Pushover Analysis of Curved Steel Bridges for Evaluating Seismic Performance and Unseating Prevention

Abstract eng:
Demand on existing bridges for seismic capacity evaluation becomes more crucial and imperative. On the other hand, the performance-based philosophy has been accepted as a more reasonable design concept for engineering structures. For this purpose, capacity evaluation, as a result, and demand prediction procedures for civil engineering structures under earthquake excitations are of great significance. This paper describes a displacement-based seismic performance verification procedure including capacity and seismic unseating predictions for curved steel bridges and investigates its applicability. Prevailing pushover analyses procedure is employed as a primary tool to investigate the bridge’s behaviors under seismic input. A failure criterion for steel members incorporated with the effect of local buckling is considered in the analytical model and an equivalent single-degree-of-freedom system with a simplified bilinear hysteretic model formulated using pushover analyses results is introduced to estimate the displacement capacity and maximum potential unseating mechanism of curved steel bridges under major earthquakes. To check the accuracy of the proposed method, seismic capacities and demands from multi-degree-of-freedom time-history analyses with artificial design earthquake inputs modeling major earthquakes are used as benchmarks for comparison. By a case study, it is clarified that the proposed prediction procedure can give accurate estimations of displacement capacities and demands of the curved steel bridge in the transverse direction, while insufficient tally with for the longitudinal direction, which confirms the conclusion drawn in other structure types about the applicability of pushover analyses.

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