Fatigue crack detection for lifetime extension of monopile-based offshore wind turbines

Abstract

Lifetime extension becomes increasingly crucial for industry, since the first offshore wind farms face the end of their design lifetime. The remaining useful lifetime of offshore foundations is driven by fatigue design and loading; both are affected by uncertainty. This paper presents a conditional probability model to link results from inspections with numerical simulations of fatigue cracks. Crack sizes are simulated with a fracture mechanics model applying Paris’ Law. The probability of detection of an existing crack depends on inspection technique and crack size. Results show that uncertainty about remaining useful lifetime significantly reduces after considering inspection outcomes. This decreases risks for the decision-making on lifetime extension of offshore wind turbines.