| Summary: | 碩士 === 逢甲大學 === 水利工程所 === 94 === The research utilize hydraulic models to simulate local scour depth and scour depth change with time for non-uniform pier diameter ratio D/D* of 0.4 and 0.7, and different type pier and initial bed level relative under the foundation top elevation under steady flow. (V/Vc=0.95)
The research results show that the different scour depth with different initial bed level relative and different type pier, and accompany different type pier will make maximum scour depth to different position. The maximum scour depth of un-exposed bridge foundation (Y=+10 mm) is less than exposed bridge foundation (Y=-10 mm) whatever type piers are.
In the same flow condition, when the bridge foundation is un-exposed (Y=+10mm) and the diameter ratio is D/D* of 0.4 with type pier (A1), (B1), (C1), the non-uniform plane of foundation can retard downflow scouring effectively and make scour depth reduced. Opposite results are found for the exposed (Y=-10 mm) bridge foundation.
Local scour depth of the diameter ratio D/D* of 0.4 with type pier (A1), (B1), (C1) is less than that diameter ratio D/D* of 0.7 with type pier (A2), (B2), (C2); when the diameter ratio is D/D* of 0.4 with type pier (B1) of an un-exposed bridge foundation (Y=+10 mm), non-uniform plane can retard scour more effectively. Considering the safety of bridge structure, an eccentric non-uniform circular pier with D/D* which equals to 0.4 with type pier B is an ideal pier style.
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