Probabilistic safety of estuary vessels based on nonlinear rolling in wind and waves

Abstract

The author was previously involved in the development of the risk-based stability analysis which is now further extended, and used for the safety assessment of estuary container vessels subjected to stochastic action of beam wind and irregular waves. The study was motivated by the new set of safety regulations for estuary vessels issued by Belgian authorities in cooperation with Lloyd's Register. These regulations introduce very innovative probabilistic ideas to ship stability regulations, and therefore present a significant step forward compared to the classical approach. Still, they do not account properly some important influences, such as wind gusts and motion nonlinearities, so considerably simplify the problem. The present investigation models the vessel motion much more realistically, analyzes the influence of beam wind and beam waves on the probability of a stability failure, and argues whether simplifications proposed by the regulations were justified. It is believed that presented method is not limited to the safety of estuary vessels only, but also gives important guidelines for a more general investigation of ship safety in wind and waves.