Dynamic Performance Analysis Of Parametric Vibration Of Super-long Stay Cable Subjected To Radom Excitations

As one of the most important force transfer components of cable-stayed bridge,the stay cable connects with the bridge deck to transfer the weight and load to the tower at the other end.With the continuous progress of new materials and technology,the span of cable-stayed bridge is growing,and the super-long stay cables over 500 meters are becoming more and more common.Due to the characteristics of small mass,low damping and high flexibility of stay cables,the increase of stay cable length further strengthens these characteristics.Therefore,super-long stay cables have smaller vibration frequency,and the modal frequency range of parametric vibration is widened,and the possibility of large parametric vibration is increased accordingly,which poses great challenges to the safety and durability of cable-stayed bridges.Therefore,it is necessary to analyze the characteristics and mechanism of parametric vibration of super-long cables.In this paper,the theoretical analysis and numerical simulation methods are used for comparative verification to explore the rules and characteristics of large amplitude parametric vibration of stay cables when the bridge deck is subjected to random load excitation.The research contents of this project include the following aspects:(1)Axial white noise displacement excitation was applied to the end of the stay cable,and the first-order modal vibration equation of the stay cable is derived from the sag of cable curve equation which takes into account the sag and the gravitational chord component.The amplitude response of the cable vibration was solved by the cumulant closure scheme.The Monte-Carlo method was used to verify and analyze the effects of cable damping,load displacement excitation amplitude and frequency on nonlinear parametric vibration response of super long stay cables,which provided theoretical guidance for the subsequent research on parametric vibration of super long cables under narrow-band random displacement excitation.(2)Considering the in-plane vibration of super long stay cables excited by axial narrow-band random displacement at the end of the cable,the cumulant closure scheme and Monte-Carlo method were used to analyze the parametric effects of 1:2,1:1 and 2:1of stay cables.The influence of cable damping,displacement excitation amplitude and bandwidth on nonlinear parametric vibration response of stay cables was analyzed,which provided a research basis for nonlinear parametric vibration analysis of stay cables considering cable bridge coupling.(3)Considering the cable bridge coupling effect,the bridge deck was simplified as a mass block,and the broadband white noise and narrow-band random load excitation were applied to the bridge deck vertically.Monte Carlo method was used to analyze the center frequency of the external excitation load when the frequency ratio of the cable bridge is 1:2,1:1 and 2:1,and the influence of the bandwidth of the narrow-band random load excitation,the amplitude strength and the damping of the system on the nonlinear parametric vibration of the system is considered.