Computational Analysis And Performance Research On Nonlinear Ultimate Strength Of Stiffened-plates Under Combined Loads

Both steel and aluminium stiffened-plates are being widely used in every field including shipbuilding industry. For a long time, the people assess strength of the ship structure or other large construction members, following the concept—working stress not exceeding allowable stress. In recent years, experts of ship structure scan the traditional methods of assessing the loading capacity again during the ship disasters. For ship design and strength assessment, the traditional allowable working stress approach which can not determine the true margin of structural safety has not suited the requirements of developing design idea. The limit strength basis is much reasonable than the traditional allowable working stress approachOrganized by the International Ship Structure Committee(ISSC),many well-known experts around the world are studying on the ultimate strength of panels,stiffened-plates and hull girders. Generally, they proceed to the non-linear ultimate benchmark calculation of panels and stiffened-plates for obtaining a widely acceptable calculation method for hull girder, and finally the whole ship herself.This thesis have mainly studied the non-linear ultimate strength of the steel stiffened-plates under combined loads provided by the benchmark calculation task of ISSC through Ansys software, focused on the calculation method,affected parameters (including thickness of plate, loads combined form, elements density, extent of models and so on).On the other hand, the aluminium stiffened-plates are being widely used as the development of extruding and welding technology in the shipbuilding industry with the benefit on less weight and higher speed. Compared to steel, the softening in the heat-affected zone(HAZ) significantly affects the ultimate strength behaviour of aluminium stiffened-plates.So this thesis have done some work about HAZ also, including the introduction of the general study method of HAZ and research on the influence of construction and welding form. The influence of the ultimate strength (combined in-plane compression and lateral pressure, amplitude of initial deformation, extent and distribution of HAZ, thickness of plate) has also been studied. A part of ultimate strength results about the steel stiffened-plates have been submitted to the ISSC for discussing.