Numerical study on the structural response of a masonry arch bridge subject to flood flow and debris impact

Extreme flood flows in rivers and the floating debris they carry have the potential to generate significant impact forces on bridges spanning the watercourse. Recent flood events have highlighted the vulnerability of masonry arch bridges in flood events. This paper explores the structural response of a typical masonry arch bridge subject to flood flow and impact from flood-borne debris using a validated numerical modelling approach. The meshless method smoothed particle hydrodynamics (SPH) is used to model the fluid behaviour giving the pressure distributions on a single-span arch bridge arising from both the fluid and debris impact. Taking the pressure-time histories derived from the SPH model, the response of the bridge structure is then simulated using a nonlinear finite element (FE) model via Abaqus/Explicit. The effects of submergence ratio of bridge components: abutment, arch barrel, spandrel wall, debris orientation and flow velocity are explored. Results indicate that the debris impact resulted in greatest increase in the stresses in the bridge with a fully submerged abutment and side-on (0-degree) debris orientation. The influence of the debris impact with end-on (90-degree) orientation on the structural response was relatively low despite its higher peak pressure values. Moreover, for the type of realistic flow scenarios considered, significant local tensile stresses can be generated in the spandrel wall and arch barrel leading to structural damage