Effectiveness of Seismic Isolation for Cable-stayed Bridges

This paper investigates the effectiveness of elastomeric and sliding types of isolation systems for the seismic response control of cable-stayed bridges. A simplified two-dimensional lumped-mass finite-element model of the Quincy Bay-view Bridge at Illinois was developed for the investigation. The seismic isolation of cable-stayed bridges is achieved using three different isolators, namely, high damping rubber bearings (HDRB), lead rubber bearings (LRB) and friction pendulum system (FPS). Time history analysis is performed for the bridge with four different earthquake ground motions applied in the longitudinal direction using Newmark's method with linear variation of acceleration over the time interval. The seismic response of the isolated cable-stayed bridge is compared with that of the bridge with no isolation system. The results show that the isolation systems are effective for reducing the absolute acceleration of the deck and the base shear response of the tower. Further, a parametric study is performed by varying the damping ratio, yield strength and friction coefficient of HDRB, LRB and FPS to investigate the influence of these parameters on the seismic response of the bridge. From such a study, optimal values can be found for the isolators for reducing the bridge responses.