A comparative study of fatigue assessments of container ship structures using various direct calculation approaches

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A comparative study of fatigue assessments of container ship structures using various direct calculation approaches

Li, Zhiyuan / Mao, Wengang / Ringsberg, Jonas W. / Johnson, Erland / Storhaug, Gaute

It is common practice today to carry out fatigue assessments of ship structures using direct calculation procedures to compute fatigue loads. Many numerical codes are available for use in such fatigue load analyses. In addition to the various degrees of computation complexity associated with fatigue estimation methods, such methods also have large inherent uncertainties. In this investigation, a comparative study was carried out for two container ships using various typical direct fatigue calculation methods. The fatigue damage amounts calculated using these methods were compared with those obtained from full-scale measurements. Most of the direct calculation approaches investigated yielded similar fatigue damage estimates. The approach that employs nonlinear time-domain hydrodynamic analysis and the finite element method yields reasonable and conservative fatigue damage results and is therefore recommended. In addition, the results of this study confirm that various measures of wave environments and of the variation in wave models are important sources of uncertainty in fatigue life prediction.