Investigations of vehicle securing without lashings for Ro-Ro ships

To reduce the area on deck occupied by each car and the labour and time required for lashing and unlashing cars, it has been proposed by the author that in some conditions, cars on decks could be transported without lashing. To evaluate cargo securing based on this “lashing-free” concept, computational code was developed to calculate the vehicle–deck interactions for various ship motions. The code was structured by incorporating a vehicle model into a piece of ship motion calculation code. A series of time-domain simulations were conducted to evaluate vehicle securing. It was found that for a target ship consisting of a 6000-unit Ro-Ro vessel, vehicle securing is mainly influenced by the ship's rolling motions and is highly dependent on the wave height and loading conditions. It was suggested from the analysis that vehicles could be secured without being lashed in a large area of the ship in specific weather conditions and on some routes with less adverse sea states. However, it is still suggested that conventional lashing holes should be constructed on the deck because in severe sea states the cars will still need to be lashed. The limitations of the current investigations are also presented. The relevant research work was carried out at the Division of Ship Design and Engineering, Department of Shipping and Marine Technology, Chalmers University of Technology.