Scouring Around Bridge Pier With Different Shapes And Skew-Angles

Bridges are among the most essential and vital communication structures that are used from the past.With the development of urbanization,significant and new bridges are being made widely on rivers,lakes,estuaries,and straits around the world,and unlike in the past,there is a need for hydraulic engineering and river engineering to deal with hydraulic issues with more in-depth knowledge as the scale of many modern bridges is much bigger.Scouring is the dislodging of particles through the flow from their initial locations to other locations.Bridge scour may occur as a result of natural changes in the flow,construction of the bridge in the flow path or as a result of human activities,such as the removal of bed materials.Over time,the sediments around the bridge's pier would be reduced and eventually leads to a deep scour hole.Significant scour hole would reduce the load capacity of the bridge pier,which may cause the bridge to collapse.There have been being many bridges failures all over the world,which were caused by pier scour.The bridge collapse would cause disturbances in the transportation system,financial losses,and even human losses.Therefore,scouring phenomena,especially local scouring,are very important.Moreover,studying the mechanism of scouring and effective parameters is essential.In this study,the scouring phenomenon was examined,and the effects of bridge pier shape and the skew angle on scouring were mainly investigated.Five different pier shapes were tested,including rhombus30(inner-angle 30°),rhombus60(inner-angle 60°),rectangular,circular,and oblong.The test conditions are identical for each pier,which includes various states such as three different skew-angle: parallel(?=0),?=15° and ?=30°,as well as three different velocities of 0.191,0.300 and 0.380 m/s.The results show that the scour depth depends on the shape of the bridge pier and the angle of its placement in the flow.The best shape of the piers,the smallest scouring around it,is the rhombus 30,rhombus 60,oblong,rectangular and cylindrical,respectively.When the rustshaped pier was placed in running water,in addition to less flow turbulence,the amount of scouring is also reduced.Also,for the test with an angle between the stream and the bridge pier,the turbulence around the pier and scouring around the pier of the rhombus30 is lower than the other piers.The shape factor can be used as 1.0 for circular,0.9 for oblong,1.2 for rectangular and 0.65-0.7 for the shape of the rhombus30 and the rhombus60.By analyzing the experiments,a suitable form for the bridge pier,a rhombus 30° inner-angle was proposed.