Coupled Analysis of a Semisubmersible Platform with Two Types of Mooring Systems

Mooring system design selection of a semi-submersible platform which works in 1500m water depth of South China Sea was carried out. The 3-dimension hydrodynamic finite element model of the semi-submersible platform is built firstly. The nonlinear time domain coupled analysis between the semi-submersible platform and its mooring system is calculated through numerical simulation. The wave forces are calculated under diffraction theory by boundary element method, and the wind forces are obtained from the wind tunnel test with the model scale 1:100, and the current forces are considered as steady. Two types of mooring system have the similar static restoring force characteristics, the same mooring line number and angle arrangement. The single mooring line is respectively consisting of chain-wire-chain and chain-polyester-chain. The polyester rope is adopted as the substitute for the wire while other conditions are kept unchanged. The mooring system is considered under intact and damaged conditions. The influences of different mooring models on the motions of the semi-submersible platform and mooring line tension are investigated. The specific numerical simulation results would be helpful for the preliminary design of semi-submersible platform.