500 m级拱桥缆索吊施工期间风缆振动特性研究

Study on Vibration Characteristics of Wind-Cables during Cable-Hoisting Construction of a 500 m-Class Arch Bridge

摘要: 某主跨500 m级特大拱桥按缆索吊装斜拉扣挂施工法设计，其缆索吊风缆跨径接近800 m，且风缆跨内无任何横向缆索或竖向吊杆，导致其几何刚度非常低。这类超长水平柔性风缆在桥梁工程中罕见，有必要分析其振动特性。本文建立了这类超长水平柔性风缆振动的理论模型，并分析了各设计参数对该桥风缆振动响应的影响。结果表明：1) 在轴向激励频率Ω与一阶固有频率f₁的比值分别为1和2附近时，风缆将分别出现明显的线性内部共振和参数共振；2) 风缆参数振动对激振频率Ω非常敏感，这与超长索的自振基频过低有关；3) 轴向激励幅值U_d对风缆的参数振动有显著影响，激励幅值较小时不足以激发参数共振，激励幅值较大时参数共振的振幅增大、但增速有所放缓；4) 风缆阻尼比ξ₁对风缆的参数振动有显著影响，阻尼比较小时不足以抑制参数共振，但适当增大后可显著抑制参数共振。本文结论可为该类超长风缆的振动控制提供指导。

Abstract: A long-span arch bridge with a main span of 500 m was designed using the cable-hoisting and stayed-cable fastening method, in which the span of the wind-cable for the cable-hoisting system approached 800 m. No transverse cables or vertical hangers were present within the span of the wind-cable, resulting in extremely low geometric stiffness. Such ultra-long horizontal flexible wind-cables are rare in bridge engineering, necessitating an analysis of their vibration characteristics. In this study, a theoretical model for the vibration of such ultra-long horizontal flexible wind-cables was established, and the influence of various design parameters on the vibration response of the cable was analyzed. The results indicated that: 1) When the ratio of the axial excitation frequency Ω to the first-order natural frequency f₁ was approximately 1 and 2, significant linear internal resonance and parametric resonance were observed, respectively; 2) The parametric vibration of the cable was highly sensitive to the excitation frequency Ω, which was attributed to the excessively low fundamental frequency of ultra-long cables; 3) The amplitude of axial excitation U_d exerted a significant influence on the parametric vibration of the cable—small excitation amplitudes were insufficient to trigger parametric resonance, whereas larger amplitudes increased the resonance amplitude, though the growth rate slowed; 4) The damping ratio ξ₁ of the cable significantly affected its parametric vibration—a low damping ratio was insufficient to suppress parametric resonance, but a moderate increase could effectively mitigate it. The conclusions can provide guidance for the vibration control of this type of ultra-long wind-cable.