Hole patterns are common in engineering design for connections and/or assembly purposes. Geometrical discontinuities can cause stress concentration in localized areas, making them more prone to fatigue crack initiation and influencing the fatigue life of the overall unit. In the past, much effort has been exerted on fatigue modelling of holed plates from both experimental and theoretical perspectives. However, most studied objects were aluminium or titanium thin plates for aviation purposes. In this work, the fatigue performance of a downscaled holed thick steel plate, extracted from a novel C1 Wedge Connection for wind turbine tower assembling, was tested and categorized according to commonly used industry codes. In particular, the influence of the surface size effect was experimentally observed and computationally discussed. Finally, a probabilistic fatigue model was proposed, which gives a favourable prediction on the fatigue behaviour of the surface polished holed thick steel plate with the help of the Smith–Watson–Topper (SWT) model.

Wind, as a sustainable and affordable energy source, represents a strong alternative to traditional energy sources. However, wind power is only one of the options, together with other renewable energy sources. Consequently, the core concerns for wind turbine manufacturers and operators are to increase its reliability and decrease costs, therefore enhancing commercial competitiveness. Among typical failure modes of wind turbines, fatigue is a common and critical source. Given the significance of fatigue reliability in wind turbine structural integrity, reliable probabilistic fatigue theories are necessary for design scheme optimization. By reducing the expenses on manufacturing, operation, and maintenance in reliability- and cost-optimal ways, the cost of energy can be significantly reduced. This study systematically reviews the state-of-the-art technology for fatigue reliability of wind turbines, and elaborates on the evolution of methodology in wind load uncertainty modelling. In addition, fatigue reliability assessment techniques on four typical components are summarized. Finally, discussions and conclusions are presented, intending to provide direct insights into future theoretical development and methodological innovation in this field.