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The application of design by finite element analysis (FEA) is becoming increasingly prevalent in applied engineering; however, codified provisions remain scarce. The vision of CEN/TC 250/SC 3 was to develop a new comprehensive document based on the existing provisions currently distributed throughout the different Eurocode 3 parts, and with extension where necessary to cover all fields of structural steel design. Within the development process, two documents are being prepared: (i) the code, prEN 1993‐1‐14 and (ii) a Technical Report. The new code aims to provide rules on the use of finite element analysis and other numerical methods for verifying ultimate limit states, serviceability limit states and fatigue. In parallel, the Technical Report will provide background information and explanations of all aspects of the code, as well as benchmark cases and design examples to support the correct application of the prEN1993‐1‐14 design rules and the necessary benchmarking required for model validation. The assumed stakeholders are mainly designers who can find direct guidance for design by finite element analysis in daily engineering practice. This current paper gives an overview of the new code and accompanying Technical Report, as well as the development process and harmonisation within the current Eurocode 3 framework. [ABSTRACT FROM AUTHOR]

An experimental investigation into the structural behaviour of steel frames made up of hybrid steel welded I‐section members is presented in this paper. The tested hybrid steel welded I‐section profile had quenched and tempered S690 steel flanges and an S355 steel web. The experimental programme comprised four two‐dimensional, single storey, single bay frames subjected to different combinations of horizontal and vertical loading, thus enabling different beam, sway as well as combined beam and sway plastic collapse mechanisms to be examined. The frames were fully laterally restrained using a bespoke lateral bracing system to ensure that no out‐of‐plane instability phenomena were experienced during testing. The experimental setup, loading schemes, instrumentation and key experimental results are reported. The experimental results are fundamental to developing an understanding of the behaviour of hybrid steel welded I‐sections at the structural system level. Further research is underway to underpin the development of suitable design rules for steel frames made of such hybrid steel welded I‐section members. [ABSTRACT FROM AUTHOR]

In this work, an experimental campaign was carried out to evaluate the post‐fire mechanical performance of high‐strength steel specimens (grade S700) when being subjected simultaneously to different combinations of tensile load and elevated temperature. To this end, transient‐state tests were firstly carried out to obtain the 'critical temperature', i.e., the temperature at which a specimen failed while being simultaneously subjected to tensile load and heated at a constant temperature rate. Secondly, post‐fire tests were performed on unloaded as well as loaded specimens. For that purpose, specimens were heated to temperatures below the critical temperature, cooled down in air and finally submitted to tensile testing. In order to investigate the influence of production route, specimens were extracted from cold‐formed circular hollow sections and hot‐rolled sheets. Moreover, coupons with five different thicknesses were tested to investigate the influence of section thickness on the post‐fire behaviour. Residual values of yield strength, ultimate strength, elastic modulus and ductility were determined from the tests and discussed. [ABSTRACT FROM AUTHOR]

Design by GMNIA (Geometrically and Materially Nonlinear Analysis with Imperfections) allows the key behavioural features of structures to be directly captured in the analysis, dramatically reducing the need for subsequent design checks. Since the analysis of frames typically employs beam finite elements, which do not explicitly account for local buckling, cross‐section classification and capacity checks remain necessary. To resolve the step‐wise and overly conservative nature of traditional checks, the alternative use of strain limits, defined using the Continuous Strength Method, has been proposed. The framework allows cross‐sections of all classes to be treated in a consistent manner, and results in an accurate and consistent representation of the true behaviour of structures. To date, the accuracy of the design approach for stainless steel has been comprehensively demonstrated for isolated stainless steel members; the design method is extended to indeterminate stainless steel structural systems herein. The method is included in AISC 370 and prEN 1993‐1‐14; inclusion of this design framework in international codes of practice presents a step change for the future direction of efficient structural stainless steel design. [ABSTRACT FROM AUTHOR]

In this paper, the flexural‐torsional buckling response of austenitic stainless steel I‐section beam‐columns is investigated. Finite element simulations are performed with the aim of analysing the parameters affecting the behaviour of the studied members. The accuracy and safety of the existing design provisions of the European structural stainless steel design standard EN 1993‐1‐4 (2015) are assessed. A new method providing more accurate ultimate resistance predictions for austenitic stainless steel I‐section beam‐columns undergoing flexural‐torsional buckling is put forward. The higher accuracy, safety and reliability of the proposed design rules relative to EN 1993‐1‐4 (2015) are demonstrated and the new proposals have now been included in the revised Eurocode – prEN 1993‐1‐4 (2021). [ABSTRACT FROM AUTHOR]

An accurate and consistent approach to the out‐of‐plane stability design of steel beams and structures utilising geometrically and materially nonlinear analysis with imperfections (GMNIA) and strain limits is proposed. The method is implemented using computationally efficient beam elements, with the ultimate structural resistance defined either by (i) the ultimate load factor or (ii) the load factor at which a strain limit, determined on the basis of the continuous strength method (CSM), is attained, whichever occurs first. In the present paper, the scope of this method is extended from the in‐plane design of steel structures and structural components to scenarios in which out‐of‐plane stability effects, with a focus on lateral‐torsional buckling (LTB), govern. First, two shapes and corresponding amplitudes of equivalent imperfections, which consider the combined influence of both geometric imperfections and residual stresses, for the out‐of‐stability design of steel and stainless steel members by GMNIA are established. The existing CSM strain limits for in‐plane design are then extended to allow for the influence of shear, torsion and warping, to enable their general applicability to three‐dimensional buckling problems. It is shown that employing the proposed design method together with the proposed equivalent imperfections generally provides more accurate and consistent ultimate strength predictions than traditional Eurocode design calculations and also streamlines the design process by eliminating the need for cross‐section classification and individual member design checks. [ABSTRACT FROM AUTHOR]

