Evaluation of wave-induced coupled dynamics between multi-purpose offshore supply vessel and suspended load during crane lifting operation

As crane lifting operation in ocean is vital to construct offshore structures and install subsea facilities on the seafloor, evaluation of safety and availability for the crane lifting operation is needed before the construction. For these analysis, it’s fundamental to predict wave-induced coupled dynamics between vessel and suspended load. The coupled dynamics makes the each mechanics more complex. In the case of the multi purpose offshore supply vessel, deep understanding about the mechanics is required because it offers various crane operations, Unfortunately it's not easy to understand how the parameters related to the suspended load (e.g. sling point) change the motion characteristics for the vessel. Therefore the objective of this paper is to understand the effect of the parameters on the coupled dynamics by sensitivity analysis using numerical simulation. The mathematical model used in the numerical simulation is explained and the accuracy of the numerical simulation is validated through scaled model experiments in this paper. The results of the sensitivity analysis show, especially in the case of irregular wave with peaks in long period range, the coupled dynamics plays significant role even if the suspended load is lightweight.