本文選題：洪水災害 + 橋梁下部樁柱�。� 參考：《長安大學》2015年碩士論文

【摘要】：洪水災害是全人類面臨的重大自然災害之一,洪水會使河流水位大幅度升高,部分河段會存在大水位差以及水流速度大于3m/s等新的水流形態(tài),跨江/跨河橋梁大規(guī)模建設使得橋梁下部樁柱周圍的水流環(huán)境顯得更加復雜,流速發(fā)生變化,樁柱直徑的增大也會造成更強的阻水作用。樁群的設計由于樁間的遮流影響,使得樁周的水流形態(tài)與單樁柱情況有所不同,樁柱周圍水位會突然涌高,相應樁柱周圍水位變化也會很復雜,致使水流動能轉換成作用于橋梁下部樁柱的橫向力,這就對跨河/跨江橋梁下部樁柱結構橫向受力提出了更大的挑戰(zhàn)。目前橋梁下部樁柱受水流力作用研究主要是圍繞亞臨界區(qū)雷諾數下二維水流場的數值模擬分析,而對于超臨界區(qū)高雷諾數水流條件下橋梁下部樁柱受水流力研究相對較少。本文以臥龍寺渭河大橋加固工程為依托,選取橋梁下部受沖刷最為嚴重的一聯,基于流體動力學(CFD)原理,運用流場分析軟件Fluent對洪水期水流形態(tài)下橋梁下部樁柱結構進行三維流場數值模擬分析,得到了超臨界區(qū)雷諾數水流形態(tài)情況下單樁以及不同L(樁凈距)/D(樁直徑)時串聯雙樁和串聯三樁的樁周水流特征,分析得出超臨界區(qū)雷諾數下樁柱水流阻力系數及各樁之間的遮流影響關系。結果顯示超臨界區(qū)高雷諾數下樁柱周圍水流特征與以往學者研究較多的亞臨界區(qū)情況不同,水流阻力系數較小,遮流關系復雜,沒有很強的規(guī)律性;基于有限元理論,結合分析得到的水流力對橋梁下部樁柱的作用,運用有限元分析軟件Midas Civil對沖刷前后結構進行了空間靜力及地震響應分析,結果表明相對于非洪水期水流力作用,洪水期水流力的作用會大幅度提高橋梁下部樁柱各控制截面的內力與位移,而對于軸力影響相對較小,結構受沖刷前后地震響應變化很大,沖刷后應及時進行結構加固;同時由洪水期水流力分析得到的水流阻力系數與規(guī)范中的數值進行比對,可以看出規(guī)范給出的阻力系數偏于安全,并且有較大富裕,實際中存在結構設計優(yōu)化的余地。
[Abstract]:Flood disaster is one of the major natural disasters faced by all mankind. The flood will cause the river water level to rise by a large margin, and there will be large water level difference and new water flow patterns such as the velocity of water flow is faster than 3m/s in some sections of the river. The large-scale construction of cross-river / cross-river bridge beam makes the flow environment around the pile column in the lower part of the bridge more complex, the velocity of flow changes, and the increase of pile column diameter will lead to stronger water blocking effect. Because of the influence of blocking flow between piles, the design of pile group makes the water flow around pile different from that of single pile, the water level around pile column will surge suddenly, and the change of water level around pile column will be very complex. As a result, the kinetic energy of the flow is converted into the transverse force acting on the pile column at the bottom of the bridge, which poses a greater challenge to the lateral force of the pile-column structure under the bridge across the river or across the river. At present, the research on the effect of the flow force on the pile column in the lower part of the bridge is mainly focused on the numerical simulation analysis of the two-dimensional water flow field under the Reynolds number in the subcritical region, but the research on the flow force of the pile column in the lower part of the bridge under the condition of the high Reynolds number flow in the supercritical region is relatively few. Based on the reinforcement project of the Wulongsi Weihe River Bridge, this paper selects the most seriously scoured joint of the lower part of the bridge, which is based on the principle of fluid dynamics and CFDs. The flow field analysis software Fluent is used to simulate the three-dimensional flow field of the pile-column structure of the bridge under the condition of flood and water flow. The characteristics of flow around piles with different L (pile net distance / D) and series double piles and three series piles are obtained in the case of Reynolds number flow pattern in the supercritical region and in different L (pile net distance) / D (pile diameters). The flow resistance coefficient of pile column under Reynolds number in supercritical region and the influence relation between pile and pile are obtained. The results show that the characteristics of the flow around the pile column under high Reynolds number in supercritical region are different from those in the previous subcritical zone where the resistance coefficient of the flow is small and the relation of blocking flow is complex and there is no strong regularity based on the finite element theory. Combined with the effect of the flow force on the pile column in the bottom part of the bridge, the spatial static and seismic response analysis of the structure before and after scouring is carried out by using the finite element analysis software Midas Civil. The results show that the effect of the flow force is relative to the flow force in the non-flood period. During flood period, the effect of flow force will greatly increase the internal force and displacement of each control section of the pile column in the bottom of bridge, but the influence on axial force is relatively small, the seismic response of the structure before and after scouring is very large, and the structure should be strengthened in time after scour. At the same time, the flow resistance coefficient obtained from the flow force analysis during flood period is compared with the value in the code. It can be seen that the resistance coefficient given by the code is more safe and more affluent, and there is room for structural design optimization in practice.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U441

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