Seismic Performance Assessment of an Isolated Multispan Bridge

Displacement-based design procedures get more attention day by day due to their high advantages accounting for inelastic behavior. This paper evaluates seismic performance of an isolated reinforced concrete bridge subjected to different earthquakes. The seismic performances and capacity curves are determined in transverse direction by nonlinear analyses. User-defined plastic hinges are constructed to define force-deformation relationship and specific performance criteria are proposed. The accuracy of bridge performance is evaluated in terms of the criteria suggested by specifications as well. In estimation of lateral strength, the capacity method is used for solutions and seismic responses are shown for different hazard levels, such as design earthquake and maximum earthquake. Vulnerability functions and time-dependent responses are illustrated for the bridge components. Furthermore, influence of the isolation system is also examined to emphasize usage of rubber bearings. The quakes are scaled up to reveal the ultimate performance state leading to the collapse mechanism. Although the analyses show that the bridge meet the performance requirements for strong quakes, the isolator deformations exceed the allowable limits. Furthermore, it has been shown that the user-defined plastic hinge model with proposed performance criteria is able to represent the hinging mechanism and it has yielded reasonable results in accordance with code regulations.