Assessment of operational risk of parametric roll

In October 1998, a post-Panamax, C11 class containership encountered extreme weather and sustained extensive loss and damage to deck stowed containers. The motions of the vessel during this storm event were investigated through a series of model tests and numerical analysis. This confirmed that parametric roll was the most likely cause of the accident. The results of this study were presented in a technical paper in 2003 (France et al 2003).
One of the remaining questions of the study is the long-term probability (risk) of such an incident because several requirements must be satisfied for parametric roll to occur. These concern the loading condition, speed and wave height and period.
In our paper the results will be presented of a first-time attempt to quantify the operational risks of parametric roll for a large containership. The attempt is based on scenario simulations over a long period of time (5 years) in which many individual voyages are simulated on a given route. In the simulations a weather hind cast (waves and wind) is used to evaluate the sustained speed and ship behavior at every individual 2-hour time step. In the calculations the voluntary and involuntary speed loss are taken into account. The paper pays attention to the statistical aspects of the interpretation of the results.