Safety evaluation of lashed trailer motions in ferry operations under rough sea conditions

Safety evaluation of a lashed trailer on the cargo deck of ships is essential for ferry operations. Although ferry accidents have occurred worldwide, few studies have focused on the dynamic analysis of trailer motion in irregular sea states. To date, effective counterapproaches have not been established. Thus, first, ferry masters were interviewed to summarize the difficulty in cargo management during rough sea voyages. Second, a modified simulation model of lashed trailer motions was constructed to evaluate the safety of cargo management, considering wave, seakeeping, and trailer motion simulations. Few studies apply the model to the irregular sea state in actual seas, using a combination of three different kinds of models. A simulation was conducted to analyze the collapse of a trailer loaded on a ferry in high waves owing to rapidly developing atmospheric pressures. Essentially, the model can reproduce the collapse of trailers, especially when a shift in the center of gravity is considered when accelerations occur in loaded cargo inside trailers. The model enables the estimation of trailer motions and lashing wire tensions in ferry operations, considering suitable lashing arrangements. •Dynamic analysis of lashed trailer motions in irregular sea state is focused.•A complete simulation model of lashed trailer motions was newly constructed.•The model can reproduce the collapse of 100 trailers for the accident in 2009.•Lashing arrangement with longer breast lines can be effective to reduce motions.•A shift in the center of gravity for cargo in large motions could be occurred.