IOMAC2027 Keynote Lecture
From Modal Parameters to Lifetime Decisions: From Individual Turbines to Fleet-Based Monitoring in Offshore Wind
Christof Devriendt, Vrije Universiteit Brussel
For nearly two decades, Operational Modal Analysis (OMA) has provided a powerful means of understanding the dynamic behaviour of offshore wind turbines under real operating and environmental conditions. What began as a quest to identify natural frequencies, mode shapes and damping ratios has evolved into a broader discipline that increasingly bridges the gap between vibration measurements and critical asset-management decisions.
Long-term monitoring has revealed how modal properties evolve with wind, waves and turbine operation, providing valuable insights into soil–structure interaction, scour, damping, structural variability and challenging assumptions made during design.
However, the questions asked of monitoring systems have gradually moved beyond modal identification. Operators increasingly need information on structural loads, accumulated fatigue and remaining lifetime to support inspection, maintenance and lifetime-extension decisions. By combining acceleration and strain measurements with physics-based structural models and data-driven machine-learning approaches, operational monitoring can increasingly provide this information.
A further challenge is scalability. Rather than treating every turbine as an independent monitoring problem, accelerometer measurements across entire wind farms can be combined with more extensively instrumented reference turbines. This opens the door to population-based monitoring strategies, in which similarities and differences between turbines are exploited to transfer knowledge across the fleet.
This keynote reflects on this evolution, from modal identification to load and lifetime assessment, and from monitoring individual turbines to learning from entire fleets. Throughout this journey, the simple accelerometer remains a common thread, connecting fundamental structural dynamics to the evidence needed for lifetime assessment and extension of offshore wind turbines. Ultimately, the value of operational monitoring lies not in the modal parameter itself, but in the engineering decision it enables.
