Control of nonlinear offshore platforms using semi-active tuned mass damper inerter under combined wave and wind loads

The present paper investigates the effectiveness of a new control system called Semi-Active Tuned Mass Damper Inerter (SATMDI) in mitigating vibrations of offshore platforms with nonlinear behavior subjected to simultaneous wind and wave loading with various return periods. This new control system is specifically evaluated on Ressalat jacket platform and this study considers the fluid-structure interaction (FSI) in addition to the added mass effect because of platform oscillation in the fluid. An interval type-2 fuzzy logic controller (IT2FLC) is used for online voltage calculation of this control system. The utilized IT2FLC is optimized with an algorithm called the observer-teacher-learner-based optimization (OTLBO). Additionally, the hysteretic behavior of the platform is simulated by means of the Bouc-Wen model. The results indicate that the proposed optimal control SATMDI + IT2FLC can significantly dissipate a considerable amount of energy applied to the structure, therefore avoid the structure from entering the plastic range. For instance, under a loading scenario with a 100-year return period, the decrease in maximum inter-story drift and absolute acceleration responses are estimated about 91 % and 83 %, respectively.