Some offshore wind turbine (OWT) support structures may fall short of required fatigue life expectations, according to a new Lloyd’s Register (LR) report.
The case study evaluated a North Atlantic offshore wind farm comprising 60–70 turbines (500–600 MW capacity).
While OWTs are typically designed for 25 years of service with a fatigue design factor of three—equating to a 75-year minimum fatigue life—the study found that a critical joint in the jacket foundation would reach its fatigue limit after just 52 years.
Rather than redesigning the joint, the study recommends a reliability-based inspection (RBI) strategy to manage potential failures through targeted, risk-based maintenance.
The approach integrates S‑N modelling with Fracture Mechanics crack-growth analysis, and applies Probability of Detection curves to dynamically update inspection schedules based on real-world findings.
Findings indicate the first inspection should take place around year nine, followed by annual checks, depending on the method, to maintain safety margins.
The study highlights limitations in visual and ultrasonic inspections for fatigue-critical components, noting that advanced techniques such as Eddy Current or ACFM offer higher reliability and can permit longer inspection intervals if operators accept slightly lower safety thresholds.
The RBI model can reduce in-service life costs and support longevity and safety of OWT structures, but requires expert input, reliable models, and software capable of complex calculations.
Ongoing work focuses on refining fracture-mechanics models and calibration of parameters such as initial crack size and stress intensity factors, which remain underdeveloped in practice.
The report calls for broader industry cooperation to refine inspection standards, share real-time monitoring data, and adopt more flexible definitions of acceptable reliability.
Kourosh Parsa, Global Head of Technology – Offshore and Subsea at LR, said: “Many offshore wind assets are designed to a standard fatigue factor, but real-world conditions often expose critical vulnerabilities. Our findings show that using reliability-based methods allows operators to focus inspections where the risks are greatest. By integrating sophisticated models and real-world inspection data, we can extend asset life, reduce costs and, most importantly, maintain safety.”
Manuel Ruiz, Head of Offshore Renewable Solutions at LR, added: “By focusing on the areas with the greatest risk, we can not only help to manage fatigue-related issues more effectively — we’re also enabling developers and operators to make better-informed decisions that optimise asset life and performance. This proactive, risk-based approach is exactly how we support our clients in navigating complexity, controlling costs, and ensuring the long-term viability of their offshore wind investments.”
Founded in 1760 and headquartered in London, LR is a global professional services organisation and maritime classification society serving clients in over 75 countries. It provides technical risk management, classification, certification, inspection, assurance, and digital solutions across industries including offshore, energy transition, oil & gas, and marine.