Parametric Study of Seismic Isolation Properties for Light-Frame Houses

Abstract

Seismic isolation is a proven technology to protect structures from large earthquakes; however, it has not been extensively implemented in light-frame residential houses in the United States because of perceived high costs, despite the susceptibility of residential houses to earthquake damage. To some extent, the high costs in implementing seismic isolation are associated with the need to accommodate large displacement demands. In this paper, parametric studies of isolation systems with a variety of properties show that a high-friction dish sliding system significantly reduces peak displacement demands compared to conventional low-friction sliding systems at maximum considered earthquake intensity, while limiting isolator restoring force under smaller displacements. Owing to the inherent high strength and stiffness to mass ratios in light-frame structures, nonlinear analyses demonstrate that the story drift ratios in a two-story house with high-friction sliding isolators are below the damage threshold deformation level (<0.2% story drift ratio). A high-friction sliding system with a small restoring stiffness, provided by a large-radius concave sliding surface, is proposed as a cost-effective approach to minimizing the risk of earthquake damage in light-frame residential houses. This approach stands in contrast to typical applications of conventional low-force isolation systems, which are best suited to structures with smaller ratios of strength and stiffness to mass.