Experimental and Theoretical Study of a Sliding Isolation System for Bridges

Abstract

A seismic isolation system for bridges has been tested on a shake table. The system consisted of Teflon disc bridge bearings and displacement control devices. These devices provided restoring force for re-centering the bridge during earthquake excitation, additional energy dissipation capacity and rigidity for service loading. The tests were carried out with a 51-kip (227 kN) model which was subjected to strong recorded earthquake motions with a wide range of frequency content, and to simulated motions compatible with CALTRANS 0.6g design spectra. In all tests, the isolated deck responded with peak acceleration less than the peak table acceleration and peak displacement less than the peak table displacement. Furthermore, results are presented on a parametric study of the response of bridges supported by this isolation system. The isolated bridges are subjected to simulated earthquake motions which are compatible with CALTRANS design spectra. The effects of isolation system properties, deck flexibility, pier flexibility, pier strength, distribution of isolation elements and earthquake type are investigated. Finally, simplified, code-type analysis methods for sliding isolated bridges are presented and evaluated.