Masonry arch analysis using discontinuity layout optimisation

Abstract

Limit-analysis techniques have been found to provide a useful means of rapidly estimating the ultimate load-carrying capacity of masonry arch bridges. However, in most limit-analysis models only the masonry elements (e.g. arches and piers) are modelled directly, and the surrounding soil backfill material is usually modelled in an indirect and highly simplified manner. Given the likely importance of the soil backfill, this can lead to considerable imprecision when estimating load-carrying capacity, particularly when non-homogeneous backfill materials are involved. In this paper the recently developed discontinuity layout optimisation (DLO) limit-analysis procedure is extended to enable rotations at the boundaries of prescribed regions to be considered, thus allowing both soil and masonry components within a problem to be be modelled explicitly. This allows masonry arch bridges to be analysed using DLO. Results are initially validated against literature benchmarks and then compared with those obtained from carefully controlled tests recently carried out on soil-filled masonry arch bridges. It is demonstrated that reasonable estimates of bridge load-carrying capacity can be obtained provided ‘mobilised' rather than peak soil strengths are used in the analysis.