Study On The Nonlinear Parametric Vibration And The Controlling Measures For Stay Cables

Due to the small rigidity, small mass and low damping, cables in cable-stayed bridge are prone to exhibit transverse oscillations of large amplitude which may affect the safety of the whole bridge, reduce the service performance and life. Usually, the multi-cable systems are extensively used in modern cable-stayed bridges, the natural frequencies of cables have a wide distribution and the basic frequencies of girders are lower. As a result, the parametric vibration, one of the kinds of cable vibrations, may provoke large amplitude and impact on the safety and stability of bridges as the occurrence conditions are met easily. Therefore, accurate investigation of vibration characteristics and rational countermeasures are very important for construction and maintenance of cable-stayed bridges.At the first chapter of the paper, the nonlinear characteristics and general situation of cable vibration are introduced, the major works that the domestic and the foreign scholars have done in the field of parametric vibration are reviewed, and the mechanism related are briefly analyzed. Based on the comprehensive effect of sag, large deformation and inclination, the nonlinear model of parametric vibration in axial motivation is built and the single-degree-of-freedom equation is deduced. Furthermore, the cable-girder-tower coupling vibration model is built and the three-degree-of-freedom nonlinear parametric vibration differential equations are gained. The paper sets Tianxinzhou Bridge as the project background and the ANSYS structural analysis procedures are used to develop the dynamic calculation model. Then the dynamic properties are obtained through modal analysis. Comparing the first thirty frequencies of the model with the natural frequencies of cables, the cables that may exhibit parametric vibration were found. The characteristics of vibration are analyzed by Runge-kutta numerical analysis method. The influence of the various parameters, such as excitation frequency, the initial force of cables, the inclination, the initial disturbances, the mass and the stiffness of girder and tower and so on, are investigated.In addition, the vibration controlling measures are introduced. The coupling vibration model proposed in this paper was used to analyze the effectiveness of the viscoelastic damper employed in vibration controlling measures. At last, the practical controlling methods are presented.