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This paper reports an experimental and numerical investigation into the minor-axis flexural buckling behavior and capacity of press-braked S690 high-strength steel channel–section columns. The experimental investigation comprised initial geometric imperfection measurements and 10 pin-ended column tests. This was accompanied by a numerical modeling program, in which finite-element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. The obtained test and numerical data were adopted to assess the accuracy of the buckling curves, as given in the Eurocode, North American specification, and Australian/New Zealand standard, for press-braked S690 high-strength steel channel–section columns prone to minor-axis flexural buckling. Overall, it was found that the Eurocode buckling curve yields many conservative capacity predictions, whereas the buckling curves in the North American specification and the Australian/New Zealand standard lead to an overall good degree of design accuracy. A revised Eurocode buckling curve is proposed, and was shown to offer accurate capacity predictions for press-braked S690 high-strength steel channel–section columns prone to minor-axis flexural buckling. [ABSTRACT FROM AUTHOR]

This paper reports laboratory testing and numerical modelling on the cross-sectional behaviour and resistances of press-braked S690 high strength steel slender channel section stub columns under combined compression and minor-axis bending. A testing programme, including initial geometric imperfection measurements and ten minor-axis eccentric compression tests, was firstly conducted. This was accompanied by a numerical modelling programme, including a validation study, where finite element models were developed and validated against test results, and a series of parametric studies, where the validated finite element models were used to generate further numerical data. The obtained test and numerical data were then adopted to evaluate the current codified design interaction curves for press-braked S690 high strength steel slender channel section stub columns under combined compression and minor-axis bending, as provided in the European code, North American specification and Australian/New Zealand standard. The evaluation results revealed that the codified design interaction curves led to conservative and scattered resistance predictions, mainly due to the conservative end points (i.e. the cross-section compression and bending resistances). Finally, a new design interaction curve, anchored to more accurate end points, was proposed and shown to result in a higher level of design accuracy and consistency than the codified design interaction curves. • The behaviour of S690 high strength steel slender channel sections under minor-axis combined loading was studied. • Minor-axis eccentric compression tests were carried out. • FE models were developed and validated against the test results and then used to perform parametric studies. • The codified design interaction curves were evaluated, revealing a high level of conservatism. • A new interaction curve, anchored to the CSM end points, was proposed and shown to yield higher design accuracy. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the cross-sectional behaviour and resistances of press-braked S690 high strength steel channel sections under combined compression and minor-axis bending. An experimental programme was firstly conducted and included initial local geometric imperfection measurements and ten minor-axis eccentric compression tests. The experimental programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to expand the test data pool over a wider range of cross-section dimensions and loading combinations. The obtained test and numerical data were then used to assess the relevant codified design interaction curves, as provided in the European code, North American specification and Australian/New Zealand standard. The assessment results revealed that all the codified design interaction curves led to excessively conservative and scattered resistance predictions for press-braked S690 high strength steel channel sections under combined compression and minor-axis bending, mainly owing to the conservative linear shapes and inaccurate end points. Finally, a new design interaction curve, with more accurate end points and nonlinear shape, was proposed and shown to offer more accurate and consistent resistance predictions than the codified design interaction curves. • The behaviour of S690 high strength steel channel sections under minor-axis combined loading was studied. • Minor-axis eccentric compression tests were conducted. • FE models were developed and validated against the test results and then used to perform parametric studies. • The codified design interaction curves were assessed, revealing a high level of conservatism. • A new design interaction curve was proposed and shown to provide much improved design accuracy. [ABSTRACT FROM AUTHOR]

