Retrofit strategies for seismically vulnerable houses built in urban areas

Abstract

In consideration of strong needs for cost-effective seismic retrofit for old houses built in urban areas, proposed is a type of retrofit techniques in which detached houses are linked together by inexpensive materials like ropes, cushions, and others. A series of shaking table tests were conducted with the type of linking, type of linking elements, and type of motions as major test variables. Although the linking elements exhibit strong nonlinearity because of gaps, slacks, etc., it is noted that they could be approximated to equivalent linear elements. Analytic formulations are presented for the equivalent linearization of the linked systems, and equivalent elastic stiffness and viscous damping ratios are derived as a unified function of the stiffness of the linked systems, stiffness and damping of the linking element, and length of the gap or the slack. The effectiveness of the analytical expressions was demonstrated in comparison with the results obtained numerically. Discussion was also extended to the inexpensive materials that may be applicable in real implementation of the system proposed in this study.