Implementation of a Simplified Method in Design of Hysteretic Dampers for Isolated Highway Bridges

Using seismic isolation systems for highway bridges modifies the structure's principal vibration modes and effectively reduces the seismic base shear conveyed from the superstructure to the substructure. However, for some low-damping rubber isolation bearings, large displacements can be a problem. Supplemental hysteretic dampers can be introduced into the base-isolated bridge, which might nevertheless increase the structure base shear, and the merit of adding dampers has to be evaluated properly. In this paper, a simplified method was implemented for the design of a low-cost hysteretic damper, and the resulting isolator-damper system was tested experimentally. The design method used is based on an equivalent linearization approach. A full-scale elastomeric isolation bearing was characterized and used in the design of a hysteretic damper. Both the isolator and the damper went through cyclic testing and real-time dynamic substructuring (RTDS) methods to verify the capacity of the method to design base isolation-damping systems. The study was further extended to extreme seismic loading by nonlinear time-history analysis. The results reveal that the simplified method is adequate for use in the performance optimization of isolated-damped bridges. (C) 2016 American Society of Civil Engineers.