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

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.