Seismic risk assessment of RC multi-span girder bridges on regional scale

In seismic countries where strategic infrastructures were built before the introduction of capacity design criteria in national codes, the managing authorities of road networks rely on risk assessment of bridges to decide retrofit intervention priorities on a regional scale. It is a current practice to assess seismic vulnerability in the form of fragility curves. The most extensively used tool currently available for the evaluation of vulnerability curves of large-scale systems is the Hazus methodology, which provides fragility curves for whole classes of structures. The Hazus model is sufficiently accurate when applied to a class of buildings or bridges very similar to those in the default system, but it shows deficiencies when applied to a community–specific database, where different typologies are represented. Present work reports on an extensive risk assessment study carried out on Northern-Italy’s Region of Veneto road system; the analysis focuses on one of the most typical bridge types of the network, multi-span RC bridges. An extensive vulnerability analysis of the entire stock has been developed, using the previously calibrated DBA procedures that strain and displacement measures as structural damage indexes and seismic performance control parameters. Analytical fragility curves were derived with the simplified displacement-based method (DBFr curves) for all the multispan rc bridges of the VR stock. In the end, seismic risk maps were drafted: spatial distribution of damage, superimposed on Google Earth maps, was the represented for all the multi-span rc bridges of the VR stock. Analytical fragility curves obtained with displacement-based approaches are proved to be sufficiently accurate, giving results significantly different compared to those produced by applying Hazus or Risk-UE charts.