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Abstract Thin-walled stainless steel channels are becoming more widely used in the residential and commercial sectors because of their high corrosion resistance, especially in situations where low maintenance is required. However, there is a need also for web perforations for ease of installation of services; as a result such sections are susceptible to crippling in the web, particularly under concentrated loads applied near to the web perforations. This paper considers the use of perforated cold-formed ferritic stainless steel unlipped channels with restrained flanges subject to interior-one-flange and end-one-flange loadings, known as one-flange loadings. A total of 288 results are presented, comprising 18 laboratory and 270 numerical results. The numerical analysis in this paper uses nonlinear quasi-static finite element analysis with an implicit integration scheme. A comprehensive parametric study is described to determine web crippling strength reduction factors for different sizes of web perforations and cross-section dimensions. It is noted that no cold-formed stainless steel standard provides strength reduction factors for any one-flange loading. The strength reduction factors are first compared to reduction factors previously recommended for lipped cold-formed stainless steel channels. It is found that these existing equations are unreliable and unconservative for unlipped channels by as much as 20%. From both laboratory and finite element results, web crippling design equations are proposed for perforated channels under one-flange loadings; the proposed equations are shown to be reliable when compared against laboratory and numerical results. Highlights • Web crippling tests of perforated cold-formed ferritic stainless steel unlipped channels are considered. • The channels with restrained flanges were tested under both IOF and EOF loadings. • Non-linear quasi-static finite element models are developed and verified against experimental test results. • A parametric study considering different sizes of circular web perforations and cross-sections sizes is performed. • New reduction factor design equations are proposed for incorporating into design. [ABSTRACT FROM AUTHOR]

Abstract The use of composite floor slabs is well established and provides an opportunity to promote the use of visually exposed composite slabs. Stainless steels, with the combination of good mechanical properties and excellent corrosion resistance, are key to this strategy, specially ferritic stainless steels, whose price is lower and more stable than that corresponding to the more widely used austenitic grades, due to their low nickel content whilst still maintaining good mechanical properties and aesthetic appeal. In addition, the emissivity of these grades contributes to lowering the heating and cooling requirements of buildings, reducing the costs associated to maintenance. Generally used as cold-formed members with high resistance-to-weight ratios, stainless steel decks are slender and highly sensitive to buckling phenomena and so the study of the structural performance of composite slabs using ferritic stainless steel decking is required due to the complex nonlinear behaviour of stainless steels, which is very different from that exhibited by carbon steel. Thus, this paper presents a comprehensive experimental programme on ferritic stainless steel trapezoidal decks for composite slabs under several structural configurations occurring during construction stage: simply supported decks under positive and negative bending moment, continuous decks and internal and end support tests. All the experimental results have been compared with the predicted ultimate loads in EN 1993-1-4, which remits to EN 1993-1-3 for carbon steel, and also with some previous tests on galvanized carbon steel decks. The paper concludes that EN 1993-1-3 provisions are applicable to ferritic stainless steels. Highlights • Experimental programme on ferritic stainless steel trapezoidal decks for composite slabs is presented. • Simply supported, continuous deck, internal and end support tests are reported. • The assessment of EN 1993-1-3 expressions for ferritic stainless steel decks is conducted. • Tests results are compared to similar experiments on carbon steel decks. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the cross-section behaviour and resistance of press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment. An experimental programme, including initial local geometric imperfection measurements and ten major-axis eccentric compression tests, was firstly conducted, with the test setup, procedures and results reported in detail. This was followed by a numerical modelling programme, where finite element models were developed and validated against the major-axis eccentric compression test results and then adopted to conduct parametric studies to expand the test data pool over a wider range of cross-section dimensions and loading combinations. Based on the obtained test and numerical data, the design interaction curves for press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment, as given in the American specification and European code, were evaluated. The evaluation results revealed that the American specification resulted in a good level of design accuracy, while the European code led to conservative resistance predictions, due to the conservative bending end point and inefficient linear shape of the design interaction curve. New design interaction curves were also developed and shown to offer more accurate and consistent resistance predictions for press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment than the codified design interaction curves. • The local buckling of ferritic stainless steel channel sections under major-axis combined loading was studied. • Ten major-axis eccentric compression tests were carried out. • FE models were developed to simulate the test results and then adopted to conduct parametric studies. • The codified design interaction curves were evaluated, with shortcomings highlighted. • New improved design interaction curves were proposed. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study of the local–flexural interactive buckling behaviour and resistances of press-braked ferritic stainless steel slender channel section columns. An experimental programme was firstly conducted, including initial geometric imperfection measurements and ten pin-ended column tests. Interaction between local buckling and flexural buckling was observed for all column specimens upon testing and discussed in detail. The test results were used in a parallel numerical modelling programme to validate finite element models, which were then adopted to perform parametric studies to generate additional numerical data over a wide range of cross-section dimensions and member effective lengths. Based on the test and numerical data, the relevant design rules for press-braked ferritic stainless steel slender channel section columns, as given in the American specification and European code, were evaluated. The evaluation results revealed that the American specification resulted in a good level of design accuracy, while the European code led to conservative and scattered interactive buckling resistance predictions. Finally, a revised Eurocode design method was proposed and shown to yield much more accurate and consistent interactive buckling resistance predictions for press-braked ferritic stainless steel slender channel section columns than its original counterpart. • The local–flexural interactive buckling of press-braked ferritic stainless steel slender channel section columns was studied. • Ten pin-ended column tests were performed, with the progression of local and flexural buckling analysed. • FE models were developed to validate against the test results and then used to conduct parametric studies. • The American specification and European code were assessed, indicating accuracy and conservatism, respectively. • A revised Eurocode design method was proposed, showing a good level of accuracy. [ABSTRACT FROM AUTHOR]

