Investigation of barge-type FOWT in the context of concurrent and cascading failures within the mooring systems

The design requirements for offshore engineering stipulate that floating structures should maintain their overall performance even in the event of a single mooring line failure. However, it is crucial to ensure that the platform does not drift or capsize in the case of two mooring line failures. Therefore, the investigation into the dynamic response of wind turbines after mooring line failures is of great significance. In this study, the aerodynamic-structural simulation capability of FAST was coupled with the hydrodynamic analysis software AQWA by modifying the dynamic link library. The dynamic response of a Barge-type floating offshore wind turbine (FOWT) and the variations in mooring line tensions were computed under different sea conditions after the successive failures of two mooring lines with varying time intervals. The findings reveal that in rated sea conditions, there is a significant increase in surge motion, reaching a maximum value 2.08 times that of the original, following the failure of two mooring lines. The tension in mooring line #3 reaches 1.57 times the pre-failure value. In extreme sea conditions, the simultaneous failure of two mooring lines at the same corner triggers a cascading failure phenomenon within the mooring system, and a shorter interval between failures amplifies the dynamic response of the platform. Therefore, it is not advisable to deploy the Barge platform in harsh environmental conditions.