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• The results of reference literature tests on tubular joints are summarized. • FE models are built and validated against the experiments. • Parametric studies examining a wide range of geometrical properties are performed. • A novel stiffness formulation for T-joints with CHS chord and branch-plate is provided. • A component model for stiffness and plastic strength of joints with CHS column and double-tee beam is suggested and verified. This paper focuses on predicting the flexural stiffness and strength of beam-to-column joints with Circular-Hollow-Section (CHS) columns and externally welded double-tee beams using the Component Method approach. Currently, Eurocode 3 Part 1.8 lacks guidelines for assessing the stiffness of these joints, resulting in their practical modelling using extreme assumptions like pin or full restraint. Nevertheless, the literature demonstrates that these joints can exhibit semi-rigid behaviour due to the relatively high local deformability of the tube in the joint area. Another concern relates to the strength of these joints. In fact, recent studies have shown that Eurocode 3 Part 1.8 formula for predicting the yield resistance of these joints is over-conservative. Within this framework, the purpose of this study is to fill the current knowledge gaps (over-conservative strength prediction and lack of rules for determining the stiffness) by undertaking a thorough investigation involving numerical and analytical activities. Specifically, the research presents a component-based modelling approach for predicting stiffness and strength of CHS to double-tee beam connections. In this regard, the work presented in this paper has involved the selection of experimental tests from literature to validate a Finite Element (FE) model, specifically focusing on X- and T-joints and internal and external beam-to-column joints. The validated numerical models have been then employed to simulate the response under monotonic loading conditions of additional sets comprising forty T-joints and thirty external beam-to-column joints, respectively. The currently available formulations for predicting the resistance of T-joints were applied to the forty cases simulated, evaluating their accuracy. This allowed the individuation of the most accurate literature formula for the strength prediction of T-joints, showing that the recent proposal of Voth and Packer (2012) yields sufficiently accurate results. Instead, analytical formulations for predicting the stiffness of T-joints were properly derived in a closed-form solution and were validated against the results of the parametric study. Finally, drawing upon knowledge regarding the stiffness and strength of T-joints, the flexural response of external beam-to-columns connections was evaluated proposing a component model, whose accuracy was verified against the cases simulated in the parametric analysis. [ABSTRACT FROM AUTHOR]

Thin-walled structures generally rely on cold-formed mild steel profiles. Due to cold forming, a significant formation of residual stresses impacts their overall fatigue behaviour. In this work, a state-of-the-art framework for fatigue life prediction is proposed and applied to both roll-formed and press-braked full-scale profiles. In summary, the profile's manufacturing process is numerically simulated to obtain a representative residual stress field. These results are then used as the initial state during a subsequent structural and fatigue analysis. A clear detrimental residual stress effect is verified. Importantly, however, is to note that prediction accuracy increases significantly when these effects are considered. • An advanced framework for fatigue life prediction in full-scale profiles is presented. • Residual stress fields due to cold-forming and pre-forming processes are investigated. • Manufacturing straining history and structural loading unified in a single model. • A clear residual stress effect on numerical fatigue life estimations is verified. • The inclusion of residual stresses increased the predicting accuracy of the model. [ABSTRACT FROM AUTHOR]

• Cold-formed steel octagonal hollow section columns were fabricated through press-braking and subsequent welding. • Variations of material properties within the cross-section and initial global imperfection were measured and are presented. • A total of 10 octagonal hollow section long columns were tested. • The finite element modelling methodology for cold-formed steel octagonal hollow section columns was developed and a total of 608 numerical models were generated. • The applicability of current design methods was assessed and modified against the experimental and numerical results. This paper experimentally and numerically investigated the global buckling behaviour of cold-formed steel octagonal hollow section columns. A test programme was first conducted on 10 OctHS steel columns made of Q460 and Q690 high strength steels. Each steel grade comprised five specimens with distinct geometric dimensions. Material properties and initial global imperfection were measured and are reported herein. Axial load versus mid-height lateral deflection curves, axial load versus axial strain curves, and failure modes of OctHS specimens are presented and discussed. In conjunction with laboratory works, finite element models were subsequently developed to replicate the load-deformation responses and failure modes of OctHS columns against the experimental results. Following the validation of proposed numerical modelling technique, extensive parametric studies were performed to evaluate the effects of steel grade, cross-section slenderness, member slenderness, and initial global imperfection. Furthermore, results from 10 test specimens and 608 numerical models were used to comprehensively assess the applicability of current codes of practice on the design of OctHS long columns. Modifications and design recommendations were proposed based on the assessment results. Corresponding reliability analyses were also performed for each design method. [ABSTRACT FROM AUTHOR]

