Field comparative tests of cable vibration control using magnetorheological (MR) dampers in single- and twin-damper setups

Publisher Summary This chapter reports the field comparative tests of the cable-damper system under different damper installation setups. In this testing phase, one utmost stay cable of the bridge, about 150 m in length, is tested without damper and with single-damper and twin-damper installations respectively. Sinusoidal-delay excitation is imposed to excite the cable vibration with different levels of response and in different frequencies. A spectrum of voltage inputs is applied to the Magnetorheological (MR) damper(s) during the testing to relate the system damping behavior with voltage strength. A Hilbert transform based identification method is used to identify amplitude-dependent frequencies and damping of the cable-damper system and to determine the optimal voltage that achieves the maximum system damping. The research emphasis is laid on the comparison of in-plane as well as out-of-plane damping performance of the system between the single- and twin-damper setups. Forced vibration tests are conducted to experimentally determine the damping performance of a Dongting Lake Bridge cable attached with MR dampers in the single-damper setup and twin-damper setup, respectively. A new identification method based on the Hilbert transform has been applied to identify the amplitude-dependent frequencies and damping. Modal damping ratios of the cable-damper system under different vibration amplitudes and various voltage inputs are experimentally determined for both the single- and twin-damper setups.