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• Experiments on the member buckling and ultimate strengths of cold-rolled aluminium alloy channel columns are performed. • The aluminium alloy 5052-H36 materials are used to fabricate the cold-rolled aluminium structural channel columns. • Non-linear FE models are developed using ABAQUS to simulate laboratory experiments and calibrated against the test results. • A parametric study based on FE models is performed to extend the data by varying cross-section dimensions and member lengths. • Experimental and numerical results are ued to calibrate the new design equations for cold-rolled aluminium alloy columns. 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. [ABSTRACT FROM AUTHOR]

• A series of compression tests to investigate member buckling behaviour and ultimate strengths of cold-rolled aluminium alloy channel columns are performed. • The aluminium alloy 5052-H36 materials are used to fabricate the cold-rolled aluminium structural channel columns. • The observed failure modes are flexural, flexural-torsional and local-global interaction buckling failure modes. • The experimental results are compared with predictions by current Australian/New Zealand, North American and European design specifications. Cold-rolled aluminium alloy sections have been recently introduced in Australia as newly developed thin-walled products. To fabricate these sections, the roll-forming process used in cold-formed steel production has been employed, which has proven to be more cost-effective than the conventional extrusion process. This paper describes a series of compression tests to investigate member buckling behaviour and ultimate strengths of cold-rolled aluminium alloy 5052-36 channel columns. Twenty-eight specimens of three commercially available sections (C10030, C25025 and C40030) were tested at the University of Sydney. Two configurations of end boundary conditions were specially designed to capture flexural, flexural-torsional and local-global interaction buckling failure modes. Prior to testing, initial geometric imperfections were measured using a laser scanning method, and flat/corner coupons were tested to determine compressive and tensile strengths of the aluminium alloy material. The experimental results are compared with ultimate column strength predictions by current Australian/New Zealand, North American and European design specifications for aluminium structures. Additionally, the test results provide data for calibration of finite element models of cold-rolled aluminium structural members for use in parametric and similar studies. A companion paper describes such parametric study and the derivation of new design guidelines for member buckling of cold-rolled aluminium channel columns based on the numerical parametric data and the experimental data presented herein. [ABSTRACT FROM AUTHOR]

• The web crippling behaviour of cold-formed steel channels with elongated un-stiffened and edge-stiffened web holes under end-two-flange loading condition was studied numerically. • The results of a total of 1536 new finite element analysis were reported. • Design formulae in the form of the web crippling reduction factors were proposed. • The direct strength method (DSM) equations were also presented to evaluate web crippling strengths. Over the last decade, cold-formed steel (CFS) channels with circular edge-stiffened web holes have been widely used in New Zealand. In the case of web crippling, previous studies have revealed that the use of an edge-stiffened hole almost results in the same strength as an equivalent channel-section having a plain web. Such circular edge-stiffened web holes could be extended to elongated holes. In terms of web crippling, however, no experimental or numerical works on such elongated holes were reported in the literature. In this paper, a numerical investigation was carried out to investigate the web crippling behaviour of CFS channels with elongated un-stiffened and edge-stiffened web holes under the end-two-flange (ETF) loading condition. The finite element (FE) models were validated against the test results of CFS channels with circular edge-stiffened web holes; good agreement in terms of the load-displacement relationships and failure modes was shown. A parametric study was then conducted, comprising 1,536 FE models. Compared to CFS channels with a plain web, for the case of channels with an elongated un-stiffened web hole, the average web crippling strength reduction for sections with an aspect ratio of two and three was 21 % and 36 %, respectively. However, for an elongated edge-stiffened hole, the reduction in the web crippling strength was only 5 % and 8 %, respectively. Finally, design equations in the form of the web crippling reduction factor (R p) and the equations based on the direct strength method (DSM) for CFS channels with elongated web holes under ETF loading conditions were recommended. [ABSTRACT FROM AUTHOR]

