Study on the Load-Stress Simulation Method for Ship Structure in Waves

The rational and comprehensive ship structural analysis and strength evaluation based on data from a good feedback of operational service experience must be effectuated in order to secure the ship hull strength in hull structural design and establish the design criteria. For that purpose, it is important to develop the estimation method by which the ship hull stresses in ocean waves are estimated with accuracy.In this background, the authors developed the simulation method of ship hull local stresses in ocean waves, and applied the method to the local stress estimation in the actual ship. As a result of the application, the several findings on the structural response characteristics of local structure in waves are obtained as follows.(1) In the vertical distribution of fluctuating stresses in side longitudinal frames the hump was found to appear beneath the L. W. L. owing to nonlinearity of wave height to wave pressure, which can not be obtained by using linear treatment. This suggests that it is necessary to pay enough attention to fatigue strength of side longitudinal located in the limited part below L. W. L.(2) Fluctuating stress level of bottom, deck and longitudinal BHD longitudinal is found to be lower than that of side longitudinal by the present estimation method.(3) From the investigation of correlation between each components of side longitudinal fluctuating stresses caused by such loads as wave pressure, inner fluid pressure and vertical/lateral bending moment, the following results are obtained.(a) The coefficient of correlation between fluctuating stress components owing to outer and inner pressure becomes -0.6.(b) The coefficient of correlation between total fluctuating stresses owing to outer/inner pressure and vertical/lateral bending moment becomes 0.4.