| Due to the inhomogeneous loading condition and empty tank,the position of bulkheads has great influence on the still water bending moment and shear force of bulk carriers.Once the cargo hold is damaged,excessive bending moment will cause serious consequences,and even cause the ship broken.In addition to the loading conditions,the still water loading of the ship is closely related to the arrangement of holds,such as the layout of the typical cross section,the length of the cargo holds,the height of the double bottom,the strength of the main support structure of the top,and hopper tank,as well as the position and arrangement form of the transverse bulkhead,which all affect the still water bending moment and shear force value of the ship.According to the latest common structural rule,the design of the new ship requires higher structural strength and permissible bending moment.Compared with increasing the size of components to enhance the structural strength,it has great significance to chang the layout of ships not only for shipowners but also for designers.This paper focuses on the effect of subdivision optimization on the reduction of ship still water loading.The traditional subdivision is mostly completed according to standard rules or by appropriate modification of the modle ship.Several subdivision schemes are put forward and compared one by one to select an optimal scheme.The efficiency of these methods is low and the search range is limited,so it is hard to find the optimal subdivision scheme in theory.In this paper,according to the requirements of SOLAS and HCSR,the hull girder mathematical model of a bulk carrier is established.By using the NAPA software,the exhaustive method with "variable step " and the genetic algorithm are used to research the subdivision optimization of bulk carrier.The offset distance of the bulkheads between cargo tanks is taken as the variables,assuming that the main dimensions,ship parameters,the number of cargo tanks and the length of all cargo area(i.e.the position of transverse bulkheads at the front and rear ends of the cargo area)of the ship are maintained.First of all,take the constraints of requirements of the total cargo tank capacity,the intact stability and the damage stability of the ship for consideration,the bulkhead position optimization of bulk carrier under the intact condition is calculated.taking the maximum still water bending moment as the optimization objective,the exhaustive method and the genetic algorithm are adopted to carry on the comparative calculation,and some results are obtained,which is that increase the middle cargo tank length and reduce the cargo tank length at both ends lead to smaller hogging bending moment.And increase the cargo tank length at both ends,and reduce the middle cargo tank length lead to smaller sagging bending moment.In the process of optimization,in order to prevent excessive trim because of the moving bulkheads,a real-time stowage program is written to adjust the ballast water to make floating condition under the requirements at any time.Then the genetic algorithm is chosen to calculate the bulk carrier optimization under damage condition.In this paper,the most dangerous conditions of hogging and sagging of hull girder are studied respectively to optimize the position of bulkheads,and the subdivision scheme to minimize the envelope area of the still water bending moment along the bulk carrier is sought. |
