Fast 3D Adaptive Limit Analysis of Masonry Arch Bridges Interacting with Backfill

In this paper, a novel three-dimensional approach for the evaluation of the load carrying capacity of masonry arch bridges with arch-backfill interaction is proposed. An adaptive upper bound limit analysis procedure is followed. NURBS solids are adopted for representing the geometry ofboth arch and backfill, allowing an accurate representation of the structure. These elements are idealized as rigid blocks with energy dissipation occurring only at interfaces, in turn represented by planar or curved NURBS surfaces. An initial mesh is obtained by subdividing the NURBS solids through additional surfaces. Then, a Genetic Algorithm mesh adaptation scheme is applied to reproduce the real collapse mechanism. As numerical example, the analysis ofatwo-ring skew arch with backfill is reported.