| The structure fatigue as the main reason for ship and ocean structure broken accident is concerning more and more attention to be researched. Fatigue mechanism loosing effectiveness is complicated. The fatigue design procedure research has important value for the exact fatigue expression of ocean structure and also for the safety and property of people. This project primary analyzes and summarizes the process of fatigue assessment simplified procedure and the main points of FE analysis guiding with the "Guide of Ship Structures Fatigue Strength" of CCS. Separately calculate fatigue life with nominal and hot-spot stress which was calculated from simplified procedure and FE analysis, compare the different results with the ship operating parameter in practice and then discuss about the affected results of choosing various parameters, abasing on the former analysis.This subject is mainly study about:(1) Exponenting the content of fatigue theory, including three main procedures of imputed fatigue life and the substance of the procedures: fatigue cumulative damage procedure basing on S-N curve and Palmgren-Miner linear cumulative damage rule; fracture mechanics procedure carried with Paris crack growth theory and reliability analysis basing on probability theory and combines the two former procedures, and also the main points of the above three procedures.(2) Researching on the main possess of the simplified procedure, as well as the key points of FE analysis, basing on the "Guide" of CCS.(3) Integrating theory with practice, analyze the reason for the outer bottom plating longitudinal damage of a 9800DWT bulk carrier. First step to finite element modeling and then analyze the yield strength and buckling stress. On the base of satisfying yield strength and buckling stress, separately research about the failure point in simplified procedure of fatigue assessment and FE analysis, make sure of the failure cause.(4) On further analysis, calculating the key points which in the middle of the vessel with simplified procedure and FE analysis, combining with the heavy ballast bulkhead effective result. Comparing results of the two procedures, with the ship operating data as reference, discuss the accuracy of the two procedures for the better choosing of the two procedures in practice.(5)Discussing the stress factors of the calculation result and changing the parameters in the calculation process, studying about the effect to the results, and discussing about the choice of calculation points to find the most dangerous point.
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