• The behaviour of press-braked S690 high strength steel channel sections under major-axis combined loading was studied. • 20 major-axis eccentric compression tests were conducted. • FE models were developed and validated and then used to perform parametric studies. • The codified design interaction curves were assessed based on the test and FE data, indicating conservatism. • New design interaction curves were proposed, showing a high level of accuracy. Testing and numerical modelling have been conducted to investigate the cross-sectional behaviour and resistances of press-braked S690 high strength steel channel sections under combined compression and major-axis bending. The testing programme included initial local geometric imperfection measurements and twenty major-axis eccentric compression (combined loading) tests. The numerical modelling programme included a validation study, where finite element models were developed and validated against test results, and a series of parametric studies, where the developed finite element models were adopted to generate further numerical data over a wide range of cross-section dimensions and loading combinations. The obtained test and numerical data were used to evaluate the existing design interaction curves for press-braked S690 high strength steel channel sections under combined compression and major-axis bending, as specified in the European code, North American specification, and Australian/New Zealand standard. The evaluation results revealed that the codified design interaction curves led to conservative resistance predictions, owing to the linear shapes and inaccurate end points. Improved design interaction curves featuring more efficient shapes and anchored to more accurate end points were then proposed. The proposed design interaction curves were shown to result in more accurate resistance predictions for press-braked S690 high strength steel channel sections under combined compression and major-axis bending than their codified counterparts. The reliability of the proposed design interaction curves was confirmed by means of statistical analyses. [ABSTRACT FROM AUTHOR]

A testing and numerical modelling programme has been conducted to investigate the flexural buckling behaviour and resistance of press-braked S690 high strength steel angle section long columns. The testing programme adopted two press-braked S690 high strength steel equal-leg angle sections and included initial geometric imperfection measurements as well as twelve pin-ended column tests. The testing programme was accompanied by a numerical modelling programme, including a validation study, where finite element models were developed and validated against the test results, and a parametric study, where the validated finite element models were used to generate further numerical data over a wide range of cross-section dimensions and member effective lengths. The obtained test and numerical data were used to evaluate the existing design rules for press-braked S690 high strength steel angle section long columns, as specified in the North American specification, Australian/New Zealand standard and European code. The evaluation results revealed that the North American specification and Australian/New Zealand standard result in a high level of design accuracy and consistency, while the Eurocode leads to excessively conservative and scattered failure load predictions. Finally, a new design approach was proposed and shown to offer more accurate and consistent failure load predictions, with less calculation works, than the design codes. • The structural behaviour of press-braked S690 high strength steel angle section long columns was studied. • Twelve pin-ended column tests were conducted. • FE models were developed and validated against the test results and then used to perform parametric studies. • The accuracy of the codified design rules was evaluated based on the test and FE data. • A new design approach was proposed and shown to result in a higher degree of design accuracy, consistency and efficiency. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical investigation into the flexural–torsional buckling behaviour and resistance of pin-ended press-braked S690 high strength steel angle section columns. An experimental programme was firstly conducted and included initial geometric imperfection measurements and twelve pin-ended column tests. The column test results, including the failure loads and deformations at the failure loads, load–mid-height torsional rotation curves and failure modes, were fully reported and discussed. The experimental programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to expand the test data pool over a wider range of cross-section dimensions and member lengths. The obtained test and numerical data were then used to assess the relevant codified design rules, as provided in the European code, North American specification and Australian/New Zealand standard, and a DSM-based design approach. The assessment results revealed that all the codified design rules lead to excessively conservative and scattered resistance predictions for pin-ended press-braked S690 high strength steel angle section columns susceptible to flexural–torsional buckling, while the DSM-based design approach yields substantially improved resistance predictions, owing to the rational consideration of the length-dependent characteristic of flexural–torsional buckling and the interaction of flexural–torsional buckling with minor-axis flexural buckling. • The flexural–torsional buckling of pin-ended press-braked S690 high strength steel angle section columns was studied. • Twelve pin-ended compression tests were conducted. • FE models were developed and validated against test results and then adopted to perform parametric studies. • The accuracy of the codified design rules was assessed, indicating inaccuracy. • A new DSM-based design approach was evaluated and shown to yield improved design accuracy. [ABSTRACT FROM AUTHOR]

