Nose-Angle Bridge Piers as Alternative Countermeasures for Local Scour Reduction

Abstract

This study investigates the performance nose-angle piers as countermeasures for local scour reduction around piers. Four nose angles were studied, i.e., 90°, 70°, 60° and 45° and tested in a laboratory. The sediment size was fixed at 0.39 mm whereas the flow angle of attack (or skew angle) was varied at four angles, i.e., skew angles, i.e., 0°, 10°, 20° and 30°. Scour reduction was clear when decreasing nose angles and reached maximum when the nose angle is 45°. Increasing the flow velocity and skew angle was subsequently increasing the scour profile, both in vertical and transversal directions. However, the efficiency of nose angle piers was only high at low Froude number less than 0.40 where higher Froude number gives minimal changes in the maximum scour depth reduction. At a higher skew angle, although showed promising maximum scour depth reduction, the increasing pier projected width resulted in the increase of transversal lengths.

Measuring scour level based on spatial and temporal image analyses

“…8 Researchers explored other possibilities including hydraulic-based flow alteration through modifying the pier shape, openings/slots and pier groupings. [9][10][11] The main objective of these methods are to disrupt the localised flow behaviour, subsequently reducing the intensity of downflow and hinders the complete formation of horseshoe vortex. 7,12 Apart from the hard structure-based approach, soft measures such as monitoring proved to be one of the key elements in the management of bridges.…”

“…Although these approaches are the most cost effective, the efficiency limits to nonextreme rainfall events or high discharges and eventual breakdown of the armouring layer is likely 8 . Researchers explored other possibilities including hydraulic‐based flow alteration through modifying the pier shape, openings/slots and pier groupings 9–11 . The main objective of these methods are to disrupt the localised flow behaviour, subsequently reducing the intensity of downflow and hinders the complete formation of horseshoe vortex 7,12 …”