Master S-N curve-based approach for fatigue assessment of wind turbines: A case study

Wind turbines are subjected to variable cyclic loading throughout their operational lifespan, with the resulting stresses potentially leading to critical fatigue damage. These threats to structural integrity are significant, yet current fatigue assessment methodologies still rely largely on nominal stresses, which are not fully consistent with the inherently local nature of fatigue phenomena. In this context, the present work aims to propose a local-scale analysis method based on structural stresses, incorporating the thickness and bending ratio effects. On the resistance side, conformity with Master S-N curves proposed in the literature is assessed using available experimental data for the relevant butt welds of the tower. On the loading side, admissible wind velocities are considered to generate dynamic loading scenarios from a calibrated aeroelastic model. The implementation in an onshore case study demonstrates that the suggested approach produces benchmarked outcomes while requiring a level of modelling effort consistent with routine structural analysis. This proposal introduces a new framework for fatigue assessment that allows for damage calculation in line with the local load transfer mechanism, thereby increasing reliability in the management of operational lifetime and its potential extension. • Innovative application of the Master S-N curve concept to wind turbine towers. • Fatigue reanalysis of representative datasets using equivalent structural stresses. • Validation of Master S-N curves proposed in the applicable literature. • Fatigue assessment based on the local properties of the mechanism of load transfer. • Analysis of an operating wind turbine tower using the proposed fatigue approach.