• The local–flexural interactive buckling of S690 high strength steel slender channel section columns was studied. • Twelve pin-ended compression tests were conducted. • FE models were developed and validated and then adopted to perform parametric studies. • The accuracy of the codified design rules was assessed, revealing inaccuracy. • A new design approach was proposed, showing a high level of accuracy. This paper reports an experimental and numerical investigation into the local–flexural interactive buckling behaviour and resistance of press-braked S690 high strength steel slender channel section columns. An experimental programme was firstly conducted and included initial geometric imperfection measurements and twelve pin-ended column tests. Interaction between local buckling and flexural buckling was observed for all specimens upon testing and discussed in detail. The experimental programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member effective lengths. The obtained test and numerical data were used to assess the accuracy of the codified design rules for press-braked S690 high strength steel slender channel section columns failing by local–flexural interactive buckling, as set out in the European code, North American specification and Australian/New Zealand standard. The assessment results revealed that the European code leads to excessively conservative and scattered resistance predictions, while the North American specification and Australian/New Zealand standard result in a higher level of design accuracy and consistency, but still with many conservative resistance predictions for columns with short to intermediate lengths. Finally, a new design approach was proposed and shown to yield substantially more accurate and consistent resistance predictions for press-braked S690 high strength steel slender channel section columns over the design codes. [ABSTRACT FROM AUTHOR]

This paper reports an experimental and numerical investigation into the cross-section behaviour and resistances of press-braked stainless steel channel sections under combined compression and major-axis bending moment. A testing programme was firstly conducted, including initial local geometric imperfection measurements and major-axis eccentric compression tests on ten press-braked stainless steel channel section stub column specimens. Following the testing programme, a numerical modelling programme was performed, where finite element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and initial loading eccentricities. Based on the obtained test and numerical data, the existing design interaction curves, as given in the European code, American specification and Australian/New Zealand standard, were assessed and shown to result in conservative cross-section resistance predictions for press-braked stainless steel channel sections under major-axis combined loading. The conservatism of the codified design interaction curves stems from the conservative end points (i.e. cross-section resistances under pure compression and pure bending), which are determined without considering the effect of material strain hardening, and the inefficient linear shape, which ignores the effect of stress redistribution. Improved design interaction curves were proposed through the adoption of (i) more accurate end points, which are calculated with a rational exploitation of material strain hardening by continuous strength method and (ii) more efficient nonlinear shape, which allows for the stress redistribution. The proposed design interaction curves were shown to result in substantially more accurate resistance predictions for press-braked stainless steel channel sections under major-axis combined loading than their codified counterparts. The reliability of the proposed design interaction curves was confirmed by means of statistical analyses. [Display omitted] • Press-braked stainless steel channel sections under combined loading were studied. • Ten major-axis eccentric compression tests were conducted. • FE models were developed and validated and then used to perform parametric studies. • The codified design interaction curves were assessed, revealing conservatism. • New design interaction curves were proposed and shown to yield higher accuracy. [ABSTRACT FROM AUTHOR]

This paper presents an in-depth experimental and numerical investigation into the behaviour and resistances of press-braked stainless steel channel sections under combined compression and bending moment about the minor principal axis. The experimental programme adopted two press-braked stainless steel channel sections and included initial local geometric imperfection measurements and ten eccentrically loaded stub column tests. The loading eccentricity was varied to achieve a range of ratios of compression load to minor-axis bending moment. Two types of failure mode, namely 'C'-orientation failure (indicating that failure specimens bent towards the web) and 'reverse C'-orientation failure (signifying that failure specimens bent towards the flange tips), were observed upon testing. The experimental programme was followed by a numerical modelling programme; finite element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and initial loading eccentricities. The obtained test and numerical data were then adopted to assess the accuracy of the current codified design rules for press-braked stainless steel channel sections under combined compression and minor-axis bending, as given in the European code, American specification and Australian/New Zealand standard. The assessment results revealed that the codified design rules yield excessively conservative and scattered resistance predictions, owing to the neglect of the favourable material strain hardening of stainless steel and the beneficial stress redistribution within channel sections under combined loading. Improved design rules featuring more efficient interaction curves, anchored to more accurate end points (i.e. cross-section resistances under pure compression and pure bending), were then proposed. The new design proposals were shown to yield more accurate and consistent resistance predictions over the existing design rules. Statistical analyses were also conducted to confirm the reliability of the new design proposals. • The behaviour of press-braked stainless steel channel sections under minor-axis combined loading was studied. • Ten eccentrically loaded stub column tests were carried out about the minor principal axis. • FE models were developed and validated against the test results and then used to conduct parametric studies. • The codified design interaction curves were assessed based on the test and FE data, indicating inaccuracy. • New design interaction curves were proposed and shown to substantially improve the resistance predictions. [ABSTRACT FROM AUTHOR]

