Direct Strength Method Design Research Articles

Plastic mechanism models for use in DSM localised loading design of hat sections

The Direct Strength Method (DSM) of design has been recently developed for the design of cold-formed steel members under localised loading. The method requires a yield load (Py) and an elastic buckling load (Pcr) as input variables to the DSM design equations. This paper summarises test results used to develop plastic mechanism models for calculating Py for hat sections subject to practical loading cases. All four loading cases, including Interior Two Flange (ITF), End Two Flange (ETF), Interior One Flange (IOF) and End One Flange (EOF) loading cases were investigated. The yield/plastic mechanism behaviour of multiple web sections is not yet fully understood, while several publications in the literature have discussed the mechanical behaviour of hat sections under localised loading. Hence, this paper explains and proposes a plastic mechanism model based on the experimental data for calculating the yield load (Py) to be used in the DSM for localised loading design of hat sections in conjunction with the elastic buckling load Pcr.

Axial capacity of cold-formed steel channel sections with slits

Cold-formed steel (CFS) studs often include slits in their webs to improve thermal performance. However, the inclusion of such slits reduces their axial capacity. The literature contains limited experimental studies on the axial capacity of these studs with slits, and no non-linear elasto-plastic finite element studies have been reported. This research aims to address this gap. Non-linear elasto-plastic finite element models were developed and validated against experimental test results. A parametric study consisting of 960 finite element analysis (FEA) models was then conducted, covering the effects of different channel dimensions, slit sizes, section thicknesses, and stud lengths. Ultimate axial capacities obtained from these analyses were compared to the current codified direct strength method (DSM) predictions as per the Australian/New Zealand Standard AS/NZS 4600. Finally, design recommendations in the form of strength reduction factors are proposed. Based on these recommendations, modified DSM design equations with a reliability index above 2.5 are presented.

Lateral-Torsional Failure and DSM Design of CFS Lipped Channel Beams at Room and Elevated Temperatures

About a decade ago, in-depth investigations on the behaviour of cold-formed steel (CFS) single-span simply supported lipped channel beams failing in lateral-torsional modes at both room and elevated temperatures were reported at QUT (Queensland Technical University). They revealed a significant underestimation of the lateral-torsional (LT) failure moments by the Direct Strength Method (DSM) global design curve at room temperature, then codified in the Australian/New Zealand and North American specifications. In order to remedy this situation, these authors proposed two novel DSM-based beam strength curve sets, which were found to substantially improve the LT failure moment prediction quality, both at room and elevated temperatures. This work aims at extending the scope of the above investigations, by analysing a visibly larger set of CFS lipped channel beams at elevated temperatures (up to 800 °C), exhibiting (i) various cross-section dimensions and yield stresses, selected to cover wider LT slenderness ranges, (ii) two end support conditions, differing only in the end cross-section wall displacement/rotation and warping restraints (either fully free or fully prevented), and (iii) temperature-dependent steel material properties according with the model prescribed in Part 1-2 of Eurocode 3. The results presented and discussed consist of beam LT post-buckling equilibrium paths and failure moments, obtained through Abaqus shell finite element GMNIA that include critical-mode (LT) initial geometrical imperfections. Lastly, the numerical failure moment data obtained in this work and reported in the literature are used to develop and propose a new unified set of DSM-based strength curves capable of adequately handling beam LT failures at room or elevated temperatures. Since it is shown that the proposed strength curve set provides a quite good LT failure moment prediction quality, it is fair to argue that it constitutes a good starting point to search for an efficient general DSM-based design approach for CFS beams failing in LT modes at room and elevated temperatures.

