On the collapse mechanisms of multi-span masonry bridges

An incremental-iterative procedure for the non-linear analysis of multi-span masonry arch bridges is developed and implemented by standard programming of a commercial F.E. code assuming masonry no tensile resistant (NTR) and perfectly elasto-plastic in compression. The procedure is applied to different arch geometries pointing out the effect on the collapse mechanism of the arch geometric parameters and of the material mechanical ones. Twin- and three-span models are studied and compared to a classical single-span assessment method; the elasto-plastic response of masonry is found to have great effect on the limit load of both shallow and deep arches, while abutment compliance and interaction between adjacent spans has to be taken into account for shallow arch bridges only, being of minor importance for deep arches