Contraction scour analysis at protruding bridge abutments

Bridge collapse has dramatic consequences in transportation systems. Bridges are constructed with little adherence to the quality design, mostly in developing countries. Engineers need reliable methods for accurate estimation of the scour depth and location to design the bridge footing foundation safely. Scouring at the contracted section of approaching flow is a significant cause of bridge abutment failure. The main objective of this study was to estimate the geometry of the equilibrium contraction scour at a protruding abutment bridge in the compound channel, using parametric analysis (PA). Data from clear-water contraction scour experiments in uniform sand were collected for PA modelling methods. The main variables investigated were the abutment protrusion ratio, the contraction degree and the ratio of the maximum contraction scour owing to approaching flow depth. Results from PA were compared with those of the existing empirical methods for predicting the maximum contraction scour geometry. Statistical and graphical tests indicated that the PA method gives reliable prediction of the contraction scour depth around a protruded abutment in a compound channel.