Validation and Implementation of a Simplified Analysis Procedure for Bridges Crossing Earthquake Fault Ruptures

This paper discusses the implementation and validation of an approximate analysis method for determining the seismic displacement demands of curved bridges crossing fault rupture zones. The considered method is the Fault Rupture-Response Spectrum Analysis (FR-RSA) procedure, which was initially developed for ordinary straight bridges crossing fault ruptures and has been recently shown to be adequate for curved bridges crossing fault ruptures. In the FR-RSA method, the bridge displacement demands are estimated by superposing the peak values of quasi-static and dynamic bridge responses. These responses are respectively calculated by combining nonlinear static analysis of the bridge under the ground displacement offset associated with fault rupture and peak response from linear response spectrum analysis. An actual three-span curved bridge in California was selected and analyzed in this paper. The bridge displacement demands were first estimated by implementing the FR-RSA procedure in the Open System for Earthquake Engineering Simulation (OpenSees), which captures the nonlinear bridge pier response using fiber elements with distributed plasticity. Secondly, the procedure was implemented in CSiBridge TM which has a user friendly interface and considers the nonlinear bridge pier response through beam-column elements with lumped plasticity. The paper compares the results from OpenSees and CSiBridge TM . It is shown that the FR-RSA implemented in CSiBridge TM provides results similar to those from OpenSees.