Design selection analysis for mooring positioning system of deepwater semi-submersible platform

Aiming at design selection analysis for mooring positioning system of a semi-submersible platform applied in South China Sea, catenary mooring system, semi-taut mooring system and taut mooring system are respectively considered. The three types of mooring positioning system have the similar static restoring force characteristics, the same mooring line number and angle arrangement. The dynamic coupling effects between the semi-submersible platform and its mooring lines are investigated through numerical simulation method. The 3-dimension hydrodynamic finite element model of semi-submersible platform is built firstly. 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. The platform motions under combined action of wind, wave and current are solved by Runge-Kutta method respectively under working and extreme conditions in South China Sea. The specific numerical results and analysis conclusions would be helpful for selecting the mooring system and the motion performance study in the semi-submersible platform preliminary design. Copyright © 2012 by the International Society of Offshore and Polar Engineers (ISOPE).