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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 paper presents an experimental program on a structural system, consisting of three long-span portal frames. The primary structural members, including columns and rafters, were constructed using cold-rolled aluminium back-to-back built-up channel sections. The system configuration featured two bays of single-span cold-rolled aluminium portal frames connected in parallel by a series of purlins spanning between the rafters to create a free-standing structure. A total of three full-scale tests (Frame Tests 1,2 & 3) were conducted with two loading scenarios. Frame Tests 1&2, which were identical to ensure accuracy, were subjected to vertical loads only, while Frame Test 3 underwent testing with combined horizontal and vertical loads. In all the tests, the columns were unbraced. The main objectives of this paper are, first, to describe the test setups and observe the structural behaviours of the portal frame systems. Consequently, the ultimate capacities were determined, and the predominant failure modes of the portal systems were identified as flexural-torsional buckling of the unbraced columns. The paper also provides information on the mechanical properties of the aluminium alloy 5052-H36 materials used to fabricate the structural members and frame components, obtained from compressive and tensile coupon tests. Further, the elastic buckling loads of the columns in the frame systems are reported in this paper, as determined from the measured load-deformation curves. While this paper primarily delves into the behaviour of the cold-rolled aluminium portal frames with a focus on flexural torsional buckling failures of unbraced columns, the authors have also conducted a separate study on the same system. In that separate study, the portal frames with the columns predominantly restrained against flexural-torsional buckling were investigated to enhance the ultimate capacities of the portal frame systems. • Three full-scale portal frames fabricated from cold-rolled aluminium back-to-back built-up channel sections are tested. • Aluminium alloy 5052-H36 materials are used to fabricate the cold-rolled aluminium structural members and frame components. • Portal frames are tested under two loading cases, including vertical loads only and combined horizontal and vertical loads. • Observed failure mode of the portal frames is flexural-torsional buckling of the unbraced columns. • Elastic critical loads of the columns of the portal frame tests are determined using the measured load-deformation curves. [ABSTRACT FROM AUTHOR]

This study proposes an innovative type of simple connection utilizing power-actuated fasteners to join a cold-formed steel channel to a rectangular hollow section column via a web-side plate or a T-section. An experimental program composed of 26 specimens was carried out to investigate the behavior of the connections under the combination of shear and rotation. The experimental results are discussed in two limit states including bearing and pull-out by shear. An analytical model is proposed to predict the shear strength of the connections based on the provided information of vectorial force at a fastener, displacement, and rotation at the connections. The proposed model yields a conservative prediction for the tested connections with a mean test-to-prediction ratio of 1.05 and the coefficient of variation of 6% or 9%, depending on the limit state. A design example is provided to illustrate the implementation of the proposed model in practice. [ABSTRACT FROM AUTHOR]

The complex behavior of high-strength steel staggered-hole bolted connections failing in block shear with a combination of tension and inclined shear behavior was studied in this work. In particular, the location of the fracture paths in the staggered zones correlated with the angle of the staggered holes instead of appearing on the centerline between the staggered holes. Furthermore, the nominal shear strength of the staggered-hole bolted connections in the staggered paths was affected by the combination of shear and tension rupture, accounting for two components, which were the shear strength on failure paths parallel to the force and the tension strength on the segments perpendicular to the force. Consequently, a design equation for block shear strength with staggered holes was proposed to account for the combined actions. It demonstrated better correlation with the experimental results than the predictions from current design standards. A total of 88 specimens with two G450 sheets with thicknesses of 1.9 and 2.4 mm were modeled by means of a finite-element model validated against the actual tests to achieve reliable data using a parametric procedure. In addition, four different types of configurations, including not only four holes but also three and five holes were modeled to investigate the effect of the inclined shear and tension zones on the block shear strength and behavior of the connections. The large data set was used for the verification procedure of the proposed formula. [ABSTRACT FROM AUTHOR]

