Experimental Investigations on the Seismic Response of a Base-Isolated Reinforced Concrete Frame Model

Abstract

The existing knowledge based on the physical characteristics of rubber-based seismic isolators and the validity of assumptions involved in design can be strengthened with shake table tests and field monitoring during earthquakes. Existing structures can be retrofitted with seismic isolators and successful examples are coming up day by day. This paper presents the results of analytical and experimental investigations of a one-third scaled model of a reinforced concrete soft first-storied structure mounted on natural rubber-based isolators and subjected to uniaxial seismic motion. Translational and rocking responses of the scaled model were measured under four different synthetic time histories, covering a wide range of frequencies. Through base isolation, the time period of the horizontal mode is far removed from the peak spectrum but the rocking modes may well be entrapped in the peak region. Hence, a simplified fail-safe system for protection against overturning was also studied.