An experimental investigation into the structural performance of wire arc additively manufactured (WAAM) steel single‐lap shear bolted connections is presented in this paper. Sixty specimens of different thicknesses, printing strategies and geometric features, including end distances and plate widths, were manufactured using steel wire of a nominal yield strength of 420 MPa and subjected to single shear lap tests. The test results are analysed while the observed failure modes, featuring shear‐out, net section tension fracture, end‐splitting, localised tearing and curl‐bearing failure, are discussed. Digital image correlation (DIC) was used for detailed monitoring and visualisation of the surface strain fields that developed during testing, providing valuable insight into the developed failure mechanisms. The experimental results, which generally followed the anticipated trends, were used to assess the applicability of current design specifications developed for conventional steel bolted connections to WAAM steel bolted connections. It was found that both the cold‐formed steel specifications (AISI S100 and AS/NZS 4600) and the structural steel specifications (AISC 360 and EN 1993‐1) yield considerable overestimations or underestimations of the test capacities, depending on the specimen geometry. Further research is underway to underpin the development of improved design provisions. [ABSTRACT FROM AUTHOR]

A comprehensive investigation into the behaviour of structural stainless steel members under concentrated transverse loading is presented in this paper. A total of 34 member tests and over 500 finite element simulations have been performed covering three types of concentrated transverse loading – internal one‐flange, internal two‐flange and end one‐flange loading, three stainless steel grades – austenitic, duplex and ferritic and key influential parameters such as bearing length, web slenderness and beam span. The results have shown that existing design recommendations are conservative and that there is considerable scope for the development of more economical design guidance. New design equations are proposed that offer 10% to 20% improvements in capacity predictions over the current design formulae in EN 1993‐1‐4. These proposed design equations are to be included in the next revision of the European standards. An alternative design approach based on numerically generated reference loads – i.e. the plastic collapse and elastic buckling loads – in conjunction with strength curves, has also been proposed. This advanced FE‐based design approach allows the extension of the design scope to non‐standard cases, such as webs with partial depth stiffeners and members with web holes. The reliability of both design approaches has been successfully verified by statistical analysis. [ABSTRACT FROM AUTHOR]

With the growing use of stainless steel in the construction and offshore industries, there is an increasing interest and need to study the performance of stainless structures at elevated temperatures. The behavior and design of stainless steel I-section beam-columns in fire is investigated in this paper, addressing a scarcity of previous research on this topic. Finite element (FE) models of stainless steel beam-columns, able to replicate their response at elevated temperatures, are created and validated; the validated models are then used to perform parametric studies to generate extensive benchmark structural performance data. The design rules set out in the European structural steel fire design standard EN 1993-1-2 are assessed and shown to provide rather inaccurate and often unsafe ultimate strength predictions for stainless steel I-section beam-columns in fire. New fire design rules for stainless steel beam-columns are put forward. It is shown that the new proposals are able to offer improved accuracy and design efficiency relative to the EN 1993-1-2 beam-column design rules. The reliability of the proposed design rules is also verified on the basis of the fire design reliability criteria set out by Kruppa [Eurocodes–Fire parts: Proposal for a methodology to check the accuracy of assessment methods, CEN TC 250, Horizontal Group Fire, Document no: 99/130 (1999)], thereby demonstrating the suitability of the proposed design rules for inclusion in the upcoming revised version of EN 1993-1-2. [ABSTRACT FROM AUTHOR]

Formulae for determining elastic local buckling half-wavelengths of structural steel I-sections and box sections under compression, bending and combined loading are presented. Knowledge of local buckling half-wavelengths is useful for the direct definition of geometric imperfections in analytical and numerical models, as well as in a recently developed strain-based advanced analysis and design approach (Gardner et al., 2019a, 2019b). The underlying concept is that the cross-section local buckling response is bound by the theoretical behaviour of the isolated cross-section plates with simply-supported and fixed boundary conditions along their adjoined edges. At the isolated plate level, expressions for the half-wavelength buckling coefficient k Lb , which defines the local buckling half-wavelength of a plate as a multiple of its width b , taking into account the effects of the boundary conditions and applied loading, have been developed based on the results of finite strip analysis. At the cross-sectional level, element interaction is accounted for through an interaction coefficient ζ that ranges between 0 and 1, corresponding to the upper (simply-supported) and lower (fixed) bound half-wavelength envelopes of the isolated cross-section plates. The predicted half-wavelengths have been compared against numerical values obtained from finite strip analyses performed on a range of standard European and American hot-rolled I-sections and square/rectangular hollow sections (SHS/RHS), as well as additional welded profiles. The proposed approach is shown to predict the cross-section local buckling half-wavelengths consistently to within 10% of the numerical results. • Formulae for the elastic local buckling half-wavelengths of structural sections were developed • I-sections and SHS/RHS subjected to compression, bending and combined loading were considered • Predictions were compared against 45,000 finite strip analysis results in CUFSM and were consistently within 10% • Formulae may be used to define geometric imperfections or in novel method of design by advanced analysis [ABSTRACT FROM AUTHOR]