The paper presents the development of new design guidelines for cold-rolled aluminium alloy 5052-H36 channel beams subject to global buckling. The validation data are obtained from the experimental and numerical Finite Element (FE) results as performed in previous studies by the authors. The failure modes in the experiments were observed as flexural–torsional buckling modes, and good agreement was achieved between the experimental and FE results. Based on the reliable and calibrated FE models, a parametric study is carried out in this paper to extend the data range by varying section dimensions and member lengths. Subsequently, all experimental and FE ultimate strengths of the parametric study are compared with nominal member capacities of aluminium beams as predicted by the current Australian/New Zealand, American and European aluminium design standards. Additionally, the Direct Strength Method (DSM) design rules from the Australian and New Zealand standard - AS/NZS 4600 for cold-formed steel structures are applied to predict member bending capacities for comparisons. Finally, reliability analyses are performed to evaluate the efficiency of the abovementioned design methods. It is found that the design guidelines for nominal member bending capacities to the AS/NZS 4600 standard provide accurate predictions and are therefore proposed to be used for the design of cold-rolled aluminium alloy channel beams as investigated in this paper. • New design guidelines for cold-rolled aluminium alloy H36-5052 channel beams subject to global buckling are developed. • The 5000-series high magnesium alloy, 5052-H36, is used for fabricating cold-rolled aluminium channels. • Detailed finite element (FE) models using the software ABAQUS are developed for a parametric study. • Experimental and FE ultimate strengths are compared with nominal member capacities of aluminium beams in the current aluminium design codes. • Design rules for member bending capacities to the AS/NZS 4600 standard are proposed for design of cold-rolled aluminium channel beams. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) is a popular form of construction in New Zealand and the developed world because it can be cost-effective, durable, sustainable, resilient to extreme environmental and seismic loads and easy to install. When used in domestic and medium-rise buildings, T-Stub connection between CFS channel sections is formed by using self-drilling screws which connect the flanges. In the literature, no prior investigation on the tension capacity of such connection has been reported. Therefore, this paper describes a novel test procedure for determining the tension capacity of such CFS T-Stub connection and the associated mechanism of failure. An experimental test program that comprises thirty experimental tests is reported in this paper. Three channel section thicknesses were examined: 0.55 mm, 0.75 mm, and 0.95 mm. All specimens failed as a result of tilting of the screws and bearing failure. Non-linear elasto-plastic finite element (FE) models were developed, and the predictions were validated against the experimental test results. It was adjudged that there was reasonable agreement in terms of connection strength and failure mode prediction. Finally, the design strengths derived from current design standards were compared with the experimental failure loads. It was found that the American Iron and Steel Institute (AISI 2016) and Australian and New Zealand Standard (AS/NZS 2018) are conservative by 6% and unconservative by 10% for the initial and final failure loads of T-Stub CFS connections, respectively. • A novel cold-formed steel T-stub connection was studied experimentally and numerically. • The results of a total of 30 new experimental tests were reported. • Finite element analysis was conducted and validated against the test results. • The prediction accuracy of current design standards was evaluated. [ABSTRACT FROM AUTHOR]

Built-up box sections are becoming increasingly popular for column members in cold-formed steel (CFS) construction; uses of such sections include CFS trusses, space frames, and portal frames. In this article, the built-up box sections are formed through two identical lipped channels connected at their flanges with self-drilling screws. In such an arrangement, independent buckling of the individual channels is prevented by the screws. This paper presents an experimental investigation on axial capacity of built-up CFS box sections. Tests were conducted for different values of slenderness from short to slender columns. In total, the results from 16 experimental tests are reported. Of these, 8 tests were conducted on built-up CFS box sections and the remaining 8 tests were conducted on single channel sections. Load-axial shortening relationship, and failure modes are discussed for built-up columns. Nonlinear finite element (FE) models were developed for built-up CFS box sections and single channels. FE models considered material nonlinearities, initial imperfections and modeling of intermediate fasteners. FE results showed good agreement against the test results. A parametric study was conducted which comprises 148 models to investigate the effect of fastener spacing on axial capacity of built-up CFS box sections. Both FE and test results were compared against the design strengths calculated in accordance with the American Iron and Steel Institute (AISI) and Australian and New Zealand Standards (AS/NZS). From the comparison, it was observed that the AISI & AS/NZS are conservative by around 17% while determining the axial capacity of such built-up CFS box columns. • Experimental tests were conducted on CFS built-up box sections under axial compression. • Results from an experimental regime and elasto-plastic finite element are reported. • Local and overall imperfections are considered in FE models • The validated FE model was used for a parametric study to investigate the effect of screw spacing. • The design strengths in accordance with the AISI & AS/NZS are conservative by around 17% for CFS built-up box columns [ABSTRACT FROM AUTHOR]

