Imperfection sensitivity of slender/stocky metal plates

Buckling and postbuckling behavior of metal plates is governed by their slenderness parameter. Using nonlinear finite element simulations, unstiffened mild carbon steel, stainless steel and aluminum plates under the action of axial compression are first classified into slender, moderate and stocky plates. Then the effects of initial imperfection amplitude on each plate type and material is studied via sensitivity analyses. The results show that the transition from slender to stocky plates, regardless of material type, occurs at the slenderness parameter of 2. Empirical equations for evaluating the buckling and postbuckling capacities of imperfect plates are drawn out. It is observed that the increase of imperfection amplitude decreases the buckling load of slender plates, but their postbuckling reserves and ultimate capacities are unaffected. In contrast, the ultimate strength of stocky plates is highly affected by initial imperfections.