STUDY OF ELASTOPLASTIC BRIDGE SEISMIC ISOLATION SYSTEM

Seismic isolation beatings consisting of lubricated sliding bearings a nd steel dampers exhibit nearly elastoplastic behavior. Accordingly, t hey can transfer force to bridge substructures which is independent of the level and frequency content of seismic excitation. While this is a desirable property, it is achieved at the expense of potential for d evelopment of significant permanent displacements. This paper reports on a study of one such system that consists of E-shaped steel dampers and which found a number of applications in bridge seismic isolation. The paper demonstrates that indeed significant permanent displacement develop, particularly in earthquakes with shock-loading characteristic s. Moreover, the paper demonstrates the significance of restoring forc e in isolation systems and concludes that the current American Associa tion of State Highway and Transportation Officials (AASHTO) design gui delines for these systems are appropriate.