Influence of uncertain mechanical parameters on the load-bearing capacity of multi-span masonry arch bridges: a numerical study

The present paper deals with the assessment of the load-bearing capacity of existing ma-sonry arch bridges by means of numerical models. The problem related to the selection of uncertain parameters is addressed by reproducing a past experimental test performed on a reduced-scale bridge prototype vertically loaded until its collapse. The test is reproduced in Abaqus software by representing masonry elements through the Finite Element macro-modelling approach, in which masonry is considered as a homogeneous material having a plastic-damage constitutive behaviour in the nonlinear field. The fill material is introduced by means of a nonlinear continuum behaving under similar Mohr-Coulomb hypotheses. An appropriate interaction law that entails a frictional response in the tangential direction, avoids interpenetration, and allows for the separation between the two materials, is also considered. A wide parametric investigation is performed to obtain a good fitting with the experimental evidence by varying the uncertain mechanical parameters (i.e. Elastic Modu-lus of backfill, tensile strength of masonry and contact law between the two materials). Thus, a reliable numerical model exhibiting a response consistent with the experimental outcome in terms of both failure mode and force-displacement curve is proposed. The in-fluence of each investigated parameter on the overall response of the bridge is then deeply analysed and discussed, also with the aim to identify possible retrofitting strategies.