3D-MODELING OF SCOUR AROUND BRIDGE SUPPORTS USING COMPUTATIONAL FLUID DYNAMICS

Abstract

Historically, scour under bridge supports is considered one of the main reasons causing bridge failures across flooding routes and rivers. To account for scour in bridge design, empirical and experimental formulas have always been used worldwide to estimate anticipated scour depths in order to be taken into the design. The empirical approach has been preferred on the engineering level due to the difficulty in simulating the 3D hydrodynamic and sediment transport in the vicinity of bridge supports in a numerical and deterministic approach. In this study a simplified numerical model using 3D computational fluid dynamics is developed to estimate scour depths in the vicinity of bridge supports. The model is called SCFDS (Simplified Computational Fluid Dynamics Scour) and is coded using both ANSYS workbench scripting and C++. The general idea of the model is to lower the riverbed in the vicinity of the flow obstruction until the shear stresses in the vicinity of the obstruction is reduced to certain stable target values. The model is validated through its application to two different cases of pier configurations: a simple cylindrical pier from the literature and a complex pier of a real bridge over the Nile-River. The results of SCFDS model are then compared to the available data related to each pier’s case either from literature or from the available commonly used scour calculation approaches. The outcomes of validation show that the developed model can simulate the scour in the vicinity of bridge supports. The developed approach is an attractive approach especially in cases of complex bridge foundations where