Ricerc@Sapienza

The present paper deals with the dynamics of a two-degrees-of freedom system consisting of a nonlinear absorber attached to a primary linear structure under external excitations. The nonlinear attachment exhibits a hysteretic restoring force modeled with the classic Bouc–Wen law [hysteretic vibration absorber (HVA)]; furthermore, the mechanical characteristics of the nonlinear oscillator are tuned to regulate the ratio between the two natural frequencies and to lead the system near to internal resonance conditions.

Noise barriers for high-speed train lines are subject to strong vibrations due to fluid pressure generated by moving trains. The barriers, generally made of steel cantilever beams, suffer fatigue. For their safety, it is necessary to adopt more resistant solutions or reduce their vibration, as is applied in this study. Following the fundamental work by Den Hartog on viscoelastic tuned mass dampers, later contributions on vibration mitigation have shown a variety of phenomena exhibited by a primary structure connected to a nonlinear light attachment.

The dynamic behavior of a 2DOF system consisting of a primary structure and a hysteretic vibration
attachment is investigated. With respect to viscoelastic tuned mass damper, which works in internal resonance
condition (1:1), the systems with the nonlinear attachment can exhibit different internal resonance conditions
(n:1), with n>1. Such these conditions be met, hysteresis produces bifurcations and superabundant nonlinear
modes which are shown to be very effective in reducing the response of the primary structure