The seismic design of plywood sheathed shear walls.

A design methodology for earthquake resistant plywood sheathed shear walls is presented. The sheathing nailing is selected as the ductile load limiting element, whereby the large displacement demands imposed during an earthquake can be sustained without failure of the timber members in bending, shear or tension. Analytical models for predicting the elastic behaviour and ultimate strength of shear walls are formulated in order to develop the design procedure. An experimental study of nailed sheathed joints was undertaken, and showed that such joints were able to sustain large reverse cycles well into the inelastic range. Complementary to the experimental study, an analytical strength model for nailed joints is described, and identifies nail diameter, nail length and nail coating as being the variables most influential on joint strength. Eleven full scale plywood sheathed shear walls were subjected to reverse cyclic quasi-static loading and shaketable excitation. The performance of the sheathing nailing, framing connections and anchorage connections is reported in detail. The test walls exhibited progressive stiffness degradation resulting in pinched hysteresis loops, prior to failure through the nail heads pulling through the plywood, or the nail point withdrawing from the framing. A theoretical time-history single degree of freedom idealisation is described to predict the dynamic response of shear walls. Theoretical predictions compared well with the experimental shaketable behaviour of the full scale test walls. The displacement demands on shear walls which exhibited pinched hysteresis loops are compared with the corresponding displacement demands on an elastoplastic structure