• Repair of CFRP with asymmetric damage through double-sided adhesive patch. • Investigation on the mechanical performance of the repaired CFRP with different bondline thicknesses. • A numerical damage model was constructed using FEM, aiding the analysis of damage evolution and failure mode in the repaired CFRP with different bondline thicknesses. As a common CFRP repair method, double-sided adhesive patch has been widely used in the automotive and aeronautic industry. More specific research is thus needed to help better understanding the effect of repairing parameters on the mechanical performance of CFRP structures after patch bonding. In this paper, experimental and Finite Element Modelling (FEM) efforts were made on the adhesive repaired CFRP laminate with different bondline thicknesses. Artificial damage was prefabricated in the centre of the CFRP laminate, which was then repaired through double-sided adhesive patch. Quasi-static tensile tests were conducted on the repaired specimen up to failure, to obtain the load-displacement curves. With a bondline thickness of 0.5 mm, the repaired CFRP structure reached its maximum peak load, increased by 25.3% and 26.4% compared to 0.2 mm and 1.0 mm bondline thicknesses, respectively. SEM observations were used to analyse the influence of adhesive thickness on the fracture modes. Combined with Cohesive Zone Model (CZM) for the adhesive layer and Hashin damage criterion for the CFRP, the FE model of the CFRP laminate repaired with double-sided adhesive patch subjected to tensile loading was established. Finally, the damage evolution as well as the failure modes in the parent laminate and adhesive layer with different bondline thicknesses were compared and analysed. It was revealed that bondline thickness can effectively affect the mechanical performance of CFRP laminate after adhesive patch repair. [ABSTRACT FROM AUTHOR]

• Presents an innovative light steel floor-ceiling system using external insulation sandwiched between two gypsum boards. • Used a combination of dimensional stability tests, thermal and structural FE models and load bearing small-scale fire tests. • A high density rigid Rockwool stone wool panel with a suitable insulation joint adhesive was shown to provide 130 min FRL. • The new floor system achieved 45 % higher FRL than conventional systems, improving both fire resistance and thermal comfort. • The new floor system is practical and meets the higher FRL requirements, indicating strong potential for industry adoption. Light Gauge Steel Framed (LSF) floor-ceiling systems, composed of thin-walled cold-formed steel (CFS) structural components, offer a high strength-to-weight ratio and cost-effectiveness, leading to their widespread adoption in modern construction. However, research on the fire behaviour of LSF floor-ceiling systems is limited. The industry-standard approach of using two 16 mm gypsum plasterboards for ceilings achieves a maximum Fire Resistance Level (FRL) of 90 min, mainly due to the significant fall-off associated with gypsum plasterboard. Traditional methods for increasing FRL involve adding more layers of gypsum plasterboard; however, the efficacy of achieving a 120-min FRL with three 16 mm gypsum plasterboards remains uncertain. This paper addresses these issues by developing innovative LSF floor-ceiling systems that incorporate external insulation (rigid stone wool) to mitigate the impact of critical ceiling fall-off behaviour and enhance FRL. The research includes dimensional stability tests of rigid stone wool, thermal and structural finite element modelling, and load-bearing small-scale fire tests. The new LSF floor-ceiling system has been shown to achieve an FRL of 130 min, approximately 45 % higher than conventional floor-ceiling systems, offering enhanced fire resistance and increased thermal comfort as a single, integrated solution. [ABSTRACT FROM AUTHOR]

