Spherically-Hinged Short-to-Intermediate Angle Columns Stability, Non-Linear Behavior and DSM Design

This work reports a numerical investigation on the buckling, post-buckling (elastic and elastic-plastic), strength and design of spherically-hinged short-to-intermediate equal-leg angle columns. It extends the scope of similar studies recently carried out by the authors for cold-formed and hot-rolled (lower leg width-to-thickness ratios) steel fixed and pin-ended angles with the same characteristics. After briefly reviewing the most relevant findings unveiled in the above studies, the paper addresses the buckling behavior of spherically-hinged columns − the results presented and discussed, which include the selection of the column geometries to be considered, are obtained by means of Generalized Beam Theory (GBT). Then, the post-buckling behavior and strength of columns containing initial geometrical imperfections and residual stresses (special attention is paid to modeling the latter in hot-rolled angles) is investigated. The results obtained, by means of ABAQUS shell finite element analyses, include a parametric study intended to gather failure load data covering a wide slenderness range. The above numerical failure loads are subsequently used to develop, validate and assess the merits of a rational design approach for such members, which is based on the Direct Strength Method (DSM) and adopts ideas and procedures similar to those employed recently by the authors (Dinis & Camotim 2015, 2016a,b, Dinis et al. 2016) in the context of fixed-ended and pin-ended (cylindrical hinges) short-to-intermediate equal-leg angle columns. The need for modifications arises from the change in major-axis flexure support conditions, which influences the column flexural-torsional behavior significantly. It is shown that the proposed/modified DSM strength curves lead to safe and reliable failure load predictions for spherically-hinged short-to-intermediate equal-leg angle columns exhibiting a wide slenderness range, thus extending the scope of the existing rational DSM-based design approach to cover also columns with these end support conditions.

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