深水斜拉桥地震响应对比分析

发布时间：2018-02-27 21:31

本文关键词： 动水压力地震响应流固耦合附加质量比 Morison方程斜拉桥　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：如今伴随着我国高速发展的经济,我国的交通运输行业也在蓬勃发展,桥梁作为交通运输链中不可或缺的一部分也在快速的发展。在受到地震环境的影响下,位于深水中的桥墩会在地震的激励下随之振动,进而带动围绕在墩身附近的水体振动,而水体的振动又会对桥墩的动力特性造成一定的影响,也就是桥墩与水体之间的耦合振动。目前已有的文献以及相关资料当中,研究地震作用下的动水压力的方法不多,对大型深水桥梁的研究也较少,只有部分文献对位于深水环境中的桥墩在受到地震激励时的动力响应做过研究。因此本文以深水环境下的桥墩,以及桥墩入水深度较大的大型斜拉桥为研究对象对其地震响应做了如下研究:讨论流体声单元法、附加质量比法、Morison方程附加质量三种方法在桥墩受地震激励下动水压力的计算效率,并对比了不同方法下不同截面尺寸的正方形截面以及圆形截面桥墩的一阶频率及一阶频率降低率,同时分析了墩顶位置处的位移以及墩柱结构底部的反力及弯矩受动水压力作用时的影响。对比发现,随着截面尺寸的增大桥墩自振频率逐渐增大,一阶频率降低率逐渐减小,且减小幅度也在逐渐缩小;在动水压力存在的条件下,墩顶位移及墩底反力、弯矩均受其影响有所增大,增大幅度随着桥墩截面尺寸的增大而逐渐减小,墩柱结构底部反力所受动水压力作用时发生的改变较其弯矩而言较大。Morison方程计算出的结果较为保守,随着截面尺寸的增大,附加质量比法与流体声单元则较为实用。以此为开端,本文以奉节长江大桥作为工程实例,采用上述三种方法,使用大型通用有限元软件ANSYS建立了斜拉桥的梁单元模型和实体单元模型,以沿纵桥向的地震波对桥梁结构在深水以及无水条件下进行时程分析。通过计算发现,深水条件下水对大型桥梁的固有频率影响不大。水体对地震作用下的桥梁动力响应影响较大,塔顶以及主梁两端的纵向位移均有增大,塔底的剪力以及弯矩也有大幅的增大,并且剪力的增幅大于弯矩,同时墩身的剪力及弯矩随墩高的变化而变化,相较无水条件下的极值也有所增大。三种方法相较而言,附加质量比法计算出的动力响应结果最小与流体声单元法较为接近,Morison最大偏于安全,流体声单元法所得结果适中。
[Abstract]:Nowadays, with the rapid development of China's economy, the transportation industry in China is booming, and bridges, as an indispensable part of the transportation chain, are also developing rapidly. Under the influence of the earthquake environment, The pier in deep water will vibrate under the excitation of earthquake, which will lead to the vibration of the water around the pier, and the vibration of the water will have a certain impact on the dynamic characteristics of the pier. That is, the coupling vibration between piers and water bodies. Among the existing documents and related data, there are few methods to study the dynamic water pressure under earthquake, and less research on large deep water bridges. Only part of the literature has studied the dynamic response of piers in deep water environment when subjected to earthquake excitation. The seismic response of large cable-stayed bridge with high depth of piers entering water is studied as follows: the fluid acoustic element method is discussed. Additional mass ratio method and Morison equation three methods for calculating dynamic water pressure of pier under earthquake excitation are presented. The first-order frequency and first-order frequency reduction rate of square section and circular section pier under different methods are compared. At the same time, the effects of the displacement at the top of the pier and the reaction force and bending moment at the bottom of the pier structure under the action of dynamic water pressure are analyzed. It is found that with the increase of the cross section size, the natural vibration frequency of the pier increases gradually, and the reduction rate of the first order frequency decreases gradually. Under the condition of dynamic water pressure, the displacement of pier top and the reaction force and bending moment of pier bottom are affected by it, and the increasing range decreases gradually with the increase of the section size of pier. The change of the reaction force at the bottom of the pier column under the action of dynamic water pressure is larger than that of the bending moment. The results calculated by Morison equation are more conservative, and with the increase of the section size, The additional mass ratio method and the fluid acoustic unit are more practical. In this paper, the Fengjie Yangtze River Bridge is taken as an engineering example and the above three methods are used. The beam element model and solid element model of cable-stayed bridge are established by using the large-scale general finite element software ANSYS. The seismic waves along the longitudinal bridge are used to carry out the time-history analysis of the bridge structure in deep water and under the condition of anhydrous. The deep water has little effect on the natural frequency of large bridges. The water body has a great influence on the dynamic response of bridges under earthquake. The longitudinal displacement of the tower top and the two ends of the main beam is increased, and the shear force and bending moment of the tower bottom are also greatly increased. And the increase of shear force is greater than that of bending moment, and the shear force and bending moment of pier body vary with the height of pier, and the extreme value of pier body is also increased compared with the maximum value under the condition of anhydrous condition. The minimum dynamic response obtained by the additional mass ratio method is close to that of the fluid acoustic element method, and the maximum deviation of the fluid acoustic element method is relatively safe. The results obtained by the fluid acoustic element method are moderate.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U442.55;U448.27

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