This study proposes a general modeling framework for large-amplitude vertical-torsional coupled nonlinear flutter, which may have great potential to be applicable to most bridge decks. The framework mathematically models various nonlinear behaviors (including mechanical nonlinearity, non-wind-induced aerodynamic nonlinearity, amplitude-dependent flutter complex mode and wind-induced aerodynamic damping, and nonlinear coupling of vertical aerostatic deformation) present in free-vibration wind tunnel tests. The identification of parameters of all concerned nonlinear models in this framework only requires displacement responses from simple free-vibration wind tunnel tests, which makes it convenient for practical engineering applications. Meanwhile, a corresponding numerical solving procedure for nonlinear aeroelastic responses is also developed. The feasibility of the proposed modeling framework is then cross-validated through wind tunnel tests with a novel large-amplitude testing device, and the coupled vertical aerostatic deformation observed under large amplitudes can be well predicted by an asymmetric lift force model in the framework. Then, based on the validated nonlinear aerodynamic force model, a three-dimensional (3D) nonlinear flutter analysis method for full-bridge is established, and the influences of 3D effects on nonlinear flutter are investigated. The results show that ignoring 3D effects will significantly misestimate the nonlinear flutter amplitudes. Finally, based on the results of wind tunnel tests, it is verified that the proposed modeling framework has the ability to predict nonlinear bifurcation behavior (i.e., the final state of vertical and torsional vibrations at a given wind speed depends on the initial conditions) that occurs in 2DOF (two-degree-of-freedom) coupled flutter.

中文翻译：

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基于自由振动风洞试验的大振幅二自由度耦合非线性桥梁颤振通用建模框架


本研究提出了大振幅垂直扭转耦合非线性颤振的通用建模框架，该框架可能具有适用于大多数桥面的巨大潜力。该框架对自由振动风洞试验中存在的各种非线性行为（包括机械非线性、非风致气动非线性、振幅相关颤振复模和风致气动阻尼以及垂直空气静力变形的非线性耦合）进行数学建模。该框架中所有相关非线性模型的参数辨识仅需要简单的自由振动风洞试验的位移响应，方便实际工程应用。同时，还开发了相应的非线性气动弹性响应数值求解程序。然后通过风洞试验和新型大振幅测试装置对所提出的建模框架的可行性进行了交叉验证，并且框架中的不对称升力模型可以很好地预测大振幅下观察到的耦合垂直气动变形。然后，基于经过验证的非线性气动力模型，建立了全桥三维（3D）非线性颤振分析方法，并研究了3D效应对非线性颤振的影响。结果表明，忽略 3D 效应将严重错误估计非线性颤振幅度。最后，基于风洞试验的结果，验证了所提出的建模框架具有预测非线性分岔行为的能力（即，给定风速下垂直和扭转振动的最终状态取决于初始条件），这种振动发生在 2DOF（二自由度）耦合颤振中。