Effect of the backfill material in the seismic response of multi-span masonry arch bridges under seismic loading

The present study deals with numerical modelling of multi-span masonry arch bridges under seismic loading. Based on the evidence coming from an experimental program reported in the literature, a reference 3D nonlinear Finite Element model is calibrated. The numerical model is realized in Abaqus software by adopting a macro-modelling strategy for simulating the masonry behavior. To this purpose the Concrete Damage Plasticity material model is used. The backfill material follows a Drucker-Prager behavior, while the interaction between the two materials is simulated by means of an appropriate contact constitutive law. After calibration, the response of the bridge under longitudinal seismic loads is thus investigated. In particular, a mass proportional load distribution is adopted. Then, the effects of the mechanical parameters of the backfill material on the global response of the bridge are investigated by means of a parametric analysis, which is carried out by varying: i. elastic modulus, ii. cohesion, iii. backfill-masonry contact law, and iv. backfill friction angle. The obtained results provide preliminary indications about reliable retrofitting techniques for cases similar to the one under consideration.