In the literature, the block shear and tear-out phenomena and strengths of cold-formed steel bolted connections have been well understood and thoroughly investigated. However, the strength of these failure modes in the bolted connections between thin and thick plates may be governed by the effect of out of plane curling of the thin plate, and this phenomenon has not been studied in detail yet. It is apparent that the curling not only affects the shear strength but also changes the behaviour of the bolted connections. In particular, the design shear strength of the bolted connections remains unchanged with high ductility even though the end distance between the bolt holes and the free edge is becoming larger. An experimental program on the block shear and tear-out behaviour of bolted connections was performed at the University of Sydney in order to provide a better understanding on the effect of the curling. A total of 48 tests including thicknesses of thin plates (1.0 mm, 1.2 mm and 1.9 mm) and 10 mm thick plates was conducted at the University of Sydney with three configurations of bolted connections in conjunction with two different hole diameters (9 mm and 14 mm) and various end distances as the main variables. Three different failure modes being block shear, tear-out and curling were observed in the tests. In addition, different material properties of the cold-formed sheet steels (i.e., G300, G450, G500 and G550) were also considered in this program to create a large database for the investigation. Consequently, a design equation for block shear and tear-out strength accounting for the curling effect is proposed in this paper. It provides a better correlation with the experimental results than those predicted in the current Australian and New Zealand Standard (AS/NZS 4600) and the North American Specification for cold-formed steel structures (AISI S100). In addition, a calibrated Finite Element Model (FEM) was subsequently developed using the commercial finite element program ABAQUS to verify against the test results. The reliable data set of the FEM models is further utilised to extend the data range in a parametric study and is finally used for the verification procedure of the proposed formula over a wider range of data. • An experimental program on the block shear and tear-out behaviour of bolted connections is performed • Effect of curling phenomenon on the shear strength and the behaviour of the bolted connections is investigated • Finite Element Method (FEM) models are developed using the commercial FEM program ABAQUS to verify against the test results • Reliable FEM data set is used for extending the data range and for the verification procedure of the proposed formula • A design equation for block shear and tear-out strengths accounting for the curling effect is proposed [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]

For flexural thin-walled section beams, the ultimate strength is significantly affected by the interaction of different local buckling modes associated with combined bending and shear stresses. This paper provides a comprehensive analytical and numerical study of elastic buckling of thin-walled channels subjected to different combinations of bending and shear stresses. The commercial ABAQUS software package using Finite Element Method (FEM) has been used to perform the elastic buckling analyses of the channel sections. The results are benchmarked against those from the Semi-Analytical Finite Strip Method (SAFSM) for the cases of pure bending and shear only. Two typical types of channels with and without lips are selected for investigation. To study the effect of different combinations of bending and shear on the buckling stresses, different normal stress distributions and equilibrating shear stresses are applied at two end cross-sections of the channels to maintain static equilibrium. Different types of interactions which occur during the buckling analyses are studied by varying the ratios of bending moments resulting from the modelled longitudinal stresses. A new concept for the elastic local buckling interaction based on the Average Bending Moment (ABM) at buckling is provided. In addition, an explicit approach for local buckling loads of channels under different combinations of bending and shear is also introduced for the practical design use. The results from this explicit solution for elastic buckling can be used as direct inputs for an explicit Direct Strength Method (DSM) design of members under combined bending and shear. • A comprehensive study of elastic buckling of thin-walled channels under combined bending and shear stresses is performed • ABAQUS software package using FEM is used to conduct elastic buckling analyses of thin-walled channel sections • Results are benchmarked against those from the Semi-Analytical Finite Strip Method for the cases of pure bending and shear only cases • A new concept for elastic local buckling interaction based on the Average Bending Moment (ABM) at buckling is provided • Results from the explicit solution for elastic buckling analyses can be used in the Direct Strength Method (DSM) of design [ABSTRACT FROM AUTHOR]

Thin-wall structural sections and members are susceptible to three fundamental instabilities: local, distortional and lateral-torsional buckling. For cold-formed purlins or girts commonly used in roof and wall systems, distortional buckling may govern the predominant failure mode when the compression flange is not attached to sheathing or panels. The paper presents an experimental and numerical investigation on the behaviour and strength of cold-rolled aluminium beams subjected to distortional buckling. A total of eighteen specimens were tested in a four-point bending configuration with six various types of cross-sections and two different thicknesses. In the pure bending region between the two loading points, the upper compression flanges were kept free to allow distortional buckling to form. Subsequently, detailed finite element (FE) models of cold-rolled aluminium beams using the software ABAQUS were developed with the incorporation of measured material inelasticity and initial geometric imperfections. Good agreement between the experimental results and the FE models was achieved. The reliable and verified FE models along with the test data in this paper will be used in a separate publication to undertake a detailed parametric study and calibration of new proposed design rules for cold-rolled aluminium beams subjected to distortional buckling. [Display omitted] • An experimental program of cold-rolled aluminium channel beams subject to distortional buckling is performed. • The 5000-series high magnesium alloy, 5052-H36, is used for fabricating cold-rolled aluminium channels. • The experimental behaviour and distortional buckling strengths of cold-rolled aluminium channel beams are presented. • Detailed finite element (FE) models using the software ABAQUS of cold-rolled aluminium beams are developed. • Good agreement between the experimental results and the FE models is achieved and will be used for a parametric study. [ABSTRACT FROM AUTHOR]

