Hydrodynamic effects of debris blockage and scour on masonry bridges: Towards experimental modelling

Abstract

This paper describes the preliminary stage of an ongoing project investigating the hydrodynamic effects of debris blockage at masonry bridges. Debris blockage is cited as one of the primary causes of bridge failures in the UK and around the world. Masonry bridges, many of which are valuable historical assets, are particularly vulnerable to debris blockage due to their short spans and low clearance. This paper presents work done as part of the first phase of the project involving experimental research to understand the scientific relationships between debris characteristics and flow conditions. The study, being carried out at Centre for Water Systems at University of Exeter, utilizes a 0.6m-wide and 10m-long flume to run hydraulic experiments in order to characterize the impact of debris blockage on flow hydrodynamics, scour, and hydrodynamic pressures and forces at masonry bridges. This paper outlines the design of the experimental setup and the reasoning behind the choices for preliminary experimental parameters. The experiments are to include testing of bridge models and various 3D-printed debris shapes under realistic flow conditions. Geometry of the bridge and debris models are kept approximately similar to prototype conditions, with hydraulic conditions of the experiments designed to the degree that experimental constraints allow based on Froude similarity. Velocities, scour and hydrodynamic pressures are measured using an Acoustic Doppler Velocimeter, echo-sounding concept and pressure sensors, respectively. Preliminary results indicate that the designed experiments have the potential to enhance our understanding of the hydrodynamic effects of debris blockage.

Invited perspectives: Challenges and future directions in improving bridge flood resilience

“…The characterization of the joint effects of the flood actions is complicated, and laboratory and numerical studies often focus on one or few specific actions (Ebrahimi et al, 2017). Experimental tests of the actual process of bridge failure have to address the challenge of scaling (Oudenbroek, 2018a, b), while computational analysis must overcome the issues related to modelling sediment transport and scour under complex, real-world conditions.…”

Flood-Induced Hydrodynamic and Debris Impact Forces on Single-Span Masonry Arch Bridge

“…6(a). The bridge geometry was chosen such that the span and the span to rise ratio are representative of many masonry arch bridge forms in the UK (Kamiĕski, 2010;Ebrahimi et al, 2016;Sarhosis et al, 2016;Mathews and Hardman, 2017). Based on this and the studies conducted by In the present work, not only flood-induced hydrodynamic forces but also the combination of hydrodynamic and floating debris impact forces on the single-span arch bridge were investigated.…”

“…The hydraulic conditions were set based on the flow depth in relation to the submergence ratio of the structural components, the abutment, arch barrel and spandrel wall. The dimensions of the cylindrical debris (representing a tree log) were designated regarding the span length of the bridge and the diameter-length ratio of the debris, 0.059, as suggested by several studies (Comiti et al, 2006;Magilligan et al, 2007;Ebrahimi et al, 2016). The effect of debris impact was additionally examined with two different initial debris orientations (θ).…”

Prediction of flow around a sharp-nosed bridge pier: influence of the Froude number and free-surface variation on the flow field

“…The computational model is based on the set-up used in flume experiments by Ebrahimi et al (2017Ebrahimi et al ( , 2018. The geometry of the computational model, given in Fig.…”