Parametric Study of Base-Isolated Structures

Abstract

A parametric study of base-isolated structure with different isolation systems is conducted for understanding their dynamic behaviour. The superstructure is idealized as a one-storey structure isolated by different isolation systems. The various isolation systems considered are: the elastomeric bearings (with and without lead core) and the sliding systems (with and without restoring force). The governing equations of motion of the isolated structural system are derived and solved in the time domain. Three time histories of simulated earthquake ground motion are applied to the isolated system and the peak average superstructure acceleration and bearing displacement of the system are plotted under different system parameters in order to study the comparative performance of different isolation systems. The important parameters considered in the study include (i) the time period and damping of the superstructure, (ii) the ratio of the base to superstructure mass, (iii) the isolation period, damping and yield strength of the elastomeric bearings and (iv) the isolation period, damping and coefficient of friction of the sliding systems. It was found that the above isolation system parameters significantly influence the earthquake response of structure. However, the damping and the period of the superstructure do not have noticeable effects on the peak response of base-isolated structure. In addition, the effects of viscous damping are found to be insignificant when the additional damping in the isolation system in the form of such as hysteretic (due to yielding of lead-core) or friction is present.