Effect of Corrosion Wastage on the Limit States of Monopile‐Type Offshore Wind Turbines Under Combined Wind and Rotor Blade Rotation

ABSTRACT In digital healthcare engineering (DHE) for aging monopile‐type offshore wind turbines, predictive health analysis is essential for robust future maintenance planning. This paper presents the development of a DHE module for the predictive health analysis of corroded monopile‐type offshore wind turbines, focusing on wind and rotor blade rotation effects. An empirical formula for predicting time‐variant corrosion wastage is derived from a statistical analysis of a decade‐long corrosion wastage database and applied to predict the corrosion depth of a 5 MW monopile‐type offshore wind turbine, serving as an illustrative example. Nonlinear finite element analyses using LS‐DYNA are performed on the corroded turbine tower under combined wind‐induced loads and rotor‐induced thrust forces. Two types of corrosion wastage, pitting, and uniform (general) corrosion, are considered. The health condition of the corroded tower is evaluated based on serviceability limit state and ultimate limit state criteria. The methodology developed in this paper will be integrated into the DHE system currently being developed by the authors for aging monopile‐type offshore wind turbines.