Reliability Analysis Of Ship Hull Girder Ultimate Strength And Reserch On Related Infuential Factors

In the designing,construction and operation of ship hull structure,many uncertainties affect the ship in the reliability of the structural strength.Considering these uncertainties as random variables,the reliability index of hull girder ultimate strength can be obtained by SRA method,which can more clearly reflect the ship's capability of resisting longitudinal bending failure.The main content of this paper is to study the ultimate strength reliability of ship hull girder for the typical inland river ship.Based on the SRA method,IACS CSR and relevant background materials,considering the main uncertainties affecting the structural safety of the ship,a set of reliability analysis method for the ultimate strength of ship hull girder is proposed,and the reliability index of ultimate strength of a series of inland river ships is calculated,then the target failure probability is determined,the partial safety factor is calculated and optimized,and the checking formula of ultimate strength based on reliability is obtained finally.In addition,for an inland container ship with a large cargo hold opening,the effect of torsional deformation on the ultimate strength is to be taken into account.In this paper,finite element models are established for the cabin between two adjacent strong frames of the container ship by the nonlinear finite element analysis software ABAQUS for five typical inland container ships.The ultimate strength of the model considering the large torsional deformation is calculated and re-substituted into the reliability analysis process,the security of the calculation method for the reliability of container ships was investigated.Moreover,by comparing the results of nonlinear finite element method and smith method,the correctness of the two ultimate strength calculation methods is determined.The IACS CSR assumes that each load case is considered to be equally probable.However,the probability of occurrence of each load case is not actually equal from the survey results of the sample vessels,so the difference between this assumption and the actual situation is quite different and that may has an impact on the safety level implicit in the hull girder ultimate strength criterion.In this paper,the reliability of the hull girder of a series of BC-A bulk carriers is analyzed by considering the effect of loading conditions on the random distribution of the external load.The comparison of the reliability analysis results with the original safety level shows that the reliability level obtained by considering the loading condition distribution still satisfies the requirements of rules,and the IACS CSR provides a sufficiently conservative security margin.