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Abstract Structural design formulae for beam-columns require accurate end points (i.e. accurate resistance predictions for pure compression and pure bending), should be of suitable form to capture the interaction between the different components of loading and should take due account of the influence of a moment gradient along the member length. However, existing design rules for stainless steel beam-columns do not fully capture the interaction responses observed in experiments and numerical simulations, and are often tied to inaccurate end points; the adopted equivalent uniform moment factors can also be unconservative in the case of high moment gradients. As a consequence, previous comparisons of stainless steel beam-column experimental and finite element results with codified strength predictions have often revealed a rather high degree of scatter. This prompted the present research, to develop improved design proposals for stainless steel square hollow section (SHS) and rectangular hollow section (RHS) beam-columns under moment gradients. To this end, revised design approaches are proposed firstly through the derivation of more accurate design interaction curves for stainless steel SHS and RHS beam-columns under uniform bending moment and then through the employment of more suitable equivalent uniform moment factors, underpinned by and validated against over 1500 test and numerical data points. The new design approaches are shown to lead to improved (safe-sided, accurate and consistent) resistance predictions for stainless steel SHS and RHS beam-columns under moment gradients over the current codified design rules. Finally, statistical analyses are performed to demonstrate the reliability of the proposed approaches, according to the requirements specified in EN 1990. Highlights • Current codified design rules for stainless steel beam-columns under moment gradients were briefly reviewed. • Shortcomings in the existing design codes were identified, and methodologies for overcoming them were described. • Improved design approach for stainless steel beam-columns under moment gradients was proposed. • Assessment of the new proposal indicates a higher level of design accuracy and consistency. • The reliability of the new proposal has been confirmed by means of statistical analyses. [ABSTRACT FROM AUTHOR]

This paper reports an experimental and numerical investigation into the buckling behaviour and resistance of press-braked ferritic stainless steel slender channel section beam–columns under combined compression and minor-axis bending moment. An experimental programme was firstly performed, including material coupon tests, initial global and local geometric imperfection measurements and ten beam–column tests. The experimental programme was followed by a numerical modelling programme, where finite element models were developed and validated against the experimental results and then adopted to conduct parametric studies to generate additional numerical data. Based on the obtained test and numerical data, the existing design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were evaluated and found to result in conservative and scattered resistance predictions. An improved design interaction curve, anchored to more accurate end points and featuring more appropriate shape, was then developed and shown to offer more accurate and consistent resistance predictions for press-braked ferritic stainless steel slender channel section beam–columns over the codified design interaction curves. Statistical analyses were also performed to confirm the reliability of the new proposal. • The behaviour of press-braked ferritic stainless steel slender channel section beam–columns was studied. • Ten beam–column tests were conducted. • FE models were developed to validate against the test results and then used to conduct parametric studies. • The codified design interaction curves were evaluated, revealing conservatism. • A new improved design interaction curve was developed. [ABSTRACT FROM AUTHOR]

This paper reports the second part of the study on the structural behaviour of stainless steel circular hollow sections subjected to combined axial load and bending moment. A series of numerical parametric studies is presented, using the validated finite element (FE) models from the companion paper, with the aim of generating further structural performance data over a wider range of stainless steel grades, cross-section slendernesses and combinations of loading. The considered parameters include the outer cross-section diameter, the ratio of outer cross-section diameter to thickness and the initial loading eccentricity. Both the experimentally and numerically derived section capacities were compared with the strength predictions determined from the current European code, the American specification and the Australian/New Zealand standard, allowing the applicability of each codified method to be assessed. The comparisons revealed that the current design standards generally result in unduly conservative and scattered strength predictions for stainless steel circular hollow sections under combined loading, which can be primarily attributed to the neglect of strain hardening in the determination of cross-section resistances and to the use of linear interaction formulae. To overcome these shortcomings, improved design rules are proposed through extension of the deformation-based continuous strength method (CSM) to the case of circular hollow sections subjected to combined loading. Comparisons between the proposals and the test and FE results indicate a high level of accuracy and consistency in the predictions. The reliability of the proposed approach was confirmed by means of statistical analyses according to EN 1990. [ABSTRACT FROM AUTHOR]

