Research On The Methods Of Improving Multi-mode Vibration Control Effect Of Stay Cables

Stay cables,as the indispensable load-bearing components of cable-stayed bridges,which slenderness ratios are increased with the increasing span of cable-stayed bridges.Stay cables are highly susceptible to harmful vibrations caused by wind,wind and rain coupling and other external environmental excitations.With the popularization and application of super-long stay cables,the installation height ratios of dampers are further reduced,and the target control mode orders of stay cables are greatly increased.The supplemental modal damping provided by conventional passive viscous dampers(VDs)for stay cables is limited,which is difficult to mitigate multi-mode cable vibrations.Relying on the project of the National Natural Science Foundation of China “The theory and technology of three-element passive mitigation of structural vibration and its performance improvement for vibration control of stay cables”(51878274),this paper takes a 306.7m long cable of a domestic cable-stayed bridge as the research object.Based on the methods of complex modal theoretical analysis and finite difference numerical simulation,the multi-mode vibration control performances of negative stiffness nonlinear viscous damper(NSNVD),inertial mass nonlinear viscous damper(IMNVD)and two inertial mass dampers(IMDs)at the same cable end,are investigated respectively.The main conclusions are summarized as follows:(1)The passive negative stiffness effect of NSNVD significantly improves the singlemode and multi-mode vibration mitigation performance of stay cables,and the nonlinear viscous damping characteristics help to improve the multi-mode vibration mitigation performance of stay cables.For the single-mode vibration mitigation,the negative stiffness can significantly increase the maximum supplemental modal damping ratios of stay cables,and can effectively reduce the corresponding optimal damping coefficients of NSNVD.For the multimode vibration mitigation,the negative stiffness can improve each order modal damping ratios of stay cables uniformly,and can also effectively reduce the corresponding optimal damping coefficients of NSNVD.While the nonlinear viscous damping of NSNVD can effectively reduce the difference between each order supplemental modal damping ratios of stay cables,and can significantly reduce the optimal damping coefficients of NSNVD.(2)The inertial mass of IMNVD significantly improves the single-mode vibration mitigation performance of stay cables,but the excessive inertial mass reduces the multi-mode vibration mitigation performance of stay cables.The nonlinear viscous damping characteristics help to improve the multi-mode vibration mitigation performance of stay cables.For singlemode vibration mitigation,the inertial mass can significantly increase the maximum supplemental modal damping ratios of stay cables,and effectively reduce the corresponding optimal damping coefficients of IMNVD.For multi-mode vibration mitigation,excessive inertial mass can significantly increase the difference between each order modal damping ratios of stay cables,and improve the corresponding optimal damping coefficients of IMNVD.While the nonlinear viscous damping of IMNVD can effectively reduce the difference between each order supplemental modal damping ratios of stay cables,and can significantly reduce the optimal damping coefficients of IMNVD.Compared with NSNVD,the performance of IMNVD on single-mode vibration mitigation of stay cables is similar,but the performance of IMNVD on multi-mode vibration mitigation of stay cables is significantly reduced.(3)When two IMDs with reasonable parameter matching are installed at the same end of the cable,the single-mode and multi-mode vibration mitigation performance are superior to that of installing a single IMD at a further distance from cable anchorage.For single-mode vibration mitigation,the single-mode vibration mitigation performance of two IMDs with reasonable parameter matching is not only better than the single IMD installing at a further distance from cable anchorage,but also better than the sum of the respective vibration mitigation performance of two IMDs.For multi-mode vibration mitigation,the multi-mode vibration mitigation performance of two IMDs with reasonable parameter matching is better than the single IMD at a further distance from cable anchorage,and it has significant advantages for high-order mode vibration mitigation of stay cables.