This report supplements and extends the scope of Report No. 319, ;lStructural Performance of Light Gage Steel Diaphragms , by Dr. Larry D. Luttrell. Eleven static load tests were conducted on 22 gage narrow rib roof decks to investigate the effect of length of the diaphragm, type of welding, and diaphragm material tensile properties on the shear stiffness and strength of the diaphragm. The behavior of a diaphragm under reversed load at two different levels) one at 0.4 x ultimate static load and the other at 0.6 x ultimate static load was explored by conducting five tests. The tests at a high level of reversed load (0.6 x Pu) were motivated by the fact that during earthquakes and blasts structures are subjected to high levels of reversed load for a few cycles. Three static load tests were performed on standard corrugated diaphragms to supplement the tests done by Dr. Luttrell and reported in Report No. 319 so as to formulate the strength (Plf.) of a diaphragm without intermediate fasteners* as a function of its thickness. It is confirmed by the above investigations that the shear stiffness of a diaphragm is dependent mainly on the length of the diaphragm, and the type and spacing of fasteners. The strength of a diaphragm is seen to be dependent mainly on the thickness of the diaphragm, and the type and spacing of the • The definition is the same as in Report 319. fasteners. Five cycles of reversed load at +0.6 x ultimate load of an identical diaphragm under static load resulted in a maximum reduction of 25% in strength of the diaphragm
