Comparison of Bridge Piers Shapes According to Local Scour Countermeasures

Abstract

Comparisonof experimental study was carried out between bridge piers to find out the efficientbridge pier to countermeasures the local scour. In addition the present studyis to provide a new method to reduce scour depth in front of bridge pier .Theidea of this method is dependent on change the position of two piers (normalpier (10-4) cm and straight aero foil shaped pier) with respect to flowdirection (named after here as opposite bridge pier and opposite aero foilpier). The down flow deflected away from the front the opposite piers and thehorseshoe vortex becomes small and does not affect the piers.In the presentstudy five piers (normal pier (10-4), opposite pier (4-10), straight aero foil,opposite aero foil and circular) were tested under live-bed condition with flowintensity 58 l/sec. for duration 3 hrs. The velocity field measurements wereobtained using an Acoustic Doppler Velocimeter. The results showed that theopposite piers reduce the local scour around the piers. For opposite pier thereduction of scour depth was about 40% compared with normal pier and 54%compared with circular pier. The reduction of the scour hole volume was about83% compared with circular pier and 23.6% when normal pier compared withcircular. For opposite aero foil the maximum depth of scour reduced 58%compared with straight aero foil and 69% compared with circular pier. Thereduction of the scour hole volume was about 89% compared with circular pierand straight aero foil reduced scour hole volume about 27% when compared withcircular pier.It is clearly from the comparison that the opposite piers are effectivecountermeasures for reducing local scour depth and scour hole volume,especially opposite aero foil pier. We hope that the results of the presentstudy will be benefitted by the designers and engineers.