On the Nonlinear Motions of Ships and Structures in Narrow Band Sea

The extensive analysis carried out in last years on nonlinear rolling motion of ships allowed to discover some very peculiar features of this motion. As a results, terms as subharmonic, bifurcation, jump in amplitude, symmetry breaking, deterministic chaos, non deterministic, non Gaussian and even fractals start appearing with increasing frequency in the literature. At the same time, their exact meaning and importance in the context of ship seakindliness and safety from capsizing and of the behaviour of floating structures at sea, is circulating among restricted areas of researchers in the field. In this paper the author, while presenting preliminary results relative to the possibility of bifurcations in a narrow band stochastic sea, tries to draw some conclusion about the relevance of the above phenomena from what could be called \u201cthe point of view of the Naval Architect\u201d