A 'parsimonious' 3D discrete macro-element method for masonry arch bridges

Masonry multi-span arch bridges represent cultural heritage structures that still play a strategic role in many railway networks of numerous countries and particularly in Europe. Most of these bridges appear in good state although they are several decades old and have been subjected to continuous dynamic loadings during their life. In order to assess the structural behaviour of these structures both simplified and rigorous approaches are useful. Simplified approaches, if sufficiently accurate, can lead to fast structural evaluation that can help the heath-judgment related to the periodic inspections scheduled for railway-network structures. On the other hand, rigorous models are also needed for a reliable structural assessment of these structures, often characterized by very complex geometrical layouts and structural modifications not always sufficiently documented. In the present work, a recently introduced Discrete three-dimensional Macro-Element Method (DMEM) for curved masonry structures is improved and applied to typical multi-span masonry railway arch bridges. The model is based on a discrete element approach that allows a reliable simulation of the linear and nonlinear response of masonry structures and masonry bridges with a lower computational burden, compared to classical nonlinear FEM analyses. Aiming at obtaining a first numerical validation and showing the capability of the proposed approach, a real masonry bridge is investigated and the results are compared with those obtained from a three-dimensional nonlinear FEM model both in linear and nonlinear context.