Analysis Of Local Bending Stress And Nonlinear Vibration Characteristics Of CFRP Cables

In recent years, many successful applications of CFRP cable bridges at home and abroad have attracted the attention of many bridge engineers. By virtue of its high intensity, light quality, corrosion resistance and other excellent properties, CFRP material is an ideal material for cable–structures. In addition, cable bridges’ spanning capacity and bearing capacity can be effectively improved by replacing traditional steel cable with CFRP material. Through the efforts of many scholars, many research results of the overall performance of the CFRP cable stayed bridge have been obtained, However, few studies have been involved in the local stress behavior and nonlinear vibration characteristics of CFRP cable, which makes the static and dynamic performance of CFRP cable can not be fully recognized, and the application of CFRP material in the practice of super large span cable stayed bridge is hindered. In this paper, the local bending stress of the CFRP cable, the "self coupling" phenomena of the CFRP cable, and the "mutual coupling" phenomena between the CFRP cable and the beam structure were studied. Specific work contents are as follows:Firstly, the bending stress at the end of the cable with uniform bending stiffness was analyzed by the analytic method. Then several Sutong Bridge’ cables were selected as research objects, and the elastic modulus, length of cable, initial tension and other factors which may influence the bending stress at the end of CFRP and steel cables were discussed under the same conditions. Finally, the tension-bending fatigue properties of two kinds of cables were analyzed by the classical fatigue analysis method. It is concluded that the CFRP cable’ local bending stress is smaller than that of steel cable, and its fatigue properties are superior to that of steel cable too.Secondly, the three-dimensional nonlinear vibration equation of cable was established, and the condition and vibration modes of cable’s internal resonance were analyzed by the method of multiple scales. The 1:1 internal resonance of cable under the main resonance was emphatically solved. Then the internal resonance response of CFRP and steel cables under forced vibration were calculated by the numerical method, and the influence of initial disturbance, damping ratio and other factors on the internal resonance of cable were discussed. Analysis shows that the internal resonant rules of two kinds of cables are basically the same, but the time required to move into a steady state of CFRP cable is shorter, and its maximum amplitude and steady amplitude are less than that of steel cable.Thirdly, the vibration equation of the cable under the moving boundary condition and the two dimensional nonlinear vibration equation of the cable-beam structure were established respectively. Then, the free vibration and forced vibration response of the CFRP cable-beam and steel cable-beam structures were analyzed by the multiple scale method and the numerical method. Finally, the influence of cable’s damping and initial disturbance on the resonant response of two kinds of cable-beam structures were discussed. The results show that the coupling resonance characteristics of CFRP cable-beam structure are better than that of steel cable-beam structure.