Pier

Abstract: A design method for the estimation of equilibrium depths of local scour at bridge piers is presented. The method is based upon envelope curves drawn to experimental data derived mostly from laboratory experiments. The laboratory data include wide variations in flow velocity and depth, sediment size and gradation, and pier size, shape, and alignment. Local scour depth estimation is based upon the largest possible scour depth that can occur at a cylindrical pier, which is 2.4D, where D=thepierdiameter. According to the method, this depth is reduced using multiplying factors where clear‐water scour conditions exist, the flow depth is relatively shallow, and the sediment size is relatively coarse. In the case of nonrectangular piers, additional multiplying factors to account for pier shape and alignment are applied. The method of estimation of local scour depth is summarized in a flow chart.

Abstract: The results of laboratory experiments on the clear-water local scour of cohesionless bed sediment at cylindrical piers are presented. Based on the data, equilibrium depth of local scour is related to the particle size distribution of the bed sediment, mean particle size of the bed sediment, relative to the pier diameter, flow depth relative to both the pier diameter and the mean particle size of the bed sediment. A formula for estimating the maximum depth of local scour is also given.

Abstract: Scour related to bridge hydraulics received much attention in the past decade, including its relation to flood hydrology and hydraulic processes in addition to steady flow. This paper presents new research on bridge pier and abutment scour based on a large data set collected at ETH Zurich, Switzerland. In total six different sediments were tested, of which three were uniform. Also a large variety of scour elements were considered, from 1 to 60% of the channel width, and flow depths ranging from 1 to about 40% of the channel width. Using similarity arguments and the analogy to flow resistance, an equation for temporal scour evolution is proposed and verified with the available literature data. The agreement of the present scour equation with both the VAW data and the literature data were considered sufficient in terms of river engineering accuracy, provided limitations relating to hydraulic, granulometric, and geometrical parameters are satisfied. These limitations are discussed and refer particularly to e...