Reliability-Based Calibration of Partial Safety Factors for Wind Turbine Blades

The reliability of a wind turbine blade can be estimated using a response surface technique, the First Order Reliability Method (FORM) and Monte Carlo simulation. The response surface is here estimated based on nonlinear finite element analysis by which nonlinear failure modes due to e.g. buckling can be taken into account. Stochastic models for the material properties and the load-effect are formulated in order to take physical, model and statistical uncertainties into account. The blade fails due to buckling of the main spar cap which results in high stresses in the transverse direction of the unidirectional laminas. For this failure mode the reliability is estimated along the centreline of the main spar cap. The results show significant variations in the reliability along the blade length.