Behavior, Failure, and Direct Strength Method Design of Steel Angle Columns: Geometrical Simplicity versus Structural Complexity

Abstract

This work provides a state-of-the-art report on the current knowledge concerning the structural behavior and design, by means of the Direct Strength Method (DSM), of steel equal-leg angle columns with short-to-intermediate lengths, that is, those buckling in flexural–torsional modes – although cold-formed columns constitute the main focus of the paper, hot-rolled columns are also addressed. The columns dealt with are either fixed-ended or simply supported – the latter designation includes columns with both cylindrically and spherically-hinged end cross-sections. Initially, numerical results concerning the mechanics underlying the buckling and postbuckling behavior of the previous angle columns are presented and discussed: (1) highlighting the main differences between the fixed-ended and simply supported column responses, and (2) evidencing the need for specific design procedures. Next, the paper collects the experimental and numerical failure load data available in the literature, reported by various researchers and dealing with cold-formed and hot-rolled fixed-ended and simply supported columns with several geometries (cross-section dimensions and lengths). Then, the paper presents the mechanical reasoning behind a recently proposed novel DSM-based design approach, as well as the main steps involved in developing and calibrating the corresponding strength curves. Finally, the merits of this design approach are assessed through (1) the estimation quality of the available failure load data, and (2) the evaluation of the associated Load and Resistance Factor Design (LRFD) resistance factors, which are compared with those currently recommended by the North American Design Specifications. The paper closes with an overview of the findings reported and a reference to future developments of this research effort.