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Re: Plywood use reply (Rigidity and Stiffness).

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Normally, I would agree with you. In the case of the new code, I am not sure 
that that isn't what the code writters are suggesting. The goal appears to be 
to equalize the stiffness of all shear-resisting elements so as to minimize 
torsion in the diphragm. This means balancing shearwalls in adjacent grid 
lines so that they will deflect as close as possible to each other.
The new code also requires the walls in a common line of shear to be designed 
by rigidity - implying that the stiffer wall may actually take all of the 
force at the onset of loading and then transfer shear once the stiffest 
element yeilds. This implies too that each wall in a grid line should be the 
same stiffness. Unless the walls have the same aspect ratio, the only way to 
get them to the save stiffness is to work with their sheathing, nailing (size 
and spacing) or increase the stiffness of the chords and holddowns. 
In the past, I would have said you are right, but am no so sure that this is 
in keeping with the intentions of the new code.


In a message dated 7/20/99 3:29:12 PM Pacific Daylight Time, 
luis(--nospam--at) writes:

<< Dennis- I would not mix thickness or type of plywood.
 My two cents.
 J. Luis Ortega, P.E.
 The Crosby Group-Sacramento,CA
 (916) 563-7600 >>