Research On Ultimate Strength Of Hull Structures Contain Y-stiffeners

Ultimate strength is a critical and fundamental assessment in the design of ship structures.Only when the load carrying capacity is fully defined,the reserved strength of a ship structure can be truly evaluated.Thus not only can damage accidents be avoided effectively,but also the economy of the ship design will be improved.The existing methods for calculating ultimate strength of hull structures can be classified into five categories: direct method,progressive collapse method,nonlinear finite element method(nonlinear FEM),idealized structural unit method(ISUM)and experimental method.Many scholars have studied Y stiffened panel since it was first proposed by Ludolphy.However,researches mainly focus on the energy absorption characteristics and impact resistance of Y stiffened panel,while little on the ultimate strength.In this paper,a series of researches on Y stiffened plate structures are carried out in reference to the method of studying the ultimate strength of conventional stiffened plate structures.Firstly,the nonlinear FEM is applied to analyze the ultimate strength of Y stiffened panel.The influence of different conditions on the accuracy of the calculation results,and the influence of the dimensions of Y stiffened panel on the ultimate strength will be discussed.Then based on the theory of progressive collapse method mentioned in the common structural rules(CSR),a program SUS_CSR is developed to calculate the ultimate strength of hull structures,and it is verified by existing girder models tests and a Suezmax class double hull oil tanker.Finally,the conventional stiffener profiles are replaced by the novel Y stiffener profiles on the outer and inner bottom panels of the Suezmax oil tanker for modified design.On the one hand,the modified SUS_CSR program will be used to calculate the ultimate strength of the whole hull structure after modification;on the other hand,the nonlinear FEA is used to calculate the ultimate strength of the local structure of the outer bottom plate.The comparison of the results between the two methods will be used to verify the feasibility of the design of Y-stiffeners.