To: SEAonc seaint <seaint(--nospam--at)seaint.org>
Subject: rigid plywood diaphragm??????
From: merrick group <merrickgroup(--nospam--at)compuserve.com>
Date: Tue, 4 May 1999 14:12:06 -0400
Rigid plywood diaphragms are of code and
Maybe something is wrong with the design if
there is a radical difference between analysis
for a rigid or flexible horizontal diaphragm.
Plywood stiffness is nearly directly related to
its nailing shear capacity. The force is
balanced by being delivered to where it can be
resisted. Exception would be large h/t walls
with flexible hold-downs. Replace the HD.
Tributary area methods for the flexible
diaphragms places the rigid diaphragm shear
center near to the mass center.
A test of rigidity is a global concern. Maybe
the deflection test of rigidity should be from
outside to outside wall where extreme affects
of torsion occur.
APA publishes force deflection curves of
wood shear walls. They are flat near their
capacity and continue for a very large
deflection. The walls will eventually share the
load relative to their strength. Compare the
results to the ductility factors of steel and see
which is superior!
The above are issues for discussion only and
are not to be considered as opinions.
David B. Merrick, SE