• Web crippling analysis and design of channel sections were presented. • Parametric studies were performed on sections having different stiffened flanges. • FE strengths, load-displacement relationships and failure modes were predicted. • A reliability analysis was performed. • NAS, AS//NZS, EC and previously published design rules were assessed. Web crippling analysis and design of cold-formed high strength steel channel sections having different stiffened flanges are presented in this paper. 3D finite element models were developed for the analysis of sections with unstiffened flanges, stiffened flanges with simple lips, stiffened flanges with inward return lips and outward return lips loaded under End-Two-Flange (ETF) and Interior-Two-Flange (ITF) loading conditions. The models were verified against tests recently reported by the authors on cold-formed high strength channel sections having different stiffened flanges. The web crippling strengths, load-displacement relationships and failure modes were predicted numerically and compared well against that measured experimentally. Extensive parametric studies were performed using the validated models on 280 channel sections having different web slenderness, ratios of bearing length to web thickness, cross-section geometries and shapes of flange lips. The web crippling numerical strengths were compared with the web crippling design strengths specified in North American Specification, Australian/New Zealand Standards and Eurocode as well as with other proposed design equations in the literature. In addition, a reliability analysis was performed to assess the reliability of the design rules. It is found that the design strengths were either unconservative or conservative, and generally unreliable for the cold-formed channels with unstiffened and stiffened flanges investigated. Therefore, a modification for the North American Specification design equation was proposed. The modified proposed design equation provided more accurate and reliable web crippling strengths compared with specified and available in the literature web crippling design strength predictions. [ABSTRACT FROM AUTHOR]

• Compressive behavior of DSTCs with a brace is comprehensively explored. • DSTM T-joints exhibite a ductile behavior provided that the joint region is appropriately strengthened. • The compressive behavior of the chord with a brace-to-chord diameter ratio of 0.5 is hardly affected by the brace. • The existing model can well predict the axial load-strain curves, nonetheless further validation is needed. Hybrid fiber reinforced polymer (FRP)-concrete-steel double-skin tubular members (DSTMs) are a promising form of structural members with superior mechanical performance and durability, which have great potential for application in ocean structures. Such hybrid DSTMs consist of three components: an inner steel tube, an outer FRP tube, and concrete filled between the two tubes. Despite a significant number of studies demonstrating the excellent performance of hybrid DSTMs, no studies have been concerned with the joints of these members. The lack of a reliable design method for DSTM joints is certainly a huge obstacle to their wide application in practice. Against the above background, a research project has been proposed to understand the static behavior of circular DSTM T-joints through a combined experimental, modeling, and theoretical study. This paper presents the results of an experimental program on the axial compressive behavior of the chord in DSTM T-joints. The effects of various important factors, such as FRP tube thickness, steel tube thickness, brace-to-chord diameter ratio, void ratio, and concrete strength, on the performance of the DSTM T-joints were examined in detail. The test results demonstrated that the DSTM T-joints exhibited a ductile behavior provided that the joint region was appropriately strengthened and the presence of a brace did not significantly affect the compressive behavior of the chord in the joints with a brace-to-chord diameter ratio of 0.5. Finally, a simple method was proposed to predict the axial load-axial strain behavior of the DSTM T-joints. [ABSTRACT FROM AUTHOR]

An efficient modelling technique based on one dimensional (1D) beam finite element analysis for buckling of thin-walled laminated composite beams having open/closed sections is proposed. The formulation derived has sufficient generality for accommodating arbitrary stacking sequences of the individual beam section walls, and includes all possible couplings between axial, shear, bending and torsional modes of deformation. The effects of transverse shear deformation of the section walls and out-of-plane warping of the beam section are considered where provision exists to restrain or allow warping deformation. The incorporation of shear deformation leads to a problem in the finite element implementation of the proposed beam kinematics, but this is successfully addressed adopting a novel modelling concept. Numerical results obtained for the sample cases of open sections I beams and closed section box beams are presented. The numerical results are benchmarked/compared to data available in open literature, and it is shown that the proposed model performs very well. Finally, a study of the effect of axial and end moment loading, acting alone or in combination, on the buckling response of thin-walled composite beams is presented. [ABSTRACT FROM AUTHOR]