This paper provides a review of recent developments in research and design practice surrounding the structural use of stainless steel, with an emphasis on structural stability. The nonlinear stress-strain characteristics of stainless steel, which are discussed first, give rise to a structural response that differs somewhat from that of structural carbon steel. Depending on the type and proportions of the structural element or system, the nonlinear material response can lead to either a reduced or enhanced capacity relative to an equivalent component featuring an elastic, perfectly plastic material response. In general, in strength governed scenarios, such as the in-plane bending of stocky beams, the substantial strain hardening of stainless steel gives rise to capacity benefits, while in stability governed scenarios, the early onset of stiffness degradation results in reduced capacity. This behaviour is observed at all levels of structural response including at cross-sectional level, member level and frame level, as described in the paper. Current and emerging design approaches that capture this response are also reviewed and evaluated. Lastly, with a view to the future, the application of advanced analysis to the design of stainless steel structures and the use of 3D printing for the construction of stainless steel structures are explored. • Constitutive modelling of stainless steel reviewed. • Influence of material nonlinearity of structural stability explained. • Current and emerging structural stainless steel design methods described. • Future trends, including design by advanced analysis and 3D printing, explored. [ABSTRACT FROM AUTHOR]

An experimental study was conducted into the degree of composite action that can arise between cold-formed steel joists and wood-based flooring panels. A series of material, push-out and 4-point bending tests were carried out, and alternative means of shear connection, featuring fasteners and adhesives, were investigated. It was found that the spacing of the fasteners and the application of structural adhesive at the beam-board interface had a significant influence on the attained degree of shear connection and, hence, the moment capacity and flexural stiffness of the system. The highest degree of shear connection (up to approximately 60%) was obtained using the structural adhesive, bringing corresponding increases in capacity and stiffness of approximately 100 and 40%, respectively, over the bare steel. Smaller, but still very significant, increases in capacity and stiffness were achieved through the use of screws alone. On the basis of the results of the push-out tests, a load-slip relationship for screw fasteners in wood-based floorboards was proposed; this was designed for use in future analytical and numerical models. The findings of this research demonstrate, for the first time, the benefits that can be derived through the practical exploitation of composite action in cold-formed steel flooring systems in terms of enhanced structural performance and efficiency of material use. [ABSTRACT FROM AUTHOR]

Laser-welding is a high precision fabrication process suitable for joining a wide range of steels and stainless steels. Laser-welded structural stainless steel members, for which there are currently little experimental data owing to their recent introduction to the construction industry, are the focus of the present study. To address the lack of test data and to investigate their structural response, a total of 9 stub column tests and 22 flexural buckling tests (14 buckling about the minor axis and 8 about the major axis) have been performed on laser-welded austenitic stainless steel I-section members. Complementary tensile coupon tests, initial geometric imperfection measurements, and residual stress measurements have also been carried out and are reported herein. Based on the results obtained, a representative residual stress pattern is proposed, the design provisions of Eurocode 3 Part 1.4 and the continuous strength method are assessed, and column buckling curves for laser-welded stainless steel I-section members are recommended. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stiffness reduction method developed based on the European column buckling curves. [•] Finite element models validated against existing experimental results. [•] Comprehensive verification of the stiffness reduction method against FE results. [•] Illustration of the application and accuracy of the method for irregular members. [Copyright &y& Elsevier]

The lateral stability of imperfect discretely braced steel beams is analyzed using Rayleigh-Ritz approximations for the lateral deflection and the angle of twist. Initially, it is assumed that these degrees of freedom can be represented by functions comprising only single harmonics; this is then compared with the more accurate representation of the displacement functions by full Fourier series. It is confirmed by linear eigenvalue analysis that the beam can realistically buckle into two separate classes of modes: a finite number of node-displacing modes, equal to the number of restraints provided, and an infinite number of single harmonic buckling modes, where the restraint nodes remain undeflected. Closed-form analytical relations are derived for the elastic critical moment of the beam, the forces induced in the restraints, and the minimum stiffness required to enforce the first internodal buckling mode. The position of the restraint above or below the shear center is shown to influence the overall buckling behavior of the beam. The analytical results for the critical moment of the beam are validated by the finite-element program LTBeam, whereas the results for the deflected shape of the beam are validated by the numerical continuation software AUTO -07p, with very close agreement between the analytical and the numerical results. [ABSTRACT FROM AUTHOR]

• Tests on ten cold-formed S700 circular hollow section (CHS) beam-columns were performed. • Digital image correlation (DIC) was employed in the experimental programme. • Finite element simulations were carried out to expand test data pool for CHS beam-columns. • Existing EC3 beam-column design rules for Class 1–3 CHS were assessed. • New stability design method was proposed to capture influence of increased yield strength. An experimental and numerical study into the global buckling behaviour of structural steel circular hollow section (CHS) beam-columns with normal and high strength steel grades is presented in this paper. Two cold-formed S700 CHS profiles – 139.7×4 and 139.7×5 (diameter × thickness, in mm), were used in the beam-column testing programme. Ten CHS specimens were tested under eccentric compression, resulting in a combination of axial compressive force and uniform first-order bending moment. Digital image correlation (DIC) was used in the experiments to enable full-field monitoring of the strain and deformations in the specimens. Finite element (FE) modelling was also carried out with the aims of first replicating the test results and then generating further numerical data to complement the test data pool. Assessment of the existing EC3 design provisions was carried out against the test and FE data, which revealed that the lack of account taken for the full influence of varying yield strengths leads to inaccuracies in the EC3 resistance predictions. Improved design rules were proposed accordingly and shown to result in considerably more consistent predictions of buckling strength across a wide spectrum of steel grades. Lastly, a reliability assessment of both the EC3 and proposed design approaches was performed in accordance with EN 1990. The statistical results confirmed that the current EC3 partial safety factor is suitable for use with the new design proposals. [ABSTRACT FROM AUTHOR]

