Author(s): Chenxiang Zhang; Zhenju Chuang; Zhengjiang Wang; Kang Wan
Linked Author(s):
Keywords: FPSO; Ice loads; Rainflow counting method; Ice-induced fatigue; Fatigue life
Abstract: This study establishes a refined fatigue life assessment methodology for moored polar FPSOs. Focusing on a typical vessel in the Arctic Baffin Bay, high-fidelity ship-ice collision simulations using the explicit dynamic finite element method directly provide random ice load histories at hull hot spots. The load spectra are converted into equivalent stress spectra at weld toes via rainflow counting, the hot-spot stress method, and Goodman mean stress correction. Fatigue damage at three key locations over a 30-year life is then evaluated using the D-class S-N curve and Miner's rule. Results show: (1) the ice load stress spectrum has a significant "heavy-tailed" distribution; (2) damage is "extreme-event-driven" by rare, high-amplitude cycles (<1% of total); (3) Hotspot 2 is the most vulnerable location (cumulative damage 0.8052), with Loading Case 1 (ice thickness 2.0 m, speed 0.4 m/s) as the governing condition. Although the overall structure meets the design life, Hotspot 2's safety margin is relatively limited. This work provides crucial theoretical and quantitative support for the anti-ice design and targeted maintenance of polar FPSOs.
Year: 2026