Study of Standardization for Longitudinal Strength of Ships.

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There are three non-linearities for the response of ships structures in big waves. (1) non-linearity of gluid resistance against vertical moment of ships (2)slamming of exposed hull (3)whipping due to elastical behavior of ship. Longitudinal moment and shear force distribution for several types of ships were estimated by the authors according to numerical simulations considering those non-linearities.Plate thickness effect in fatigue strength (so called "DEn Thickness penalty code") was investigated using non load carrying T shaped fillet welded joint in pulsating bending. It has been revealed that good finish of weld toe results in remarkable improvement of fatigue strength and almost vanish so called "platethickness effect". Regarding fatigue crack propagation under random loading, several patterns of power spectrum with different band widths in frequency were used, and meanstress level was changed from compression to tension to identify the crack closure effect. The various stress r … More ange DELTAS_r of random loading was converted into fixed value DELTAS_<eq> ( equivalent stress range ). Using this DELTAS_<eq> and considering crack closure effect, a possibility has been shoxun that the fatigue behavior under random loading may be predicted from constant amplitude test.A numerical method was developed evaluation of wave loads, motion responses of general shaped floating bodies including ship hulls and also for evaluation of structural responses of complex structures composed by plural number of floating bodies and connecting elastic members. This method is based on both the three dimensional source distribution method and the wave interaction theory. High speed estimation method was adopted for evaluation of the Green functions in the three dimensional source distribution method and combining this with the wave interaction theory, efficient calculations of wave loads and motion responses can be accomplished.New statistical theory is developed, which gives probability density function and extreme values of a weekly non-linear response to Gaussian input. It is determined that the theory gives good estimates of them by comparing with measured surge respons of a ship model moored in random waves.The highly nonlinear structural analysis codes based on the low-order finite elements, which are (1) analysis code for space frames using linear Timoshenko beam elements, (2) analysis code for thin shells using constant-moment Mindlin plate elements, and (3) analysis code for axisymmetric solid using constant-strain quadrilateral elements, have been developed. Their accuracy and efficiency have been estimated, through the comparison with the results of the crush tests. Less