When a chain link is constrained from free rotation such as over a fairlead, the chain link is subjected to an out-of-plane bending (OPB) moment in addition to tension. Much research has been carried out to investigate the failure mode. This paper presents the nonlinear finite element analysis (FEA) studies on mooring chain OPB stiffness, OPB stress and moment. The effects of proof loading, pretension and friction coefficient on OPB stiffness are investigated. In addition, this paper provides the findings of the relationship between the interlink angle and total chain angle from linear FEA using the beam model. With the inputs from the numerical simulations, chain link tension-bending fatigue damage calculation procedures are summarized. Finally, OPB moment mitigation measurements are proposed to reduce the impact of OPB effect on chain fatigue life.

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