Ultimate Strength behavior of Aluminum Stiffened Panel under Combined Load
Port-Said Engineering Research Journal
This boat was powered by a steam engine that ran on oil  . Boat and high speed catamaran builders, for the first time during 1990's, implemented Aluminum panels for marine applications (Collette). The main role of these panels is strengthening against in-plane compression. It is not accepted to extend the formulations for of steel panels strength to the aluminum panels since to have different stress-strain relationship than that of structural steel. In the elastic-plastic range after the
... range after the proportional limit as compared to structural steel, the strain hardening has a significant influence in the ultimate load behavior of aluminum structures whereas in steel structures, the elastic-perfectly plastic material model is well adopted  . Studying the ultimate strength of aluminum was performed by many authors. Wang el al., 2005 developed a criterion for buckling and ultimate strength of plate and stiffened panels subjected to longitudinal compression, and validate the criteria by non-linear Finite Element Method. The authors investigated typical -marine‖ grade aluminum alloys. Buckling and ultimate strength formulas for plate panels and stiffened panels in aluminum ship structures were proposed. Based on the previous experiences from steel structures, a modified Faulkner's formula was put forward for ultimate strength of plate under longitudinal compression and a reduction factor is introduced to take into account the heat affected zone HZA softening effect. Closed-form empirical ULS formulas for aluminum stiffened plate structures were developed by the regression analysis of experimental and numerical Ultimate strength database obtained from the present study  . ABSTRACT Aluminum has become the material of choice for many types of vessels, particularly high-speed vessels where lightweight structure is important for meeting design goals. The methods of design and fabrication of aluminum contain many areas of conservatism that if overcome by proper research will lead to even greater performance at reduced cost. This paper studies the ultimate strength of Aluminum stiffened panel under combined loading conditions. A Finite Element Model had been developed based on published experimental study, this model was validated by comparing the output results with experimental work. The model calculated the ultimate strength of the panel under axial load. After validation of the model, it is used to estimate the ultimate strength of the aluminum stiffened panel under combined load. It is intended to investigate the effect of initial imperfection on the ultimate strength of the aluminum panels into the finite-element models studied. The effect of change in panel aspect ratio and the effect of column slenderness ratio are investigated. It has been found that an increase in aspect ratio affects the ability of the panel withstand any increase in load especially in case of imperfections. The analysis for the forcedisplacement relationships and post-collapse deformed shapes is also investigated.