Supplementary force effect of nonlinear energy sink inerter on vortex-induced vibration mitigation in a multiple-span structure

Abstract

Nonlinear energy sinks (NESs) with broad energy absorption and inerters with substantial mass amplification effect have found widespread investigation for vortex-induced vibration (VIV) control in recent years. However, these studies commonly overlook the sensitivity of vertical nonlinear vibration systems to additional loading effect, especially in terms of weight variations. To this end, the present study delves into the examination of the influence exerted by weighty nonlinear energy sink inerters (NESIs), specifically the bistable nonlinear energy sink inerter (BNESI) and the cubic stiffness nonlinear energy sink inerter (CNESI), on the control efficacy of VIV in structures. Universal models for the NESI-beam system, accounting for the effects of weight, have been established and numerically solved. It has been found that VIV is more sensitive to weight effects compared to harmonic forced vibration (HFV), as under weight, VIV vibrations generate more transient resonance capture (TRC) frequency ratio components, leading to a decrease in vibration control capability. The degradation of the VIV control capability is essentially due to the variation in the effective control parameter range of NESI caused by weight effects. The adoption of inerters with small inertance coefficients and large spacing between ends can significantly overcome this limitation. Moreover, the enhanced NESI system balances weight by positive linear stiffness elements, thus circumventing the impact of weight on the nonlinear stiffness system. It not only eliminates weight effects but also restricts static displacement of the mass block.