DSM design of cold-formed steel fixed-ended lipped channel columns undergoing distortional-global interaction

This work reports a numerical investigation dealing with the post-buckling behaviour, strength, and Direct Strength Method (DSM) design of cold-formed steel fixed-ended lipped channel columns experiencing coupling between distortional and global (flexural-torsional) buckling − distortional-global (D–G) interaction. Various cross-section dimensions and lengths are considered, to ensure that the columns selected undergo different levels and types (“true”, “secondary-bifurcation distortional” or “secondary-bifurcation global”) of D–G interaction. The results presented and discussed, determined by means of Abaqus shell finite element geometrically and materially non-linear analyses, consist of elastic and elastic-plastic post-buckling equilibrium paths, failure loads and collapse modes. The steel material behaviour is deemed elastic-perfectly plastic and several yield stresses are considered, thus making it possible to cover a wide column D–G slenderness range. Particular attention is devoted to identifying the most detrimental initial geometrical imperfection shapes, in the sense that they lead to the lowest column failure loads. The numerical failure load data gathered are subsequently used to assess the merits of the available DSM-based design approaches developed to handle cold-formed steel columns undergoing D–G interaction. Since these design approaches are shown to be either inefficient and/or improvable, the above failure load data are also used to propose modifications/improvements aimed at achieving an efficient failure load prediction in the specific context of fixed-ended lipped channel columns. The success of this endeavour provides encouragement to the authors in their search for a safe, accurate and reliable DSM-based design approach capable of handling cold-formed steel columns with arbitrary cross-section shapes and/or end support conditions that fail in D–G interactive modes.

Member capacity of cold-rolled aluminium alloy channel columns – Part II: Numerical investigation and design

The paper first presents the development of detailed finite element (FE) models for investigating the member capacity of cold-rolled aluminium alloy 5052-36 channel columns. The numerical non-linear FE models are developed using the commercial FE software package ABAQUS to simulate laboratory experiments and calibrated against the test results. The experimental program was performed by the authors at the University of Sydney and the detailed test results are fully described in a companion paper. The calibrated numerical FE models with actual mechanical properties and measured geometric imperfections in analyses accurately predict the experimental results and behaviours, including flexural and flexural-torsional buckling as well as local-global interaction buckling failure modes. A parametric study is subsequently performed to extend the data range by varying cross-section dimensions and member lengths. The effects of loading eccentricity positions and initial geometric imperfections are also considered in the parametric study. The experimental and numerical results are compared with design strength predictions from current Australian/New Zealand, American and European specifications for aluminium structures in the companion paper. In this paper, the Direct Strength Method (DSM) for the design of compression members as per the Australian/New Zealand standard AS/NZS 4600 for cold-formed steel structures is adopted for comparison. The DSM design rules for cold-formed steel compression members are found to provide more accurate predictions than those of current specifications for aluminium structures and therefore used to propose improved design equations for cold-rolled aluminium alloy columns. Finally, a reliability analysis is performed to evaluate the safety level of current design specifications and the proposed design rules.

CFS lipped channel beams buckling in distortional modes at elevated temperatures: Behaviour, failure and DSM design

This work reports the findings of a comprehensive numerical investigation on the post-buckling behaviour, failure and Direct Strength Method (DSM) design of cold-formed steel (CFS) single-span simply supported lipped channel beams buckling in distortional modes at elevated temperatures (up to 800 °C) due to fire conditions. It extends the scope of a previous investigation carried out by Landesmann and Camotim [1], by analysing a substantially larger lipped channel beam set, exhibiting various cross-section dimensions and yield stresses, selected to cover wider distortional slenderness ranges. As done before, (i) the beams analysed display two end support conditions, (ii) the Eurocode 3 (part 1.2) model to describe the temperature-dependence of the CFS material properties is adopted and (iii) the results are obtained by means of Abaqus shell finite element GMNIA. After presenting and discussing the main features of the beam distortional post-buckling behaviour, extensive beam failure moment sets are gathered and used to develop and validate DSM-based design approaches. The methodology followed consists of modifying the most performant available DSM-based design curves (developed for beams at ambient temperature [2]), which naturally involves the temperature-dependant reduction factors of the CFS model. A merit assessment procedure shows that the modified DSM-based strength curves predict the lipped channel beam distortional failure moments with remarkable accuracy and reliability, thus constituting an excellent starting point to search for a DSM-based design approach capable of handling arbitrary CFS beams failing in distortional modes at elevated temperatures.

