多主跨悬索桥颤振形态演化机理研究

As a new type of bridge, suspension bridges with multiple main spans have broad application prospects in sea-crossing and island-linking projects. In full aeroelastic model wind tunnel tests of the Maanshan Bridge, a unique flutter-mode-evolution phenomenon is observed: under the flutter critical wind speed, the model oscillation with first anti-symmetrical torsional mode transfers to alternative torsional oscillation between double spans, then transfers to oscillation with first symmetrical torsional mode, and violent oscillation happens at last. Because the reason for the phenomenon is unknown and there isn't a method to simulate it, it has academic value for further researches. And also, the flutter critical wind speed of the Maanshan Bridge is increased by the phenomenon sharply, so it's a potential flutter control measures for bridges with multiple main spans. In order to find out the mechanism of the phenomenon and get ready for it becoming a kind of brand-new flutter control measures, methods that combine theoretical analysis, numerical calculation and CFD are used to investigate the main contents as follows: firstly, two inferences about the causes of the phenomenon, soft flutter and internal resonance, will be verified. At the same time, an algorithm to analyse energy transformation of bridges in 3d will be presented and used to research the transfer, dissipation and radiation process of flutter energy for the Maanshan Bridge. Secondly, an approach to predict flutter-mode-evolution phenomenons of typical suspension bridges with multiple main spans will be proposed and then used to simulat and reproduce the phenomenon the Maanshan Bridge in numerical calculation. Last but not least, the condition for the occurrence of flutter-mode-evolution phenomenons of typical suspension bridges with multiple main spans will be argued, and as a flutter control measures, the effectiveness and robustness of the phenomenon will be discussed.

多主跨悬索桥作为一种新兴桥型在跨海连岛工程中有广阔的应用前景。马鞍山大桥全桥气弹模型风洞试验中发现了一种独特的颤振形态演化现象，即接近颤振临界风速时由两跨反对称扭转振动，经两跨交替扭转振动，过渡到两跨正对称扭转振动发散。该现象机理不明，暂无可以模拟其全过程的分析方法，具有深入研究的学术价值；它可以大幅提高颤振临界风速，是一种潜在的颤振控制措施，具有普遍推广的应用价值。拟采用理论分析、数值模拟和数值风洞等手段相结合的研究方法，针对该现象进行机理探索和应用研究，主要内容有：（1）验证关于现象成因的两个基本推断，即软颤振和内共振，并建立桥梁三维颤振能量转换分析的一般方法，研究该桥颤振能量传递、耗散和辐射的过程；（2）建立典型多主跨悬索桥颤振形态演化现象的预测方法，并在数值计算中模拟和再现上述现象的全过程；（3）论证典型多主跨悬索桥颤振形态演化的发生条件，研究其作为颤振控制措施的有效性和鲁棒性。

马鞍山大桥是一座跨径布置为2×1080m的三塔双主跨悬索桥，申请者在其全桥气弹模型风洞试验中发现了一种独特的颤振形态演化现象，即接近颤振临界风速时由两跨反对称扭转振动，经两跨交替扭转振动，过渡到两跨正对称扭转振动发散。该现象机理不明，暂无可以模拟其全过程的分析方法，具有深入研究的学术价值；它可以大幅提高颤振临界风速，是一种潜在的颤振控制措施，具有普遍推广的应用价值。本课题采用理论分析、数值模拟和数值风洞等手段相结合的研究方法，针对该现象进行机理探索和预测模型研究。首先验证了关于现象成因的两个基本推断，即软颤振和内共振，并建立桥梁三维颤振能量转换分析的一般方法，研究该桥颤振能量传递、耗散和辐射的过程；然后利用小波变换分析了马鞍山大桥风洞试验信号的时变功率谱和瞬时相位差，在此基础上建立了典型多主跨悬索桥颤振形态演化现象的预测方法，并在数值计算中模拟和再现上述现象的全过程；最后研究了颤振形态演化与颤振分支跳转的联系，论证了典型多主跨悬索桥颤振形态演化的发生条件。

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