The Analysis Of Ultimate Longitudinal Strength Of Ship Hull

The scholars in the field of the ship structure mechanics pay great attention to the ultimate strength of the ships , which is an important problem in the ship design. Traditionally ,the ultimate strength is estimate by comparing allowable stress with the stress at the farthest point distant from the neutral axis on the deck or on the ship bottom, with the affecting of the mean vertical wave induced bending moment . This method is available for the traditional ship types, but can not get the real estimate of the ultimate strength of the ships, what's more is less accuracy for the modern ships. The process of the calculation of the longitudinal strength is complex ,due to the nonlinear factor of the material and geometry. The increment method is needed to obtain the integrated curve of the bending moment -curvature, thus to obtain the maximum of the ultimate strength of the ship.Recently, there are 3 methods to estimate the ultimate strength of the ships. They are Finite Element Method(FEM), directly calculation and the gradually failure analysis. The method of FEM can not be used widely in the practices ,due to its ultra large computational scalar requirement and its high cost. The gradually failure analysis is presented in this paper.The numerical method of the curve between the relationship of the stress-strain on the reinforced plate panel element is established, applied the theory of the beam-column , referenced the newly published "Rules and Regulations for the Classification of Steel Sea Ship" by CCS in 2006, and related program is coded in FORTRAN language. On the base of those, the calculation process of the gradually failure analysis of the longitudinal ultimate strength of the ships is established, and its FORTRAN codes is also obtained.The longitudinal ultimate strength of the model Reckling NO.23 and Bowling NO.2 by the method of the gradually failure analysis is derived in this paper. The result show that the method applied in this paper is reliable and precise, can be used in the design of ship structure and strength check.Finally , the method and the program is applied in the process of the strength check of the 300,000 tons oil tanker.