Assessment of Multi-Span Masonry Arch Bridges. Part I: a Simplified Approach

A step-wise iterative procedure for the non-linear analysis of multi-span arch bridges, suitable for implementation by standard programming of commercial F.E. codes, is discussed. Relying on the plane section hypothesis, masonry is assumed elastic-perfectly plastic in compression and no tensile resistant (NTR); a collapse condition is found when an ultimate strain is reached. The iterative procedure is that of an elastic prevision and subsequent non-linear correction of the nodal forces: tensile stresses are not allowed in the mortar joint by adapting the effective height of the arch to its compressed part, while the plastic response is represented by additional external fictitious forces accounting for the compressive plastic plateau. The procedure is first tested by comparison with experimental data and then applied to sample bridges, pointing out how the collapse mechanism and the ultimate load depend on the geometric and mechanical parameters