Test and direct strength method on slotted perforated cold-formed steel channels subjected to eccentric compression

This paper aims to investigate the buckling behaviors of cold-formed steel (CFS) channels with slotted web holes determined by the Steel Stud Manufacturers Association (SSMA) under eccentric compression, and propose the simplified direct strength method (DSM) formulas for engineering practicing. An experimental study on 20 specimens was conducted, including 18 slotted perforated specimens with nine eccentricities increasing from −20 mm to 20 mm and 2 unperforated specimens subjected to axial compression. Two kinds of nominal lip lengths for cross sections were selected as 15 mm and 20 mm. The experimental results indicated that the failure modes of slotted perforated specimens subjected to eccentric compression depended on the position of the eccentricity. Compared with the slotted perforated specimens subjected to pure axial compression, the ultimate loads of specimens subjected to positive eccentric compression decreased by 21.70 % on average, while they decreased by 16.38 % on average for those subjected to negative eccentric compression. Moreover, a nonlinear elasto-plastic finite element model (FEM) was developed and validated against the experimental results. Furthermore, combined with the experimental results, extensive FE parametric analyses were conducted to predict the eccentricity impact coefficient formulas. Finally, based on DSM of unperforated CFS members subjected to pure axial compression in AISI S100-16 and the eccentricity impact coefficient formulas, the suitable DSM design formulas for slotted perforated CFS channels determined by the SSMA under eccentric compression were proposed, without the need to calculate the elastic buckling critical stress for slotted perforated CFS channels.

Distortional buckling of cold-formed steel rack section under uniform and non-uniform bending—Numerical analysis and DSM

Due to the wide variety of cross-sections and their good mass/strength ratio, cold-formed steel (CFS) components are gaining prominence among steel structures, although this material is more susceptible to local, distortional, and global buckling. The design procedure based on the direct strength method (DSM) presented in some codes such as the Brazilian (NBR), the American Iron and Steel Institute (AISI), and the Australia/New Zealand (AS/NZS), has been well accepted for estimating simply and safely the ultimate strength of beams subject to distortional buckling for many situations. However, more recent studies show that DSM design can lead to unsafe ultimate strength for beams with a high slenderness factor of distortional buckling. This study analyzes the behavior from 768 models developed using the finite element analyses (FEA) with the ABAQUS software. Beams were analyzed with 2 support conditions (SCA and SCB), under uniform major axis bending alone. The selection of the specimens in which the distortional buckling mode is predominant (modal participation analysis) was performed through a linear stability analysis using the GBTUL software. The finite element models used in nonlinear elastoplastic analyses included geometrical initial imperfections and material nonlinearity. A parametric study was developed to investigate the influence of the slenderness factor of distortional buckling (λd) on CFS rack beams’ ultimate strength. The FEA results were compared with DSM results to verify the accuracy of this method to predict distortional ultimate strength. It is shown that, for CFS rack beams subject to uniform and non-uniform bending and distortional buckling with λd > 1.0–1.5, the DSM overestimates the ultimate strength. Modifications were proposed in the DSM to improve the accuracy in predicting the ultimate strength of the analyzed conditions.

Design of locally buckling cold-formed steel built-up columns formed by unlipped channel sections

