MOB Platform Nonlinear Dynamics in a Realistic (Random) Seaway

In this work, our previously developed approach is extended to include parametric excitation. This approach makes use of a closed-form analytic solution, which is exact up to the first order of randomness and takes into account the unperturbed (no forcing or damping) global dynamics. The result of this is that very large amplitude nonlinear vessel motion in a random seaway can be analyzed with similar techniques used to analyze nonlinear vessel motions in a regular (periodic) seaway. The practical result is that dynamic capsizing studies can be undertaken considering the true randomness of the design seaway. The capsize risk associated with operation in a given sea spectrum can be evaluated during the design stage or when an operating area change is being considered. Moreover, this technique can also be used to guide physical model tests or computer simulation studies to focus on critical vessel and environmental conditions which may result in dangerously large motion amplitudes.