The present generation of international structural steel design codes treats material nonlinearity through simplified elastic-plastic or rigid-plastic material models. However, the actual stress-strain response of structural steel is more complex than this and features, in particular, strain hardening. Strain hardening refers to the increase in strength beyond yield because of plastic deformation. The influence of strain hardening on the behavior and design of steel structures is examined in this study through both the experimentation and the analysis of existing data, and a method to exploit the additional capacity that arises is outlined. Both determinate and indeterminate structures are considered. The proposed design method, referred to as the continuous strength method (CSM), is a deformation-based design approach employing a continuous relationship between cross-sectional slenderness and cross-sectional deformation capacity, together with a material model that allows for strain hardening. Comparisons are made between test results generated as part of the present study and collected from existing studies, and the predictions from the CSM and Eurocode 3 (EC3). For all cases considered, the CSM, through a rational exploitation of strain hardening, offers a more accurate prediction of observed physical behavior. [ABSTRACT FROM AUTHOR]

The influence of yield strength on the in-plane stability and design of structural steel square and rectangular hollow section (SHS and RHS) beam-columns under compression plus uniform bending is investigated in this study. Ten buckling tests were carried out on hot-finished S690 SHS 100×100×4 (in mm) specimens under combined compression plus uniaxial bending. Finite element (FE) models of SHS and RHS beam-columns were established, validated and employed to perform parametric studies, where supplementary buckling resistance data were numerically derived. Through comparisons with the test and FE data, shortcomings of the current EC3 beam-column interaction curves were revealed, particularly in the higher yield strength domain. A modified EC3 approach was developed accordingly, featuring more accurate compression end points and re-calibrated interaction factors, and was shown to significantly improve the design accuracy and consistency for both hot-finished and cold-formed SHS and RHS beam-columns over a wide spectrum of steel grades. Subsequent reliability analysis confirmed the applicability of the current EC3 partial safety factor to the proposed modified EC3 design approach. [Display omitted] • Ten hot-finished S690 square hollow section beam-columns were tested. • Finite element modelling of SHS and RHS beam-columns was carried out. • Current EC3 design rules for SHS and RHS beam-columns were assessed. • Modifications were proposed to improve the accuracy of EC3 interaction curves. • Reliability of the new design proposals was confirmed through statistical analysis. [ABSTRACT FROM AUTHOR]

A comprehensive experimental and numerical study into the cross-sectional behaviour of structural steel circular hollow sections (CHS), with an emphasis on high strength steel, is presented in this paper. Six cold-formed high strength steel S700 CHS profiles – 168.3×4, 139.7×4, 139.7×5, 139.7×6, 139.7×8 and 139.7×10 (diameter × thickness, in mm), spanning from Class 1 to Class 4 in compression according to EN 1993-1-1, were experimentally examined. The test programme consisted of twelve tensile coupon tests, local geometric imperfection measurements, six stub column tests, six four-point bending tests, six three-point bending tests and fifteen short beam-column tests. In parallel with the experimental study, finite element (FE) models of CHS were established and validated against the obtained experimental results, and parametric studies were subsequently carried out using the developed models to expand the cross-sectional resistance data pool. Finally, the cross-section design provisions specified in the European code prEN 1993-1-1:2018 and the American Specification ANSI/AISC 360-16 were assessed using the freshly generated experimental and numerical results as well as the existing test data on hot-rolled and cold-formed CHS from the literature. The present study provides the basis for the development of improved cross-section design rules for normal and high strength steel CHS in future research. • Six cold-formed S700 circular hollow section profiles were examined. • Six stub columns, twelve beams and fifteen short beam-columns were tested. • Digital image correlation was employed in the experiments. • Numerical models were developed to replicate the test results and to generate additional data. • Codified design provisions in EN 1993-1-1 and ANSI/ASIC 360 were assessed. [ABSTRACT FROM AUTHOR]

The flexural-torsional buckling response and design of stainless steel I-section beam-columns are investigated in this paper. First, a series of laboratory tests on laser-welded stainless steel I-section beam-columns susceptible to flexural-torsional buckling is presented. The results obtained are supplemented by further data generated by means of numerical parametric studies on both conventionally arc-welded and laser-welded stainless steel members covering a wide range of member slenderness and combinations of loading. Existing provisions for the design of welded stainless steel I-section elements against flexural-torsional buckling are then assessed and found to require improvement. Finally, new formulae for the design of stainless steel I-section beam-columns susceptible to flexural-torsional buckling are proposed. The new proposals yield improved accuracy and consistency over existing provisions and their suitability for inclusion in the upcoming version of the European structural stainless steel design code EN 1993-1-4 is confirmed by reliability analysis in accordance with EN 1990. • Flexural-torsional bucking response of stainless steel I-section beam-columns is investigated. •Experimental study on laser-welded stainless steel I-section beam-columns undergoing flexural-torsional buckling are presented. •FE models able to mimic flexural-torsional buckling response of stainless steel beam-columns are created and validated. •Numerical parametric studies are performed, whose results are utilised to assess accuracy of existing design provisions. •New design provisions are established, whose reliability is verified against the criteria set out in EN 1990. [ABSTRACT FROM AUTHOR]

