Nonlinear Dynamic Analysis of Multi-component Mooring Lines Incorporating Line-seabed Interaction

Abstract: In this study, a deterministic approach for the dynamic analysis of a multi-component mooring line was
formulated. The floater motion responses were considered as the mooring line upper boundary conditions while the
anchored point was considered as pinned. Lumped parameter approach was adopted for the mooring line modelling.
The forces considered were the submerged weights of mooring/attachment, physical/added inertia, line tension,
fluid/line relative drag forces and line/seabed reactive forces. The latter interactions were modelled assuming that
the mooring line rested on an elastic dissipative foundation. An iterative procedure for the dynamic analysis was
developed and results for various mooring lines partially lying on different soils were obtained and validated by
conducting a comparative study against published results. Good agreement between numerical and published
experimental results was achieved. The contribution of the soil characteristics of the seabed to the dynamic
behaviour of mooring line was investigated for different types of soil and reported.
Keywords: Fluid drag force, lumped mass method, multi-component mooring line, moored floating structure, semisubmersible
platform