Research On Design Methods Of Vehicle Deck Thickness Under Tyre Pressure Loads

The vehicles are not lifted vertically during loading and unloading,but go into the cabin directly through a gangplank,and then are fixed on the vehicle deck for ro-ro ships and other specialized ships used to carry vehicles.As one of the most important part in ro-ro ships,vehicle deck can support vehicles when mooring or navigating.Vehicle loads consist of vehicle weight and inertial force due to ship motion,and are different from general cargo loads or liquid cargo loads.They are also called tyre pressure loads because of functioning on deck concentratedly.Tyre pressure loads are patch loads,resulting in local area response,and make deck a high stress level and deformation level usually.Vehicle deck thickness is based on plastic design concept,but classification societies don’t explicitly give the utilization degree of plastic carrying capacit when deriving thickness formula.It is useful to study on the design formula of vehicle deck thickness.On one hand,it is conducive to understanding the principles of thickness formula in classification society rules and ensuring structural safety of ro-ro ships during operation,on the other hand,it can provide a reference to further improving the formula.Ro-Ro vehicle deck is focused on in this paper,and design theory and method of vehicle deck thickness under patch loads is researched.The study has carried out on the following 3 aspects: First,analyze and compare each vehicle deck formulae of classification societies,explore the design principles of previous study;then,investigate plastic degree of each formulae from stress and permanent deformation,give a reasonable thickness design standard;and finally,according to the selected design standard,propose a new thickness formula considering wheel print size and plate size effect by a large number of finite element analysis,and verify the new formula.