【作者】 彭元诚；

【导师】 方秦汉； 李黎；

【作者基本信息】 华中科技大学 ， 结构工程， 2006， 博士

【摘要】 随着计算技术的提高、新型材料的运用和施工技术的进步,桥梁向大跨、轻质方向发展,稳定性及抗风方面的问题日益突出。因此,对此类桥梁结构的稳定及抗风进行深入的研究将是十分必要的。本文主要以沪蓉国道主干线宜昌至恩施段一座高墩大跨连续刚构桥——龙潭河特大桥为工程背景,对其静力稳定性及风致抖振响应时域分析展开研究,包括如下四个方面的内容。在静力稳定性方面,通过对薄壁构件局部稳定的解析分析,给出不同约束条件下满足混凝土薄壁局部稳定的最小宽厚比的限制值。分别采用ANSYS中梁单元和壳单元建立了龙潭河特大桥在不同阶段的空间有限元模型,对其在不同施工阶段以及成桥阶段的各工况进行了第一类稳定分析;引入单边日照效应产生的初始缺陷,考虑结构几何非线性因素的影响,采用改进的Newton-Rahpson迭代法分析其在施工、成桥阶段不同荷载工况下的第二类稳定性。最后,对龙潭河特大桥的稳定安全性能作出评价。在风洞试验研究方面,首先通过节段模型试验和CFD计算方法确定了龙潭河大桥梁、墩截面的气动力系数。在此基础上,对龙潭河特大桥主桥结构的施工阶段最长双悬臂状态和主墩自立状态在不同风攻角和风偏角以及有背景梁情况下的驰振稳定性、涡激共振特性和抖振性能进行了试验和分析研究。在脉动风场随机模拟方面,首先细致的描述了脉动风场的自然特性,给出了谐波合成(WAWS)法的计算公式,证明了其模拟结果的无偏性和各态历经性,依据用FFT加速的WAWS法,绘出了编制模拟程序的流程图,并给出了模拟结果检验的数值方法。最后,用Fortran语言编制了实用的模拟程序,并利用该程序模拟了龙潭河特大桥的脉动风速场。在风致抖振方面,依据准定常理论抖振力计算理论,推导了实用的静风风力计算公式和抖振力计算公式;基于模拟的脉动风速场,分别模拟了成桥状态和施工状态的抖振力时程;并利用ANSYS将该荷载时程加载于有限元模型上,进行动力时程分析,求得了两种状态下的风致抖振响应分析结果。最后,对本文的研究工作进行了总结,给出了研究中的一些结论,并指出了在进一步研究中亟待解决的问题。更多还原

【Abstract】 With the improvement of the calculation technique, development of the construction technique and employment of new type material, the bridge structures gradually develop towards the long span and light weight aspects, the problem about stability and wind-induced response of the great bridge increasingly represent prominent. Therefore, it is very necessary to conduct the comprehensive and systemic investigation on the bridge stability and wind-induced response. In this paper, combined with the a long-span continuous rigid frame bridge with thin-wall high piers-Long-Tan River Long-Span bridge which is a part of the Shanghai-Chengdu express way in the west Hubei province (from Yichang to Enshi), the static stability and time domain analysis of wind-induced buffeting response is studied, including the following four aspects.On the static stability. First on all, the local stability analysis solution about the thin-wall component is obtained in order to determine the limit value of the minimum width-thin ratio under the different constrained conditions. By utilizing the great current finite element program ANSYS, two types of finite element models in different stage, i.e., beam model and shell model are established for Long-Tan River great bridge, respectively. The first kand of stability analyses are conducted for the some cases in the construction and completed bridge stage. In addition, the second kind of stability analyses are made by adopting the Modified Newton-Rahpson iterative method, the initial deflection induced by the unilateral sunlight and the geometrical nonlinearity effect are considered. Finally, the stability safety capability estimation is conducted for the Long-Tan River great bridge.On the wind tunnel tests. The aerodynamic force coefficients of both the girder and the pier sections of the Long-tan river bridge are measured by performing sectional model tests. The aero-elastic models of the main bridge structure are modeled in worse-case state during erection stage and only-pier state. For variating wind attack angles and yaw angles, with or without the neighborhood background girders, the galloping stability, vortex-excited resonant, and buffeting responses of the bridge are investigated respectively by performing corresponding wind tunnel tests.On the wind field simulation. The fluctuating velocities of wind fields is depicted by the statistical characteristics, like power spectral density functions, mean velocities, etc. These are firstly given here. As far as the weighted amplitude wave superposition (WAWS) method for simulation of the wind fields is concerned, its formula are derived. The simulated wind fields will be unbiased and ergodic, that is, the estimated first and second order moments are equal to the corresponding targets not only in the ensemble sense, but also in the temporal sense. The computation efficiency can be improved by the FFT technique. Flow chart of the simulation procedure is given, as well as the numerical methods to obtain statistics from the simulated results. The FORTRAN language is employed to program the formulas of the WAWS method, so that fluctuating velocities of the wind field around the Long-tan river bridge are simulated.On the time domain buffeting analysis. Practical formulas for evaluating the static and buffeting aerodynamic loading on the bridge decks are derived, on the basis of the quasi-steady aerodynamic theories. The loading time histories, both during the construction stage and the full stage, are then calculated from the simulated wind fields. Using the ANSYS software, FE (finite element) models of the bridge is established and loaded. Then, the wind-induced time domain buffeting responses of the bridge during the two stages are predicted, by conducting the time history dynamic analysis.Finally, the work in this paper is summarized and some conclusions about the study are drawn, besides, the further research problems are indicated.更多还原