Analysis, testing, and implementation of seismic isolation of buildings in Chile

Abstract

This article Summarizes the work done by the authors in seismic isolation over the past six years in Chile. First, a general evaluation of the optimal values of the yield level of the isolation system is performed, focusing oil the idea of, but not restricted to, the use of lead-rubber bearings. These optimal values are obtained for two performance objectives: to minimize the base shear in the superstructure and to control the isolator deformation. They were used in the design and construction of two important isolated buildings that are described herein; a short description of the more relevant aspects of the design and implementation of the isolation system in these two buildings is also presented. Furthermore, results from a long testing program conducted on more than 260 full-size elastomeric isolators are Summarized and discussed. It is shown that these experimental results enable the elastomeric compounds to be characterized quite accurately by testing reduced-scale specimens with elastomer thickness identical to that used in the full-size isolators. Also, results front isolator constitutive modeling, scragging, and creep in the short term are briefly discussed. Inelastic analyses were performed in the structures in order to evaluate realistic interstory drift and floor acceleration response reduction factors due to the isolation design used. It is shown that in spite of the isolation system, minor inelastic excursions of the primary structure are expected, leading to smaller drift and acceleration reduction factors than those obtained from assuming an elastic response of the Superstructure. In any case, seismic isolation is shown to be a very competitive alternative, technically and economically, for building design in Chile. Although it may be difficult to extrapolate this experience to other environments, the results presented herein demonstrate that seismic isolation is a technique that can be effectively used to mitigate seismic hazards in developing countries. Copyright (C) 2004 John Wiley Sons, Ltd.