考虑三维和振动效应的箱梁断面气动导纳识别方法研究

The strip-theory assumption fails since the typical turbulence length scales and the characteristic size of a long-span bridge deck are of the same order of magnitude, and hence the effect of three-dimensionality should can not be ignored. In addition, the effective aerodynamic shape of bridge deck during the buffeting response vibration could been modified relatively compared to its original section in the stationary state. Therefore, effective identification of the bridge deck aerodynamic admittances with the consideration of three-dimensionality effect under oscillation conditions is critical to accurately predict the buffeting response of long-span bridges. However, the existing research is not able to identify the two-wavenumber aerodynamic admittances of bridge decks caused by various turbulence components, and the study of oscillation effect on aerodynamic admittances is also scarce. This project plans to take the closed-box bridge deck as the example to systematically establish an effective identification method for aerodynamic admittances of a closed-box bridge deck considering both the three-dimensional and vibration effects based on wind tunnel tests in conjunction with theoretical analyses. Firstly, the aerodynamic forces on sections and surrounding fluctuating wind speeds, as well as the response of model, will be measured according to the synchronous pressure, vibration and wind measurement technique on a spring-suspended sectional model. Secondly, the buffeting force and self-excited force on section will be separated considering the incomplete correlation of the self-excited force in turbulent flow. Then, the identification method of two-wavenumber aerodynamic admittances with respect to along and vertical turbulence components will be developed. Finally, the influence of bridge vibration on aerodynamic admittances as well as the underlying mechanics will be examined. The project will contribute to both the theoretical significance and practical engineering in the aspect of gust-induced response of bluff structures.

大跨度桥梁的特征尺寸与来流湍流积分尺度相当，片条假设失效，湍流三维效应不容忽略；另外，桥梁处在稳态抖振响应中，断面的有效气动外形较静止状态时发生了一定的变化；因此，如何识别出振动状态下考虑三维效应的桥梁断面气动导纳是预测大跨度桥梁抖振响应的关键。但现有的研究还不能识别出不同湍流分量引起的桥梁断面二波数气动导纳，振动效应的研究也比较匮乏。本项目拟以箱梁断面为研究对象，结合风洞试验和理论分析，建立一种可考虑三维和振动效应的箱梁断面气动导纳识别方法。首先，通过弹簧悬挂节段模型同步测压测振测风试验获得箱梁断面气动力、周围脉动风速和模型响应；然后，考虑湍流场中自激力沿跨向的不完全相关性，分离箱梁断面抖振力和自激力；随后，建立可识别出不同湍流分量引起的箱梁断面二波数气动导纳的方法；最后，研究振动对箱梁断面气动导纳的影响以及影响的机理。该研究对钝体结构阵风响应具有理论意义和工程实用价值。

大跨度桥梁抖振分析的精度严重依赖于桥梁断面气动导纳函数，因此，需考虑湍流三维效应和桥梁振动对气动导纳函数的影响。本项目首先调试出湍流度以及湍流积分尺度单独变化的各3种湍流场，开展了固定状态下桁架梁节段模型同步测力试验和箱梁节段模型同步测压试验，并进行了振动状态下箱梁弹簧悬挂节段模型同步测压试验；然后研究考虑三维效应的桥梁气动导纳识别方法，提出了基于实测抖振力跨向根方相干函数的桥梁二维气动导纳直接识别法，并证实了识别二维气动导纳时有必要对非各向同性湍流场的各湍流分量进行修正；接着研究考虑桥梁振动影响的桥梁气动导纳识别方法，提出了一种将气动力分离为自激力和抖振力然后根据提取的抖振力来识别气动导纳的方法，并证实了桥梁断面气动导纳与其振动状态有关；最后，紧跟桥梁抖振研究前沿，研究了列车-桥梁系统和双幅桥间的气动干扰效应以及桥址风参数与预测和桥梁抖振响应与控制。在本项目的资助下，在国内外期刊上发表论文9篇，其中SCI检索6篇，参加国际国内学术会议4次，其中特邀学术报告1次，培养硕士研究生6名，其中毕业4名。本项目的研究成果对大跨度桥梁抗风具有理论价值和工程应用前景。