Analysis Of Ultimate Strength Of Thin-walled Box Girder

It is very important to estimate the load carrying capacity of a ship's hull as a whole from the viewpoints of safety and economy.The concept of the longitudinal strength of ship hulls has changed and advanced greatly as the study on the failure mechanism of the hull is getting deep. By taking account the failure modes of yielding, buckling and their combination, as well as the non-linear interactions between structural members, the ultimate longitudinal bending moment is defined by the moment corresponding to the point with zero slope on the moment-curvature curve of the ship hull. The definition has considered as the most reasonable so far.The calculation of the ultimate longitudinal bending moment is extremely complicated because of the non-linearity both in material properties and in geometry of deformations. There are four main methods by far, nonlinear finite element method, idealized structural unit method, direct calculation method and simplified method.With great developments in modem mechanics, computational mathematics and computer technology in hardware and software, finite element analysis has made rapid progress in both theory and computational technology. More and more general-purpose or specialized programs have been developed in use, and costs on performing FEA are reduced shapely. The most popular softwares around the world are so many such as MSC/NASTRAN, ANSYS, ABAQUS and ADINA, etc.. They both supply users with user-friendly interface, strong analysis capability and powerful pre- and post-processing functions. Currently, FEA and its programs have become the standard tool for engineering design.Some calculation indicated that general-purpose programs can predict load carrying capacity of a ship's hull accurately if one take sufficiently into account every load and boundary combination, structure imperfections and initial stresses, together with geometric and material non-linearity.In this thesis, the load carrying capacity of several hull or hull models have been analyzed by using the general-purpose program ANSYS, and some detailed results are obtained. Through comparing FEA results with existing calculation results or experiment data, this thesis put forward some suggestions, which may be useful for future FEA.