Parametric Vibrations Of Stay Cables And Its Suppression Methods

In recent years,the transportation infrastructures in China has been developed significantly,and a large number of large-span cable-stayed bridges have been completed and used to improve traffic quality,which has promoted the rapid development of the national economic constructions.As the main force-bearing member of the cable-stayed bridge,the stayed cable has the characteristics of long,thin,soft,and low-damped,and it is prone to large vibrations.When the excitation frequency of the lower ending is 2 times of the cable frequency,the large-amplitude parametric vibrations may be excited.In this paper,for parametric vibrations and its suppression methods of stay cables,a refined model of the stay cable is established.The parameter vibration and main resonance characteristics of the stay cable and their influencing factors are studied,and the effect of hybrid cable-damper-auxiliary cable is discussed.The dynamic characteristics of the control system are expected to provide useful suggestions for the actual engineering of bridge parameter vibration control.The main research work of this paper includes:(1)A comprehensive review of the research progress of stay cable vibration,especially the parametric vibration problem and its control,is given.(2)A refined model of cable end axial excitation considering the chord component of the stay cable is established,and deduced into a unified form with the tension string model and the model considering the cable sag;The scope of application of the three models is compared;The harmonic balance method is used to deduce the stable interval of the cable parametric vibration.The minimum damping and the maximum end excitation amplitude required for the corresponding parametric vibration control is also obtained;The influence of the frequency range,end excitation size,cable damping ratio,inclination angle,initial tension and excitation type is analyzed.(3)A coupling model combining cable and deck for cabe parametric vibrations is established and written in a unified form with the axial excitation model.The influence of the system frequency ratio,initial disturbance,mass ratio,and damping ratio on the vibration characteristics is analyzed by numerical methods.(4)The coupled parametric vibration model of the stayed cable-deck-wake oscillator was further established,and the parametric vibration of the stayed cable under the vortex excitation of the main girder was simulated.The experimental data for a cable-stayed bridge with vortex-induced vibrations was obtained through wind tunnel test research.The parameters of the coupling model were obtained by optimizing the difference between the experimental and numerical results.The identified wake oscillator model parameters were substituted into the cable-deck-wake oscillator coupling model.The effects of stall parameters,static lift coefficient amplitude,coupling coefficient and other parameters were studied.The influence of the vibration characteristics of the cable-deck-wake oscillator coupling model was discussed.(5)The vibration characteristics of the cable damper hybrid control system were studied,and the cable-damper-auxiliary cable vibration model was established.The characteristic equation numerical method and the QR damp method in ANSYS were used to analyze the cable-damper-auxiliary coupling system.The influence of the installation position of the auxiliary cable and the stiffness of the auxiliary cable on the vibration characteristics of the system is discussed.