The flexural-torsional buckling behaviour and resistances of pin-ended hot-rolled stainless steel angle section columns have been studied in the present paper, based on laboratory testing and numerical modelling. The testing programme adopted four hot-rolled stainless steel angle sections and included initial global and torsional geometric imperfection measurements and twelve pin-ended column tests. The key obtained test results, including the failure loads and deformations at the failure loads, the load–mid-height lateral deflection curves and failure modes, were fully reported and discussed. Strong interaction between flexural-torsional buckling about the major principal axis and flexural buckling about the minor principal axis was observed for each pin-ended hot-rolled stainless steel angle section column specimen during and upon testing. The testing programme was followed by a numerical modelling programme; finite element models were developed and validated against the test results, and afterwards used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. On the basis of the experimentally and numerically obtained data, the accuracy of the codified design methods, as adopted in Europe, America and Australia/New Zealand, and a recently proposed DSM-based design approach for pin-ended hot-rolled stainless steel angle section columns susceptible to flexural-torsional buckling, were evaluated. Overall, it may be concluded that (i) all the three considered design codes result in conservative flexural-torsional buckling resistance predictions, (ii) the current European code leads to more accurate resistance predictions for pin-ended columns with non-slender hot-rolled stainless steel angle sections, but a lower degree of design accuracy for pin-ended columns with slender hot-rolled stainless steel angle sections, in comparison with the American specification and Australian/New Zealand standard, and (iii) the DSM-based design approach yields substantially improved resistance predictions, due to the rational consideration of the length-dependent characteristic of flexural-torsional buckling and the interaction of flexural-torsional buckling with minor-axis flexural buckling, but with many predictions lying on the unsafe side. • The flexural-torsional buckling behaviour of pin-ended hot-rolled stainless steel angle section columns was studied. • Twelve pin-ended hot-rolled stainless steel angle section column tests were conducted. • FE models were firstly developed and validated against the test results, and then used to conduct parametric studies. • Based on the test and FE results, the current design provisions were assessed and their shortcomings were highlighted. [ABSTRACT FROM AUTHOR]

The buckling behaviour and resistances of press-braked stainless steel channel section beam-columns under combined compression and minor-axis bending have been studied in the present paper through laboratory testing and numerical modelling. The testing programme adopted two press-braked stainless steel channel sections and included initial global and local geometric imperfection measurements and ten beam-column tests. Two types of failure mode, namely 'C'-orientation buckling (indicating that failure specimens buckled towards the web) and 'reverse C'-orientation buckling (signifying that failure specimens buckled towards the flange tips), were observed upon testing. The testing programme was followed by a numerical modelling programme; finite element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data on press-braked stainless steel channel section beam-columns over a wide range of cross-section dimensions, member effective lengths and loading combinations. The obtained experimental and numerical data were employed to assess the accuracy and consistency of the relevant codified design rules for press-braked stainless steel channel section beam-columns, as given in the European code, American specification and Australian/New Zealand standard. The results of assessment revealed that the European code yields many unsafe resistance predictions for Class 1 and 2 press-braked stainless steel channel section beam-columns but overly conservative resistance predictions for Class 3 press-braked stainless steel channel section beam-columns, although the resulting overall design accuracy is good, but with a high level of scatter of the resistance predictions. Compared with the European code, the American specification and Australian/New Zealand standard result in slightly more accurate resistance predictions for press-braked stainless steel channel section beam-columns with buckling in the 'C' orientation, but lead to significantly more conservative predicted resistances for press-braked stainless steel channel section beam-columns with buckling in the 'reverse C' orientation. In terms of the design consistency, the American specification and Australian/New Zealand standard were shown to result in more consistent resistance predictions (regardless of cross-section dimensions and buckling orientations) than their Eurocode counterpart. • The buckling behaviour and resistances of press-braked stainless steel channel section beam-columns were studied. • Ten press-braked stainless steel channel section beam-column tests were performed. • FE models were developed and validated against the test results and then employed to conduct parametric studies. • The codified design interaction formulae were evaluated, based on the test and FE results. [ABSTRACT FROM AUTHOR]

