Study on Damping of Structural Cables and Development of High-Damping Cable

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1. The modal damping of flexural oscillation in suspended cable was investigated through free oscillation experiments with cable model and through finite element analyses. The brief conclusions obtained are as follows: (1) Primary causes of modal damping of cable are the internal damping caused by the hysteretic energy loss and the support damping due to the energy loss at support. (2) The internal damping of cable is in proportion to the square of additional dynamic strain of free oscillation. The modal damping of in-plane symmetric mode is, therefore, larger than other modal damping in the modal transition region. (3) The internal damping of cable is larger for lower initial tension but almost independent on the initial tension when the initial tension exceeds about 20 percent of the tensile strength. (4) The flexibility of support has significant effect upon the modal damping of symmetric mode in the region of modal transition. (5) Contribution of support damping to modal damping of suspended cable is approximately proportional to the square of modal support-amplitude.2. The feasibility study on high-damping cable was conducted with the following ideas; the increase of hysteretic energy loss due to the increase of dynamic strain which may be caused by making the cable non-uniform; the addition of shear damping by inserting viscoelastic materials into cable; and the addition of external damping by using small spherical damper with liquid or lead grains.