An experimental study on extreme responses of a moored semi-submersible rig

Abstract

In this paper, the extreme motion & tension response characteristics of a deep water semi-submersible rig are investigated in various environmental conditions. A series of model tests of semi-submersible rig with 1:50 scale has been conducted in order to verify the motion responses in regular, irregular & current at the ocean engineering basin, MOERI/KORDI. The spread catenary mooring system of semi-submersible rig was considered and the mooring system in model tests was applied to truncated mooring system for full water depth of 1,000m to the limitation of the basin. The motion, mooring tension & air-gap responses of semi-submersible rig in harsh environmental conditions involving extreme wave using focusing wave were also measured and the results are discussed. A numerical simulation using higher order boundary element method and time domain based finite element method to investigate the dynamic behavior of the truncated mooring system of semi-submersible rig has been carried out and the results are compared with those of some selected model tests Copyright ？ 2011 by the International Society of Offshore and Polar Engineers (ISOPE).