Fatigue reliability analysis of mooring system for fish cage

Fish cages in the open sea are exposed to cycle loads due to irregular wave climate during their service life, and thus the fatigue reliability assessment of mooring system should be conducted to ensure the safe operation. The aim of this study is to evaluate the fatigue failure probability of mooring system for fish cage. Numerical simulation of net cage in random waves is performed and the time dependent approach is applied to conduct the fatigue reliability analysis of shackle chains based on S-N curve method. The sensitivity analysis of fatigue reliability of mooring line to the uncertainty of random variables in the fatigue limit state is conducted. In addition, the system reliability for mooring system is analyzed and the effect of the initial pretension and safety factor on system reliability is investigated. The results indicate that a case without the initial pretension on anchor lines is helpful to decrease the failure probability of mooring system and the safety factor of mooring lines in the current regulation is conservative for the system reliability against fatigue damage.