A Reliability Model for Bridge Abutment Scour

Deterministic scour prediction equations for bridge abutments consider only the effects of hydraulic parameters and do not take the uncertainties of scouring parameters into account. Treatment of these uncertainties would provide the means for risk evaluation in bridge foundation design. Herein, a static reliability model is developed for the assessment of local scouring reliability around bridge abutments having relatively short lengths. This model is based on resistance-loading interference incorporating dependent parameters. In the model, the relative abutment footing depth, which can be considered at least the relative maximum scour depth, and the linear combination of the relative approach flow depth and Froude number are defined as the system resistance and external loading, respectively. By examining the statistical randomness of extensive laboratory data, a bivariate lognormal distribution is found to represent the joint probability density function of dependent resistance and loading. Reliability expressions are developed in terms of resistance. In an example, it is shown that the results of the proposed model and a Monte Carlo simulation are in good agreement. It is also observed that the execution of this model is less time consuming than the Monte Carlo simulation