Mitigating deepwater jacket offshore platform vibration under wave and earthquake loadings utilizing nonlinear energy sinks

The random vibrations of jacket offshore platforms under wave and earthquake actions can reduce the service life and exacerbate fatigue damage of the offshore platforms. Aiming to mitigate those unwanted vibrations, this paper introduces the nonlinear energy sinks (NES) to the deep-water jacket offshore platform as a passive control device. Its coupling dynamic model is built with assumed parameters of wave and earthquake loads, and the wave forces of the platform structure are calculated by Morison's equation. Further, the optimal parameters of the NES system are obtained by an exhaustive search algorithm under the objective function. The results show that the NES system can effectively contribute to mitigating the maximum, minimum, and root mean squares (RMS) of deck-level responses of the platform structure. What's more, despite various mass or stiffness of platform structure, the NES system not only greatly reduces the response peaks, but also demonstrates a more steady phenomenon, in which the robustness is presented clearly. In this way, it strongly proves the feasibility and robustness of the NES system under wave and earthquake loadings.