Station-keeping capability of offshore oil rig is important so that mooring integrity become a critical design factor. Several unexpected accidents of chain mooring failure were related to new mechanism called Out-of-Plane Bending (OPB) and In-Plane Bending (IPB). The main factors causing OPB-induced fatigue are tension, friction, and interlink angle. To consider this mechanism during the design stage, chain interlink angles from global-system simulation should be computed accurately in time domain. The results are sensitive to the degree of accurate modeling of fairlead connection.

In this study, time-varying chain interlink angles with underwater chain stopper system (chain-hawse) are investigated with hull-mooring-riser coupled time-domain simulation program CHARM3D, which has been developed in TAMU for the past two decades. Several scenarios of chain-hawse system and environment are investigated to observe the corresponding effects on interlink angles.

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