• Structural performance of cold-formed steel built-up section members under synchronous non-uniform bending and compression was investigated. • Thirty-five beam-column tests under unequal end moments were conducted to examine the effect of moment gradients. • Failure modes involving local, distortional and flexural buckling were found in the experiments. • Comparisons of experimental loading capacities with nominal strengths were performed to evaluate existing design rules. • Reliability analysis was performed to examine the appropriateness of current design codes. The experimental study presented in this paper aimed to examine the performance of cold-formed steel built-up section beam-columns experiencing non-uniform bending. The test program was performed on built-up open and closed sections that were manufactured from steel grades G500 and G550 zinc-coated sheets. The test specimens were assembled by connecting two identical channels with discrete connectors along the longitudinal direction. Two member lengths and two plate thicknesses were considered for the test specimens to investigate the stability of the newly designed thin-walled section beam-columns. In total, thirty-five beam-column tests were carried out under pinned supports. The test results including loading capacity, failure mode and axial load-lateral deflection response were obtained and are fully reported in this paper. Moreover, the comparison of experimental loading capacities with nominal strengths was conducted to evaluate the applicability of the interaction curves specified in the North American Specification AISI S100, the Australian/New Zealand Standard AS/NZS 4600, the European Code EN 1993–1-1 and the American Specification ANSI/AISC 360 with nominal bending and compression resistances calculated by direct strength method for the thin-walled section beam-column members under moment gradients. Overall, these design methods were conservative for strength predictions of the built-up open section beam-column members under unequal end moments. For the built-up closed section members experiencing synchronous non-uniform bending and compression, the aforementioned design methods generally offered slightly conservative strength predictions, except for the interactive formula in the European Code with bending and compression resistances determined by direct strength method. [ABSTRACT FROM AUTHOR]

• The structural behaviour of cold-formed steel T -stub connections with HRC and screws was studied experimentally and numerically. • The results of a total of 15 new experimental tests were reported. • Finite element analysis was conducted and validated against the test results. • The prediction accuracy of current design standards was evaluated. Cold-formed steel (CFS) T -Stub connections are widely used in single-story buildings, and their use is increasing in multi-story and long-span buildings. Recently, an innovative CFS T -Stub connection was developed using self-drilling screws and the Howick Rivet Connector (HRC), and such a newly-developed connection demonstrated excellent structural performance in the building industry. In this paper, a comprehensive experimental and numerical investigation was conducted to investigate the failure mechanism and structural behaviour of CFS T -Stub connections with a combination of HRC and screws under tension force, considering the effects of screw numbers. Firstly, a total of 15 new experimental tests were conducted on the CFS T -Stub connections with various numbers of screws. From the experiments, it was observed that the HRC was subjected to shear failures, while screws failed primarily due to tilting and bearing failures in all investigated specimens. Then, a non-linear elasto-plastic finite element (FE) model was developed and validated against the experimental results in terms of connection strength and failure modes. Finally, the design strengths obtained from the American Iron and Steel Institute (AISI 2016) & Australia/New Zealand standards (AS/NZS 2018) and Ahmadi et al. (2016) were compared with the test and FEA results, showing that the ultimate design strength of CFS T -Stub connections was overestimated by 16% and 14%, respectively. However, for T -Stub connections with HRC alone and with HRC and one screw, these design guidelines were unconservative by 5%. [ABSTRACT FROM AUTHOR]

