A Study on the Structural Optimization of Double Bottom Part of Ship Structure under Considering Stress and Buckling Constraints

A structure optimization for the initial design stage using FEM of ship is under consideration in this paper. General bulk carrier is selected as the object of the optimization. Both the size and the plate thickness of the bottom structure of the ship are taken as design variable simultaneously for the weight minimum optimization problem. The individual mesh-subdivision technique and the multi-point constraint method are used for change the bottom shape in this paper. Five design variables for the shape and thirty-one design variables for the plate thickness are considered for the optimization of ship structure. The yield stress constraint conditions for each element and buckling stress constraint conditions for each buckling plate on the bottom plate, the inner bottom plate, the girder plate, the floor plate, and the bilge hopper plate are considered. The optimal calculations are performed with several conditions of the types of design variable and constraint condition, and the designs obtained in the calculations are coMPared. It is shown that the Structural optimization with shape and plate thickness design variables can reduce the weight of ship structure effectively. Genetic algorithm is used for the optimal calculation since the design variables are discrete resulting in a combination optimization problem.