Lower Bound Stress Fields in the Limit Analysis of Soil-Filled Masonry Arch Bridges

Abstract

Limit analysis has been used for many years to rapidly estimate the ultimate load-carrying of masonry arch bridges. However, often only masonry elements are modelled directly, with the surrounding soil backfill modelled in a simplified, indirect, manner. Due to the importance of the soil backfill, this may lead to inaccurate predictions of the load-carrying capacity of a bridge. In this contribution, a soil backfill model based on lower-bound (stress field) theory is proposed, similar to that used to compute the bearing capacity of shallow foundations. In the model the Mohr-Coulomb criterion is strictly obeyed in the stress fields in the soil fill surrounding the masonry elements of bridge. The model is applied to backfilled masonry arch bridges, with results compared with the upper-bound (failure mechanism) solutions obtained using the discontinuity layout optimization (DLO) numerical limit analysis procedure.