Research On Nonlinear Train-Induced Vibration Of Stayed Cables Based On Cable-Beam Vibration

Long-span cable-stayed bridge has light and soft property, and its cables are always have large flexibility, light mass and low damping. The cables will be most easily prone to exhibit vibration with frequent features and large amplitude subjected to train load or wind load, which will aggravates cable’s fatigue damage. In this thesis, the local vibration characteristics of cables under train load was investigated by taking a railway cable-stayed bridge with a main span of 600m as an engineering background. The dynamic responses of bridge’s major structure (beams and towers) as cables’ end excitation were obtained based on train-track-bridge coupling vibration analysis, and the localized vibration responses of a cable was solved by large stiffness method.Firstly, the dynamic analytical model of cables subject to train load was introduced, which including the description of train-track-bridge coupling vibration model and the solving theory of cables’ nonlinear localized vibration responses.Secondly, according to the structure form and design parameters of a cable-stayed bridge with a main span of 600m, the whole bridge model and the single cable model were described in detail, and the modal analysis and comparison between these two models were carried out.Thirdly, the vibration correlation of bridge’s major structure and its cable components was investigated by a comparison of time-frequency analysis between the dynamic responses of bridge’s major structure and the localized vibration responses of cables, the dynamic responses of bridge’s major structure were excited by train (CRH2) excitation with vehicle speed of 200km/h. The results indicates that the vibration energy transfers easily in the condition that the frequency of bridge’s main structure is close to the frequency of cables. The more proportion this part of frequency components have, the more easily main resonance of cables occurs.Fourthly, the variation of cables’ localized vibration responses subjected to train (CRH2) excitation with design speed of 200-350km/h shows that cables’ localized vibration characteristics is more sensitive to the change of train speed. When the train speed increases, the first-order resonance are more likely to occur in cables whose fundamental frequency is relatively higher.Lastly, in order to investigate the influence of viscous damping coefficient and reference frequency on the localize vibration responses of cables, two different patterns of cable-damper system were established. And a comparison of dynamic responses between these two different patterns of cable-damper system was carried out. One pattern of the cable-damper system was a system with a cable model and an external damper model, the other pattern was a system whose external damper model was replaced by Rayleigh damping model. The research shows that the influence of viscous damping coefficient and reference frequency on damping effect is obvious. The contribution of modal damping of a external damper can be well reflected by use of Rayleigh damping model when the value of modal damping ratio of cables is the same.