This study proposes a design procedure for the local buckling strength prediction of cold-formed steel (CFS) built-up I and box section columns based on the Effective Width Method (EWM) and the Direct Strength Method (DSM). For this, the ultimate strength of the built-up sections made of two plain unlipped channels is obtained using the finite element (FE) analysis. First, some compression tests on built-up sections are performed to validate the FE models. Then, a detailed parametric study using the validated FE models is conducted for sections with a wide range of slenderness (1≤λl≤3) where λl is the square root ratio of yield stress to the local buckling stress of the cross-section. The results show that the local buckling strength of built-up I sections is equal to the sum of its section’ strength, whereas for box sections, the strength can be 20%–25% higher as the nesting of sections will alter the local buckling characteristics. The EWM (with k factor approach) and authors’ DSM based design procedure can predict the strengths of the built-up I sections well but predict conservative strengths for the built-up box sections. This issue is resolved in this paper by proposing a simple cross-sectional model based on the constrained local buckling deformations of the built-up box section. When the buckling stress results of the proposed model were used with the EWM and authors’ DSM design procedures, the predicted local buckling strength results matched well with those of the present numerical study. In addition, the proposed design procedure provided more accurate strength predictions than the existing DSM and those presented in the literature for the built-up section columns.

Global–global interaction in cold-formed steel plain and lipped channel columns

While investigating how accurately the current Direct Strength Method (DSM) global strength curve predicts the major-axis flexural–torsional failures of cold-formed steel columns, the authors (Dinis et al., 2019; 2020) found strong evidence that, for some column lengths and end support conditions, the ultimate strength is eroded by the coupling between major-axis flexural–torsional (FMT - critical) and minor-axis flexural (Fm) bucking (the first two global buckling modes) - i.e, a global–global (G–G) coupling/interaction. This finding is at the root and provided the motivation for the ongoing numerical investigation whose first results are reported in this work. The paper presents and discusses results concerning the behaviour and DSM design of cold-formed steel (CFS) fixed-ended plain and lipped channel columns that buckle in FMT modes and undergo G–G interaction. After a brief review of the DSM-based design approach that was proposed to handle column FMT failures (Dinis et al., 2020), attention is turned to investigating the column (i) buckling behaviour, essential for the selection of column geometries susceptible to G–G interaction, and (ii) FMT non-linear (post-buckling) behaviour — special care is devoted to the identification of the most detrimental initial geometrical imperfection shape. Then, the FMT failure loads of the selected columns are obtained for five yield stresses (to cover wide slenderness ranges) and the gathered failure load data are used (i) to clearly show that the existing DSM-based design approach cannot adequately predict them and (ii) as guidance for its modification, which brings about the Fm-to-FMT buckling load ratio and enables the adequate handling of also G–G interactive failures. The excellent failure load prediction quality exhibited by this modified design approach is very encouraging and makes the authors believe that its domain of application can be extended to CFS columns with other cross-sections and/or end support conditions — research is under way to assess whether this belief is well founded.

Design of Cold-formed Steel Built-Up Closed Section Columns using Direct Strength Method

Structural behavior of Cold-formed Steel (CFS) face-to-face connected built-up closed cross-section columns is investigated in the present study. The CFS built-up columns are designed as long (L > 20r) and locally slender (λl > 1) to verify the influence of intermediate longitudinal connection spacing and check the appropriateness of the current AISI’s Direct Strength Method (DSM) design. A total of 31 axial compression tests were carried out with fixed–fixed end conditions, the design parameters such as local slenderness (λl), global slenderness (λc), intermediate longitudinal fastener spacing (a), and length of the column (L) are varied. The failure modes of the column are summarized and the reason for them is elucidated. The influence of intermediate longitudinal connection spacing was observed in the failure modes and ultimate loading capacity. The test results including ultimate load and failure modes were compared with the current direct strength method design predictions. As a preliminary work towards improving the current AISI design approach, a modified local slenderness (λlm) expression is suggested to consider the influence of intermediate longitudinal fastener spacing in the design strength of cold-formed steel built-up closed cross-section columns.

Design of cold-formed steel wall studs subject to non-uniform elevated temperature distributions

The current design rules for cold-formed steel studs used in wall systems subject to non-uniform elevated temperature distributions are complicated with iterations and different elevated temperature section properties. This paper first investigates the accuracy of the current effective width method (EWM) and direct strength method (DSM) based design equations, and then simplifies the calculation process without compromising the accuracy in calculating the load ratios (elevated to ambient temperature capacity ratio). It also improves the accuracy of the current DSM based design equations. It then investigates the possibilities of using uniform temperature based DSM design equations for non-uniform temperature distributions and identifies the possibilities of using hot flange mechanical properties and uniform temperature based DSM design equations. Hence, it proposes a simplified uniform temperature based DSM design method with hot flange mechanical properties and a correction factor based on hot and cold flange temperatures, yield strength, length and depth of studs.