Experimental and numerical studies on hot-rolled stainless steel channel sections subjected to combined compression and minor-axis bending moment have been conducted and are fully reported in the present paper. The testing programme included initial local geometric imperfection measurements and ten minor-axis eccentric compression (combined loading) tests. The numerical modelling programme comprised a validation study, where finite element models were developed and validated against the 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 experimentally and numerically obtained data were used to assess the accuracy of the design interaction curves for hot-rolled stainless steel channel sections under minor-axis combined loading, as given in the European code and American specification. The assessment results generally reveal that the design interaction curves provided in the main body of the two design codes lead to unduly conservative and scattered failure load predictions, mainly owing to the conservative end points (i.e. the cross-section compression and bending resistances), which are calculated without considering material strain hardening. The appendix of each design code also provides an alternative method that uses the continuous strength method to account for material strain hardening in calculating the end points of the design interaction curve, and is shown to result in much more accurate and consistent predictions of failure load for hot-rolled stainless steel channel sections under combined compression and minor-axis bending moment. • The behaviour of hot-rolled stainless steel channel sections under minor-axis combined loading is studied. • Ten eccentric compression tests on hot-rolled stainless steel channel section stub columns are conducted. • FE models are developed and validated against the test results and then used to conduct parametric studies. • The codified design interaction curves are assessed, indicating conservatism. • The CSM-based codified design interaction curves are shown to yield higher accuracy. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigated the bending strength of girth-welded stainless steel circular hollow sections by numerical method. At first, finite element simulation of girth welding process was carried out to obtain the weld-induced residual stresses and deformations employing sequentially coupled three-dimensional thermo-mechanical finite element formulation. Then, nonlinear finite element analysis in which the moment versus end-rotation response, the ultimate moment resistance and the failure mode of the girth-welded circular hollow sections under pure bending were explored incorporating the residual stresses and depressions along with the initial global geometric imperfections was performed. Feasibility of adopting the current codified provisions (Eurocode 3) for stainless steel circular hollow sections in bending as the cross-section slenderness limit for girth-welded stainless steel circular hollow section flexural members was also examined. Results showed that the flexural behavior of girth-welded stainless steel circular hollow sections always involves local buckling near the girth weld on the compression side, which significantly affects the moment versus end-rotation behavior. Moreover, the results demonstrated that the Class 3 slenderness limit of 280 from Eurocode 3 for stainless steel circular hollow sections in flexure may be applied to girth-welded stainless steel circular hollow sections subjected to bending. [Copyright &y& Elsevier]

The global buckling behaviour of hot-rolled stainless steel channel section beam–columns under combined compression and minor-axis bending moment has been studied based on testing and numerical modelling and reported in this paper. A testing programme was conducted on ten hot-rolled austenitic stainless steel channel section beam–columns, with five buckling towards webs and the other five buckling towards flange tips. This was followed by a numerical modelling programme, in which finite element models were firstly developed and validated against the test results and then used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions, member effective lengths and loading combinations. The test and numerical results were adopted to assess the current design interaction curves given in the European code and American guide, both of which were found to result in inaccurate and scattered failure load predictions. The inaccuracy of the codified design interaction curves stems from the inaccurate end points (i.e. the member resistances under pure compression and pure bending) and the inappropriate shape. To address these shortcomings, a new design interaction curve was developed firstly through the adoption of more accurate end points and secondly through the derivation of a more proper shape. The proposed design interaction curve was shown to yield accurate and consistent failure load predictions for hot-rolled stainless steel channel section beam–columns. The reliability of the new proposal was also confirmed by means of statistical analyses. • The buckling behaviour of hot-rolled stainless steel channel section beam–columns is studied. • Ten beam–column tests were conducted. • FE models were firstly developed and validated against the test results and then adopted to perform parametric studies. • The codified design interaction curves were assessed, indicating inaccuracy. • A new design interaction curves was proposed, with the accuracy and reliability demonstrated. [ABSTRACT FROM AUTHOR]