A NEW DESIGN EQUATION FOR ESTIMATION OF THE ULTIMATE COMPRESSIVE STRENGTH OF ALUMINUM WELDED PANELS

The high strength-to-weight advantage of aluminium alloys has made it the potential material for building airplanes and sometimes for the construction of land-based structures. For marine applications, the use of high strength, weldable and corrosion resistant aluminium alloys, have made them the material of choice for weight critical applications such as high speed crafts, military patrol crafts, luxury yachts and to lighten the top-side of offshore structures and cruise vessels. It is commonly accepted that the collapse characteristics of aluminium structures are similar to those of steel structures until and after the ultimate strength is reached, regardless of the differences between them in terms of material properties. However, it is also recognised that the ultimate strength design formulae available for steel panels cannot be applied directly to aluminium panels even though the corresponding material properties are properly accounted for. This is partly due to the fact that the stress-strain relationship of the aluminium alloys is different from that of structural steel. That is the elastic plastic regime of material after the proportional limit and the strain hardening plays a significant role in the collapse behaviour of aluminium structures, in contrast to steel structures, where the elastic-perfectly plastic material model is well adopted. Besides, the softening in the heat-affected zone significantly affects the ultimate strength behaviour of aluminium structures, whereas it can normally be neglected in steel structures. In this paper, the ultimate strength characteristics of aluminium stiffened panels under axial compressive loads are investigated using ANSYS elastic plastic large deflection finite element analyses with varying geometric panel properties. An average level of initial weld-induced deflection and softening in heat-affected zone is assumed. Closed-form ultimate compressive strength formulae are derived for aluminium stiffened panels by regression analysis of the computed results.

Keywords:

Aluminum stiffened panel , Buckling , Post buckling , Ultimate strength , Design equation