Research Of Ship Stowage System Based On Table Of Offsets

A ship's buoyancy, stability and longitudinal strength, as the main contents of her stowage process, are directly related to the safety of the ship. Current stowage software mostly bases on the information such as light weight distribution, hydrostatic table, Bonjean's table etc, which are supplied by the dockyard. Its purpose is to finish calculating and checking the ship's buoyancy, stability and longitudinal strength. This method has several limitations as follows. On the one hand the information supplied and used to stow is mostly in the condition of right floating. And in most cases, ship's data is insufficient; On the other hand the calculation usually bases on the hypothesis that floating center is invariable in condition of the ship's transverse inclination and trim. But actually, the practical center of floating is variable in the state of ship's transverse inclination and trim at large angles, so the calculating results are often imprecise. Ship's shape under the waterline in trim at large angles is different with that of right floating state. And the initial metacentric height and stability curve are changed.In view of the existing problems, the paper studies the traditional methods of floatation calculation and the difference of the ship's stability between the longitudinal inclination and the right floatation and the reason of alternation of the weight and buoyancy from the right floatation to the longitudinal inclination. The method of floatation calculation is proposed. Having the displacement and the center of gravity, we obtain the floatation diameters, through inclining a small angle and parallelly shifting the position of water plane. Lastly the ship's balance conditions of float are satisfied by iterating. And on the condition of lacking of the light weight distribution, hydrostatic table, Bonjean's table etc, this paper presents a method of calculation of stability at large angles and strength. And the method is applied in the ship's stowage software. The ship's stability and strength results are more closely in accordance with the actual condition. The cubic splint curve is used to fit the integral curve and interpolated densely data, then the algorisms of numerical value integral is used to obtain more accurate results via trapezoid integral method. The paper mainly includes the following contents: Firstly it introduces the disposal and revision of the table of offsets and the methods of the algorisms of the approximate integral of ship's hull using the cubic splint curve. Secondly it expatiate the method of the ship's floatation calculation, iterative calculation through a small angle in details and sets forth the calculating model of the ship stability and strength based on the table of offsets and floatation calculation. Lastly the paper discusses the stowage software developed with VC++ 6.0 using data-base accessing technology of ODBC on the basis of offsets. A loading case and its results analysis are given at the same time, and this new calculation method proves to be feasible and effective with the right outcome.