Cable vibration control using magneto-rheological (MR) dampers

As the world's first time implementation of MR-based smart damping technique in bridge structures, a total of 312 semi-active magneto-rheological (MR) dampers (RD-1005, Lord Corporation) have recently been installed for rain-wind-induced cable vibration control on the cable-stayed Dongting Lake Bridge, China. This project has undergone several stages of experiments and tests: (i) modal tests of undamped cables, (ii) forced vibration tests of MR-damped trial cables, (iii) monitoring of MR-damped and un-damped cable responses under rain-wind excitations, (iiii) comparative tests using different damper setups, (v) full installation, and (vi) field measurements and real-time control tests after the installation. After briefly introducing the above six stages of the whole project and addressing the experience and lessons learned from them for both the open-loop control and closed-loop control, this paper will focus on the design considerations on cable vibration control using MR dampers, taking into account the effect of the damper stiffness, damper mass, stiffness of damper support, nonlinearity of the damper, and sag and inclination of the cable. Some issues will be addressed on designing an improved MR-damper particular for application to bridge cables, based on the theoretical studies and several stages of field tests in the cable-stayed Dongting Lake Bridge, which have been being carried out for three years.