displaced from the calculated center of mass in each direction
	distance equal to 5 percent of the building dimension at that level
	perpendicular to the direction of the force under consideration.
The effect
	of this displacement on the story shear distribution shall be

	Diaphragms shall be considered flexible for the purposes of
distribution of
	story shear and torsional moment when the maximum lateral
deformation is
	more than two times the average story drift of the associated story.
	may be determined by comparing the midpoint in-plane deflection of
	diaphragm itself under lateral load with the story drift of
	vertical-resisting elements under equivalent tributary lateral
	Bill Cain, SE
	Oakland, CA

		-----Original Message-----
		From:	vicpeng [SMTP:vicpeng(--nospam--at)]
		Sent:	Monday, May 03, 1999 10:15 AM
		To:	seaint(--nospam--at)
		Subject:	Re: 94 UBC and Rigid Plywood

		I don't have a copy of the UBC.  Could someone send a copy
of that
	definition of rigid vs. flexible diaphragm?

		Thor Tandy  P.Eng  MCSCE
		Victoria BC
		vicpeng(--nospam--at) <mailto:vicpeng(--nospam--at)> 

			-----Original Message-----
			From: Robert J Bossi, PE < rjbossi(--nospam--at)
	<mailto:rjbossi(--nospam--at)> >
			To: seaint(--nospam--at) <mailto:seaint(--nospam--at)>  <
	seaint(--nospam--at) <mailto:seaint(--nospam--at)> >
			Date: Monday, May 03, 1999 10:08 AM
			Subject: Re: 94 UBC and Rigid Plywood

			I was surprised to find that the current definition
	flexible versus rigid diaphragm first appeared in the 1988 UBC
(2312(e)6 on
	page 148).