Examination of the dynamic effects on the hull girder ultimate strength of ultra large container ships

After two major accidents that occurred in the last ten years, the slamming-induced whipping has received much attention from ship designers and classification societies. Since the whipping-induced stresses have a higher frequency than the ordinary wave-induced stresses, some authors have suggested that dynamic effects, i.e. inertia and strain rate, provide additional hull girder ultimate capacity in the context of whipping. Even if it is known that the dynamic effects are important in the case of collision or grounding, there is no evidence that it is true for whipping. This paper focuses on the dynamic ultimate strength of the hull girder, which is compared with the quasi-static ultimate strength in order to obtain a proper estimator of the dynamic collapse effect. To this purpose, the nonlinear finite element method is used for the analysis of three frame-bay models, representing the structure of two different container ships.