Coupled analysis method of a mooring system and a floating crane based on flexible multibody dynamics considering contact with the seabed

The mooring system keeps the position of a floating body in the ocean under environmental loads. Mooring analysis should be performed based on the accurate mathematical model in order to predict the behaviors of the floating body and the mooring system. For this purpose, the finite element method (FEM)-based model has been widely used in recent years to model the mooring line numerically. However, existing studies were only applicable to a single floating body, and solved the equations of motion for the floating body and the mooring lines separately. For the application to a floating crane, which consists of several bodies connected to each other, the coupling effect due to the relative motion of each body should be taken into account. Therefore, in this study, the FEM-based mooring line model applicable to a multibody system is introduced based on flexible multibody dynamics. Then, to realize the interaction between the mooring line and the seabed, the non-interpenetration and slope constraints are suggested, and the friction model including sticking are adopted. For the verification of the suggested model, comparisons with the analytic solution and the commercial software are performed. Finally, the applications for a floating crane under various environmental loads are simulated. The results show that the suggested model can be properly adapted for mooring analysis.