Vibration mitigation of offshore structures subjected to wave and wind loads using optimum semi-active tuned mass damper inerter (SATMDI)

This study focuses on mitigating vibrations in offshore structures exposed to dynamic loads. It begins by examining the combined effects of wave and wind -induced loads with varying return periods on a jacket platform. To control platform vibrations, an optimal Tuned Mass Damper Inerter (TMDI) system is adopted. Recognizing the inherent limitations of passive dampers in real-time parameter adaptation, this study dynamically tunes proportional parameters for the damper in response to input excitations. This effort results in the introduction of the SATMDI damper for the first time in this research. In this context, an MR damper, coupled with an optimal fuzzy controller, is deployed. Parameter optimization for TMDI, as well as fine-tuning of membership functions and control rules for the fuzzy controller, is achieved through the implementation of a genetic algorithm. Additionally, the analysis considers both fluid -structure interaction and the influence of the added mass caused by the platform's oscillations in the fluid. The findings elucidate that, in cases of simultaneous wave and wind -induced loading, wind forces can yield a favorable influence in dampening platform vibrations during wave -induced loading. Furthermore, the SATMDI system significantly enhances energy dissipation by 67%, three times more than the optimum TMDI system.