The minor-axis flexural buckling behaviour and strengths of pin-ended press-braked stainless steel channel section columns have been investigated in the present paper through laboratory testing and numerical modelling. An experimental programme was firstly conducted, and included initial global and local geometric imperfection measurements and twelve pin-ended column tests about the minor principal axis. The key obtained test results, including the failure loads, the mid-height lateral deflections at the failure loads, the load–mid-height lateral deflection curves and the failure modes, were reported and discussed in detail. The experimental programme was followed by a numerical modelling programme; finite element models were developed to simulate the test responses and then adopted to perform parametric studies to generate further numerical data on press-braked stainless steel channel section columns over a wide range of cross-section dimensions and member effective lengths. The obtained experimental and numerical data were employed to assess the accuracy of the relevant design rules for press-braked stainless steel channel section columns failing by flexural buckling about the minor principal axis, as given in the European code, American specification, Australian/New Zealand standard and SCI design manual. The results of the assessment indicated that (i) the European code yields unsafe flexural buckling strength predictions for those relatively short and intermediate press-braked stainless steel channel section columns with member non-dimensional slendernesses less than around 1.0, (ii) the American specification leads to unsafe predictions of flexural buckling strength for press-braked stainless steel channel section columns over the whole considered range of member non-dimensional slendernesses up to 3.0, and (iii) the Australian/New Zealand standard and the SCI design manual result in lower levels of design accuracy than the European code and American specification, but with significantly reduced number of unsafe flexural buckling strength predictions. • The minor-axis flexural buckling behaviour of press-braked stainless steel channel section columns was studied. • Twelve pin-ended press-braked stainless steel channel section column tests were carried out. • FE models were firstly developed and validated against the test results, and then adopted to conduct parametric studies. • The accuracy of the relevant codified design rules was evaluated, based on the test and FE results. [ABSTRACT FROM AUTHOR]

• The flexural-torsional buckling behaviour of fixed-ended press-braked S690 high strength steel angle columns was studied. • Twelve compression tests of fixed-ended press-braked S690 high strength steel angle columns were carried out. • FE models were developed and validated against the test results, and then adopted for parametric studies. • The accuracy of the codified design rules and a new DSM-based design approach was evaluated. The flexural-torsional buckling behaviour and resistances of fixed-ended press-braked S690 high strength steel angle section columns have been studied based on testing and numerical modelling, and reported in this paper. A testing programme, employing four different equal-leg angle section sizes, was firstly conducted, and comprised material tensile coupon tests, initial global and torsional geometric imperfection measurements and twelve fixed-ended column tests. The column test setup and procedures were thoroughly presented, and the key obtained test results, including the failure loads and deformations at the failure loads, load–end shortening curves, load–mid-height torsional rotation curves and failure modes, were fully reported and discussed. This was followed by a numerical modelling programme, where finite element models were initially developed to simulate the experimental responses and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. The obtained test and numerical data were then used to evaluate the accuracy of the relevant codified design rules, given in the European code, North American specification and Australian/New Zealand standard, and a recently proposed DSM-based design approach. The results of the evaluation revealed that all the codified design rules yield excessively conservative and scattered flexural-torsional buckling resistance predictions for fixed-ended press-braked S690 high strength steel angle section columns, while the DSM-based design approach leads to substantially improved resistance predictions, owing to the rational consideration of the length-dependent characteristic of flexural-torsional buckling and the interaction of flexural-torsional buckling with minor-axis flexural buckling. [ABSTRACT FROM AUTHOR]

