Local Equilibrium Sediment Scour Prediction at Bridge Piers with Complex Geometries

Accurate estimation of local scour depths at piers is important since underestimation can result in structural failure and possible loss of lives and overestimation in needless structure cost, which can be significant for large structures. An improved mathematical model for estimating equilibrium structure-induced (local) sediment scour depths at bridge piers with complex geometries founded in noncohesive sediment is proposed. It is the result of an increased understanding of local scour processes, the contributions of individual pier components to the effective pier width, and the quantity and quality of recently published laboratory data. A large quantity of published laboratory data was compiled and screened for test duration, method of extrapolation to equilibrium, flume dimensions, and instrumentation used. This resulted in a data set of 454 complex pier local scour tests with which to test the model presented here and other commonly used models. The methods compared are those designed for use with a wide range of complex pier shapes founded in noncohesive sediments and subjected to either clearwater and/or live-bed flow conditions.