冲刷后结合洪水期水流力对连续梁桥进行静力与地震响应分析

发布时间：2018-05-30 12:31

本文选题：洪水灾害 + 桥梁下部桩柱　；参考：《长安大学》2015年硕士论文

【摘要】：洪水灾害是全人类面临的重大自然灾害之一,洪水会使河流水位大幅度升高,部分河段会存在大水位差以及水流速度大于3m/s等新的水流形态,跨江/跨河桥梁大规模建设使得桥梁下部桩柱周围的水流环境显得更加复杂,流速发生变化,桩柱直径的增大也会造成更强的阻水作用。桩群的设计由于桩间的遮流影响,使得桩周的水流形态与单桩柱情况有所不同,桩柱周围水位会突然涌高,相应桩柱周围水位变化也会很复杂,致使水流动能转换成作用于桥梁下部桩柱的横向力,这就对跨河/跨江桥梁下部桩柱结构横向受力提出了更大的挑战。目前桥梁下部桩柱受水流力作用研究主要是围绕亚临界区雷诺数下二维水流场的数值模拟分析,而对于超临界区高雷诺数水流条件下桥梁下部桩柱受水流力研究相对较少。本文以卧龙寺渭河大桥加固工程为依托,选取桥梁下部受冲刷最为严重的一联,基于流体动力学(CFD)原理,运用流场分析软件Fluent对洪水期水流形态下桥梁下部桩柱结构进行三维流场数值模拟分析,得到了超临界区雷诺数水流形态情况下单桩以及不同L(桩净距)/D(桩直径)时串联双桩和串联三桩的桩周水流特征,分析得出超临界区雷诺数下桩柱水流阻力系数及各桩之间的遮流影响关系。结果显示超临界区高雷诺数下桩柱周围水流特征与以往学者研究较多的亚临界区情况不同,水流阻力系数较小,遮流关系复杂,没有很强的规律性;基于有限元理论,结合分析得到的水流力对桥梁下部桩柱的作用,运用有限元分析软件Midas Civil对冲刷前后结构进行了空间静力及地震响应分析,结果表明相对于非洪水期水流力作用,洪水期水流力的作用会大幅度提高桥梁下部桩柱各控制截面的内力与位移,而对于轴力影响相对较小,结构受冲刷前后地震响应变化很大,冲刷后应及时进行结构加固;同时由洪水期水流力分析得到的水流阻力系数与规范中的数值进行比对,可以看出规范给出的阻力系数偏于安全,并且有较大富裕,实际中存在结构设计优化的余地。
[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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441

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