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Plywood shear walls with 3x sills...

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Hello again,

I have a few questions regarding U.B.C. Table 23-II-I-1, footnote no. 3
(fourth printing):

1.  The requirement is that in seismic zones 3 & 4 where "allowable shear
values" exceed 350plf, 3x sill plates and 3x framing members where panel
edges meet are required. Suppose I had a shear wall with 19/32" C-D plywood
on both sides of the wall with 10d nails at 6"o.c. The individual "tabulated
allowable shear value" is 340plf, however with two layers, the "total
allowable shear value" would be twice as high. Since the "tabulated" value
of the individual panel used is less than 350plf, would the 3x member
requirements still apply?  [By the way, I think this is a silly question
since, practically speaking, It seems that the intent is for the allowable
shear value of the "total" wall pier (i.e. regardless of whether one or two
layers of plywood is used), not just the tabulated value. I believe this
came in response to Northridge.]

2.  How does this requirement relate to "upper-level" shear walls? They do
not have "foundation plates" nor "anchor bolts".

3.  I've had some contractors whine (no...really?) about this, saying that
they either cannot get 3x pressure-treated members or they are very
expensive. Some building officials also are not enforcing this
(no...really?). Anyone run across this?


Thanks for your responses (in advance).

Dave K. Adams, S.E.
Lane Engineers, Inc.
Tulare, CA