Seimic assessment and retrofit of masonry arch bridges

The existing stock of road and railway masonry arch bridges in Italy and in most European countries frequently exhibits insufficient performance, both in terms of structural safety and functionality. Many of these structures are located on major traffic lines, in high seismicity areas, and most of them need to be improved in terms of their carrying capacity and to be upgraded to the standards of the current seismic codes. Quick and reliable procedures are then needed to assess the capacity of these structures and methodological approaches are required for the retrofitting interventions. In this work, a simplified procedure for the seismic assessment of masonry arch bridges is proposed. The ultimate capacity of homogeneous classes of single span and multi-span bridges is evaluated in terms of limit peak ground acceleration curves. The subsequent choice of retrofitting interventions is therefore discussed by presenting some reference examples. It is shown how the seismic enhancement of the structural behaviour is often coupled with a strengthening intervention of the resisting system for vertical loads, and with the functional renovation of the bridge.