Seismic assessment of a railway masonry arch bridge using sensor-based model updating

A large proportion of Iranian railway bridge assets comprises masonry arch bridges, which have been in service for over 70 years. Seismic assessment of such structures is very important, particularly for highly seismic regions. This study assesses the seismic performance of Veresk masonry arch bridge, the longest masonry arch bridge in the Iranian railway network (span length 99 m), spanning a valley 110 m deep, through reliable sensor-based model updating. Dynamic tests are conducted using a test train, composed of six-axle locomotives and four-axle freight wagons, which travels across the bridge; the vibration response of the instrumented bridge is subsequently measured. A high-fidelity three-dimensional finite-element model of the bridge is developed and updated using the measured vibration characteristics: mid-span displacements and natural frequencies. Finally, a seismic performance assessment of the bridge is performed using non-linear static and dynamic analyses for two seismic hazard levels with return periods of 150 and 1000 years. It is found that, for the hazard level with a return period of 150 years, both non-linear static and dynamic analyses give very similar results. However, for the seismic hazard level with a return period of 1000 years, the results of the static analysis are more conservative.