The present paper describes an in-depth experimental and numerical investigation into the flexural responses and strengths of press-braked S690 high strength steel channel section beams bent about the minor principal axes in both the 'u' and 'n' orientations. The experimental study was performed on eight press-braked channel sections, and comprised twenty-four material flat and corner coupon tests, initial local geometric imperfection measurements, and twelve beam tests in the four-point bending configuration. This was followed by a complementary numerical modelling programme, where finite element models were firstly developed and validated against the test results and afterwards adopted for performing parametric studies to obtain an additional numerical data bank over a wide variety of cross-section geometric sizes. The acquired test and numerical data were then employed to evaluate the applicability of the Eurocode slenderness limits for welded and hot-rolled internal webs (in compression) and outstand flanges (in stress gradients) to their press-braked counterparts, revealing that the Eurocode slenderness limits can be safely extended to cover the classifications of plate elements and cross-sections of press-braked S690 high strength steel channel section beams. Evaluation of the accuracy of the cross-section flexural strengths predicted from various design codes established in Europe, North America and Australia/New Zealand was also made, based on the test and numerical data. The results of the quantitative evaluation generally revealed that (i) all the examined design codes lead to overall conservative and scattered predicted cross-section flexural strengths for press-braked S690 high strength steel channel section beams, and (ii) the European code results in more precise design flexural strengths for beams with relatively stocky channel sections, but less accurate strength predictions for beams with relatively slender channel sections, compared to the North American and Australian/New Zealand standards. • Flexural responses and strengths of press-braked S690 channel section beams were studied. • Press-braked S690 channel section beams bent about the minor principal axes in both the 'n' and 'u' orientations were tested. • FE models were developed and validated against the test results, and afterwards employed to conduct parametric studies. • Evaluation of the flexural strength predictions by the current design codes was made based on the test and FE results. [ABSTRACT FROM AUTHOR]

• Material responses and compression capacities of press-braked S690 angle and channel section stub columns were studied. • Thirty-six tensile flat and corner coupon tests on press-braked S690 angle and channel sections were conducted. • A total of twenty-four press-braked S690 angle and channel section stub columns were tested. • Numerical models were developed and validated against test results, and then used to perform parametric studies. • Current design codes and direct strength method were assessed against test and numerical results. This paper reports an experimental and numerical investigation into the cross-section behaviour and compression resistances of press-braked S690 high strength steel angle and channel section stub columns. The experimental study was carried out on four equal-leg angle sections and eight plain channel sections with a range of cross-section sizes (covering both non-slender and slender sections), and included thirty-six material tensile flat and corner coupon tests, initial local geometric imperfection measurements and twenty-four concentrically loaded stub column tests. The experimental study was then supplemented by a numerical modelling programme, where numerical models were firstly developed to simulate the test structural responses and subsequently adopted to derive further numerical data. The experimentally and numerically derived results were utilised to assess the applicability of the Eurocode Class 3 slenderness limits for hot-rolled and welded sections to their cold-formed (press-braked) counterparts. The results of the assessment generally revealed that the Eurocode Class 3 slenderness limits for hot-rolled and welded sections can be safely adopted for the classification of press-braked (cold-formed) S690 high strength steel angle and channel sections subjected to compression. The accuracy of the codified design provisions established in Europe, North America and Australia/New Zealand as well as the direct strength method (DSM) to the design of press-braked S690 high strength steel angle and channel section stub columns was also assessed, based on the test data and numerical results. The North American, Australian and New Zealand standards were found to result in accurate and consistent compression capacity predictions for press-braked S690 high strength steel channel section and non-slender angle section stub columns, but greatly underestimate the compression capacities for those slender angle section stub columns, while the European code and DSM were shown to yield overall precise and consistent design compression capacities. [ABSTRACT FROM AUTHOR]