A significant part of the Italian and worldwide bridge heritage consists of masonry arch structures. This typology of bridges was widely realized until the first decades of the last century based on empirical criteria and mainly accounting for vertical actions rather than horizontal ones. Since they often represent strategic infrastructures, the estimation of their safety against exceptional loads, such as seismic actions, is an issue of noteworthy importance for the engineering community. On the other hand, seismic vulnerability assessment of masonry structures is usually performed by resorting to numerical models, whose reliability is difficult to appraise mainly due to the uncertainties in selecting the mechanical parameters of the material and the interaction between them.

Based on this premise, the present paper deals with the seismic vulnerability assessment of a masonry arch bridge. A detailed nonlinear Finite Element Model was created in Abaqus software, calibrated against the results of an experimental test on a three-span masonry arch bridge reported in the literature. The numerical model was assembled by considering the nonlinearity of the main constructive elements (i.e. backfill and masonry), as well as an appropriate contact constitutive law to describe their interaction. Thus, the response of the bridge under seismic loads is assessed and discussed.