Modelling of a bridge pier subjected to scour

Abstract Scour is the erosive action of water carrying away sediments from river bed and riverbanks, and around piers and abutments of a bridge. This phenomenon is considered as the main cause of bridge failure in the United States: nearly 60% of bridge collapses are caused by this hydraulic problem. In France, the most known case is the collapse of the Wilson Bridge at Tours in 1978. All around the world, guides and manuals were published in order to help technicians and engineers protect and monitor scoured bridges. It is not the case in France where very few research were published. Therefore, the French national project ANR SSHEAR (2015-2018) was launched in order to better understand this phenomenon and develop new techniques of bridge monitoring. One goal is to assess the vulnerability of a given bridge with at least one scoured pier, and to propose monitoring techniques for the evolution of scour. This paper investigates the effect of scour on the natural frequency of a single pier. Small scale tests were performed in the laboratory and compared to a numerical 3D finite-element model. This model was then used to perform a local sensitivity study.