The Effect of Asymmetric Approach Embankments of Skewed Bridges on Flow

Document Type : Original Article

Authors

1 M.Sc., Grad., Department of Civil Engineering, Imam Khomeini International University, Qazvin, Iran.

2 Assistant Professor, Transportation Research Institute, Road, Housing and Urban Development Research Center, Tehran, Iran.

3 Associate Professor, Faculty of Engineering and Technology, Imam Khomeini International University, Qazvin, Iran.

Abstract

When building a bridge over a river section, to reduce the length of the bridge deck structure for economic and operational reasons, usually part of the river floodplain is blocked on both sides by access embankments. This causes narrowing of the river and changes in the hydraulic conditions. As the velocity gradient increases in the narrowed section, the shear stress on the riverbed also increases. Increased shear stress can cause erosion in the riverbed and at the base of foundations and backpacks, exposing the bridge to hydraulic damage. On the other hand, sometimes the direction of the axis of the bridge is not perpendicular to the direction of the flow, and the so-called bridge has an angle of inclination. In these bridges, access embankments can be called flow-guiding and embankment embankments according to their location in the water flow path and how they operate. In this paper, the effect of symmetric and asymmetric progress of Bihadar bridge access embankments in floodplain on hydraulic flow is investigated. To improve the hydraulic conditions of the flow through the rift embankment, the asymmetric advance of the access embankments has been proposed and investigated. For this purpose, three-dimensional flow modeling was put on the agenda. Initially, the numerical model was validated based on previous experimental studies. Then, the effects of symmetrical advancement of access embankments at different angles of the bridge were evaluated and then the asymmetric progression of access embankments to reduce shear stress in the river section was proposed and investigated. The results show that the 70% advance of the flow-conducting embankment at the critical peak angle, due to the constant flow cross section, reduces the maximum velocity and shear stress by 14 and 35% in the studied river section, respectively.

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References

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