Narrow Plywood Shear Panels

The Uniform Building Code allows plywood sheathed narrow shear panels having a height-to-width ratio of 3.5-to-one (UBC Table 25-I) to be used as lateral force resisting elements. Previous laboratory testing has concentrated on panels having a height-to-width ratio of one-to-one. This paper presents some results from the testing of plywood shear panels with a height-to-width ratio of two-to-one. Three panels were tested; each was configured to model a different construction scenario. The panels were subjected to fully reversed cyclic pseudo-static loads. Comparison of the results from the three panels indicate that the tie-down anchors must be installed with careful attention to bolt tightening sequence and torque in order to better resist lateral displacements in an earthquake. Vertical dead loads were found to reduce uplift of the panel which, in turn, reduces lateral displacements resulting from panel rotation. Decreased shear values for plywood shear walls subjected to cyclic loading and additional decreased shear values for walls with a height-to-width ratio of two-to-one are recommended.