Narrow Plywood Shear Panels

Abstract

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.

Earthquake Damage to Wood-Framed Buildings in the ShakeOut Scenario

“…With the exception of the City of Los Angeles, most of the building jurisdictions in the areas subjected to the ShakeOut Scenario have relied upon the seismic provisions of the Uniform Building Code (UBC) until very recently. Seismic building codes have progressively incorporated many of the "lessons learned" from past earthquakes, and design and construction practice have evolved significantly through time -although some changes resulted in increased damageability (Schmid et al 1994). In particular, gypsum wall board became prevalent in the 1960s as a low-cost substitute for gypsum lath and plaster.…”

“…From the 1950s to the 1980s, the UBC and other local codes permitted designers to use gypsum wallboard (drywall) and stucco (portland cement plaster) as structural sheathing capable of resisting shear forces from wind and earthquakes. Earthquakes in the 1980s and 1990s produced high levels of damage to buildings sheathed in gypsum wallboard and stucco (e.g., Schierle 2003), and recent tests (e.g., Gatto and Uang 2002, SEAOSC 2001) have demonstrated the stiffness and strength-degrading characteristics of these materials. Since the 1988 UBC, the allowable shear capacity of gypsum walls for wind and seismic forces was reduced drastically in UBC Seismic Zones 3 and 4.…”

Seismic Damage Characteristics of Cripple Walls

“…The above code requirements are generally not based on experimental testing of cripple walls but are based on extrapolation of test results obtained from timber shear walls, which typically have a height-to-length ratio in the range of 1 to 2 (e.g., Ficcadenti et al 1998, Schmid et al 1994. Cripple walls, however, are characterized by much smaller height-to-length ratios, which may result in a lateral response that is different from that of full-height shear walls, since shear deformation may dominate their response.…”

Effect of Numerous Small Deformations Due to Moderate Earthquakes on Seismic Response of Wooden Houses

“…Studies of the shear performance of shear-resisting walls have been conducted in North America on light-frame timber structures [3,4]. Projects, such as the CUREE-Caltech Wood frame project in the United States, have performed static and dynamic experiments on wooden shear walls [5][6][7][8][9][10]. There are also reports evaluating the residual capacity of shear walls after major earthquakes that use energy as an indicator.…”