Ultimate Strength Assessment Of Ship Structures Subjected To Random Corrosion

Since the ultimate strength capacity of structure is the important guarantee of ship security,it plays an important part of strength assessment.According to the statistics,structure corrosion is the main reason for the structural failure of about 90% of the bulk carrier.Therefore,the changes on structural performance caused by corrosion must be taken into account in the ship ultimate strength analysis.Because of the complicated corrosion environment and a mass of influent factors on hull corrosion,the reliability method is adopted here.However,there is still no perfect theory on the reliability analysis of the ship structure ultimate strength considering corrosion,and this issue becomes a research focus.Based on the background above,a random corrosion model according to a large number of bulk carrier corrosion data has been established,in this paper,and it also has been applied to the reliability analysis for the ultimate strength of ship structures subjected to corrosion.The effects of the random corrosion model on the reliability analysis of the ship structures ultimate strengths have been investigated and discussed.The main contents of this paper are as follows:(1)Corrosion data from 80 bulk carrier reports on thickness measurement were collected and studied.The distribution law and the changing rule of corrosion data about main deck,side plate,bottom plate of the middle ship cabin and their longitudinal were given.(2)Corrosion models of the above research objects were established based on corrosion data,and then a random corrosion model using random corrosion theory was proposed.(3)The corroded unstiffened plate,stiffened plate and box girder was modeled by random thickness generated by the random corrosion model above.The quasi-static method of the nonlinear finite element method was adopted to analyze the ultimate strength of structures with corrosion.(4)After analysing the ultimate strength of structures with corrosion,the reliability index of ultimate strength was obtained through JC method.