The purpose of this study is to investigate the nonlinear torsional flutter of a long-span suspension bridge with a double-deck truss girder. First, the characteristics of nonlinear flutter are studied using the section model in the wind tunnel test. Different aerodynamic measures, e.g. upper and lower stabilizers and horizontal flaps, are applied to improve the flutter performance of the double-deck truss girder. Then, the full bridge aeroelastic model is tested in the wind tunnel to further examine the flutter performance of the bridge with the optimal truss girder. Finally, three-dimensional (3D) flutter analysis is performed to study the static wind-induced effects on the nonlinear flutter of the long-span suspension bridge. The results show that single-degree-of-freedom torsional limit cycle oscillations occur at large amplitudes for the double-deck truss section at the attack angles of 0∘ and +3∘. The upper and lower stabilizers installed on the upper and lower decks, respectively, and the flaps installed near the bottoms of the sidewalks can all effectively alleviate the torsional flutter responses. Meanwhile, it is found that the torsional flutter responses of the truss girder in the aeroelastic model test are much smaller than those in the section model test. The 3D flutter analysis demonstrates that the large discrepancies between the flutter responses of the two model experiments can be attributed to the additional attack angle caused by the static wind-induced displacements. This finding highlights the importance and necessity of considering the static wind-induced effects in the flutter design of long-span suspension bridges.

中文翻译：

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双层桁架大跨度悬索桥非线性扭转颤振试验研究

本研究的目的是研究具有双层桁架梁的大跨度悬索桥的非线性扭转颤振。首先，利用风洞试验中的截面模型研究非线性颤振的特性。采用不同的气动措施，例如上下安定面和水平襟翼，以改善双层桁架梁的颤振性能。然后，在风洞中对全桥气动弹性模型进行测试，以进一步检验具有最优桁架梁的桥梁的颤振性能。最后，进行三维（3D）颤振分析，研究静态风致对大跨度悬索桥非线性颤振的影响。0∘和+3∘. 分别安装在上下甲板上的上、下稳定器和安装在人行道底部附近的襟翼都可以有效缓解扭转颤振响应。同时发现，气动弹性模型试验中桁架梁的扭转颤振响应远小于截面模型试验。3D颤振分析表明，两个模型实验的颤振响应之间的巨大差异可归因于静态风致位移引起的附加攻角。这一发现强调了在大跨度悬索桥的颤振设计中考虑静态风致效应的重要性和必要性。