I am trying to compare the FEMA 273 equations for the deflection
computation of blocked and unblocked plywood diaphragm
The unblocked diaphragm stiffness is given by equation 8-5 with a G
(subscript: d) value of 800,000 or 400,000 (FEMA 273)
The blocked diaphragm stiffness is given by equation 8-6 & 8-7 (FEMA 273)
Using these equations will yield unblocked diaphragm stiffer than the
It appears that the equation 8-5 may be incomplete and missing the web
shear defection contribution. Using ATC-7-1 one could compute unblocked
diaphragm stiffness which calcs out to be much less than FEMA 273.
Any comments, suggestions???
Niaz A. Nazir, PhD, PE