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Re: Relative Stiffness of Wood Shearwalls

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For what it is worth, in LA and Santa Monica it is not permissible to use
proprietary systems in the same line as wood shear walls. I jockey the
shear wall nailing (and sometime use plywood on two sides on the shorter
walls) so that the drift of all walls in the same line are approx. equal

And then in  SM use the rigid diaphragm analysis as prescribed. In LA it
is premissible to use the flex. diaphragm analysis and add a 20%
surcharge.

Stan Scholl, P.E.
Laguna Beach, CA


On Fri, 14 May 2004 12:36:29 -0700 "Paul Crocker" <pcrocker(--nospam--at)reidmidd.com>
writes:
> "I've always believed that it is best to calculate a uniform drift if 
> you
> design plywood shearwalls according to stiffness rather than simply 
> to take the diaphragm shear and divide it uniformly into the total 
> length of wall on hand."
> 
> My understanding is that the implications of the research behind the 
> new code provisions in the '03 IBC 2305.3.3 for aspect ratios 
> between 2:1 and 3.5:1 is that assumed uniform plf shear 
> distributions for walls of different lengths isn't too bad when used 
> for reasonable aspect ratios.  It isn't exactly right, but it seems 
> to work out well enough.  The meaning of the word "best" in your 
> statement is tough to quantity, but it looks like the traditional 
> assumptions work well for many cases.  If you start mixing and 
> matching light-framed walls and proprietary systems along the same 
> line, or perhaps mixing light-framed walls with different plywood 
> thicknesses and nail spacings along the same line (not sure why you 
> would do the latter if the plf can be taken to be the same), then 
> the outcome might be different.  As with most things, the more 
> "cook-book" the method you want to use the more you have to limit 
> the method's use to fairly typical cases, and not to very unique 
> cases.  
> 
> Paul Crocker, PE, SE
> 
> 
> 
> 
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