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

1. 通过索模型自由振动试验和有限元分析，研究了悬索弯曲振动的模态阻尼。所得结论如下：(1)索模态阻尼的主要原因是滞回能量损失引起的内部阻尼和支座处能量损失引起的支座阻尼。(2)索的内部阻尼与自由振荡附加动应变的平方成正比。因此，平面内对称模态的模态阻尼大于模态过渡区的其他模态阻尼。(3)当初始张力较低时，索的内部阻尼较大，而当初始张力超过抗拉强度的20%左右时，索的内部阻尼几乎与初始张力无关。(4)支座柔度对模态过渡区对称模态阻尼有显著影响。(5)支座阻尼对悬索模态阻尼的贡献近似与支座模态幅值的平方成正比。采用以下思路进行了高阻尼索的可行性研究；由于动应变的增加而导致的滞回能量损失的增加，这可能是由于使电缆不均匀造成的；通过在电缆中插入粘弹性材料来增加剪切阻尼；采用带液体或铅粒的球形小阻尼器增加外阻尼。

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.