Steel framed structures are affected, to greater or lesser extent, by (i) geometrical nonlinearity associated with the change in geometry of the structure under load and (ii) material nonlinearity related to the onset and spread of plasticity. In traditional design approaches, the design forces and moments within structural members are usually determined from simplified structural analyses (e.g. first or second-order elastic analysis), after which member design checks are performed to assess the strength and stability of the individual members. The extent to which the strength and deformation capacity of cross-sections is affected by local buckling is typically assessed through the concept of cross-section classification. For example, only compact (Class 1) cross-sections are considered to possess sufficient rotation capacity for plastic hinges to develop and for inelastic analysis methods to be used. This approach results in step-wise capacity predictions and is considered to be overly simplistic. Since the structural analysis of steel framed structures is typically performed using beam finite elements, which are unable to explicitly capture local buckling, a more sophisticated treatment of the available deformation capacity is required if inelastic analysis methods are to be used for all cross-section classes. A novel method of design by advanced inelastic analysis has recently been developed (Gardner et al., 2019a; Fieber et al., 2019a, 2018a, 2018b 1–4), in which strain limits are employed to represent the effects of local buckling in beam finite element models and thereby control the spread of plasticity and level of force/moment redistribution within a structure. It is thus possible to use a consistent advanced analysis framework to design structures composed of cross-sections of any class. In the present paper, application of the proposed design method to continuous beams and planar frames is illustrated and assessed. Ultimate load capacity predictions are compared against results obtained from benchmark shell finite element models that explicitly capture local buckling and to conventional steel design. It is found that the proposed method predicts safe-sided ultimate capacities that are consistently more accurate than current design methods, particularly for structures benefiting from strain hardening and for structures composed of non-compact cross-sections where inelastic redistribution is typically ignored. • Novel method for the design of steel structures using advanced analysis with strain limits is presented. • Capacity predictions compared against benchmark shell FE models for continuous beams and frames with I-section, SHS/RHS profiles. • Cross-section slenderness dependent levels of force/moment redistribution and effect of local moment gradients are captured. • The proposed design method is consistently more accurate than current EN 1993-1-1 design. [ABSTRACT FROM AUTHOR]

• Structural behaviour and design of semi-compact (Class 3) EHS were studied; • Parametric studies were conducted to numerically expand the existing data pool; • New design methods were developed to exploit partial plastification in semi-compact EHS; • Accuracy of both the existing and proposed design methods were assessed; • Reliability of the design proposals was confirmed through statistical analyses. Current structural steel design codes typically feature a step in the cross-sectional resistance functions at the Class 2 slenderness limit due to the abrupt switch between elastic and fully plastic capacities. To address this issue, new design rules, featuring a gradual transition between elastic and plastic resistances, have been recently developed for semi-compact (Class 3) I- and box sections to account for the partial spread of plasticity. This approach is extended herein to the cross-section and member buckling design of semi-compact elliptical hollow sections (EHS). Finite element models were first established and validated against previous test results; particular attention was given to the modelling of local geometric imperfections. Parametric studies were then conducted, where over 4000 structural performance data were numerically generated covering a wide range of cross-section aspect ratios, material properties, local and global slendernesses and load combinations. Upon completion of the numerical simulation programme, structural design rules of semi-compact EHS were developed. The classification of EHS under biaxial bending and compression plus biaxial bending was initially addressed. Following this, new design expressions featuring elasto-plastic section properties were developed to exploit partial plastification at both cross-section and member buckling levels. The accuracy of the design proposals was evaluated through comparisons between the test/numerical data and the resistance predictions; the comparisons revealed that the proposed elasto-plastic cross-section and member buckling design rules lead to both improved accuracy and consistency over the existing elastic provisions. The reliability of the proposals was verified through statistical analyses in accordance with EN 1990, demonstrating their suitability for incorporation into the next revision to EN 1993-1-1. [ABSTRACT FROM AUTHOR]

• Design of steel members using advanced inelastic analysis with strain limits. • Strain limits mimic local buckling and control spread of plasticity in beam FE. • Capacity predictions were compared against 6188 benchmark shell finite element models. • Proposed design method is consistently more accurate than current EN 1993-1-1 design. Structural steel design is traditionally a two step process: first, the internal forces and moments in the structure are determined from a structural analysis. Then, a series of design checks are carried out to assess the strength and stability of individual members. The structural analysis is typically performed using beam finite elements, which are usually not able to capture local buckling explicitly. Instead, the assessment of local buckling and rotation capacity is made through the concept of cross-section classification, which places class-specific restrictions on the analysis type (i.e. plastic or elastic) and defines the cross-section resistance based on idealised stress distributions (e.g. the plastic, elastic or effective moment capacity in bending). This approach is however considered to be overly simplistic and creates artificial steps in the capacity predictions of structural members. A more consistent approach is proposed herein, whereby a second-order inelastic analysis of the structure or structural component is performed using beam finite elements, and strain limits are employed to mimic the effects of local buckling, control the spread of plasticity and ultimately define the structural resistance. The strain limits are obtained from the continuous strength method. It is shown that not only can local buckling be accurately represented in members experiencing uniform cross-sectional deformations along the length, but, by applying the strain limits to strains that are averaged over a defined characteristic length, the beneficial effects of local moment gradients can also be exploited. The proposed method is assessed against benchmark shell finite element results on isolated members subjected to bending, compression and combined loading. Compared to conventional steel design provisions and even to existing advanced design approaches utilising second-order elastic analysis, the proposed design approach provides consistently more accurate capacity predictions. [ABSTRACT FROM AUTHOR]