DSM design of fixed-ended slender built-up back-to-back cold-formed steel compression members

Built-up back-to-back cold-formed steel channel (BC) sections have gained increased application as compression members in building structures. Although many researchers have studied the behaviour and design of BC compression members, the design equations in the current standards are still inadequate for them, while the new design equations proposed in recent studies are inconsistent and lead to predictions with varying accuracy. This study focuses on slender BC members with fixed ends, which are sensitive to local-global interaction or global buckling. Many tests of fixed-ended slender channel and BC compression members, which failed mostly by local-global interaction buckling, were conducted first, followed by developing validated finite element models. The models were then used in a parametric study of BC compression members with varying sections, screw arrangements and lengths, to investigate their failures by local-global interaction and global buckling. The outcomes from tests and finite element analyses provided improved understanding of the behaviour of BC members, and were used to compare their compression capacities against twice the individual member capacities, and show the limitations of the current design equations available in the standards and research publications. Finally, reliable design guidelines were proposed using the Direct Strength Method (DSM).

Global buckling strength of discretely fastened back-to-back built-up cold-formed steel columns

This study proposes a design equation for built-up cold-formed steel (CFS) columns to eliminate the inconsistencies present in Section I1.2 of AISI S100 specification. The proposed equation was developed by using the results from the authors' compound spline finite strip-based numerical framework and 228 experimental and numerical results from literature on built-up CFS columns, failing by minor axis buckling. Investigations were conducted using numerical models with mode-specific deformations incorporated in compound spline finite strip framework. The shear slip behaviour between the individual columns, characterised by (i) fastener spacing and (ii) slenderness ratio of fully-composite cross-section, was investigated using parametric variations. The study shows that the modified slenderness ratio (MSR) in Section I1.2 of AISI S100 yields conservative strength predictions with increased fastener spacing. This is possibly because the MSR considers the effect of fastener spacing and overall slenderness ratio as disjoint and treat them as additive components. In reality, they interact, and hence a compound slenderness ratio (CSR) is proposed with a term that captures the interaction of these two entities. The prediction of strength by the proposed CSR and direct strength method (DSM) is in good agreement with the results of experimental and numerical studies, with the mean close to one. When incorporated in the DSM design equations, the proposed CSR yields matching reliability with AISI S100.

Flexural–torsional failure and DSM design of fixed-ended cold-formed steel columns at elevated temperatures

Recently, Dinis et al. (2019,2020) reported in-depth numerical investigations showing that the current Direct Strength Method (DSM) global design curve may severely underestimate the flexural–torsional (FT) failure loads of fixed-ended cold-formed steel (CFS) columns with slenderness above 1.5. This finding was based on the analysis of columns exhibiting various cross-section shapes and geometries, and covering wide slenderness ranges. Moreover, these authors used the failure load data gathered to develop, and propose a novel DSM column strength curve set that was shown to improve considerably the FT failure load prediction for those columns. The purpose of this work is to extend the scope of the previous investigations to fixed-ended CFS cold-formed columns failing in FT modes under elevated temperatures (up to 800 °C). The results presented and discussed consist of column FT post-buckling equilibrium paths and failure loads, obtained through geometrically and materially non-linear Ansys shell finite element analyses — to ensure covering wide FT slenderness ranges, several room-temperature yield stresses are considered. The model prescribed in Part 1–2 of Eurocode 3, for cold-formed steel, is adopted to describe the temperature-dependence of the steel material properties. Lastly, the numerical failure loads assembled in this work, together with numerical and experimental ones collected from the literature, are used to propose a modification of the DSM-based FT strength curve set developed by Dinis et al. (2020), making it capable of handling FT failures under elevated temperatures. Since the merit assessment of the modified strength curve set shows a visible improvement in FT failure load prediction quality, it is fair to argue that it constitutes a good starting point to search for an efficient general DSM-based design approach for CFS columns failing in FT modes at elevated temperatures.

