Research reveals hidden fatigue risks in structures in offshore wind turbines 

However, the case study highlights the limitations of current inspection methods. Visual and ultrasonic inspections were found to be less effective for fatigue-critical components. More advanced techniques, such as eddy current or alternating current field measurement, offer greater reliability and allow for longer inspection intervals, but only when operators were willing to adopt slightly lower safety thresholds. 

While RBI planning is effective in reducing in-service life costs and ensuring the longevity and safety for structures for offshore wind turbines, it requires expert input, reliable models and software tools that can handle complex calculations.  

LR says ongoing research aims to refine the models and address the challenges during their application. Reliability updating, especially when integrating PoD curves, requires complex modelling and precise calibration of parameters such as initial crack size and stress intensity factors, areas often underdeveloped in practice. 

LR global head of technology offshore and subsea Kourosh Parsa says, “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.” 

LR head of offshore renewable solutions Manuel Ruiz says, “By focusing on the areas with the greatest risk, we not only help to manage fatigue-related issues more effectively, we are 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.” 

“The fatigue reliability-based inspection strategy is a powerful tool to minimise in-service life costs while ensuring safety for the offshore wind turbines structures,” LR concludes.

“The fatigue reliability analysis for developing an inspection schedule is an integrated approach which considers sophisticated and advanced fatigue analysis methods, fatigue cracking, reliability, and inspection of offshore structures. This approach aids professionals involved in design, structural appraisal, and subsea inspection of steel jacket structures.  

“This requires extensive effort and expertise in understanding and mastering various techniques and tools required to perform the assessment. Although the standards and various literature available discuss the methodology and the procedure, there are areas which need more research and information.”

Having undertaken the study, LR has called for wider industry collaboration to refine inspection standards, share real-time monitoring data to refine fatigue predictions, and adopt more flexible definitions of acceptable reliability where appropriate. 

It recommends in-service loading data based on real-time monitoring should be effectively utilised for the updating of reliability (as reduced equivalent stresses or factors on SCFs). It also recommends the target reliability should be determined appropriately considering the accuracy of fatigue calculation models and the in-service loading data.

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