Fatigue reliability analysis of jacket-type offshore wind turbine considering inspection and repair

In this paper prediction of the fatigue reliability of a fixed jacket offshore wind turbine designed for a North Sea site in a water depth of 70 m is performed. The longterm statistical distribution of stress ranges of tubular joints is obtained by combination of time domain simulation for representative sea states. The load histories are normalised to ensure that fatigue design criteria based on the SN-Miner-Palmgren approach is satisfied. Hence the reliability estimates obtained refer to fatigue design of tubular joints that satisfy design criteria. The reliability analysis is based on fracture mechanics (FM) analysis of crack growth. The effect of inspection and repair is quantified based on the quality of inspection in terms of probability of crack detection curves. The sensitivity of the reliability index on random variables is estimated considering the effect of inspection.