西部山区风特性参数及大跨度钢桁拱桥抖振响应研究

发布时间：2018-03-04 14:08

本文选题：大宁河峡谷　切入点：大跨度钢桁拱桥　出处：《重庆大学》2014年博士论文　论文类型：学位论文

【摘要】：钢桁架拱桥具有结构轻巧、受力合理、便于节段拼装和施工快捷等优势，在我国西部沟壑纵横的山区桥梁建设中获得了越来越广泛的应用。由于跨越峡谷的需要，拱桥的跨度一般超过300m。跨度的提升将导致拱桥整体刚度的下降、阻尼比的减小，使得结构对风的敏感性增加，风致振动对结构设计和施工的影响变得重要，尤其对于刚度较弱的悬臂施工阶段。而现行《公路桥梁抗风规范》条文中对于山区桥梁抗风问题未给出相关的细则，不便于山区桥梁的抗风设计。论文以位于西部山区的大宁河特大桥为研究对象，开展了桥位风观测，分析了桥址区域风场分布的规律。利用现场实测获得的风场特性参数，参考规范中的建议风谱，，拟合了符合桥位区风场特性的风谱参数。利用桥位区风场的风谱，开展了大跨度桁架拱桥成桥状态、合龙施工态和最大悬臂施工态结构的抖振响应，并与规范中建议风谱的计算结果进行了对比分析，以检验现行规范对于山区桥梁抗风计算的指导程度。本文的工作主要有以下几个方面： 1）利用C#程序开发语言，采用WPF（Windows Presentation Foundation）框架开发了风特性观测和分析处理软件。程序具有数据文件分割处理的功能，能够快速准确地对风观测数据进行计算分析，输出风场特性参数，可为桥址处海量的风场观测数据的处理工作提供便利的分析工具。 2）通过对风特性数据的分析得到了大宁河峡谷区桥位处风场的分布规律。桥址处平均风速沿高度的变化规律不符合规范给出的指数分布或对数分布。对于西部山区的这类山地地貌来说，风的脉动成分比较大，离拱脚10m高度测得的水平向湍流强度超过了40%，离拱脚90m高度所测得的也可达20%，远大于规范中D类地表粗糙度下的参考值。此结论表明西部山区的桥梁抗风设计需要考虑大紊流度影响。 3）采用数理统计方法对大桥桥址处的实测风速谱进行拟合，得到水平脉动风速谱和垂直脉动风速谱表达式，发现该桥桥址处实测脉动风速谱与我国桥梁抗风规范中建议使用的脉动风速谱存在差异，其低频段的能量小于规范风谱的值。该现象将直接影响低频段模态对抖振共振响应的贡献。 4）利用ANSYS有限元分析软件，建立了大宁河特大桥成桥态、合龙态和悬臂施工态三类空间有限元模型，获得了结构动力特性。分别利用实测拟合风谱和规范建议风谱，开展了三种状态下结构的抖振响应分析。 5）抖振响应结果表明，该桥成桥状态的侧向位移较大，竖向和扭转向抖振位移响应较小，且跨中位移显著大于两侧位移。成桥态和合龙态的抖振响应主要受到对称和反对称模态共同作用，而最大悬臂施工态基本只受到对称模态影响，其抖振响应幅值显著大于另外两个状态，且其扭转抖振受到的是对称扭转模态影响，而非附带扭转形态的横向弯曲模态影响。 6）三种状态结构的抖振计算结果表明，规范建议风谱的计算值要显著大于现场实测拟合风谱的计算值，且在刚度相对较弱的横向差异较大。通过对比抖振响应谱可以进一步发现，两类风谱对于结构背景响应的贡献是相当的，在共振模态的阶次和分布上也是一致的；不同的是规范风谱所引起的共振响应更大，尤其对于低频段模态。计算结果也表明，现行规范关于抖振计算的条文可以指导山区大跨度拱桥的抗风计算，但其在山区桥梁抖振计算中的通用性还需要通过更多研究结果的证明。
[Abstract]:The steel truss arch bridge has a compact structure, reasonable stress, easy segmental and quick construction and other advantages, is widely used in the construction of bridges in mountainous areas in Western China. Due to the ravines across the canyon, the span of arch bridge is generally more than 300m. span lifting arch bridge will lead to the overall stiffness decreased, the damping ratio decreases, increased sensitivity makes the structure of the wind, the wind-induced vibration of structure design and construction become important, especially for the cantilever construction stage stiffness is weak. While the current rules for highway bridges Standard < > the provision of mountain bridge wind resistance are not related, for the wind resistant design of bridges in mountainous areas the thesis is located in the western mountainous area. The Daning River Bridge as the research object, carry out the bridge wind observation, analysis of the bridge site area wind field distribution. The wind field obtained by field test The characteristic parameters, reference standard in wind spectrum, fitting with the bridge area wind field characteristics of wind spectrum parameters. By using the bridge area of the wind field wind spectrum, to carry out a large span truss arch bridge, buffeting state and maximum closure construction of cantilever construction structure response, and code proposed the calculation of wind spectrum results were analyzed. The degree of guidance to test the existing standard for mountain bridge wind calculation. The main work of this paper are as follows:
1) the use of C# programming language, using WPF (Windows Presentation Foundation) framework for the development of Wind Characteristics Observation and analysis software. The program has a data file segmentation function, can quickly and accurately calculate the wind observation data, the characteristic parameters of wind field output, provide convenient analysis tool for wind field observation data can work for the bridge site is massive.