Mode Interaction in Cold‐Formed Steel Members: State‐of‐Art Report

AbstractThis work provides a state‐of‐art report on the most recent findings concerning the behaviour, strength and Direct Strength Method (DSM) design of cold‐formed steel (CFS) columns and beams affected by mode coupling phenomena not adequately covered by the current specifications for CFS members, namely local‐distortional (L‐D), local‐distortional‐global (L‐D‐G), distortional‐global (D‐G) and global‐global (flexural‐torsional/flexural ‐ FT‐F) interaction. The paper addresses experimental tests, numerical simulations and DSM‐based design approaches, intended to (i) acquire in‐depth knowledge on the non‐linear behaviour (elastic and elastic‐plastic), load‐carrying capacity and failure mode nature of the members under consideration, and (ii) make use of the above knowledge to develop, propose and assess the merit of efficient DSM‐based design approaches to estimate their failure loads or moments. Initially, illustrative column results are briefly presented to help grasp some fundamental concepts, namely the characterisation of the (i) above mode coupling phenomena, (ii) different sources of mode interaction that may lead to failure load/moment erosion and (iii) the most detrimental initial geometrical imperfections ‐ also presented are the currently codified DSM design curves, as well as two recently developed strength curves for column flexural‐torsional and beam distortional failures. Then, the paper addresses separately each mode coupling phenomenon dealt with, for columns, and only L‐D and D‐G interaction for beams. For columns undergoing L‐D and L‐D‐G interaction, beams experiencing L‐D interaction and angle columns susceptible to FT‐F interaction, the work reported includes experimental studies, numerical simulations and DSM‐based design considerations and/or guidelines. For the remaining coupling phenomena only numerical results are reported, but they unveil interesting (and unexpected) behavioural features that will help plan future test campaigns and achieve efficient design approaches. Finally, the paper closes with a few concluding remarks and a perspective about future developments in this field.

DSM design of CFS columns subject to distortional buckling at elevated temperatures

Cold-formed steel (CFS) columns are subject to distortional buckling unlike hot-rolled steel columns. Many experimental and numerical investigations have been conducted on the distortional buckling behaviour and capacity of CFS columns at ambient and elevated temperatures. However, constitutive laws of CFS at ambient and elevated temperatures are different with varying levels of nonlinear stress-strain characteristics. Thus, the ultimate distortional buckling capacities predicted by the elevated temperature design rules can be unconservative when the ambient temperature design equations are used with elevated temperature mechanical properties. However, no study has fully incorporated the effects of nonlinear stress-strain characteristics of CFS at elevated temperatures. Therefore, this research study investigated the effects of nonlinear elevated temperature stress-strain characteristics on the distortional buckling capacities of CFS columns using three parameters, namely, nonlinearity, strain hardening and yield strength to Young's modulus ratio, through a numerical parametric study. A comparison of ultimate capacities from the parametric study with those predicted by the current AS/NZS 4600 direct strength method (DSM) showed that the current design equations cannot accurately capture the effects of nonlinear elevated temperature stress-strain characteristics. Consequently, modified DSM equations were proposed to accurately predict the distortional buckling capacities of CFS columns at elevated temperatures.

