2D Limit Analysis for Masonry Arch Bridges with Full Modeling of Backfill

This paper proposes a new discretization for backfill when analyzing the collapse of masonry arch bridges under the framework of limit analysis. We extend the deformable triangular elements, employed in many contributions, to arbitrary polygon shapes, remaining also the assumption of constant strain rate field. After that, Prestwood bridge is selected as a case study to understand the performance of the proposed polygon element. The collapse behavior of this bridge where the backfill is discretized by triangular or polygon elements is compared. The results show that the collapse of the bridge with triangular and polygon mesh for backfill presents a consistent collapse mechanism, and the general motion is also in line with the experimental result. Compared with the triangular case, the number of cracks predicted in the polygon one is numerous but with minor separation. Employment of polygon element will give rise to a better prediction of both strain rate distribution and collapse load (5.85 – 10.0% drop compared with the triangular case). Therefore, according to this case study, the performance of the polygon mesh is better.