Nonlinear Dynamic Behavior Research of a Simplified Two-Layer Floating Raft System with Series-Coupled Nonlinear Energy Sinks

As one of the basic engineering structures in marine engineering, FRSs play an indispensable role. Controlling the floating raft systems’ (FRS) undesired vibration is essential for ensuring their safety and stability. To effectively absorb or isolate the undesired vibration of the two-layer FRSs, some vibration-controlling appliances are installed between the two-layer FRSs. This work proposes the series-coupled NESs and introduces such NESs into a two-layer FRS. The vibration analysis model of a two-layer FRS with series-coupled NESs is established. Then, the characteristics and parameter influence of the two-layer FRS with series-coupled NESs are systematically researched. According to the analysis, the current method is suitable for correctly predicting the simulating behavior of the two-layer FRS with series-coupled NESs. Series-coupled NESs can synchronously suppress the vibration of the top and bottom floating raft. Introducing series-coupled NESs can ensure the stability of the two-layer FRS and improve the isolating capacity of the two-layer FRS. Additionally, the core parameters of series-coupled NESs should be designed reasonably to control the vibration of the two-layer FRS. Under reasonable parameter combinations of series-coupled NESs, one can effectively suppress the vibration of engineering structures while ensuring their stability. Overall, suitable utilization of the proposed series-coupled NESs is beneficial for vibration suppression or isolation of the two-layer FRS without changing their original vibration characteristics, which has the potential to control the undesired vibration in engineering structures.