Fragility curves for stone arch bridges by incremental dynamic analysis method and using DEM

Abstract

One of the most important tools for determining the vulnerability of structures to earthquakes is use of fragility curves. Considering the importance of existing masonry arch bridges in transportation networks, in this research, the process of determining the fragility curve by the analytical method through using the discrete element method (DEM) is discussed. The seismic behavior of two railway bridges is investigated using the incremental dynamic analysis method (IDA). Bridge A is smaller and is totally 66.7 m long and has four similar arches spanning 12 m each. Bridge B is the larger bridge, with a length of 160 m. It has a large central arch span of 48.6 meters and a height of 22.8 meters. By introducing an appropriate number of control points in the bridge body, the seismic response of the bridges are obtained. By examining the IDA curves and status of damage in the bridges, the performance criteria for immediate occupancy (IO), life safety (LS), and collapse prevention (CP) limit states have been determined. The fragility curves of the bridges are calculated for the above three limit states. The results show that both bridges require seismic strengthening for the IO performance level with a probability greater than 90%. Also In the event of design earthquake, larger bridge will not be safe with a probability of more than 50% for the LS limit state, and the probability of exceedance the CP limit state for bridge A is 12% and bridge B is 32%.