• A total of 41 cold-formed steel built-up I-sections were tested under ETF, ITF, EOF and IOF loading conditions. • Finite element models were developed to replicate the experiments. • Parametric study of 258 specimens was performed. • The existing codified web crippling design provisions were assessed. • Design rules were proposed based on the unified equation and direct strength method. This paper reports the experiments, numerical modelling and design of cold-formed steel built-up I-sections subjected to localised loadings. The built-up I-sections were made up of two equal-sized plain channels fastened back-to-back in the web. The web crippling tests were undertaken on 41 built-up I-section members under Interior-Two-Flange (ITF), End-Two-Flange (ETF), Interior-One-Flange (IOF) and End-One-Flange (EOF) loading conditions. The effects of the arrangement of screws along the web height were investigated. After the experiments, finite element (FE) analyses considering the initial local imperfections of the web of the specimens were performed and the validity of the FE models was assessed using the test results. A parametric investigation including 258 numerical simulations was conducted to expand the database and evaluate the influences of the screw arrangements in the web height. The test and numerical results indicated that the failure modes of the specimens with different screw arrangements were generally similar in each loading condition, and the screws located close to the flange-web junctions of the sections could generally provide maximum web crippling resistances of the built-up I-sections. The design recommendations on the arrangements of screws along the web height were proposed. The experimentally and numerically generated web crippling resistances were utilized to assess the current North American specification (AISI S100), Australian and New Zealand standard (AS/NZS 4600) and European code (EN1993-1-3). The results show that the existing codified design formulas lead to either conservative or highly unsafe results. Therefore, two sets of design formulas were derived on the basis of unified equation and direct strength method. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the buckling behavior of cold-formed steel built-up closed section members subjected to combined minor axis bending and compression. The channels were fabricated from zinc-coated steel sheets of grades G500 and G550 to compose built-up closed sections. A total of 30 beam-column specimens with nominal member lengths of 300, 900, and 1,500 mm as well as nominal plate thicknesses of 0.75 and 1.2 mm were eccentrically loaded under pin-ended boundary condition. The initial loading eccentricity was varied for the specimens in each test series to obtain the data evenly distributed in the axial load-moment interaction diagram. Experimental results including failure modes, loading capacities, and full-history responses of the test specimens were obtained. In addition, the experimental loading capacities were compared with nominal strengths to evaluate the suitability of the provisions as stipulated in the North American specification, Australian/New Zealand standard, European code, and American specification for the built-up section beam-columns. It is shown that the aforementioned design codes are overall unreliable and unconservative for strength predictions of the cold-formed steel built-up closed section members under combined minor axis bending and compression. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) Tab connections are popular due to their rapid fastening and ease of installation, and their applications have increased recently in Pacific countries, including Australia and New Zealand. This type of connection consists of a Tab plate formed from the web of the supporting beam and is screwed to the joist web, providing a dependable load path from the joist to the galvanized C-section supporting beam. However, no studies have been reported in the literature for the shear capacity of such connections. This paper presents a shear test program designed to determine the shear capacity of CFS Tab connections and to identify their failure mechanism. The experimental program included three different beam sizes, C-150, C-190 and C-240. Each test was repeated three times, resulting in nine tests in total. All the specimens failed in plate yielding and plate tearing, which occurred on the tension side of the plate (top region). Nonlinear finite element (FE) models were then developed and verified against the test results. The FE results showed good agreement with the test results in terms of connection stiffness, connection strength and failure modes. Finally, it was shown that the design equations given in the Australia/New Zealand standard (AS/NZS 4600) and American Iron and Steel Institute (AISI S100) for predicting the combined bending and shear capacity could predict the ultimate shear capacity of CFS Tab connections investigated in this study. • The results of monotonic shear tests of a novel CFS Tab connection are reported. • CFS Tab connections failed in plate yeailding and tearing. • A nonlinear FE model is developed. Results showed good agreement with the test results. • A design procedure is proposed for predicting the shear capacity of CFS Tab connections. [ABSTRACT FROM AUTHOR]

