Ship Structure Fatigue Assessment And Analysis Based On CCS Rule

Fatigue destruction is one of the main causes of ship structure failure, which has extensively caught the attention of the industy and become a hot investigation point. Anti-fatigue design tends to be an important part in ship structure design, however it needs both an improved fatigue assessment method and aboudant accumulation data of ship assessment. The China Classification Society has being committed herself to improve her own level of fatigue assessment and design. After years of practice and study, she successfully made supplement and improvement in many item of her fatigue guidance in 2007, which would help the civil ship structure assessment to make further effort.Base on the CCS fatigue rule, this paper trys to find and carry out the problems of the rule when practising in ship fatigue assessment, search ways that are briefer and more accurate for ship fatigue assessment, give advices to revise the rule to be more perfect, and try the best to check and value the whole ship as more detailedly as possible in order to make the results to be reference to further comparative study.Firstly, findamental principles and methods on ship fatigue assessment was explained, also some important theories like S-N curve and Weibull long-term distribution of stress were analysed deeptly in the paper.Secondly, CCS fatigue assessment methods were introduced, the new-added hot stress method's interpolation problem was posed, say, it may fail. So another method named quadratic parabola was recommended to replace it after comparative analysis.Then, several longitudes and complicated typical structure spots in a bulk-carrier were assessed applying nominal stress method and hot stress method respectively. The difference between simplified method and finit elemt direct calculation method was carried out. Comparative analysis on how the asymmetry-lower-stool bulkhead acts in different bulkhead cargo pressure, and how to choose assessment objects were also done.Lastly, after analysis, some but few mistakes and unsuitable edit were posed which may bring the rule users to puzzle.