Design of simply supported hot‐rolled steelshort‐to‐intermediate angle columns

Abstract

Selected, extended paper from the SDSS 2019 special session ECCS/TC8 – Structural Stability This work reports on the results of an ongoing investigation of the direct strength method (DSM) design of hot‐rolled steel equal‐leg angle columns with pinned (spherically hinged) supports and short‐to‐intermediate lengths, i.e. buckling in flexural‐torsional modes. It extends the scope of similar studies involving cold‐formed steel angle columns with the same characteristics (but higher leg width‐to‐thickness ratios). After collecting the experimental and numerical failure loads available in the literature concerning columns with several geometries, the paper addresses the mechanical reasoning behind a DSM‐based design approach proposed in the context of fixed‐end and cylindrically hinged cold‐formed and hot‐rolled steel short‐to‐intermediate angle columns, which must be modified to handle spherically hinged supports. After that, the failure loads gathered are used to assess the quality of their estimates using this design approach, namely, by determining LRFD resistance factors. It is shown that this approach can be successfully applied to predict hot‐rolled steel simply supported angle column failure loads, leading to LRFD resistance factors above 0.90.

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

“…They concern 84 specimens with measured cross-section dimensions such that 18.5 ≥ b/t ≥ 12.5 and whose material/steel properties and failure loads can be found in [16]. The parametric studies reported in [16][17][18] concern columns with (i) cross-section dimensions such that 20 ≥ b/t ≥ 10 and (ii) lengths and yield stresses (elasticperfectly plastic material model) selected to ensure buckling in FT modes and covering a wide slenderness range − the yield stress interval is 700 ≥ fy ≥ 150 MPa. Sets of 108 F, 108 PC and 144 PS columns were analysed, all containing 3-point residual stress distributions ( Fig.…”

“…In order to assess the performance/merits of the above DSM-based design approaches in estimating hotrolled steel angle column failure loads, one considers next the predictions (Pnfte) concerning the whole set of F (numerical), PC (numerical) and PS (experimental and numerical) failure loads gathered in Section 3 − the corresponding failure-to-predicted strength ratios Pu /Pnfte can be found in tables presented in [16][17][18]. Moreover, the failure load prediction quality is also assessed through the determination of the LRFD resistance factor (φc) associated with the estimates provided by the proposed DSM design approaches.…”

“…from the role played by residual stresses and the absence of well defined "flexural-torsional plateaus" in the signature curve. This situation has just been altered by the authors [16][17][18], who presented and discussed numerical results concerning the buckling, post-buckling (elastic and elastic-plastic) and ultimate strength behaviours of fixed-ended (F columns) and pin-ended short-to-intermediate hot-rolled equal-leg angle columns − the last work concerns columns with end supports (i) pinned with respect to minor-axis flexure and fixed with respect to major-axis flexure, torsion and warping (materialised by rigid plates resting on cylindrical hinges − PC columns) and (ii) pinned with respect to major and minor-axis flexure and fixed only with respect to torsion and warping (materialised by rigid plates resting on spherical hinges − PS columns).…”

“…The objectives of this work are (i) to summarise the findings reported in [16][17][18] for equal-leg angle hot-rolled steel columns with stocky-to-moderate legs, (ii) to gather the experimental and numerical failure load data available in the literature, concerning columns with several geometries (cross-section dimensions and lengths), (iii) to provide a brief overview the DSM-based design approach proposed in [11] for angle columns with slender legs, and (iv) to assess whether the above experimental and numerical hot-rolled steel angle column failure loads are adequately predicted by this design approach.…”

“…3(a1)). The investigations reported in [16][17][18] included also numerical studies performed to compare the influence, on the failure load of short-to-intermediate hot-rolled angle columns, of the two residual stress distributions displayed in Fig. 4(a), namely (i) the 3-point linear diagram commonly adopted (e.g., [20]) and (ii) the 4-point linear residual stress distribution proposed by Može et al [21].…”