Time-dependent reliability analysis of local scour around bridge piers

Local scour around bridge piers is known for being an important factor threatening the safety of bridges. It is related to the subjects of turbulence, vortex, sediment transport, and others. Because of the random nature and complexity of the scouring phenomenon around bridge piers, the risk of failure due to excessive local scour around a pier during its service life always exists. Thus, the time-dependent reliability analysis of local scour is important in designing new bridges and in evaluating the vulnerability of existing bridges to local scour. There have been numerous empirical formulae developed in the past to estimate the maximum scour depth under the conditions of live-bed scour or clear-water scour, whereas still little work has been done in a probabilistic manner. In this paper, a framework of time-dependent reliability analysis of local scour around bridge piers is presented which considers both hydrologic uncertainty as well as the hydraulic and model uncertainties. A hypothetical example is used to illustrate how the factors, such as service life, pier dimensions, and footing depth of pier, affect the reliability of the pier