Predicting Collapse in Masonry Arch Bridges Using Advanced 2D and 3D Continuum FEM Models

Masonry arch bridges constitute a significant portion of the aging European transport infrastructure, yet their structural behavior remains challenging to assess due to material heterogeneity, geometric complexity, and pronounced nonlinear response. This study presents a comprehensive review of numerical modeling strategies currently employed for the analysis of masonry arch bridges, with particular emphasis on the treatment of their nonlinear behavior. The review is complemented by an investigation of the potential collapse mechanisms and load-bearing capacity of a large-scale multi-arch, multi-ring masonry bridge laboratory specimen. Two finite element modeling approaches are proposed: a two-dimensional textured continuum model, representing an intermediate strategy between detailed micromodelling and conventional continuum modeling, and a three-dimensional continuum macromodel. Both masonry and infill are modeled using a plastic damage constitutive formulation. The proposed continuum-based representation of the infill is capable of realistically reproducing its soil-like mechanical behavior and its interaction with masonry. The numerical results are compared with limit state and kinematic analyses to identify the most probable collapse mechanisms to occur during the experimental campaign. The findings highlight the crucial role of infill and spandrel walls in the structural response of a multi-arch systems.