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 (Zhao et al., submitted for publication). 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 combined loading tests were varied to provide a wide range of bending moment-to-axial load ratios. For each type of test, the test setup, experimental procedures, full experimental load–deformation histories and key test results are reported in detail. All the experimental results are then employed in the companion paper (Zhao et al., submitted for publication) for the validation of finite element (FE) models, by means of which a series of parametric results is generated, and for the assessment of the design provisions given in EN 1993-1-4 (2006) and SEI/ASCE-8 (2002). Improved design rules for stainless steel cross-sections under combined loading are also sought through extension of the deformation-based Continuous Strength Method (CSM). [ABSTRACT FROM AUTHOR]

The use of numerical models in the advanced analysis and design of steel structures, particularly under extreme loading conditions, is becoming increasingly widespread. A crucial component of such models is an accurate description of the material response. A systematic study into the dynamic constitutive modelling of structural steels is presented herein. The key features of the dynamic stress–strain characteristics of structural steels at various strain rates, i.e., test methods, material strength, strain-rate effect index and strain-rate effect models, are examined and discussed. Supplementary SHPB tests on both normal- and high-strength structural steels (Q235, Q355, Q460, and S960) under a wide range of strain rates up to 5000 s−1, filling gaps in existing datasets, are then carried out. A database of dynamic test results, containing 453 stress–strain curves, is systematically established and analyzed. Finally, a continuous dynamic constitutive model, capturing the dependency of both yield strength and strain rate, is proposed to predict the dynamic stress–strain response for structural steels, from normal- to high-strength material (235–960 MPa), and from static to high strain rate loading conditions (up to 5000 s−1). • SHPB tests on Q235, Q355, Q460 and S960 steels at high strain rates are presented; • A comprehensive database of 453 dynamic stress–strain results is established; • A continuous dynamic constitutive model dependent on both yield strength and strain rate is proposed. [ABSTRACT FROM AUTHOR]

An accurate and consistent approach to the out-of-plane stability design of steel beams and structures utilising second-order inelastic analysis with strain limits is proposed. The method is implemented using computationally efficient beam elements, with the ultimate structural resistance defined either by (i) the ultimate load factor or (ii) the load factor at which a strain limit, determined on the basis of the continuous strength method (CSM), is attained, whichever occurs first. Thus far, the method has been established for the in-plane design of steel structures and structural components; in the present paper, its scope is extended, for the first time to the scenarios in which out-of-plane stability effects, with a focus on lateral–torsional buckling (LTB), govern. The accuracy and safety of the method are assessed against the results of nonlinear shell finite element (FE) modelling. It is shown that the proposed method consistently provides more accurate results than the traditional LTB design method of prEN 1993-1-1. In addition to its accuracy, the proposed approach also streamlines the design process by eliminating the need for cross-section classification and member design checks. [Display omitted] • Advanced out-of-plane stability design method for steel beams and structures proposed • Provisions for considering shear-torsion effects for different sections presented • Accuracy of proposed design method verified against shell finite element results • Proposed method consistently provides more accurate ultimate strength predictions [ABSTRACT FROM AUTHOR]

The structural response of stainless steel I-sections in fire is investigated in this paper. Finite element models of stainless steel I-section members, capable of replicating their cross-section behaviour at elevated temperatures, are created and validated against existing experimental data from the literature. The validated finite element models are then utilised to perform comprehensive numerical parametric studies, where over 1000 numerical simulations of the response of stainless steel I-sections in fire are carried out, considering different cross-section dimensions, loading conditions, stainless steel grades and elevated temperature levels. On the basis of the findings from the parametric studies, the existing design rules of the European structural steel fire design standard EN 1993-1-2 and the recent design recommendations of Xing et al. [1] , together with the plastic effective width method of Bambach and Rasmussen [2] , are assessed in terms of their accuracy and reliability. It is observed that relative to the existing fire design rules set out in EN 1993-1-2, the design methods of Xing et al. [1] and Bambach and Rasmussen [2] are able to provide more accurate and reliable ultimate cross-section resistance predictions for stainless steel I-sections in fire, providing further verification of the suitability of the design provisions of Xing et al. [1] for inclusion in the next revision of EN 1993-1-2. • Local buckling behaviour of stainless steel I-sections in fire is investigated. • FE models replicating local buckling of stainless steel I-sections in fire are created. • Extensive parametric studies are performed to assess accuracy of design provisions. • Higher accuracy of the Xing et al. method relative to Eurocode 3 are observed. [ABSTRACT FROM AUTHOR]

