Seismic Fragility Analysis of Space Special-Shaped Steel Box Arch Bridge

Seismic fragility analysis is of paramount significance in studying the seismic characteristics of bridges, especially for special structures like special-shaped bridges. Special-shaped bridges exhibit more complex geometric and mechanical properties. Therefore, it is even more essential to conduct seismic fragility analysis for special-shaped bridges. Analyzing the response of special structures to lateral seismic loads benefits the evaluation of their seismic performance and facilitates enhancements in seismic design. A finite element model was established using Midas/Civil to investigate the seismic fragility of a space special-shaped steel box arch bridge under lateral seismic loads. To assess the seismic fragility of space special-shaped steel box arch bridges, displacement data from bridge abutments, arch support platforms, and bearings were selected as damage indicators. The seismic fragility curves for bridge components were constructed using the incremental dynamic analysis (IDA) method. In the end, the weighting method was adopted to calculate the seismic fragility curve for the entire bridge system. The bearings and bridge abutments are more susceptible to seismic damage under lateral seismic loads, making them the vulnerable components of the bridge. Among the four bearings, the ones located near the arch ribs have poorer seismic performance and constitute vulnerable areas in the bearing layout. Through the case study of the seismic fragility analysis of space special-shaped steel box arch bridge, common issues in the fragility analysis of special bridges were explored. This further provides rational recommendations for enhancing and improving the seismic design of special-shaped bridge structures.