Effectiveness of a novel magnetic negative stiffness eddy-current damper for multi-mode vibration control of stay cables : experimental and numerical investigations

Abstract

In recent years, an increasing number of field observations have reported rain-wind-induced and vortex-induced multi-mode vibrations of stay cables on bridges. These multi-mode vibrations may significantly reduce cable lifespan, which adversely affects the safety and serviceability of bridge structures. This paper proposes using a novel magnetic negative stiffness eddy-current damper (MNSECD) to mitigate multi-mode vibrations of stay cables, and performs experimental and numerical studies to investigate its control effectiveness. Specifically, the mechanical model for the developed MNSECD is first presented, followed by validation against experimental data. Subsequently, a numerical model of the coupled cable-MNSECD system is established to investigate its dynamic characteristics, and a multi-mode design methodology is adopted to optimally design the MNSECD. Experimental tests were then conducted to demonstrate the control effectiveness of the MNSECD prototype for the first three modal vibrations of an 11.4 m-long scaled cable. Finally, the performance of the optimized MNSECD in suppressing wind-induced multi-mode vibrations of a 493.72 m-long full-scale cable is comprehensively evaluated through numerical simulations. Experimental and numerical results indicate that the developed MNSECD significantly outperforms the conventional eddy-current damper (ECD) for multi-mode cable vibration control due to the additional negative stiffness, increasing the first, second, and third modal damping ratios of the scaled cable by 168.55 %, 62.10 %, and 26.84 %, respectively. In addition, the developed MNSECD requires a lower damping coefficient than the conventional ECD, providing an appealing alternative for structural vibration control.