EXPLICIT EXPRESSION FOR TENSION FORCE MEASUREMENT OF SAGGED CABLE WITH 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 and arch bridge with vertical suspenders or horizontal cables to offset the thrust force. However, the string vibration theory ignores the effects of flexural rigidity, sag of inclined cable and attached high damping rubber dampers, which will cause unacceptable errors in the practical applications. In this paper, the effects of bending, sag of inclined cable, the intermediate support on the cable force measurement of a stay cable are analytically studied. A dynamic model of cable considering the effects of bending, sag of inclined cable, and the intermediate support is presented and solved by the energy principle. The cable force is expressed by the explicit expression which is important for vibration-based cable-force measurement. The capabilities of the proposed method are compared with the FEM method by using two examples, namely a numerical simulation for one short cable and another long cable with attached absorber, and the field cable force tests on a cable-stayed bridge before and after the installation of the intermediate absorber. The results demonstrate that the expressions for cable force are simple and practical for considering the complex boundary condition and geometrical nonlinearity of the cable.