Dynamics of masonry arch bridges under impact loads using a Heuristic Molecule-based strategy

The paper presents a numerical strategy for the structural modelling of masonry arch bridges subjected to in-plane impacts. The approach is based on a Rigid Body and Spring model - RBSM (Casolo, 2004), recently generalized as Heuristic Molecule approach (Casolo, 2021a). This approach allows to describe some relevant aspects of masonry behavior, such as shear orthotropy, interlocking and masonry-infill contact, using a reduced number of degrees of freedom while remaining computationally efficient in dynamic applications. As a reference case study for the implementation of a specific MatLAB code, San Marcello Pistoiese bridge (Italy), whose characteristics are available in the literature, has been used. The masonry elements of the bridge are modelled using a “Central, Shear, and Polar Forces” planar molecule topology, characterized by rigid atoms interconnected by axial, shear and diagonal elastic-plastic springs. The infill is modelled with a similar molecule, but without diagonal springs. The masonry-infill contact is modelled using no-tension axial springs and frictional shear springs. Several numerical simulations have been conducted, considering different positions and inclination angles of the impacting bodies. The results demonstrated that the model is capable of realistically reproducing the structural response capturing texture effects and masonry-infill interaction and can represent an effective tool for assessing existing infrastructure assets.