Residual Ultimate Strength Analyses Of Cracked Ship Structures

The strength of the ship hull structures is one of the most important index to expressing the safety and reliability of the ships. It is also one of the most important factors which have to be reviewed during the design, construct and the service of the ships. Plates and stiffened panels are two kinds of basic structure components of the ships and ocean engineering structures, the strength evaluation of these structures is very important. The initial damage and the complex loading condition will reduce the strength of the structures significantly. It is of crucial importance and to estimate the ultimate strength of the damaged structures.Crack is one of the most common types of damages in the aging ships. As a result of the complexity of the stress distribution around the crack and the diversity of the parameters, the strength assessment of cracked structures is different from the integrated ones. Systematic analyses are insufficient currently and the research method relating to crack problems is generally limited to theoretical elastic fracture mechanics or fully plastic estimation method, which could not be conveniently applied in engineering practice. As one of the new research field, the ultimate strength analysis of the ship structures is still in its initial developing phase. The investigation of the relationship between the damages and the strength of the structures and the establishment of the reasonable analysis model are new research directions of the assessment of the strength of the ships.The objective of this thesis is to investigate the general situation of the analysis of the ultimate residual strength of the cracked structures. A serious of researches are carried out to find out how the dimension of crack and the loading condition affect the ultimate residual strength of cracked structures under two direction of tensive stresses. At last we analyze the ultimate strength of cracked structures under compressive stresses considering the effect of the initial deformation. The work we done in this thesis shows that: we can find out how the crack affect the ultimate residual strength of the structures using the nonlinear finite element method; the existence of the crack weaken the strength of the structures definitely. We have to pay enough attention to the effect of the cracks when evaluating the strength of the ships and ocean engineering structures. Actually, the number and the location of the cracks in the ships in service are stochastic. Based on the conclusion we obtained in this thesis, we can analyze the strength of structure with random multiple crack damages in succession...