Seismic Demand Evaluation for a Three-Span Curved Bridge Crossing Fault-Rupture Zones

Abstract

This paper evaluates the seismic demands for a three-span curved bridge crossing fault rupture zones. Two approximate procedures which have been proved adequate for ordinary straight bridges crossing fault-rupture zones, i.e., the fault rupture-response spectrum analysis (FR-RSA) procedure and the fault rupture linear static analysis (FR-LSA) procedure, were considered in this investigation. These two procedures estimate the seismic demands by superposing the peak values of quasi-static and dynamic bridge responses. The peak quasi-static response in both methods is computed by nonlinear static analysis of the bridge under the ground displacement offset associated with fault rupture. In FR-RSA and FR-LSA, the peak dynamic responses are respectively estimated from combination of the peak modal responses using the complete-quadratic-combination rule and the linear static analysis of the bridge under appropriate equivalent seismic forces. The results from the two approximate procedures were compared to those obtained from the nonlinear response history analysis (RHA) which is more rigorous but may be too onerous for seismic demand evaluation. It is shown that the RSA and LSA procedures which require less modeling and analysis efforts provide reasonable seismic demand estimates for practical applications.