ENERGY-BASED EVALUATION OF MODAL DAMPING IN STRUCTURAL CABLES WITH AND WITHOUT DAMPING TREATMENT

The modal damping characteristics of single structural cables are analytically investigated in this paper. An energy-based representation of modal damping in structural cables is first derived in the form of the product of modal strain energy ratio and loss factor. The ratio of the modal strain energy to the total potential energy associated with modal vibration is next calculated numerically for both axial and bending deformation, by applying a finite element method, and the characteristics of each strain energy ratio in each mode of the structural cable is studied. It is deduced from the present analysis that the modal damping in a structural cable is generally very low because of the very large contribution of the initial cable stress to the total potential energy, causing very small modal strain energy ratios. The modal damping of the damping treated structural cable [1] is also estimated by using the same energy-based representation. The performance and the effectiveness of this damping treatment on structural cables is finally discussed, based on the estimated values of the modal damping.