Ferritic stainless steels, with their lower nickel content, supplement the desirable features offered by different stainless steel grades with a more controlled and lower initial investment requirements, which have encouraged the use of these materials in construction. The nonlinear behaviour of stainless steel grades is not usually considered when extending design expressions codified for carbon steel to these alloyed materials, leading to overconservative design approaches and the applicability of the different design expressions initially developed for carbon steel needs to be adjusted for every stainless steel grade. The study of stainless steel elements subjected to combined flexural buckling and bending moment loading conditions only covers the most usual austenitic, duplex and lean duplex grades, but experimental results on ferritic grades are still necessary to complete the analysis. Hence, an experimental programme on ferritic stainless steel RHS and SHS pin-ended elements has been conducted where the flexural buckling and beam-column behaviour of these elements has been investigated. Furthermore, the assessment of the different design approaches for flexural buckling and interaction expressions for combined loading has been derived from the obtained experimental results, and current specifications provided in Standards have been found to be, in general, safe but overconservative. [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]

Stainless steels are ideal for sustainable structural performances due to their excellent corrosion resistance, appropriate mechanical properties, aesthetic appearance and easy maintenance. However, the nonlinear behaviour and strain-hardening effects characterizing these materials make them different from carbon steel and some specific guidance is necessary. Although some investigations regarding the behaviour of stainless steel beam–columns subjected to combined compression and bending moment have already been published, most of them are based on the most commonly used austenitic and duplex grades. Hence, the work presented in this paper deals with the flexural buckling resistance of ferritic stainless steel RHS and SHS columns subjected to combined loading. The assessment of several design approaches codified in EN1993-1-4 and proposed in the literature has been conducted by comparing numerical results with the predicted ultimate capacities. The partial safety factor γ M 1 currently coded in EN1993-1-4 has been found to provide unsafe ultimate flexural buckling resistance predictions and new coefficients for the k interaction factor for ferritic RHS and SHS elements are proposed. [ABSTRACT FROM AUTHOR]

