Faitgue reliability assessment for life extension of offshore structures

This study is focused on the prediction of the remaining life of an offshore structure using the fatigue reliability analysis. Our objective is to propose an alternative approach to assess long-term fatigue damage using a reliability analysis for life extension studies of offshore structures. In this approach, hot-spot stress response spectra in the frequency domain, considering stress concentration factors and stress transfer function, are generated using spectral fatigue method. Damage of the hot spots for a given sea state is carried out using products of the hot-spot stress response spectra. For reliability analysis, the limit state for fatigue damage is formed in terms of fatigue damage, fatigue capacity, randomness of environmental data, and other critical parameters of S-N curves. The probability of failure due to long-term fatigue damage is evaluated using reliability methods. The results of long-term reliability of fatigue damage are validated against other approaches such as Monte Carlo simulations.