Load carrying capacity and collapse mechanisms of masonry arch bridges

The structural models for the assessment of masonry bridges need to represent all the features of the mechanical response of both the material and the structure. In this work, two bi-dimensional procedures are discussed: i) a non linear incremental approach assumes for masonry an elasto-plastic model with controlled ductility in compression and No Tensile Resistance (NTR) in traction; ii) on the bases of limit analysis applied to FEM procedures, and taking into account the arch/fill interaction, upper bounds to the load carrying capacity of the bridge are given. The procedures account for inelastic strains of masonry, adjacent-span, span-pier and arch-fill interaction, among the others. The results partially explain the observed good behavior of masonry bridges and shows a promising way to masonry bridge refurbishment