Collision Analysis and Residual Longitudinal Strength Evaluation of a 5 MW Spar Floating Offshore Wind Turbine Impacted by a Ship

Abstract

As an emerging energy transition form, many floating offshore wind turbines are expected to be located far away from the coast of Ulsan, South Korea. Due to the unintended ship’s berthing mistake which could be occurred because of the huge traffic for the installation and maintenance purpose within the wind farm, however, the spar-type substructure could be impacted by a ship collision and the residual strength of the damaged structure could be reduced. In this work, the finite element analysis of a circular tube subjected to the impact loading was performed to compute the permanent deformation after a collision in ABAQUS and the numerical results were validated with an experimental data. The validated approach was further expanded for the application to calculate the permanent damage of the spar-type substructure of 5 MW floating offshore wind turbine impacted by a ship, then a residual longitudinal strength calculation approach was implemented to evaluate the residual strength based on the relation between an increase in bending moment and the corresponding curvature. Under the collision case of a ship with 3 m/s speed to a floater, the evaluation showed 4.1% reduction in the residual strength, which could be used as a basis for the assessment by O&M service providers whether the damaged substructure can be safely towed to the coast or can be maintained on-site with safety.