13.11: DSM design approach for hot‐rolled steel angle columns

Abstract

ABSTRACTThis work reports the latest results of an ongoing investigation on the Direct Strength Method (DSM) design of hot‐rolled steel equal‐leg angle columns with fixed and pinned (cylindrical or spherical hinges) supports and short‐to‐intermediate lengths, i.e., buckling in flexural‐torsional modes. It extends the scope of similar studies carried out by the authors for cold‐formed (higher leg width‐to‐thickness ratios) steel angles with the same characteristics. After reviewing (i) the most relevant findings unveiled in the studies concerning hot‐rolled steel angles, including the role played by residual stresses in eroding their ultimate strength, and (ii) the available experimental and numerical failure load data, comprising fixed‐ended and pin‐ended columns with several geometries (cross‐section dimensions and length) and reported by various researchers, the paper briefly addresses the mechanical reasoning behind an efficient DSM‐based design approach proposed by the authors in the context of cold‐formed steel (slender legs) short‐to‐intermediate angle columns. Then, the available failure load data is used to assess the quality of their estimates provided by this DSM design approach, including the determination of the corresponding Load and Resistance Factor Design (LRFD) resistance factors. It is shown that the proposed design approach can be also successfully applied to predict hot‐rolled steel angle column failure loads, leading to LRFD resistance factors above the value currently prescribed, for compression member design, by the North American Specification (ϕc=0.85).