In current structural stainless steel design codes, local buckling is accounted for through a cross-section classification framework, which is based on an elastic, perfectly-plastic material model, providing consistency with the corresponding treatment of carbon steel cross-sections. Hence, for non-slender cross-sections, the codified design stress is limited to the 0.2% proof stress without considering the pronounced strain hardening exhibited by stainless steels, while for slender cross-sections, the effective width method is employed without considering the beneficial effect of element interaction. Previous comparisons between test results and codified predictions have generally indicated over-conservatism and scatter. This has prompted the development of more efficient design rules, which can reflect better the actual local buckling behaviour and nonlinear material response of stainless steel cross-sections. A deformation-based design approach called the continuous strength method (CSM) has been proposed for the design of stocky cross-sections, which relates the strength of a cross-section to its deformation capacity and employs a bi-linear (elastic, linear hardening) material model to account for strain hardening. In this paper, the scope of the CSM is extended to cover the design of slender stainless steel cross-sections under compression, bending and combined loading, underpinned by and validated against 794 experimental and numerical results. The proposed approach allows for the beneficial effect of element interaction within the cross-section, and is shown to yield a higher level of accuracy and consistency, as well as design efficiency, in the capacity predictions of slender stainless steel cross-sections, compared to the effective width methods employed in the current international design standards. Non-doubly symmetric sections in bending, which may be slender, but still benefit from strain hardening, are also discussed. The reliability of the CSM proposal has been confirmed by means of statistical analyses according to EN 1990, demonstrating its suitability for incorporation into future revisions of international design codes for stainless steel structures

Stainless steel has been gaining increasing use in a variety of engineering applications due to its unique combination of mechanical properties, durability and aesthetics. Significant progress in the development of structural design guidance has been made in recent years, underpinned by sound research. However, an area that has remained relatively unexplored is that of combined loading. Testing and analysis of stainless steel cross-sections under combined axial load and bending is therefore the subject of the present paper and the companion paper [1]. The experimental programme covers both austenitic and duplex stainless steels, and five cross-section sizes including three square hollow sections (SHS) and two rectangular hollow sections (RHS). In total, five stub column tests, five four-point bending tests, 20 uniaxial bending plus compression tests and four biaxial bending plus compression tests were carried out to investigate the cross-sectional behaviour of stainless steel tubular sections under combined loading. The initial loading eccentricities for the Zhao, O., Rossi, B., Gardner, L., & Young, B. (2015). Behaviour of structural stainless steel cross-sections under combined loading -Part I: Experimental study. Engineering Structures, 89, 236-246. Improved design rules for stainless steel cross-sections under combined loading are also sought through extension of the deformation-based Continuous Strength Method (CSM).

Experimental and numerical studies of ferritic stainless steel beam-columns have been carried out and are described in this paper. Two cross-section sizes were considered in the physical testing: square hollow section (SHS) 60×60×3 and rectangular hollow section (RHS) 100×40×2, both of grade EN 1.4003 stainless steel. The experimental programme comprised material tensile coupon tests, geometric imperfection measurements, four stub column tests, two four-point bending tests, two axially-loaded column tests and ten beam-column tests. The initial eccentricities for the beam-column tests were varied to provide a wide range of bending moment-to-axial load ratios. All the test results were then employed for the validation of finite element (FE) models, by means of which a series of parametric studies was conducted to generate further structural performance data. The obtained test and FE results were utilized to evaluate the accuracy of the capacity predictions according to the current European code, American specification and Australian/New Zealand Standard, together with other recent proposals, for the design of stainless steel beam-columns. Overall, Zhao, O., Gardner, L., & Young, B. (2016). Buckling of ferritic stainless steel members under combined axial compression and bending. Journal of Constructional Steel Research, 117,[35][36][37][38][39][40][41][42][43][44][45][46][47][48] 2 the Australian/New Zealand Standard was found to offer the most suitable design provisions, though further improvements remain possible.

