Effective slenderness ratio approach for thin-walled angle columns connected by the leg

Abstract

This paper reports results of experimental and numerical investigations on a novel design approach to cold-formed steel angle columns connected by the leg that uses effective slenderness ratios. A FEM model (ANSYS) validated by experimental results obtained at the University of São Paulo enabled the development of a parametric study that involved 170 thin-walled angles connected by the leg by two bolts. An analysis of two types of initial geometric imperfections revealed the imperfection effects can be neglected in the mechanical behavior of the members, in contrast to the existing load eccentricity imposed by the bolted connection on the leg. From the parametric study, a new design approach based on effective slenderness ratio method and with a width/thickness ratio (b/t) is proposed with high accuracy mainly for intermediate angle columns. Although the design formulation was defined for the 20–36 b/t ratio range, the approach can be conservatively applied to angles with up to 50 b/t. Its effectiveness was validated by 3200 structural reliability problems of variable geometrical properties. The results of reliability indexes, with or without the model error, met the requirements of design standards and proved the adequate performance of the proposed design rule for large ranges of b/t and slenderness.