The decrease in structural capacities under the limit states caused by structural corrosion is a potential hazard for the safety of offshore structures. Considering the influence of corrosion factors, a fatigue analysis of the typical tubular joints of an offshore wind turbine (OWT) substructure under operation and wave loads during the service period was performed. The structural corrosion was equivalent to a two-parameter Weibull distribution in the analysis. According to the Miner linear fatigue accumulation criterion, the accumulated fatigue damage of three different typical tubular joints in the initial stage and at operation periods of 10, 20, and 30 years was calculated. The most critical tubular joint of the studied OWT substructure is located at the connection between the pile foundations and braces. Owing to the increase in structural corrosion during the operation period, a remarkable decrease in the tubular joint fatigue capacities under the operation and wave loads was observed.

This study proposes an integrated fatigue life assessment methodology to accurately evaluate the time-domain evolution in tubular joint fatigue damage in offshore wind turbine (OWT) jacket structures under long-term combined wind and wave actions. A customized post-processing module was developed via secondary development on the MLife platform, employing a conditional probability distribution model to perform joint probabilistic modeling of measured marine environmental data, thereby establishing a long-term joint wind–wave distribution database. The reconstruction of hotspot stress time histories at the tubular joints was achieved through a hybrid analytical–numerical approach, integrating analytical formulations of nominal stress with a multi-axial stress concentration factor (SCF) matrix. Long-term fatigue damage assessment was implemented using the Palmgren–Miner linear cumulative damage hypothesis, where a weighted summation methodology based on joint wind–wave probability distributions rigorously accounted for the statistical contributions of individual design load cases. An ultimate bearing capacity analysis was also conducted based on S-N fatigue endurance characteristic curves. This research specifically investigates the influence mechanisms of tuned mass dampers (TMDs) on the time-domain-coupled fatigue performance of tubular joints subjected to long-term combined wind and wave loads. Numerical simulations demonstrate that parametrically optimized TMD systems significantly enhance the fatigue life metrics of critical joints in jacket structures.