I've never seen horizontal values for a 48" span of unblocked 3/4" plywood,
which doesn't mean they don't exist. You may try calling APA. As a side
note, I think that 3/4" plywood is only rated to span 48" maximum for roof
vertical loads when the edges are blocked, unless you use T&G plywood or
panel clips. See Table 23-I-S-1 in the 1994 UBC. This may force the
blocking issue anyway.
Bruce Resnick, SE
Parker Resnick Str. Eng.
In a message dated 4/2/99 10:42:04 AM Pacific Daylight Time, DHLAssoc(--nospam--at)aol.com
<< I have a commercial project where the architect wants to use exposed 3/4"
plywood over exposed 4x rafters at 48" o.c. He does not want to see any
blockings between the rafters. Prelim calcs show maximum diaphragm shear to
be around 150 plf. Does anyone know--- for plywood horizontal diaphragm
values; if there is any place in the UBC where one can find diaphragm shear
values for framing member spacing more than 16" o.c.?