Dynamics of lashed trailers on a ship under roll and pitch excitations

Abstract

The prediction of the dynamic behaviour of lashed trailers placed at various locations on the vehicle deck(s) of a ferry is discussed. Excitations on the lashed trailers are produced by the combined roll and pitch motions, caused by steep waves encountered by the ship from various angles. Firstly, the typical requirements of the IMO's Cargo Securing Manual, as implemented for an existing ferry, are presented. Thereafter the mathematical model that has been developed for the needs of the present study is set out. The characteristics of the lashings, as well as of the trailer support (trestle) and suspension systems, are taken into account. Ship motions are simulated with a well-known panel code, and they are subsequently imported into the mathematical model of lashed trailers. This is a step towards an integrated ‘performance-based’ framework for the investigation of cargo safety on board that is ship and environment specific.