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.