Structural Performance Of Seismically Isolated And Fiber-Reinforced Concrete Bridges

An analytical study was carried out to assess the improved seismic performance of typical reinforced concrete bridges in California by utilizing two performanceenhancement techniques. The technologies considered were lead rubber bearing isolators located underneath the superstructure and fiber-reinforced concrete for the construction of the bridge piers. Seismic performance was measured in terms of different engineering demand parameters on major bridge components in addition to traditional force and displacement demands. A typical five-span, single column-bent reinforced concrete bridge was redesigned using the two performance enhancement techniques and modeled in the OpenSees structural analysis package. Two alternative designs of the isolated bridge were analyzed, one with elastic column behavior and the other with minor inelastic column behavior (maximum displacement ductility demand of 2). Special reinforcement details were used for the plastic hinge zone of the fiber-reinforced concrete columns, previously tested in a separate experimental study. Pushover and nonlinear time history analyses using 140 ground motions were carried out for the different bridge systems. The static and dynamic analysis results demonstrate the effectiveness of bridge isolation in significantly reducing the displacement and force demand on the bridge piers. The use of fiber-reinforced concrete in the construction of bridge columns results in increased damage-tolerance, shear strength, and energy dissipation under cyclic loading of these structural members. The cost-effectiveness of these two performance enhancement strategies is demonstrated in a companion paper