Hydraulics of Scour in the Vicinity of a FlexiArch bridge

Floods and scour are major causes of failure of bridges and with the increase in short-duration and high intensity rainfall events the occurrence of such failures is increasing. While standard free flow scour at bridge piers is an extensively researched area, the increased scour that occurs when the upstream water level is at or above the crown of an arch bridge (pressure-flow scour) is comparatively less well studied. As the frequency and magnitudes of floods increase, more bridges may be at a higher risk of being subject to pressure-flow scour. A modern masonry arch bridge system called the ‘FlexiArch’, that does not involve any mortar or steel reinforcement and can be rapidly constructed on site, has been developed by Queen’s University Belfast. The behaviour of the FlexiArch bridge system under developing scour has not been studied previously. This paper will present a series of experiments aimed at modelling pressure-flow on a scaled model of the FlexiArch bridge with a view to developing and understanding of the scour – bridge interactions.