This communication presents the design principle and experimental validation of two novel configurations of magnetic negative stiffness dampers (MNSDs), both of which are composed of several permanent magnets arranged in a conductive pipe. The MNSD, as a passive device, efficiently integrates negative stiffness and eddy-current damping in a simple and compact design, in which the negative stiffness behavior depends on the different arrangements of the permanent magnets. When applied to structural vibration control, passive MNSD may achieve a performance comparable with semi-active or active control in some applications. Laboratory experiments of small-scale prototypes successfully verified the proposed MNSD design concept.

This paper systematically investigates the dynamic behavior of stay cables with passive negative stiffness dampers (NSD) installed close to the cable end. A passive NSD is modeled as a combination of a negative stiffness spring and a viscous damper. Through both analytical and numerical approaches, parametric analysis of negative stiffness and viscous damping are conducted to systematically evaluate the vibration control performance of passive NSD on stay cables. Since negative stiffness is an unstable element, the boundary of passive negative stiffness for stay cables to maintain stability is also derived. Results reveal that the asymptotic approach is only applicable to passive dampers with positive or moderate negative stiffness, and loses its accuracy when a passive NSD possesses significant negative stiffness. It has been found that the performance of passive NSD can be much better than those of conventional viscous dampers. The superior control performance of passive NSD in cable vibration mitigation is validated through numerical simulations of a full-scale stay cable.

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