Vibration-based Cable Force Measurement Of Inclined Cable With An Attached Vibration Absorber

The vibration method based on the string vibration theory is often used to estimate cable forces from measured natural frequency, and it is widely applicable to the construction control, performance evaluation and long-term health monitoring of cable-stayed bridge. However, the string vibration theory ignores the effects of flexural rigidity, sag of inclined cable and attached damper, which will cause unacceptable errors in the practical applications. In this paper, the energy principle and the identification algorithm based on FEM and PSO (particle swarm optimization) were employed to deduce practical formulas for the cable force measurement of inclined cable with attached damper by taking the effects of flexural rigidity, sag and attached damper into account. The effectiveness of the practical formulas was verified by the numerical analysis and the field cable force measurement. The main work in this thesis is described as follows:(1) The analytical method and FEM were employed to deduce the cable force calculation formulas of the cable without attached absorber, and a new method to identify the flexural rigidity of cables was proposed in this paper.(2) The energy principle was employed to deduce the cable force calculation formulas for the cable with attached absorber. The formulas have clear physical significance by considering the effects of flexural rigidity, sag of inclined cable, and the position and support rigidity of the attached absorber.(3) A PSO-based optimization method in conjunction with the cable vibration theory was conducted to identify the cable parameters such as the cable force, flexural rigidity, and the position and support rigidity of the attached absorber. The numerical analysis and the field cable force measurement demonstrated that the identification algorithm can significantly improve the accuracy in case more than 5 modal frequencies could be measured.(5) The field test on the cable force measurement of the Ganxigou cable stayed bridge in ChongQing and the experimental model test on the cable vibration were finally conducted to investigate the effectiveness of the proposed formulas.