Research On Ultimate Strength Of Collision/Grounding Damaged Ship Structure Considering Randomness Of Parameters

Ship structure strength is an important part of ensuring ship safety,which needs to be kept focused on today's trend of ship large-scale.The ultimate strength,as a parameter that reflects the ability of hull structure resisting loads from cargo and environment in extreme conditions and,is the key research object of structural strength analysis.The study of the ultimate strength of hull structure will help to further improve the economy of the structure and improve the design level of the ship in China.The ultimate strength of the hull is often divided into the ultimate longitudinal capacity of ship structure and loads from cargo / environmental to study.Specifically to the structural ultimate bending capacity,the early research often uses elastic beam method,assuming stress distribution method and other analytical methods,which consider the material yield/buckling strength of the components that make up the hull structure,and with the development of information technology and people's understanding of the elastoplastic characteristics of the material,non-linear FEM,ISUM and other advanced methods began to become the mainstream method of research.As a simplified method derived from those methods,the incremental-iterative method takes into account accuracy and computational efficiency,and is less influenced by the user themselves than FEM,and is in fact widely used as a recommended method of HCSR.The incremental-iterative method defined by HCSR does not directly consider the geometric/load asymmetry effect caused by structural collision/grounding damage,and avoids the calculation of neutral axis rotation by expanding the damage range.Further research found that considering asymmetric effects meant the need to add a neutral axis rotation iteration process to the incremental-iterative method,which would significantly increase the time cost of calculations and not reflect the advantages of incremental-iterinal method as a simplified method,which needed to be improved.The main research of this article is as follows:(1)The basic research methods and research progress of the analysis of the ultimate strength and reliability of the intact and collision/grounding damaged hull structure are introduced,which provides the support for the subsequent research work.(2)Using the assumed stress distribution method,the incremental-iterate method,the nonlinear finite method to analyze the ultimate vertical vertical bending capacity of the intact model.The effect of the average stress-strain relationship and buckling failure mode of the structural element was studied,and the variation law of the neutral axis of the hull girder cross-section during the curvature loading process was analyzed in the context of the typical time cross-sectional stress distribution.(3)For collision/grounding-damaged hulls,taking into account the asymmetric effects such as geometry and load,the ultimate strength calculation program is written on the basis of the incremental-iterative method,and support for neutral axis rotation is introduced.Taking into account the computational efficiency caused by neutral axis deflection,the iterative process of the neutral axis is optimized according to the bisection principle.In view of the problem of the determination of the intact and collision/grounding damage hull structure under the great angle of heeling,the alternative notation of the neutral axis equation is adopted.Referring to the definition of damage of HCSR,the effect of the damage range on the ultimate longitudinal bending capacity of the models was studied by using the improved incremental-iterative method to compare the damage range.(4)On the basis of the ultimate strength calibration of the intact and collision/grounding damaged hull by referencing HCSR,the reliability of the ultimate strength is further studied.In reliability analysis,the FORM of determining the most possible point combined with RIA,the classic Monte Carlo simulation and the Monte Carlo simulation combined with important sampling method were used to examine the incidence of component size(thickness)and material yield strength randomness on the model's ultimate carrying capacity,and the failure probability of the longitudinal strength of the intact and collision/grounding hull structure was calculated.