Ultimate Strength Analysis Of Typical Hull Structure

Outer hull structure will be buckling under external load, however, the structure won’tfail down immediately after buckling. It still have a certain carrying capacity. When theexternal load continues to increase, the structure that cannot withstand the extra load willbreak down. The maximum load the structure withstands before breaking down is calledultimate load and is also called ultimate strength of the structure. It’s taking fully account ofthe post-buckling behavior when ultimate strength of the structure is defined so that theultimate strength express the truly capacity of the hull structure. In recently years, the conceptof ultimate strength has been widely used in marine engineering field and the methods of theresearch have been becoming mature increasingly. Ultimate strength of the hull structures isdiscussed in the paper based on nonlinear finite element method. The main contents of thispaper are as follows:1) Explain the concept of ultimate strength and review the study of the ultimate strengthof the hull structures. The calculation using nonlinear finite element method in the existingsoftware is described briefly.2) The sources and computing methods of the initial defection of the hull structures areshowed and the empirical formulas to estimate the initial defection are given. Besides, theinitial defection is simulated using finite element method.3) The stiffened panel’s mechanical properties are analyzed compared to simple plate bycalculating its ultimate strength values under different combinations of external loads.Furthermore, the impact of different types of load on the ultimate strength is discussed.4) The ultimate bending moment of Nishinara box girder is calculated. The influence ofmesh size, element type, boundary condition, initial defect and local load on the ultimatebending moment are discussed. Errors caused by finite element simulation and feasibility ofthe analysis procedure is discussed.