Currently, the assembled-type light steel (ATLS) modular house is increasingly used for apartments, schools, hotels, and other similar buildings with repetitive units, in which the non-symmetric cold-formed angular section is usually served as column in the module unit. However, the compressive behavior and design method of the non-symmetric cold-formed angular column remain unknown due to the complex edge. In this paper, a series of tests were conducted on the axial compressive behavior of the non-symmetric cold-formed angular column. A total of 12 specimens with complex edge were tested under monotonic axial compression. A special support was designed at the end of the column to apply the axial compression along different loading axes of the complex section. The failure mode and axial compressive capacity of the test specimens were revealed and discussed in detail. It indicated that the loading axis significantly influenced the failure mode and axial compressive capacity of the non-symmetric cold-formed angular column. Furthermore, a 3D finite element model was developed and validated against the test results to broaden the research. Lastly, given that the current design codes for steel structures, as used in Europe, Australia/New Zealand and North, the relevant codified design was utilized to evaluate the axial compressive capacity of unequal angular column with a double edge fold stiffener, based on the obtained test data. • Experiment on non-symmetric angular column with complex edge. • Twelve specimens were tested and axial compressive capacity was obtained. • Elaborated FEM was developed and validated based on the test results. • The relevant codified design was utilized to evaluate the test specimens. [ABSTRACT FROM AUTHOR]

In this paper, the structural stability and compressive capacity of pin-ended cold-formed stainless steel angle columns with different slenderness were experimentally investigated. The experimental programme was performed on press-braked lean duplex stainless steel equal-leg angle sections with nominal dimensions of 80 × 80 × 4 mm, and involved material testing, initial imperfection measurements and 11 column tests. The test setup and procedure, together with the key experimental results, axial load vs. lateral deflections, axial load vs. torsional rotations and characterised failure modes, were fully reported and analysed. The experimental observations reveal that the failure mode type, including local/torsional, flexural-torsional and flexural effects, is highly dependent on the column's slenderness and initial imperfections. The measured compressive strengths were compared with the resistance predictions determined according to European and Australia/New Zealand codified design procedures. It was found that experimentally obtained ultimate capacities are significantly higher than those calculated according to the specifications. However, the database of test results is still quite limited, and a further research is needed to amplify the data needed to enable a more precise assessment of the codified procedures. • Eleven pin-ended cold-formed stainless steel equal-leg angle columns were tested. • Different buckling failure modes were systematically investigated. • Failure loads conservatively predicted by European and Australian design procedures. [ABSTRACT FROM AUTHOR]

Recently, a new generation of cold-formed steel (CFS) channel sections with edge-stiffened circular holes have been developed by industry in New Zealand. No previous research, however, has considered the web crippling strength of CFS channel sections with edge-stiffened circular web holes under the interior-two-flange (ITF) loading conditions. In this paper, a combination of experimental investigation and non-linear finite element analysis (FEA) are used to investigate the effect of edge-stiffened holes under ITF loading conditions; for comparison, channel sections without holes and with unstiffened holes are also considered. In total, 30 web crippling test results are reported. A non-linear finite element (FE) model is described, and the results were compared against the test results, which showed a good agreement in terms of both the web crippling strength and failure modes. The results indicate that the stiffened web holes can significantly improve the web crippling strength of CFS channel sections. Using the validated FE model, a parametric study was conducted which include 1116 FE analyses, covering the effect of different hole sizes, edge-stiffener lengths and fillet radii, length of the bearing plates and position of the holes in the web. From the results of the parametric study, design recommendations in the form of web crippling strength reduction factors are proposed, that are conservative to both the experimental and FE results. • Web crippling tests of cold-formed channel section with edge-stiffened web openings was conducted. • The results indicate that the stiffened holes can significantly improve the web crippling strength. • Non-linear finite element (FE) models were developed and validated against the test results. • A parametric study involving 1116 FE analyses was performed. • Design recommendations in the form of web crippling strength reduction factors were proposed. [ABSTRACT FROM AUTHOR]