Abstract Summary
When dealing with cable-suspended structures, it is essential to have an accurate estimation of the tensile force on cable elements. This is firstly to guarantee the structural safety of the structure but also to allow scheduling of the maintenance operations. Being the direct measurement often related to expensive and invasive operations, many indirect methods exist to solve the problem. Among them, the most popular are the ones based on vibration methods, able to relate the measured natural frequency with the tension force value through the taut string theory. However, in case the cable is part of a more complex system (like a suspended or cable-stayed bridges) or it is endowed with dampers, the vibration method based on the string theory may be inaccurate. This requires a more complex method able to include a detailed description of the cable geometry and constraints, along with modelling the effects of the dampers. To this purpose, referring to the cables of the Hovenring Bridge, a roundabout flyover for bicycles in Eindhoven (the Netherlands), a novel method is presented and applied to such structure. It is based on a combined experimental and numerical approach, where the experimentally based measure of the first natural frequency of the cable is combined with a FEM model of each cable to finally obtain an estimation of the tension force. Specifically, the FE model has been built by considering equivalent tensioned beam elements and it includes the modelling of threated bars and sockets that realize the constrains of the cable. Moreover, it is inclusive of the two Stockbridge type tuned mass dampers that are installed in each cable of the Hovenring Bridge, through equivalent mass-spring-damper systems. In the present paper, a complete description of the method will be carried out, together with the application to the 24 cables of the Hovenring Bridge. A validation of the proposed method is presented as well, through a comparison with a direct measurement of the tension force in 4 cables. Despite here presented with reference to a specific case, the method is suitable for generalization.
