Base isolation for mid-rise buildings in presence of soil-structure interaction

Abstract

Base isolation has been commonly used for seismic protection of lowrise (short period) buildings on firm ground. For taller buildings on soft soil, however, the following concerns arise: soil-structure interaction (SSI) alters the resonant characteristics of the whole system and its dynamic response. The efficiency of base-isolation depends on the dynamic properties of the system and the shape of the site response spectrum. In this work, SSI effects on the dynamic response of base-isolated mid-rise buildings are examined. A discrete shear-building model with linear elastic elastomeric bearings and flexible foundation is analyzed by a suitable method for systems with non-classical damping. The model is applied to evaluate the feasibility of using seismic isolation at soft-soil sites of Mexico City, where typical buildings of 10–15 stories were the most damaged during the great 1985 Michoacán earthquake. It is concluded that base isolation can be effectively used to control the detrimental SSI effects anticipated for these buildings located at sites with dominant period longer than the fundamental fixed-base period of the superstructure.