Experimental investigation of the pier streamlining effect on bridge local scour under clear water conditions

A series of experimental tests were conducted to investigate the effect of pier streamlining on bridge local scour under clear-water conditions. A total of four testing cases were included in this study. Test conditions in all cases were kept the same except that the pier geometry in each case had sequentially increased extents of streamlining. These streamlining features were adopted from a previous numerical study by the authors. This paper compared the time evolution of local scour among cases. Contour maps of the scoured bed were obtained using the structure from motion (SfM) technique. The streamlined piers generally showed advantage over the traditional oblong pier in terms of the scour rate, the maximum scour depth and the total scoured volume at equilibrium. This study suggests that streamlining can be a viable scour countermeasure, but more real-life scenarios including variabilities in soil and flow properties need to be further investigated.