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Abstract
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Introduction
Bed Material
Experimental Procedure
Results
Discussion
Conclusions
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Engineering
Civil and Environmental Engineering

EXPERIMENTAL STUDY OF BRIDGE PIER SHAPE TO MINIMIZE LOCAL SCOUR

Profile image of Zaid HadiZaid Hadi

Abstract

The study of local scour around bridge piers is very important for safe design of piers and other hydraulic structures. In this study, shape of pier is the main concern with three different velocities (0.18, 0.25, and 0.3) m/sec and other parameters like flow depth, bed material and etc. are remain same for all experiments. The experiments were conducted using laboratory flume, operated under the clear water condition using sand as a bed material. The test program was done on ten different streamline. were used to investigate the effect of the bridge pier's shape on local scour to conclude the optimal shape that gives minimum depth of scour. Comparison of results show that scour at upstream is directly proportional to exposed area of upstream nose of pier. The results showed that the rectangular pier gives the largest scour depth (7.6) cm, while the streamline shape gives the lowest scour depth (3) cm. The equilibrium scour depth of pier models compared with theoretical equations has been developed by some researchers and the results were very close.

Figures (10)
was measured by a V- notch installed at the downstream to fitted at regulate the flume inlet. A moveable vertical gate is tail-water depth. All depth measurements are carried out using two movable carriages with point gauges were mounted on brass rail at the top of flume sides, which have an was checked and measured by mini-water velocity meter of accuracy +2% the velocity meter measures with a range (0 accuracy of + 0.1 mm. The velocity of flow to 5) m/sec.
was measured by a V- notch installed at the downstream to fitted at regulate the flume inlet. A moveable vertical gate is tail-water depth. All depth measurements are carried out using two movable carriages with point gauges were mounted on brass rail at the top of flume sides, which have an was checked and measured by mini-water velocity meter of accuracy +2% the velocity meter measures with a range (0 accuracy of + 0.1 mm. The velocity of flow to 5) m/sec.
Figure 2 Piers models used in the experiments. In this study, ten pier shapes was compared with each other, and no any attempt is made to simulate a real prototype. Piers were manufactured from 18 mm Medium Density Fiberboard (MDF) sheets. For high accuracy in models dimensions, the (MDF) sheets have been cutting by using a CNC routing machine. The MDF wood sheets were then glued and laminated together, painted with pigments and coated with varnish to increase its smoothness and to avoid MDF swelling of water.
Figure 2 Piers models used in the experiments. In this study, ten pier shapes was compared with each other, and no any attempt is made to simulate a real prototype. Piers were manufactured from 18 mm Medium Density Fiberboard (MDF) sheets. For high accuracy in models dimensions, the (MDF) sheets have been cutting by using a CNC routing machine. The MDF wood sheets were then glued and laminated together, painted with pigments and coated with varnish to increase its smoothness and to avoid MDF swelling of water.
Mechanical sieve analysis test was carried out to characterize the sand bed material used for study. The results of the test showed that the material of bed with a median particle size (dso) of 0.71 mm. The geometric standard deviation of the sand size, og is 1.14, which implies that the sand is of uniform size distribution. The og is defined as, og = (dga/dig)°°. The plot of the grain size distribution test is depicted in Figure 3.5. The pler diameter was also carefully chosen so that there was negligible effect of sediment size on the depth of scour. It is known that the bed material grain size does not affect the depth of scour if the pier width to grain size ratio exceeds a value of about 25 (Melville, 1997). For this study, the ratios are about 63.4 for the pier of 45 mm, which satisfies the criterion of Melville, 1997. »
Mechanical sieve analysis test was carried out to characterize the sand bed material used for study. The results of the test showed that the material of bed with a median particle size (dso) of 0.71 mm. The geometric standard deviation of the sand size, og is 1.14, which implies that the sand is of uniform size distribution. The og is defined as, og = (dga/dig)°°. The plot of the grain size distribution test is depicted in Figure 3.5. The pler diameter was also carefully chosen so that there was negligible effect of sediment size on the depth of scour. It is known that the bed material grain size does not affect the depth of scour if the pier width to grain size ratio exceeds a value of about 25 (Melville, 1997). For this study, the ratios are about 63.4 for the pier of 45 mm, which satisfies the criterion of Melville, 1997. »
Table 2 Measured scour depths of piers for tests series.
Table 2 Measured scour depths of piers for tests series.
Figure 5 Scour pattern developed by minimum and maximum flow intensity (sharp nose pier).
Figure 5 Scour pattern developed by minimum and maximum flow intensity (sharp nose pier).
Figure 7 Scour pattern developed by average and maximum flow intensity (streamline pier).
Figure 7 Scour pattern developed by average and maximum flow intensity (streamline pier).
6. CONCLUSIONS
6. CONCLUSIONS

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References (11)

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