Seismic Vulnerability Assessment of Stone Arch Bridges by Nonlinear Dynamic Analysis Using Discrete Element Method

Evaluation of the seismic performance of two historical stone arch bridges of the Iranian rail network is presented using a discrete element method. The total length of the bridges is 66.7 m and 106.1 m. The bridges consist of multi-span arches changing from 5 m to 48.6 m. The incremental dynamic analysis method is used to determine the damage, failure patterns, and acceleration of the collapse threshold. Using the discrete element method after static analysis under gravity load, dynamic analysis of bridges under both horizontal components of the earthquakes was performed simultaneously for different earthquake intensities until collapse. The results showed that the most extensive damage occurred in the smaller bridge with the onset of failures in the top spandrels of the arches and then the piers of the bridge, while in the larger bridge which had a large central arch span, damage and failure occurred more in the central arch and its spandrels. The collapse spectral acceleration of the larger bridge is considerably smaller than the smaller bridge such that the ratio of collapse spectral acceleration of the larger to smaller bridge varies only between 45% to 61%. The low spectral acceleration intensity of collapse indicates more seismic vulnerability of the larger bridge.