超长拉索多模态控制的黏滞阻尼器参数优化研究

Parameters optimization of viscous dampers for multi-modal control of ultra-long stay cables

苏通大桥500 m级斜拉索的振动响应实测表明:超长拉索可能存在剧烈的高阶涡振,且发生风雨振的模态阶数也远高于传统中、短索。传统的控制斜拉索前若干阶模态的黏滞阻尼器参数优化方案无法满足超长索的高阶模态振动控制要求。为此,对拉索黏滞阻尼器系统高阶模态的附加模态阻尼比及最优阻尼系数进行了推导;再以模态阻尼比为控制指标,研究了适用于控制超长拉索多模态振动的阻尼器参数方案,并与传统前若干阶模态控制方案进行了分析对比。研究表明:相邻的较低阶模态对应的最优阻尼系数之间差别巨大,导致阻尼器按照控制前几阶模态进行参数设计时,控制效果随着模态阶数的提高而急剧下降;而随着模态阶数的提高,相邻模态对应的最优阻尼系数之间差别将减小。若不考虑对第1,2阶模态的控制,从第3阶模态开始考虑(即ζ3≥ζmin)设计阻尼器参数,阻尼器对超长拉索控制的模态范围能够被大幅扩大。

Vibration responses of 500 m scale cable-stayed cables of Sutong Bridge show that:Ultra-long cables may have severe high-order vortex-induced vibrations,and the mode orders of rain-wind-induced vibrations are much higher than that of traditional medium or short cables.The traditional parameter optimization schemes of viscous dampers for controlling the first several modes of stay cables cannot meet the requirements of high-order vibration control of ultra-long cables.In this paper,the additional modal damping ratios and the optimal damping coefficients of the cable-viscous damper system are derived.Moreover,modal damping ratios are taken as the control index.The parameter optimization scheme of viscous dampers suitable for controlling the multi-modal vibration of ultra-long cables is studied,and compared with the traditional schemes.The results show that there is a great difference between the optimal damping coefficients of the adjacent lower modes,which leads to a sharp decline of the control effect with the increase of the mode order when the damper parameters are designed according to the first several modes.With the increase of mode order,the difference between the optimal damping coefficients of adjacent modes will decrease.If the control of the first and second modes is not considered and the parameter optimization of the damper starts from the third mode(ζ3>ζmin),the modal range of control can be greatly expanded.