Study on Methods to Evaluate Effectiveness of Securing Arrangements for Semi-Trailers on Ro-Ro Ferries

Following an accident on ro-ro passenger ship, guidelines for evaluation of securing arrangements have been issued by Maritime Bureau of Ministry of Land, Infrastructure, Transport and Tourism, taking into account that one of the causes of the accident was deemed as sliding failure of cargos. The method to evaluate cargo securing arrangements in the guidelines does not take into account stiffness of cargoes and securing gears, for the sake of practicality, while securing loads depend on such stiffness. The purpose of this research is to clarify the appropriateness of the method to evaluate securing arrangements in the guidelines for semi-trailers, i.e., one of representative cargoes on ro-ro ships. For this purpose, the securing loads calculated by the method set out in the guidelines and by a method considering stiffness were compared. For the calculation using the latter method, racking stiffness of a typical semi-trailer and spring coefficient of a commonly used securing gear were measured. It is concluded that the method set out in the guidelines gives appropriate results on the whole, but this method may provide too small securing load in case that acceleration acting on a cargo is small.