An investigation into the material response and local buckling behaviour of ferritic stainless steel structural cross-sections is presented in this paper. Particular attention is given to the strain hardening characteristics and ductility since these differ most markedly from the more common austenitic and duplex stainless steel grades. Based on collated stress-strain data on ferritic stainless steel, key aspects of the material model given in Annex C of EN 1993-1-4 [1] were evaluated and found to require adjustment. Proposed modifications are presented herein. The local buckling behaviour of ferritic stainless steel sections in compression and bending was examined numerically, using the finite element (FE) package ABAQUS. The studied section types were cold-formed square hollow sections (SHS), rectangular hollow sections (RHS) and channels, as well as welded I-sections. The models were first validated against experimental data collected from the literature, after which parametric studies were performed to generate data over a wide range of section geometries and slendernesses. The obtained numerical results, together with existing experimental data from the literature were used to assess the applicability of the slenderness limits and effective width formulae set out in EN 1993-1-4 [1] to ferritic stainless steel sections. The comparisons of the generated FE results for ferritic stainless steel with the design provisions of EN 1993-1-4 [1] , highlighted, in line with other stainless steel grades, the inherent conservatism associated with the use of the 0.2% proof stress as the limiting design stress. To overcome this, the continuous strength method (CSM) was developed as an alternative design approach to exploit the deformation capacity and strain hardening potential of stocky cross-sections. An extension of the method to ferritic stainless steels, including the specification of a revised strain hardening slope for the CSM material model, is proposed herein. Comparisons with test and FE data showed that the CSM predictions are more accurate and consistent than existing provisions thus leading to significant material savings and hence more efficient structural design. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical studies of the local buckling behaviour and cross-section resistances of press-braked ferritic stainless steel channel sections under combined compression and minor-axis bending. An experimental programme was firstly conducted and included material testing, initial local geometric imperfection measurements and ten eccentric compression tests. Following the experimental programme, a numerical modelling programme was conducted, where finite element models were developed to replicate the test observations and then used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and loading combinations. The obtained test and numerical data were then used to assess the relevant design interaction curves for press-braked ferritic stainless steel channel sections under minor-axis combined loading, as set out in the European code and American specification. The assessment results revealed that the codified design interaction curves result in conservative and scattered resistance predictions, mainly owing to the conservative bending end point and inefficient linear shape. Finally, new design interaction curves were developed and shown to provide a higher level of design accuracy and consistency than the codified design interaction curves. • The local buckling of ferritic stainless steel channel sections under minor-axis combined loading was studied. • Ten 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 inaccuracy. • New improved design interaction curves were developed. [ABSTRACT FROM AUTHOR]

During the last decades, various material models have been proposed describing stainless steel nonlinear behaviour through different parameters. The differences among these models are analysed herein using experimental data of different stainless steel types. An interactive computer programme, usable for any series of experimental data, is developed and presented: the procedure for the determination of Young's modulus (E0) is pointed out and the least-square adjustment to optimize the strain-hardening exponents of different material models is described. Different expressions for the calculation of the parameters, proposed by several authors and used in a variety of codes, are analysed and new ones are proposed. [ABSTRACT FROM AUTHOR]

Abstract: Cold-formed stainless steel members are widely used due to their high corrosion resistance and high resistance-to-weight ratio but their susceptibility to buckle implies that instability phenomena such as web crippling, where the web locally buckles due to concentrated transverse forces, must be considered. On the other hand, the emergent ferritic stainless steel has very low nickel content and therefore, they are cheaper and relatively price stable compared to austenitics and duplex. Their promising future has aimed to develop efficient design guidance and as a result, a new unified web crippling resistance expression based on numerical simulations and thereafter validated with experimental results has been proposed. [Copyright &y& Elsevier]

Abstract: Cold-formed stainless steel tubular structural members which may experience web crippling failure due to localise concentrated loads or reactions are investigated. A series of tests on fibre-reinforced polymer (FRP) strengthening of cold-formed stainless steel tubular structural members subjected to End-Two-Flange and Interior-Two-Flange loading conditions is presented. The strengthening only applied to a localise area of the members under concentrated load. A total of 58 web crippling tests were conducted. The investigation mainly focused on the effects of different surface treatment, different adhesive, and FRP for strengthening of stainless steel tubular sections against web crippling. The behaviour of stainless steel members strengthened by different widths of FRP plate against web crippling has been also investigated in this study. The test specimens consisted of ferritic stainless steel EN 1.4003 square and rectangular hollow sections. Two different surface treatments were considered. Furthermore, six different adhesives and six different FRPs were also considered in this study. The properties of adhesive and FRP as well as the bonding between the FRP and stainless steel tube have significant influence on the effectiveness of the strengthening. Most of the strengthened specimens were failed by debonding of FRP plates form the stainless steel tubes. Six different failure modes were observed in the tests, namely the adhesion, cohesion, combination of adhesion and cohesion, interlaminar failure of FRP plate, FRP delaminating failure and web crippling failure. The failure loads, failure modes, and the load-web deformation behaviour of the ferritic stainless steel sections are presented in this study. It was found that the web crippling capacity of ferritic stainless steel tubular sections may increase up to 51% using FRP strengthening. [Copyright &y& Elsevier]

