钢和CFRP拉索的振型阻尼特性研究

STUDY ON CHARACTERISTICS OF MODAL DAMPING OF STEEL AND CFRP STAY CABLES

应用非正交粘性阻尼理论和应变能比例阻尼理论,讨论了斜拉索振型阻尼比分布特征,通过与钢索实测值的对比,验证了粘性阻尼理论的适用性。在此基础上进一步比较了钢和CFRP拉索的振型阻尼比以及粘性减振器的阻尼效果。结果表明,由于初张力产生较大的势能,按应变能比例阻尼理论计算得到的拉索面外振型阻尼比不合理,且面内振型的阻尼比分布规律与实测值也不一致。根据实测结果推断得到的钢索粘性阻尼系数大约为10-4kN·s/m―10-3kN·s/m。拉索的垂度比对振型阻尼比影响显著,而倾角的影响不大。CFRP拉索的振型阻尼比大于钢索,且粘性阻尼器的附加阻尼效果较好。

The characteristics of damping distribution for stay cables were investigated based on non-orthogonal viscous damping theory and strain energy proportional damping theory. Effectiveness of the viscous damping theory was validated by comparing the theoretical results to those from the field test. Modal damping ratios of steel and CFRP cables, as well as the effectiveness of the viscous damper, were investigated comparatively. The results show that because of the large potential energy caused by the initial tensile stresses, the out-of-plane modal damping ratios obtained from the strain energy proportional damping theory is not reasonable and the in-plane modal damping ratios are quite different from the experimental ones. Based on the field test, viscous damping coefficient of steel cables is in the range of 10^-4- 10^-3 kN＇s/m. The sag is proved to have significant effect on the modal damping ratio, while the inclination has little influence. The modal damping ratio of CFRP cables is larger than that of steel cables, and the viscous damper is more effective for the former.