Fatigue Reliability of joint connections in support structure of offshore wind turbines

This study is my initial attempt to investigate the evolution of fatigue reliability of welded joints in offshore wind turbine support structures. This information is crucial to update the inspected data (crack sizes, probability of crack detection) to make the plan for the next inspection and maintenance of existing offshore structures in general. The thesis is limited to tracing back the fatigue reliability of welded joints from their design information. The later work for inspection planning will be continued in the framework of my Ph.D thesis. On the basis of the results of this research, it can be concluded that for the fatigue reliability problem, FORM and SORM gives results with high accuracy compared to MCS and that the design point found by FORM/SORM are really the global minimal reliability index. The assumption in dealing with cumulated damage shows a good agreement with MCS. This is the foundation for using a simplified LSF in reliability calculation of accumulative fatigue problem.