This paper reports the numerical axial behaviour of cold-formed ferritic stainless steel (CFFSS) stub columns with two circular perforations on opposite faces located centrally along the width and height of the column specimens. Numerical models are established using the finite element (FE) package ABAQUS and validated by using the test results of cold-formed carbon steel stub columns with perforations and CFFSS shallow stub columns reported in the literature. The modelling of the material properties and geometric imperfections has carefully been considered in the developed FE models and validated rigorously against the available test results. The validated FE models are adopted to perform a comprehensive parametric analysis by varying the cross-sectional geometries and the diameter-to-width ratio of the circular perforation. The parametric results are used to examine the accuracy of the current direct strength method (DSM) and the DSM proposed by other researchers in the literature on CFFSS tubular stub columns. The comparison of the strengths indicates the need for proposing specified design rules for the compression capacity of the perforated CFFSS stub columns. Accordingly, new design recommendations are proposed for DSM for accurate compression strength predictions for CFFSS tubular stub columns which are verified through reliability analysis. • A finite element model for CFFSS short columns under axial loading is presented. • Using ABAQUS, 3D finite element CFFSSs with perforations are developed and validated. • The accuracy of current and modified DSMs is checked for CFFSS stub columns. • The proposed DSM is shown to predict well the strengths of CFFSS short columns. [ABSTRACT FROM AUTHOR]

The flexural behaviour of cold-formed ferritic stainless steel (CFFSS) closed built-up beam composed of lipped channel sections orientated face to face was examined numerically, using a finite element (FE) package ABAQUS. The developed FE models were first validated against the experimental data collected from the literature before performing the desired parametric study. Thirteen different sections were analysed, with varying plate slenderness, using two different material grades (EN 1.4003, EN 1.4509) with three different material properties and wall thicknesses. The simply supported built-up closed beams were analysed under four-point bending. The moment capacity of the built-up beams dropped with the increase in the compression flange's plate slenderness. The pool of numerical strengths was used to assess the current DSM's appropriateness, proposed DSM for cold-formed steel closed built-up beams, and proposed DSM for ferritic stainless steel hollow beams. Based on the above-stated strength comparisons, suitable modifications were proposed for the current DSM specifications, mainly targetting CFFSS closed built-up beams made of lipped channel sections (typically failing by local buckling). Lastly, a reliability analysis was performed to check the reliability of the current and proposed DSM specifications for CFFSS closed built-up beams. • The CFFSS built-up closed beams composed of lipped channels were investigated. • A numerical parametric study on 108 CFFSS built-up closed beams was performed. • Current DSM and DSM proposals available in the literature were assessed. • Reliable modified DSM was proposed for CFFSS closed built-up beams. [ABSTRACT FROM AUTHOR]

In this paper, the flexural buckling behaviour and design of duplex and ferritic stainless steel I-section columns fabricated through the welding of individual hot-rolled stainless steel plates are investigated. Finite element models able to mimic the structural response of stainless steel I-section columns are developed and validated against experimental results from the literature. Employing the validated finite element models, extensive numerical parametric studies are performed for the purpose of comprehensively assessing the behaviour of duplex and ferritic stainless steel I-section columns, considering various member slendernesses and cross-section proportions. The accuracy, safety and applicability of the existing column design provisions provided in the European, North American and Australian & New Zellandian structural stainless steel design standards and guides, some of which are only recommended for the design of cold-formed stainless steel columns, are assessed for the design of welded duplex and ferritic stainless steel I-section columns. Modifications to the column design method given in the current European structural stainless steel design standard EN 1993-1-4 are proposed. The higher accuracy of the modified column design method of EN 1993-1-4 relative to the column design methods in the existing structural stainless steel design standards and guides is illustrated in addition to its safety and high level of reliability. • Behaviour and design of duplex and ferritic stainless steel I-section columns are investigated. • FE models able to mimic flexural buckling response of welded stainless steel I-section columns are developed and validated. • Accuracy of column design methods provided in structural stainless steel design standards and guides is investigated. • Modifications to EN 1993-1-4 column design method are proposed for duplex and ferritic stainless steel I-section columns. • Proposed column design rules lead to more accurate results relative to the existing column design methods. [ABSTRACT FROM AUTHOR]