| The ultimate strength of hull structure is the most important strength design index(including ultimate strength,transverse strength and local strength)for hull safety.In order to meet the development demand of high speed and large scale development of high and new ships,high strength steels are widely used in shipbuilding.It is necessary to consider the effect of pitting damage in marine environment to accurately evaluate the ultimate buckling strength of ship structures.Based on the corrosion damage characteristics of the real ship plate frame structure,the effects of the key parameters such as model range,pitting density,pitting depth,strip flexibility and flexibility ratio of plate stiffeners on the failure mode and ultimate strength of the stiffened plate are studied through the finite element analysis of the plate frame with pitting damage,and 6 kinds of stiffened plates' failure mode are discussed.In the failure mode,the percentage of corrosion volume is used as the main parameters for the ultimate strength evaluation of the hull stiffened plate with pitting damage,and an engineering evaluation criterion is established to meet the strength of the hull structure.The formula of ultimate strength reduction factor for ship stiffened plate with pitting damage under different failure modes is obtained for the hull structure with pitting damage,which provides the basis for the assessment of the residual total longitudinal ultimate strength and reliability of the hull girder with pitting damage.The effect of pitting corrosion on the failure mode of stiffened panels is also analyzed.It is concluded that serious pitting damage will lead to the change of failure mode of stiffened plate structure,which will seriously reduce the ultimate strength of stiffened panels.The engineering evaluation method proposed in this paper has high accuracy and is suitable for ultimate strength evaluation of stiffened plate structures. |
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