This paper explores the use of the finite element software package ABAQUS/Explicit to simulate the behaviour and strength of power-actuated fastener (PAF) connections joining cold-formed steel sheet to hot-rolled steel plate subjected to monotonic shear loading. The finite element (FE) models are developed for the simulation of the entire process including both installation and loading stages. The fastener is firstly driven into the steel materials to consider the initial plastic deformations around the contacts between steel plates and fastener caused by dynamic impact. Subsequently, monotonic shear loading is applied to the PAF connections until failure by a displacement control at a low speed. Various aspects of the FE models such as fracture model of the materials, loading rate, mesh sensitivity are calibrated to optimise the computing time and improve the accuracy of the FE models. The simulations are validated against experiments conducted in a separate study by the authors, and good agreement between the test and numerical results is achieved. The accurate and reliable FE models in this study are able to simulate and provide insights into the shear behaviour of the power-actuated fastener connections in terms of initial stiffness, maximum shear capacity, failure modes as observed in the experiments (i.e., bearing, shear fracture, and pull-out of the fastener), ductility, and damage patterns of the connectors. It is demonstrated that FE analysis can therefore be used to extend experimental data in a parametric study and to optimise the design of PAF connections in shear. [Display omitted] • A FE study into shear behaviour of Power-Actuated Fastener connections is conducted. • ABAQUS/Explicit is used to simulate the installation and load application stages. • Three limit states are simulated: pull-out, shear fracture and bearing failures. • The accuracy and robustness of the FE model are validated and optimised. [ABSTRACT FROM AUTHOR]

High strength cold-formed steel channel beams widely used in roof and floor systems carrying steel profiled roof sheeting or floor decking are commonly subjected to a combined action of bending and shear in practice. The design guidelines of such purlins or beams have recently been standardised utilising shear-bending interaction curves in current standards/specifications such as the Australian/New Zealand Standard (AS/NZS 4600:2018) and the North American Specification (NAS S100–2016). In order to investigate different combinations of bending and shear, an experimental program comprising thirty tests of pure bending, combined bending and shear and predominantly shear has been performed at the University of Sydney using a dual actuator test rig. All the tests are conducted on commercial plain C-lipped and Supa-Cee channels. The interaction between bending and shear is governed by varying ratios of bending moments at two ends of the test span. All testing results are plotted against the current interaction curve to validate the performance of the current design method on channel members under different combinations of bending and shear. Further, a completely new concept for the interaction between bending and shear on a theoretical basis of statics is introduced and a development of an explicit Direct Strength Method (DSM) design for the prediction of ultimate strengths of members under combined bending and shear is also provided in this study. [Display omitted] • An experimental program on high strength cold-formed steel channel beams is performed using a dual actuator test rig. • Test configurations include pure bending, combined bending and shear, and predominantly shear. • Interaction between bending and shear is governed by varying ratios of bending moments at two ends of the test span. • A completely new concept for the interaction between bending and shear on a theoretical basis of statics is introduced. • A development of an explicit DSM design for the predictions of members under combined bending and shear is provided. [ABSTRACT FROM AUTHOR]

In the current standards/specifications for cold-formed steel structures, the direct strength method (DSM) has not been developed for the shear strengths of perforated members, which is currently based on an empirical design approach using a qs factor. To extend the DSM design to members in shear with various hole shapes and sizes, new design procedures have been developed to determine shear loads including the elastic shear buckling load (Vcrh), shear yield load (Vyh), and ultimate shear strength (Vn). Vcrh can be calculated via a linear approximation for buckling coefficients (kv) based on the hole and section dimensions. Vyh can be computed based on a theoretical Vierendeel mechanism or a proposed alternative simplified model to permit an easier implementation in design checks. Vn can be determined using proposed DSM shear curves for members with and without full-transversely stiffened webs. To validate the new DSM approach, a collection of reliable historical experiments in perforated sections under shear was used for strength comparison. The experimental shear strengths were also further used for the calibration of the DSM-based proposal to determine the resistance factor (ϕ) for shear design, which is traditionally based on the LRFD methodology. [ABSTRACT FROM AUTHOR]