In current structural steel design specifications, the local buckling of cross-sections is typically treated on an element-by-element basis, with the boundary conditions along the adjoined longitudinal edges of the individual plates assumed to be simply-supported. In reality, cross-sections buckle locally as a whole and the individual plate elements interact. As a result, the boundary conditions along the adjoined longitudinal edges of the critical isolated plate (i.e. that with the lowest elastic local buckling stress) lie between lower and upper bounds of simply-supported and fixed, respectively. Based on this concept, explicit formulae to predict the elastic local buckling stress of full cross-sections of common profiles, including I-sections, have recently been developed (Gardner et al., 2019) [1]. In the present paper, the formulae for single I-sections set out in Gardner et al. (2019) [1] are extended to cover the case of three-flanged cross-sections that arise in longitudinally-stiffened plate girders and in the haunch and apex regions of portal frames. The geometry and loading of the studied cross-sections are assumed to remain constant along the member length, i.e. the influence of tapering and moment gradients on local buckling are not considered herein, but has been evaluated in parallel work (Quan et al., 2020) [2]. The proposed formulae are calibrated against results from finite strip analysis performed using CUFSM v4.05 (Li and Schafer, 2010) [3] on a range of three-flanged sections, and provide predictions of elastic local buckling stresses that are typically within 5% of the numerically obtained values. • Elastic local buckling behaviour of three-flanged cross-sections has been investigated. • Formulae for calculating the elastic local buckling stress of three-flanged cross-sections have been developed. • Accuracy of predictions using the developed formulae has been confirmed against results obtained from finite strip analysis. • The predictions using the developed formulae have also been compared with results calculated on an element-by-element basis. [ABSTRACT FROM AUTHOR]

The local buckling behaviour and design of stainless steel plates in fire are investigated in this paper. Finite element models of stainless steel plates able to mimic their response in fire are created and validated against experimental results from the literature. Parametric studies are then performed and the results are utilised to assess the current design provisions set out in the European structural steel fire design code EN 1993-1-2; shortcomings in the prediction of the local buckling response of stainless steel plates in fire are revealed. A new effective width based design approach able to reflect the variation in strength and stiffness of stainless steel at different temperature levels in the determination of the local plate slenderness and thereby the ultimate resistances of stainless steel plates in fire is put forward. The proposed approach is shown to provide significantly higher levels of accuracy and reliability relative to the current provisions in EN 1993-1-2 for a wide range of plate slendernesses, elevated temperature levels, stainless steel grades and loading conditions. The design rules proposed for the local buckling assessment of stainless steel plates at elevated temperatures in this paper are due to be incorporated into the upcoming version of the European steel fire design standard EN 1993-1-2. • Local buckling behaviour of stainless steel plates at elevated temperatures is investigated. • FE models able to replicate local buckling response of stainless steel plates in fire are created and validated. • Extensive parametric studies are performed, whose results are utilised to assess existing design provisions in Eurocode 3. • New design provisions are established for local buckling assessment of stainless steel plates in fire. • Higher accuracy and reliability of proposed design provisions relative to existing methods in Eurocode 3 are illustrated. [ABSTRACT FROM AUTHOR]

The flexural buckling behaviour and design of stainless steel I-section columns at elevated temperatures are investigated in this paper. Finite element models able to accurately replicate the response of structural stainless steel columns in fire are created and validated. The models are then utilised to carry out extensive numerical parametric studies considering a broad range of stainless steel grades, cross-section geometries, slendernesses and elevated temperature levels. Using the results from the parametric studies, the safety and accuracy of existing design rules provided in the European structural steel fire design code EN 1993-1-2 for stainless steel columns in fire are assessed. It is observed that the existing design rules provide rather scattered and inaccurate ultimate strength predictions for stainless steel columns at elevated temperatures. For the purpose of establishing an accurate and practical means of designing stainless steel columns in fire, a new design approach, compatible with existing design rules in EN 1993-1-2, is proposed. The safety, accuracy and reliability of the proposed approach are illustrated for a wide range of cases against the results obtained through nonlinear finite element modelling. The proposed stainless steel column fire design rules are due to be incorporated into the upcoming version of the European steel fire design standard EN 1993-1-2. • Behaviour and design of stainless steel I-section columns in fire are investigated. • Advanced finite element models able to mimic response of stainless steel columns in fire are developed and validated. • New design rules for stainless steel I-section columns in fire are established. • Proposed design rules lead to considerably more accurate results relative to the current design rules in EN 1993-1-2. • Accuracy, safety and reliability of proposed design rules are verified against extensive numerical data. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) enables the production of structural components with topologically optimised geometries thus leading to significant self-weight reductions for a given load-carrying capacity. A common question arises regarding the environmental performance of WAAM structural components in comparison with conventional steel structural components. Thus, a comparative cradle-to-gate life cycle assessment has been conducted where the environmental impact of producing a topologically optimised WAAM steel beam is compared with that of producing a conventional hot-rolled steel I-beam. The beams are 2 m long, simply-supported and loaded vertically at midspan. The impact of using either carbon steel or stainless steel is investigated. The results demonstrate that the carbon steel and stainless steel WAAM beams have 7% and 24%, respectively, lower climate change impact than the corresponding I-beams. It is concluded that WAAM can lead to lower CO 2 -eq. emissions than conventional hot-rolling, provided that mass reductions of the order of 50% (which are readily attainable) can be achieved by employing WAAM in conjunction with, for instance, topology optimisation. Furthermore, it is shown that the shielding gas contributes greatly to the environmental impact of WAAM, and that, by using higher deposition rates or by utilising renewable energy sources, the impact of WAAM can be reduced by more than 30%. [Display omitted] • The environmental performance of WAAM structural components is assessed. • WAAM steel beams have lower climate change impact than steel I-beams. • Topology optimisation leads to significant environmental benefits in using WAAM. • The environmental impact of WAAM is highly dependent on the deposition rate. • The use of shielding gas contributes greatly to the climate change impact of WAAM. [ABSTRACT FROM AUTHOR]

