Structural Model Test for Strength Performance Evaluation of Disconnectable Mooring Apparatuses Installed on Floating-Type Offshore Wind Turbine

Abstract

The destructive power of typhoons has been continuously increasing due to the influence of global warming. In a situation where the installation of floating wind turbines is increasing around the world, concerns about huge losses and collapses of floating offshore wind turbines due to strong typhoons are deepening. Regarding the safe operation of floating offshore wind turbines, the development of a new type of disconnectable mooring system is required. The newly developed disconnectable mooring apparatuses, such as fairlead chain stoppers (FCS) and submersible mooring pulleys (SMP), considered in this study are devised to more easily attach or detach the floating offshore wind turbine with mooring lines compared to other disconnectable mooring systems. In order to investigate the structural safety of the initial design of FCS and SMP that can be applied to MW class floating-type offshore wind turbines, scaled-down structural models were produced using a 3-D printer, and structural tests were performed on those models. For the structural tests of the scaled-down models, tensile specimens of the acrylonitrile butadiene styrene material used in the 3-D printing process were prepared, and the material properties were evaluated by performing tensile tests. Finite element analyses of FCS and SMP were performed by applying the material properties obtained from the tensile tests and the same load and boundary conditions as in the scaled-down model structural tests. Through the finite element analyses, the weak structural parts of FCS and SMP were reviewed. The structural model tests were performed considering the main load conditions of the fairlead chain stopper, and the test results were compared to the finite element analyses. Through the results of this study, it was possible to experimentally verify the structural safety of the initial design of disconnectable mooring apparatuses. Furthermore, the study results can be used to improve the structural strength of FCS and SMP in a detailed design stage.