مهندسی عمران شریف (May 2020)
EXPERIMENTAL INVESTIGATION ON AFFLUX DUE TO INCLINED CIRCULAR BRIDGE PIER
Abstract
Piers and abutments cause local contraction in the rivers. As a result of the contraction, the water level increases in the upstream section of the bridge named as afflux. Afflux is one of the key concerns in the design of a bridge construction and the afflux estimation is important when the specific regions in the upstream of the bridge is to be protected against the flood. Hence, estimation of the afflux is required for river training of the upstream sections, before bridge construction. In this research 54 experiments were conducted to investigate the effects of different parameters such as the pier angle with respect to vertical, the Froude number and the contraction ratio on afflux. Design expert software is used to design the experiments and to analyze the results. According to the results, for a downstream inclined and laterally inclined piers, the afflux increased. However, the afflux decreases due to an upstream inclined pier. Also, the effect of inclination angle on the afflux is smaller for inclined piers towards upstream than inclined pier to the downstream or laterally inclined piers. By increasing the pier angle from zero to 24 degrees, toward channel side walls and toward downstream the afflux increases by 20 and 15 percent, respectively. While in the same situation by increasing the pier angle from zero to 24 degrees toward upstream, the afflux decreases by about 5 percent. The higher affluxes were observed in larger Froude numbers and contraction ratios. The analysis showed that the Froude number and contraction ratio have more effects on the afflux as compare to other parameters. Finally, appropriate equations are presented to estimate the afflux.
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