Damage location and intensity detection in tripod jacket substructure of wind turbine using improved modal strain energy and genetic algorithm

The foundation of offshore wind turbines has various structures at different depths of the sea. At depths between 30 and 50 meters, jacket substructure is recommended as an economical solution for offshore wind turbines. During their life cycle, the substructures of offshore wind turbines are exposed to a couple of damage sources which can reduce their service life. This problem became more severe in sensitive areas such as deck, joints, or splash zone that are prone to failure. Modal strain energy (MSE) method is one of the non-destructive and practical methods in which the location and the severity of the damage is determined using changes in the dynamic properties of the structure. In recent years, some modifications have been made to the original version of this method, one of which is to consider modal frequencies in determining the location of damage. In this paper, the damage location and its severity are identified for members located in deck and splashing zone in tripod substructure of wind turbine using improved modal strain energy method (IMSE). The results showed that the improved method is more accurate in locating the damage than the original method (Stubbs index). Also, single and multiple damages, both with low and high intensity, were predicted with this method with appropriate accuracy.