Effects of marine environmental factors on wind–wave responses and fatigue damage of jacket offshore wind turbines

Assessing the effects of marine environmental factors on the dynamic responses and fatigue performance of offshore wind turbines is essential for ensuring their long-term operational safety. This study investigates a four-pile jacket offshore wind turbine founded in clay and develops a time-domain analysis framework for dynamic response and fatigue damage assessment by incorporating equivalent pile-head boundary conditions and stochastic wind–wave loads. The effects of marine growth thickness, immersion depth variation, and seawater corrosion on structural responses and fatigue damage of critical joints are systematically evaluated. The results indicate that marine growth significantly increases wave loading on submerged members and base shear, while its influence on overturning moment and global lateral displacement is limited. Immersion depth variation has a minor effect on global dynamic responses but alters the spatial distribution of acceleration responses near the mudline, jacket platform, and upper-middle tower region. Corrosion degradation primarily increases lateral displacement due to stiffness deterioration. Both marine growth and corrosion substantially increase fatigue damage in submerged jacket joints, with the upper main-leg joints near the mean sea level and adjacent brace-intersection joints identified as critical fatigue-prone regions. These findings provide insights for structural integrity assessment, fatigue damage evaluation, and maintenance optimization of offshore wind turbines.