In contrast to conventionally-produced structural steel and stainless steel elements, wire and arc additively manufactured (WAAM) elements can exhibit a strongly anisotropic material response. To investigate this behaviour, data obtained from tensile tests on machined and as-built coupons extracted from WAAM stainless steel sheets are analysed. The observed mechanical response in the elastic range is described accurately using an orthotropic plane stress material model requiring the definition of two Young's moduli, the Poisson's ratio and the shear modulus. In the inelastic range, the anisotropy is captured through the Hill yield criterion, utilising the 0.2% proof stresses in the three different loading directions relative to the deposition direction; plastic Poisson's ratios are also reported. The presented findings and constitutive description highlight significant variation in the properties of the studied stainless steel with direction, which opens up opportunities to enhance the mechanical performance of WAAM structures by optimising both the location and orientation of the printed material. [Display omitted] • Anisotropic response of wire and arc additively manufactured elements is described. • Experimental data from tensile tests on machined and as-built coupons are analysed. • Elastic response is characterised using an orthotropic plane stress material model. • Inelastic response is captured using the Hill yield criterion. • Reported parameters include Young's and shear moduli, Poisson's ratio and R-values. [ABSTRACT FROM AUTHOR]

With the increasing use of stainless steel elements in construction, the need for comprehensive rules to enable their efficient structural design is clear. To date, the fire behaviour of stainless steel I-section beam–columns has been the subject of relatively little research. In particular, there is an absence of experimental data. To address this gap in knowledge, full-scale anisothermal fire tests on six grade 1.4301 austenitic stainless steel I-section beam–columns have been carried out; the test procedure and results are reported herein. The test specimens were subjected to eccentric axial compression with two eccentricity values so as to achieve different combinations of axial compression and uniform minor axis bending. Complementary initial local and global geometric imperfection measurements, room temperature tensile coupon tests and room temperature beam–column tests were also carried out. Based on the obtained experimental results, together with additional numerical results from a previous study, the existing design rules in the European structural steel fire design standard EN 1993-1-2 and the new design method of Kucukler et al. (2021) for stainless steel beam–columns in fire, which will be incorporated into the next version of EN 1993-1-2, are assessed. • Structural behaviour of stainless steel beam-columns in fire is investigated. • Six fire tests on stainless steel I-section beam-columns are carried out. • Complementary room temperature beam-column tests are also described. • European design method and design recommendations of Kucukler et al. are assessed. [ABSTRACT FROM AUTHOR]

• Structural behaviour of stainless steel I-section columns in fire is investigated. • Eight fire tests on austenitic stainless steel I-section columns are carried out. • Complementary room temperature column buckling tests are also described. • EN 1993-1-2 and Kucukler et al.'s proposal are assessed against experimental results. Although there have been significant developments in the testing, simulation and design of stainless steel structural elements at room temperature, the structural response of stainless steel members in fire has received significantly less attention. In particular, full-scale fire tests on stainless steel I-section members, which are becoming increasingly widely used in structural engineering applications to meet growing load-carrying capacity demands, are currently scarce. In this paper, the results of eight full-scale anisothermal fire tests on grade 1.4301 laser-welded austenitic stainless steel I-section columns are reported. Complementary initial local and global geometric imperfection measurements, room temperature tensile coupon tests and room temperature column buckling tests are also described. On the basis of the findings from the fire experiments, the accuracy and safety of the European fire design standard EN 1993-1-2 and the recent design recommendations of Kucukler et al. [1] for stainless steel columns in fire, which will be incorporated into the upcoming version of EN 1993-1-2, are assessed. It is observed that, relative to the existing column fire design rules in EN 1993-1-2, the design method of Kucukler et al. [1] provides more reliable ultimate strength predictions for austenitic stainless steel I-section columns in fire. [ABSTRACT FROM AUTHOR]

• A ductile fracture criterion is extended to ELCF fracture simulation of braces. • Combined effects of buckling and fracture on fracture life of braces are assessed. • Deformation capacity and maximum ductility of CHS bracing members are quantified. • Seismic performance of a braced frame is evaluated in terms of story drift angle. The fracture behaviour of concentrically loaded circular hollow section (CHS) bracing members under extremely low cycle fatigue (ELCF) is examined in this paper. Finite element (FE) models capable of predicting fracture initiation and propagation on cyclically loaded braces were developed. A structural steel ductile fracture criterion, together with a damage accumulation rule that can account for the effects of both stress triaxiality and Lode angle, was adopted in the FE models. The FE models were validated against the available test results from different experimental programmes and shown to provide an accurate prediction of both the hysteretic response and the ELCF fracture cracking process. The coupling effects of buckling and fracture on the ELCF performance of braces were assessed through a parametric study. This parametric study examined the influences of the geometry, material and manufacturing process on the local and global deformation, and the ductility of the braces. Predictive equations for the localized strains and member ductility were proposed based on a plastic hinge model. The seismic performance of a chevron braced frame was also evaluated in terms of storey drift angle according to the requirements of the current design code. [ABSTRACT FROM AUTHOR]