Author(s): Mohsen Ranjbar Zahedani, Alireza Keshavarzi, Hadi Khabbaz
Linked Author(s): Mohsen Ranjbar Zahedani
Keywords: Local scour, bridge piers, flow diversion structure, piers - flow interaction, velocity components
Abstract:
Previous studies have shown that most waterway bridge failures are due to local scour, which is the result of flow structures and bridge piers interactions. In order to control and reduce the impact of the problem around the piers, armoring countermeasures, such as riprap and gabion are commonly used. In this study, to find the possibility of reducing local scour around the piers, a flow diversion structure is introduced and used as a countermeasure. This triangular prismatic structure with dimensions much smaller than the pier, was installed at different spacing upstream of the pier. After achieving equilibrium condition, the bed profile was measured and the volume of the scour hole was determined for each experimental test. The above results were compared to a test case with no flow diversion structure at the upstream. The results revealed that the optimum distance between the pier and flow diversion structure to achieve the maximum reduction of local scour, was approximately 1.5 times of the pier diameter. In this situation, the volume of scour hole and the maximum of scour depth reduced 61 % and 38 %, respectively. Furthermore, in the control test and the best performing test regarding the local scour reduction, three dimensional velocity components were measured at 35 grid points using an Acoustic Doppler Velocimeter (ADV). The velocity analysis indicated that the proposed flow diversion structure could change both the magnitude and the direction of velocity component at the upstream of pier, and consequently, reduced the local scour around pier. (2608, 65, 294)
Year: 2017