2) by analyzing the characteristics of data obtained in the Daning River Valley area, the bridge is located at the bridge site of the wind field. The average wind velocity along the height variation with exponential or logarithmic distribution specification is given. For this type of mountain landscape in western mountains, the wind ripple component is relatively large, from the arch height of 10m levels measured by more than 40% to the turbulence intensity, from up to 20% foot arch height of 90m as measured by the standard is far greater than the D of the surface roughness of the reference value. The conclusion shows that the wind resistant design of bridges in western mountains to consider large turbulence effects.
3) the actual wind speed of the bridge at the bridge site by using mathematical statistic method spectral fitting, horizontal wind spectrum and vertical wind spectrum expression, found on the bridge site measured wind spectrum and our bridges in standard use of pulsating wind spectrum differences, the low frequency energy is less than the standard the wind spectrum value. This phenomenon will directly influence the low-frequency mode on the buffeting resonant response contribution.
4) using ANSYS finite element analysis software, the establishment of the Daning River Bridge bridge state, the closure of three kinds of state space finite element model and cantilever construction state, the dynamic characteristics of the structure. By fitting measured wind spectrum and standard wind spectrum, carried out three kinds of buffeting response analysis under the condition of the structure.
5) the buffeting response results show that the bridge's lateral displacement is large, vertical and torsional buffeting response to small and mid span displacement was significantly greater than that on both sides of displacement. The completion and closure state of the buffeting response is mainly affected by the symmetric and antisymmetric interaction mode, while the maximum cantilever construction state only by symmetry mode, the buffeting response amplitude was significantly greater than that of the other two states, and the torsional buffeting by the symmetrical torsional mode, rather than the transverse bending mode of incidental torsion form.
6) the three state structure buffeting calculation results show that the proposed calculation specification wind spectrum value is significantly greater than the calculated fitting measured wind spectrum field value, and larger in the lateral stiffness difference is relatively weak. By comparing the buffeting response spectrum can be found, two kinds of wind spectrum is equivalent to the structure background the contribution of the response, is consistent in resonance mode order and distribution; the difference is caused by the resonance specification wind spectrum response is larger, especially for low frequency mode. The calculation results also show that the current standard about wind buffeting calculation can guide the provisions of mountain long span arch bridge calculation, but its versatility in the calculation of buffeting of bridges in mountainous area also need to prove through more research results.

【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U441.3

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