In parallel with the experimental study described in the companion paper [1], a numerical modelling programme has been carried out to investigate further the structural behaviour of stainless steel cross-sections under combined loading. The numerical models, which were developed using the finite element (FE) package ABAQUS, were initially validated against the experiments, showing the capability of the FE models to replicate the key test results, the full experimental load-deformation histories and the observed local buckling failure modes.Upon validation of the FE models, parametric studies were conducted to generate additional structural performance data over a wide range of cross-section slenderness and combinations

While the nominal material properties given in material specifications are suitable for design purposes, for the generation of realistic numerical parametric results that are 'equivalent' to physical experiments, material properties that are representative of actual structural members are required. Standardised values for these properties are proposed herein. Following analysis of a comprehensive database of material test data from different stainless steel products, values for the yield stress fy, the ultimate tensile stress fu, the strain at ultimate tensile stress εu and the Ramberg-Osgood parameters n and m are proposed. This enables the generation of standardised stress-strain curves for typical austenitic, duplex and ferritic stainless steel sections. Following this, an extensive numerical modelling study, incorporating the proposed standardised material parameters, was carried out to investigate the effect of production route (cold-formed and hot-finished) and material grade (austenitic, duplex and ferritic) on the flexural buckling behaviour and design of stainless steel square, rectangular and circular hollow section compression members. The FE generated flexural buckling data, combined with column test data from the literature, were used to derive a series of buckling curves for the design of stainless steel compression members. The suitability of the proposals was confirmed by means of reliability analysis.

Previous studies on stainless steel tubular section beam-columns have revealed shortcomings in established codified design methods. These shortcomings stem principally from inaccurate predictions of the bending and column buckling end points of the design interaction curves, where the bending moment end points are tied to the elastic or plastic moment capacities without considering strain hardening, while the column buckling end points are often overpredicted. Inaccuracies also arise due to the adopted interaction factors, which do not fully capture the structural response of the stainless steel members under combined loading. These observations prompted the present research, which is aimed at developing more efficient design rules for stainless steel tubular section beam-columns. In the presented design proposals, the deformation-based continuous strength method (CSM), allowing for strain hardening, was used to determine the bending moment capacities (i.e. the bending end points), while the column buckling strengths (i.e. the column end points) were calculated according to recently proposed buckling curves. Based on these more accurate end points, new interaction factors were derived following a comprehensive numerical simulation programme. The accuracy of the new proposals was assessed through comparisons against over 3000 . Behaviour and design of stainless steel 106,[330][331][332][333][334][335][336][337][338][339][340][341][342][343][344][345] experimental and numerical results. Compared to the current design standards, the new proposal yields a higher level of accuracy and consistency in the prediction of stainless steel square and rectangular hollow section (SHS and RHS) beam-column strengths. Use of the proposed interaction factors but with the Eurocode bending moment capacities and revised column buckling strengths as the end points was also assessed and shown to result in more accurate and less scattered strength predictions than the current Eurocode provisions. The reliability of the proposals has been confirmed by means of statistical analyses according to EN 1990, demonstrating its suitability for incorporation into future revisions of international design codes for stainless steel structures.

The current codified treatment of local buckling in stainless steel cross-sections is based on the traditional cross-section classification framework and a simplified elastic, perfectlyplastic material model, providing consistency with the corresponding carbon steel design rules. However, the cross-section classification framework treats the cross-section as an assemblage of isolated plate elements without considering the beneficial element interaction effect, and the elastic, perfect-plastic material model neglects the pronounced strain hardening exhibited by stainless steels. These limitations have been generally found to result in unduly conservative and scattered resistance predictions through comparisons against previous test data. To address these shortcomings, a deformation-based continuous strength method (CSM) has been developed, which relates the strength of a cross-section to its deformation capacity and employs a bi-linear (elastic, linear hardening) material model to account for strain hardening. The CSM has been established for the design of doubly symmetric plated sections and circular hollow sections, and shown to yield a high level of Zhao, O. and Gardner, L. (2018). The continuous strength method for the design of mono-symmetric and asymmetric stainless steel cross-sections in bending. Journal of Constructional Steel Research. 150:141-152. design accuracy and consistency. In this paper, the scope of application of the CSM is extended to cover the design of non-doubly symmetric cross-sections in bending. Global member buckling is not investigated. The developed design methodology and comparisons with existing test data and numerical results generated herein are described. Finally, reliability analysis is performed, which demonstrates the suitability of the proposals for inclusion in structural design codes.

An experimental and numerical study of ferritic stainless steel tubular cross-6 sections under combined loading is presented in this paper. Two square hollow section (SHS)