It is well known that VIM response of a floater (Spar or Semi) significantly affects fatigue of moorings. VIM response characteristic of a floater is a key measure of its performance. A dry tree Paired-Column Semisubmersible (PC-Semi) platform has deeper draft and smaller columns compared to those of a traditional Deep Draft Semisubmersible (DD-Semi) platform. PC-Semi might have more pronounced VIM response due to its larger column slenderness. Thus, there is strong interest for us to explore VIM response characteristics of the PC-Semi and how these key features are compared to the other floaters.

HOE performed a small scale VIM model tests at the UC Berkeley towing tank on May, 2012. This paper presents the key testing results and compares them against other floater VIM response curves. A typical loop current scatter diagram in GoM was employed and the measured VIM test results were adopted and applied for mooring fatigue analysis. A traditional DD-Semi was considered and analyzed to establish the base to gauge VIM performance feature of the PC-Semi. The comparison results of the PC-Semi and DD-Semi on VIM responses as well as the corresponding effects on mooring fatigues are addressed and highlighted.

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