In this paper, a total of 254 results comprising 30 shear tests and 224 finite element (FE) analysis results are reported. Simply supported test specimens of cold-formed steel (CFS) channels with aspect ratios of 1.0 and 1.5 were tested. For comparison, specimens with unstiffened web holes and plain webs were also tested. A nonlinear elastoplastic FE model was then developed and validated against the experimental results. Using the validated FE model, a parametric study was conducted to investigate the effect of various influential parameters on the shear capacity of such CFS channels. The test results show that for a channel with edge-stiffened web holes, the shear capacity increased by 14.5% on average when compared with that of a channel with unstiffened web holes. The test and FE results were compared against the design predictions. Upon comparison, it was found that the design rules of CFS channels with unstiffened web holes in accordance with the AISI and AS/NZS can be unconservative by 7% while calculating the shear capacity of CFS channels with edge-stiffened web holes. Therefore, a suitable design formula in the form of a shear capacity reduction factor was proposed for CFS channels with edge-stiffened web holes. [ABSTRACT FROM AUTHOR]

• Eighty one experimental tests on the design strength of power-actuated fasteners (PAFs) in single shear connections are presented. • Modes of failure for both the PAFs and the connected material were examined so to provide an understanding of the structural performance of nailed single lap connections. • The predominant mode of failure for all tested specimens was tilting and bearing or head shearing induced by tilting of the PAFs. • The tests results were compared against the design strengths as per the AS/NZS for both the screws and PAFs. • Based on the test strengths and failure modes, the existing design provisions for screw connections in AS/NZS were adjusted and applied to PAF connections. This paper presents the results of 81 experimental tests on the design strength of power-actuated fasteners (PAFs) in single shear connections for a light gauge steel framing (LGSF), as an alternative to self-drilling screws for selective uses. This type of connection can be employed to install a reinforcing plate on one or both sides of the frame, to connect steel strap cross bracing to framing, as well as for many other applications. These power-actuated fasteners present a very efficient and practical solution which can increase productivity and work quality by replacing time consuming screw connections. In this study, two different steel grades (G300 and G550), along with three different steel sheet configurations were investigated. Modes of failure for both the PAFs and the connected material were examined so to provide an understanding of the structural performance of nailed single lap connections and develop design recommendations and proposed formulae. The investigation covers a wide range of steel gauges (0.75 mm, 0.95 mm and 1.15 mm), commonly used in LGSF residential and commercial applications. Two groups of tests were performed. The first group of tests was conducted to determine the shear strength of connectors with two types being tested. The second tests series were carried out in various steel grade and gauge configurations for assembled connections. The results of this research and the proposed design formula can be used to establish the strength prediction model for power-actuated fasteners (PAFs) embedded into LGSF. [ABSTRACT FROM AUTHOR]

This paper presents experimental observations of cold-reduced G450 sheet steel subjected to shear. A total of 28 shear specimens of 1.5 mm and 3.0 mm thicknesses were tested. Two different test geometries were used to examine the shear state. The Digitial Image Correlation (DIC) technique was utilised to obtain the full fields of displacement and strain during the test execution. Strain distribution and evolution are used for quantifying shear stress- shear strain evolution inside the shear band. In terms of stress consideration, 0.35% proof shear strain is proposed to determine a yield stress in shear. The experimental results show that the cold-reduced G450 sheet steel follows von Mises criterion at yield (0.577), but possesses a higher ratio for the ultimate shear strength to tensile strength. Although the steel shows lower yield stress in the longitudinal rolling direction than that in the transverse, it possesses higher ultimate strength and ductility. [Display omitted] • An experimental program on shear yielding and fracture of high strength G450 steel is performed. • Digital Image Correlation (DIC) is used to obtain the full fields of displacement and strain. • Strain distribution and evolution are used for quantifying shear stress-shear strain evolution. • Cold-reduced G450 sheet steel is confirmed to follow von Mises criterion at shear yield. • Proof yield stress at 0.35% shear strain is proposed to be consistent with 0.2% strain in tension. [ABSTRACT FROM AUTHOR]