The Flexural Rigidity Of Cable Identification Method Research

As a kind of structural element which supports tension efficiently, cable is widely used in bridge, High-rise and large-span structure. As a main load-born structure, cable tension is main index in cable structural health condition evaluation and monitoring. Because of many advantages of vibration-based method, it has become mostly used method in testing cable tension. The flexural rigidity of cable is an important parameter in cable tension test and calculation formula, composed of many steel wire bundles, the flexural rigidity of suspender and cable-stayed is difficult to determined. If the flexural rigidity of cable can be identified beforehand, It will bring a lot of convenience in cable tension test and calculation. The thesis studies mainly the flexural rigidity identification method of cable and application, the main research work is presented as fllowing:1. Several commonly used cable tension test methods are summarized. Outline the research state of vibration-based method in cable tension test, and then show the existing problems in the flexural rigidity identification of cable.2. The free vibration theory of cable is the theory basis of cable tension test and calculation. In the condition of the flexural rigidity of cable is considered or not, the free vibration frequency equation and cable tension calculation formula are given based on the string model and the beam model.3. After considering the flexural rigidity、boundary condition and cable sag effect, the free vibration equation of cable is a nonlinear equation, the relation of the free vibration frequency and cable tension is a transcendental equation, and it can not be solved directly. By using singular perturbation method, an approximate analytical expression of the free vibration frequency eigenvalue and eigenfunction is deducted detailly. Using the design parameter of cable, the free vibration fruquency calculation value will be obtained conveniently, and using frequency response test data, the free vibration frequency test value can also be obtained easily. By minimizing variation of the cable free vibration frequency calculation value and test value, an optimazation problem of cable parameter identification is obtained. By solving the optimazation problem the flexural rigidity of cable can be identified.4. Based on the suspender of a92meters-long "X-style" arch bridge of The Yellow River Rail-Road bridge, Zhengzhou, and the cable-stayed of Yamen bridge, Guangdong, the flexural rigidity of cable is identified, which verify the method proposed of the thesis. It is shown that, the flexural rigidity real value of cable is about (0.3～0.4) times as the flexural rigidity maximum value (based on the whole cable section), which is correspond with the actual engineering.