Analysis of fatigue test data of retrieved mooring chain links subject to pitting corrosion

Fatigue is one of the main failure mechanisms of catenary type mooring lines. Fatigue resistance is affected by a large number of factors. In this paper, the effect of pitting corrosion on the fatigue resistance of mooring lines is empirically estimated. Data from fatigue testing of both new and used chain links are considered. The used chain link samples were retrieved from several offshore floating units. A hierarchical statistical analysis is proposed to effectively use the available information. Mean stress effect is taken into account in the analysis of the data. Results show that the effect of pitting corrosion on the structural reliability of mooring lines is significant.