Fatigue Assessment of Offshore Triceratops Restraining System Under Hurricane-driven Metocean Conditions

Compliant offshore platforms use a form-dominant approach to achieve the required compliance in ultra-deep water. They are position-restrained by taut-moored tethers, which undergo considerable stress cycles during their service life, making fatigue assessment essential. The present study investigates triceratops' restraining system at 2400 m water depth under hurricane-driven Metocean conditions. The fatigue assessment uses two approaches: T-N curve and the S-N curve. As the numerical studies show, the 10-year hurricane return period governs the fatigue life of tethers. In specific terms, peak wave and peak wind cases govern the fatigue life of tether-2, whereas the peak current case governs tether-1 under hurricane conditions. Further, the unfactored fatigue life estimated using the S-N curve is about 60% higher than that of the T-N curves. However, the factored service life estimated using both the approaches with recommended safety factors matches closely. The presented study will aid the offshore engineers in preliminary designing a restraining system for the novel triceratops.