Author(s): Haoyang Yin; Shaowei Tang; Haidian Zhang; Yan Qu
Linked Author(s):
Keywords: Offshore wind turbines; Appurtenant structures; Fatigue analysis; Ice-induced vibration
Abstract: Appurtenant structures of offshore wind turbine foundations in the Bohai ice zone, such as J-tubes, ladders, and boat landings, are directly exposed to repeated ice action near the ice-water interface. Owing to their complex welded details and geometric discontinuities, these components may become fatigue-critical in ice-covered waters. This study evaluates the ice-induced fatigue response of appurtenant structures attached to a monopile foundation using field-measured ice-load time histories from the JZ9-3MDP platform and a three-dimensional nonlinear finite element model. Different installation orientations were examined under a probabilistic ice environment model. The results show that fatigue damage is highly sensitive to the relative angle between the structural layout and the dominant ice drift direction. Lateral ice impact causes severe bending-torsional stress concentration at the brace roots and produces the most unfavorable fatigue response. Under this scenario, the predicted fatigue life of the controlling hot spot is 5.37 years with an F3 class S-N curve and 22.28 years with a D class S-N curve. These findings suggest that installation orientation should be considered in the early layout design of appurtenant structures, while practical constraints such as cable routing, access requirements, and construction sequence should also be accounted for. When unfavorable ice directions cannot be avoided, local reinforcement or improved welded-detail quality is required.
Year: 2026