Calculation Of Fatigue Damage Based On Common Structure Rules For Double Hull Oil Tankers

Fatigue is an important failure mode for ship structures. To avoid the shipwrecks due to lack of fatigue strength, many experts and scholars in the shipbuilding and ocean engineering field have done much theoretic and experimental research on the fatigue strength of ship structures. Based on the research, lots of ship classification societies in the world have put the verification of fatigue strength into their design rules. However, some research has indicated that there is much difference among the fatigue assessment methods. To unify the rules,LR, ABS and DNV enact Common Structural Rules for Double Hull Oil Tankers, whose rule length is larger than 150 meters.Based on understanding the basic principle and fatigue assessment method, this paper does deep research into the fatigue assessment procedure in Common Structural Rules for Double Hull Oil Tankers.This paper goes deep into particulars of evaluation flow of nominal stress method which mainly includes the establishment of fatigue loads, calculation and combination of fatigue stresses, influence of mean stresses, selection of S-N curves, establishment of Weibull parameter and calculation of fatigue damage. This paper indicates that the design of longitudinal stiffener should take account of those that include location of stiffener, load method and load characteristic. It's effective measure to enlarge longitudinal dimension, improve longitudinal structure shape and apend bracketes. Fixing soft toe could effectively decrease the stress concentrative fator and improve fatigue strength. After that, this paper evaluate the fatigue strength of longitudinal stiffeners at ship midsection, analysis the main reasons which cause fatigue damage and supply some advice which is useful for ship design work.Besides, this paper goes deep into particulars of evaluation procedure of hot stress method which mainly includes the establishment of finite element model, imposition of load and boundary limit, acquirement of hot stress and calculation of fatigue damage. This paper indicates that the hot stress method could be effective and safe for ship to adopt new wave load model and erosion model. After that, the procedure is to be applied to one welded knuckle between inner bottom and hopper plate at Frame 121. Besides, this paper applies the hot stress approach to the longitudinal stiffener and gets useful conclusion from the comparison between the results induced by two different methods. It points that this method...