Laboratory investigation of deflector structure effect on bridge pier scouring

Bridge pier local scouring is a crucial factor in bridge destruction. Studies from different researchers have presented solutions to control this phenomenon. These solutions are divided into two parts, namely, direct and indirect protection. In the direct method, the bed is armoured against scouring whereas in the indirect methods the flow pattern around the pier is changed with geometric parameters. This study defined an element called the deflector structure (flow diverter) to divert the bed’s flow streamline in front of the pier. Experimental scenarios were defined by stabilizing the flow conditions with 0.70, 0.83, and 0.97 relative velocities ( ) and 15, 30, and 45degree wedge deflector structure angles with flow direction for two piers with square and circular crosssections. The results showed that the dimensionless scour depth parameter ( ) close to the particle movement threshold ( ) was reduced by 70 to 75%, respectively relative to the control model for square and circle crosssection. Changing the angle from 45 to 30 and 15 degrees reduces the local pier scouring and increases the deflector structure’s effectiveness.