Vibration,Passive And Semi-Active Control Of Cables For Large-Span Cable-Stayed Bridges

Stay cable, which is one of the main components in cable-stayed bridges, is susceptible to environmental and traffic excitations because of its flexible, low damping, small weight, then the significant vibration is induced. The accurate analysis of both the static and dynamic is very import for the design of cables in cable-stayed bridges.A detailed model of non-linear parametric excitation vibration coupling the stay cable and the girder, in which the static sag as well as the geometric non-linearity are considered, is proposed in this paper. Based on several numeric examples investigated by the Galerkin method composed with the integration strategy, several kinds of factors effecting stay cable parameter vibration are studied. Another parameter vibration model by the axial excitation is presented and the corresponding nonlinear equations are derived. The smallest excitation amplitude,the transient state and steady state resonance amplitudes, and the changing characteristics of the axial force are obtained by using harmonic balance method. According to numerical examples calculated by numerical integration method, the effects of the inner damping of the stay cables are investigated.The 1:1 internal resonance of the stay cable coupling the in-plane and out-of-plane modes is analyzed. The coupling nonlinear vibration equations involving both the first in-plane and the first out-of-plane modes is generated by using the Galerkin method. According to the derived equations, the internal resonance subjected to the in-plane excitation is analyzed by the multiple scale method. The results reveal that the internal resonance of the stay cables posses the characteristics of multiple values and divergence. The cable damping can significantly affect the internal resonance. Also the response amplitude will be changed with the initial conditions due to the nonlinear properties of the cables.Taking the bending stiffness, cable sag and cable inclination into consideration, the space vibration control of the cables using the visco-elastic dampers in cable-stayed bridges is investigated by joining the center difference method and the state space strategy. Both the maximum modal damping ration and the optimal damper size are obtained, then the practical suggestions are proposed for the design of the dampers. The space nonlinear vibration equations of the cable-damper system are derived, and anew hybrid method for solving the cable-damper system is presented by combing the Newmark method and Pseudo-force technology. According to the known properties of the cable-damper system, the nonlinear transient responses are analyzed under all kinds of excitations. Based on the transient response, the control effectiveness of the visco-elastic dampers is further demonstrated.According to the LQR optimal control theory, Clipped-optimal control arithmetic, and the modified Bouc-Wen model of the MR dampers, the LQR-Clipped semi-active control is proposed. The passive, active, and semi-active control of the cables are analyzed by using the difference discretization model of the cable-dampers system. The control efficiency of MR damper is investigated.The field tests of the No. 15 stay cable attached with oil-dampers in the QianTang Jiang No.3 Bridge are conducted. The tests data are analyzed by the fitting method of the frequency response function. The dynamic characteristics of the cable and dampers are investigated.