A structure optimization for the initial design stage using FEM of ship is under consideration in this paper. General bulk carrier is selected for the object of the optimization. Shapes of the bottom structure of ship are taken as design variables. Since the design variables affect the shape of structure, FEM model should be updated during the optimization. Moreover the structure of ship is so large and complicated that make shape optimization of ship structure very difficult. Individual mesh-subdivision technique and multi-point constraint method are introduced for making this optimization possible. However, creating FEM data sets for them requires a lot of manpower. In order to remove this drawback, PrimeShip-Hull is used since it has a function recognizing structure members of ship. A FEM data set which can be applied individual mesh-subdivision technique and multi-point constraint method is made from structure members of PrimeShip-Hull automatically. Five design variables for shape optimization of double bottom structure of ship are considered here and a numerical example is shown.
At the initial design stage of ship, it is usual to design principal particulars first, general arrangement secondly and structure members of mid-ship section and bottom structure finally. Many methodologies and actual examples for optimization of ship structure have been reported. These include optimization of hull form by Yang et al. (2007), optimization of a partial mid-ship structure by Rahman and Caldwell (1992), Kitamura et.al. (2003, 2007) and Djenod et. al.(2003), and optimization of panel and girder designs by Rahman (1994, 1996, 1998). But, their targets are limited in one design stage. Since the design variables determined at one stage affect the design variables at other stages, it is desirable to give enough relationship to the design variables all over design stages. However, it is difficult to have enough cooperation to these design stages because of the difficulty of the initial design stage of ship, restriction of usable manpower, etc.