Parametric Vibrations And Its Control For Stay Cables In Cable-Stayed Bridges

The research concerning vibration of cables has attracted considerable interests in ca-ble-stayed bridges. With the development of transportation and the construction of large ca-ble-stayed bridges, especially the application of overlength stayed cables, the issues are ofparticular importance on vibration of cables. In China, it appears to replace cables due toproblems of cable-vibration after a period of operation, which influence greatly the safety ofbridges and increases the difficulty and the cost of maintenance. Parametric vibration ofcables is a kind of transverse vibration when cable ends are subjected to periodic axis move-ments, the movements of bridge deck under traffic loading or bridge tower under wind load-ings may induce parametric vibration of stay cables. In this study, the analytical and experi-mental study of cable vibration is carried out and active vibration control of parametric vibra-tion is also explored. The work and findings are listed as follows.(1)The development history of cable-stayed bridges was introduced, along with somecommon forms of vibration damage, for which, some ways of vibration reduction commonlyused were displayed.(2)The differential equation on cable-vibration was deduced to investigate parametric vi-bration theoretically. The effect of influential parameters including angle of tilt, damping, ini-tial cable forces, vibration frequency and amplitude are analyzed. By means of observing in-fluence degrees and patterns, the instability zone of cable-vibration was discovered. Moreover,the research on parametric vibration of stay-cable was conducted in the re-search center ofWind Tunnel Laboratory, in Hunan University. The operating conditions of parameters, suchas cable forces, vibration frequency and amplitude, were explored, and the results were iden-tical with that expected by numerical analysis in the scope of the project.(3)At first,take Qinglan Bridge for example, the first twenty and first ten order frequen-cies of the whole bridge and cables were respectively obtained via building finite elementmodel of whole bridge and cables, as well as the analysis of parametric vibration made in thestay-cable.(4)Due to the symmetry of the bridge, analyse the cables frequency of the1/4full-bridgeand compared it to the theoretical value. The finite-element analysis results are consistentwith the theoretical ones,except for some few cables.Established the finite element model ofsingle girder bridge, analyse the change rule of the cables’ center displacement, under the si-nusoidal load,at different frequencies,different excitation amplitude,different beam posi-tion.The numerical simulation result is agreement with the previous conclusion.(5)The optimal control of stay-cable parametric vibration was discovered on the basis of the state space equation and the optimal control theory. Parametric vibration was investigatedthrough being actively controlled, and compared with its center-displacement in non-control,it is discovered that parametric vibration could be controlled well and have obvious results.