Design of the Tension Mooring System for the Prototype Floating Platform

Japan Marine Science and Technology Center plans TLP sea test using a prototype floating offshore structure. The site is 40 m deep and 3 km offshore on the Japan Sea. In the test the performance of the tension mooring system will be evaluated in the real ocean environments. The platform is a semisubmersible which consists of twelve columns with footings, and the principal dimensions of the structure are length overall 34 m, breadth overall 24 m, height 13.5 m and displacement 527 ton. The structure will be moored by the four tension legs. Each tension leg is a chain filled and covered with rubber. This rubber-chain is applied in order to absorb the shock loads and prevent the mooring line from local abrasion. The elasticity of the rubber-chain is widely controllable with rubber hardness and the gap between the chain links. In this study, the tension mooring system has been designed to match with the environmental conditions, and the rubber hardness 50 and the chain-link gap 22 mm are finally selected for the 10 m long and grade 4 chain.