Derivation of Fragility Curves for the Seismic Vulnerability Assessment of Railway Masonry Arch Bridges

Abstract

AbstractThousands of masonry arch bridges currently in service in the Italian railway network were built almost 100 years ago. Despite having often been constructed without any specific seismic design, in general these structures exhibited in the past a non-negligible resilience to seismic shocks, even when located in areas with medium/high seismic hazard.Reliable methods are thus required for simplified seismic vulnerability assessment of such a number of structures, in order to ascertain whether more detailed analyses are needed and/or to provide information for a preliminary prioritization of interventions. In this work, the seismic capacity of single and multi-span masonry arch bridges is assessed by non-linear kinematic limit analysis. To this purpose, both “local” and “global” collapse mechanisms are identified - involving piers, abutments, arches and spandrel walls - considering both the longitudinal and the transverse direction of the bridges. For each mechanism, capacity curves are evaluated, in terms of horizontal acceleration versus displacement of a proper control point. Safety checks are hence performed comparing displacement capacity and demand at different performance limits.These criteria provide the parameters needed for the derivation of fragility curves that can be applied for the definition of a large-scale damage scenario after a seismic event and as a support tool for the prioritization of the possible interventions. The so derived fragility curves could be related to the study of a single bridge (with uncertainties on dimensional and mechanical properties) or of a homogeneous typology of bridge (taxonomy). The paper reports some examples of application to both such cases.KeywordsRailway masonry arch bridgesSimplified seismic vulnerability assessmentCollapse mechanismsNon-linear kinematic limit analysisFragility curves