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RE: 10/lw term in calculation of rho

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Ben Y,

Where in the code does it require that rho be applied to diaphragms?
If I am not mistaken, Fpx (not Eh) is used for the forces on diaphragms. 

Gerard Madden, P.E.
Civil Engineer, Associate
CRJ Associates, Inc.
email: gerardm(--nospam--at)
tel: 650.324.0691
fax: 650.324.0927

> -----Original Message-----
> From:	Yousefi, Ben [SMTP:Ben.Yousefi(--nospam--at)]
> Sent:	Thursday, October 28, 1999 12:22 PM
> To:	'seaint(--nospam--at)'
> Subject:	RE: 10/lw term in calculation of rho
> Frank
> The following was the proposed wording suggested to be inserted after the
> definition of r-max for all other walls:
> "For wood structural panel shear walls, r-max shall be taken equal to the
> shear in the most heavily loaded wall or wall pier multiplied by 4/lw
> divided by the story shear where lw is the length of the wall in feet."
> Another interesting fact is that, there was also a proposal to exempt the
> horizontal diaphragms from application of Rho factor, which also made
> sense.
> But that was unfortunately shut down. (The redundancy equations are based
> on
> the distribution of loads to vertical lateral force resisting systems. Why
> would we want to apply that factor to a horizontal diaphragm? )  
> 	-----Original Message-----
> 	From:	FEMCCLURE(--nospam--at) [SMTP:FEMCCLURE(--nospam--at)]
> 	Sent:	Thursday, October 28, 1999 2:16 AM
> 	To:	Ben.Yousefi(--nospam--at); seaint(--nospam--at)
> 	Cc:	FEMCCLURE(--nospam--at)
> 	Subject:	Re: 10/lw term in calculation of rho
> 	Ben Yousefi,
> 	What was the exact wording of the two APA failed attempts to amend
> the Rho 
> 	factor in 2000 IBC?
> 	Have you reviewed the wording the 1999 SEAOC Blue Book, Section
> 105.1.1, 
> 	which states :  "The value of the ratio of 10/lw need not be taken
> as greater 
> 	than 1.0"?  Would that wording help?
> 	Frank E. McClure