Numerical investigation on the mooring line failures of a semisubmersible platform

Abstract Numerical simulations on the mooring line failures of a semi-submersible platform under the extreme ocean environment are performed. The single mooring line and double mooring lines failures, as well as the subsequent progressive failure process of multiple mooring lines are investigated. The results show the change laws of the utilization factors after mooring line failure accidents under the 100-year and 1000-year return period environmental conditions. When two double mooring lines occur, the progressive failure of the remaining mooring lines could be triggered subsequently under the extreme 1000-year return period environmental condition. The motion responses of the platform in the surge, sway and yaw directions change significantly during the progressive failure of mooring system, leading to the large horizontal drift of the platform. The tensions of mooring lines at the fairlead positions are redistributed with the variations of equilibrium positions of the semi-submersible platform and numbers of broken mooring lines.