This paper presents the results of an experimental study to evaluate the effect of torsional moment on the ultimate strength of container ships in longitudinal bending. The progressive collapse tests are conducted using 1/13-scale three-hold models referring to a Post-Panamax container ship. The models are fixed to the rigid wall at the aft end (cantilever beam) and a couple of loads are applied to the fore end so as to generate both torsional and vertical bending moments. Several loading conditions which vary the ratio of torsional and bending moments are adopted for the progressive collapse tests and the nonlinear finite element analyses using LS-DYNA. From the results of collapse tests and numerical simulations, the progressive collapse behavior including the warping-strain distribution and the ultimate strength interaction relationship is examined.
INTRODUCTION The steady increase of global container traffic has boosted the demand for larger container ships. Currently the biggest container ship in the world can carry up to 14,000 TEU. Probst (2007) predicted that the break-even point will be governed by economics and not by technical considerations. However, Probst (2006) demonstrated that aspects such as structural integrity, maneuverability, propulsion and especially operational management must be carefully considered at an early design stage. The structural feasibility of 13,400 TEU container ships has been proven and the investigation verified that a further enlargement of Post-Panamax container ships is possible. Under such situation, the 4,400 TEU container ship MSC Napoli encountered heavy seas and suffered structural failure while on passage through the English Channel on January 2007. Though an investigation that was carried out by the Marine Accidents Investigation Board (MAIB, 2008) identified a number of factors which contributed to the failure of the hull structure, it was reported that the vessel's hull did not have sufficient buckling strength in way of the engine room.