Reliability assessment of cold-formed steel beams by the FORM method

Abstract This article presents a procedure for the reliability assessment of cold-formed steel beams based on the Direct Strength Method (DSM) and the Effective Section Method (ESM). Using a comprehensive database, a statistical analysis of the test results was performed to determine the statistical properties of the professional factor random variable. The statistical parameters related to material strength, geometric properties and load effects were obtained from established references for reliability analysis. Safety levels compatible with the North American and the Brazilian codes relating to structural design of cold-formed steel members have been established. The first-order reliability method (FORM) was used to calculate resistance factors φ for usual nominal live-dead ratios. The results of the reliability analysis showed that the DSM and ESM design methods have similar levels of reliability. The same resistance factor as the DSM can be used for the ESM, without compromising the minimum level of reliability established. The results obtained with the LRFD calibration data, presented a good approximation with the load factor φ = 0.90, except for the distortional mode. With the LSD calibration data, values well below the specified were required in order to achieve the required level of reliability. It was also found that the load factor γ = 1.25, in the format of the Brazilian standard, could reach the safety requirements established for all buckling modes.

Behaviour of cold-formed steel channels bent about the minor axis

The Direct Strength Method (DSM) in AISI S100 and AS/NZS 4600 is a newly developed alternative design method to the Effective Width Method in calculating the design moment capacity of cold-formed steel channels. The DSM uses elastic buckling stresses with an appropriate strength curve to calculate the design moment capacity. However, the current DSM design equation has been calibrated for channels bent about the major axis and is known to be conservative for channels bent about the minor axis with the web in compression. In order to extend the DSM for channels bent about the minor axis, it is necessary to prescribe and calibrate a DSM design equation for minor axis bending. This paper aims at deriving a new DSM design equation for cold-formed steel channels bent about the minor axis with the web in compression. For this purpose, the behaviour of 33 cold-formed steel channels bent about the minor axis inducing local buckling in the web are investigated using elastic finite strip buckling analysis and nonlinear finite element analysis. The cross-sectional dimensions such as thickness, web and flange widths are varied to cover a wide range of section slenderness. Deformed shapes and stress distributions at ultimate moment for various channels of different slenderness are described. Due to the considerable conservatism the current DSM design equation exhibited in comparison to the nonlinear finite element analysis results, a new DSM design equation for cold-formed steel channels bent about the minor axis is proposed.

Numerical and experimental study on CFS spherically-hinged equal-leg angle columns: stability, strength and DSM design

This paper reports a numerical and experimental investigation on the stability/buckling, elastic and elastic-plastic behaviour and strength, and Direct Strength Method (DSM) design of cold-formed steel (CFS) spherically-hinged short-to-intermediate equal-leg angle columns. It extends the scope of similar studies recently carried out for CFS fixed-ended and pin-ended (cylindrically-hinged) columns with the same characteristics. Initially, the paper addresses the stability/buckling behaviour of spherically-hinged columns − the results presented and discussed, which include the selection of the column geometries to be analysed (numerically and experimentally), are obtained by means of Generalised Beam Theory (GBT). Then, the post-buckling behaviour and strength of columns containing initial geometrical imperfections is investigated, by means of Ansys shell finite element analyses, and an experimental study, carried out at UFRJ (Federal University of Rio de Janeiro) and whose results are subsequently used to validate the previously developed numerical model, intended to perform a parametric study to obtain numerical failure load data covering a wide slenderness range for the columns considered. Such results comprise (i) initial imperfection measurements, (ii) load-displacement equilibrium paths, (iii) deformed configurations (including the collapse modes) and (iv) failure loads. The experimental and numerical failure loads obtained are then used to develop, validate and assess the merits of a DSM-based rational design approach that adopts the same concepts and procedures that were previously employed for cylindrically-hinged columns. The need for modifications arises from the new major-axis flexure support conditions, which affect the column flexural-torsional behaviour significantly. It is shown that the proposed/modified DSM strength curves lead to safe and reliable failure load estimates for spherically-hinged short-to-intermediate equal-leg angle columns exhibiting a wide slenderness range, thus making it possible to extend the scope of the existing DSM-based design approach to cover also columns with these end support conditions. The very high prediction quality achieved is attested by the fact that the LRFD resistance factors obtained are well above ϕc = 0.85 (value prescribed by the North American Specification for compression members).