Dampers have been used for vibration mitigation of stay cables;however

there are few literatures on the test of full-scale stay cable attached with nonlinear viscous damper.In this paper

a full-scale cable vibration mitigation experiment was conducted by using a 215.58 meters long stay cable and a set of home made nonlinear viscous dampers.The cable was excited by human power and then the free decay curve of cable and cable-damper system was measured.The damper force was also measured during the test.Then the logarithmic decrement of cable could be calculated from the displacement free decay curve.It was found that the internal damping of free cable is very small;the derived logarithmic decrement of cable-damper system varied with amplitude.The mean value of logarithmic decrement of cable-damper system was about 0.04

large enough for mitigation of possible cable vibration.Comparison of the mean value of measured logarithmic decrement with theoretical maximum was conducted.It was found that the measured maximum logarithmic decrement value was smaller than the theoretical maximum due to the effect of stiffness of supporter and damper.The efficiency ratio

which is the mean value of logarithmic decrement divided by theoretical maximum

was derived for possible practical damper design.