Limit Analysis of Masonry Arch Bridges Using Discontinuity Layout Optimization

Abstract

Limit analysis provides a simple yet powerful and effective means of verifying the safety of masonry arch bridges. However, a disadvantage of traditional rigid block limit analysis methods is that any soil fill surrounding the arch barrel in a bridge cannot readily be modelled directly, since the locations of potential failure planes in the soil are not known in advance. Also, it will seldom be feasible to model every individual unit in the masonry parts of a bridge with a rigid block. In this contribution discontinuity layout optimization (DLO) is used to extend the scope of the traditional rigid block analysis method, enabling direct modelling of both masonry and soil elements. DLO involves discretizing a solid body using nodes, and then interconnecting pairs of nodes with potential failure plane discontinuities. Optimization can then be used to identify the critical subset of discontinuities at failure which defines the geometry of the critical failure mechanism. In this contribution DLO is applied to both soil and masonry problems before being applied to a number of representative masonry arch bridge problems.