A new membrane equilibrium solution for masonry railway bridges: the case study of Marsh Lane Bridge

Masonry railways bridges were built and are still in use all over Europe and in many other countries all over the world. Limit analysis is widely adopted to assess the equilibrium of these structures under self and train loads and, mainly, assuming uniaxial stresses only in the span direction. In the last decade, some of these bridges, as our case study, have been subjected to detailed structural health monitoring (SHM) campaigns whose primary outcome is that these structures exhibit biaxial stresses. In this paper, within the framework of the Heyman masonry unilateral model, an application of membrane equilibrium analysis (MEA) is presented. MEA provides an efficient approach to account for biaxial stress states and, thus, taking into account beneficial 3D effects for load capacity analyses. This paper illustrates how various assumptions of the membrane behaviour yield a range of potential equilibrium solutions, all of which demonstrate higher capacity than the traditional 2D assessment methods.