9. A Study on the Capsizing Mechanism of Semi-submersible Platforms

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The present paper deals with a study on the mechanism of capsizing of a semi-submersible platform in beam sea. Especially, the authors' attention is paid to the analysis of larger steady tilt of the platform in the violent sea state. First of all, the steady heeling moment due to the wave-induced vertical steady force acting on the lower hulls are obtained by both theory and experiment. Secondly, the time-domain simulations of the platform motions predicted by the newly developed computer program are carried out to find the possibility to introduce the capsizing of a semi-submersible platform in the violent seaway. From the simulations of the platform behaviors in the combined environmental loadings, it is clarified that the larger angle of the steady tilt might be induced and is strongly influenced by GM value, fairleader height and the wave-induced vertical steady force on the lower hulls. Finally, a new computational approach for determining the required minimum <GM>^^^- (<GM>^^^-_r) is proposed to avoid the significant larger inclination. This <GM>^^^-_r consists of the basic <GM>^^^- (<GM>^^^-_o=<GM>^^^-_<WIND>) and the several correction terms (Δ<GM>^^^-) which come from the effects of various kinds of environmental loadings and the mooring system.
社団法人日本船舶海洋工学会の論文