Structural design rules for prestressed cold-formed steel beams, considering both the prestressing and imposed vertical loading stages, are presented herein. In the proposed approach, the cold-formed steel member is designed as a beam-column using linear interaction equations in conjunction with the Direct Strength Method (DSM), while the prestressed cable is designed by ensuring that its tensile capacity is not violated during the two loading stages. In the present paper, the design approach and the failure criteria, which define the permissible design zone for the prestressed system, are first introduced. The suitability of the design recommendations is then assessed by comparing a set of parametric finite element (FE) results for several combinations of prestress levels, beam geometries and cable sizes, with the corresponding design predictions. Finally, following reliability analysis, the implementation of the design recommendations is illustrated through a practical worked example. • Design recommendations for prestressed cold-formed steel beams developed. • Linear interaction equations in conjunction with the Direct Strength Method utilised. • Capacities of cold-formed steel beam and cable to be checked for both loading stages. • Design rules assessment through comparisons with parametric finite element results. • Implementation of design rules illustrated through a practical worked example. [ABSTRACT FROM AUTHOR]

This paper presents finite element investigations on the structural behaviors of circular concrete-filled aluminum tubular (CFAT) stub columns under axial compression. The finite element models are developed by considering the nonlinearities of concrete and aluminum materials and the interactions between the two components. The predicted ultimate strengths, load-axial strain relationships and failure modes are compared to those from collected experimental data. Full range analysis on the load-deformation N - ε are conducted, where the investigations on the multi-axial stress conditions of the aluminum tube and the interaction stress between the aluminum tube and concrete core are included. The verified finite element models are used to carry out a series of parametric studies on key material and geometric properties. The ductility index DI and strain at ultimate strength ε scy are studied. Equations to determine ε scy for circular CFAT stub columns are proposed. The applicability of the existing design method for CFST to CFAT stub columns is investigated. • FE models incorporating aluminum material nonlinearity have been developed. • Parametric studies are conducted on key geometric and material properties. • Equation on strain at ultimate limit state is proposed and existing design method is assessed. [ABSTRACT FROM AUTHOR]

Abstract Face-to-face built-up cold-formed steel channel sections are becoming increasingly popular for column members in cold-formed steel structures; its applications include cold-formed steel trusses, space frames and portal frames. In such an arrangement, the independent buckling of the members is resisted by intermediate fasteners. In the literature, no research is available for such face-to-face built-up cold-formed steel columns. The issue is addressed herein. This paper presents the results of 36 experimental tests, conducted on face-to-face built-up cold-formed steel channel-sections covering a wide range of slenderness from stub to slender columns. A nonlinear finite element model is then described that shows good agreement with the experimental results. The finite element model includes material non-linearity, initial imperfections and modelling of intermediate fasteners. Both finite element and experimental results are compared against the design strengths calculated in accordance with the American Iron and Steel Institute (AISI), Australian and New Zealand Standards (AS/NZS) and Eurocode (EN 1993-1-3). The verified finite element model is used for the purposes of a parametric study comprising 90 models. The effect of fastener spacing on the axial strength was investigated. From the results of experiments and finite element investigations, it is shown that the design in accordance with the AISI & AS/NZS and Eurocode (EN 1993-1-3) is generally conservative by around 15%, however, AISI & AS/NZS and Eurocode (EN 1993-1-3) can be un-conservative by 8% on average for face-to-face built-up columns failed through local buckling. Highlights • Experimental tests were conducted on face-to-face built-up CFS channel-sections. • Initial geometric imperfections were measured for all test specimens using a laser scanner. • Nonlinear finite element models were developed which includes material nonlinearity and initial imperfections. • The column strengths were compared against the design strengths calculated in accordance with AISI & AS/NZS and EN 1993-1-3. • The AISI & AS/NZS and EN 1993-1-3 design strengths are generally conservative by around 15% but un-conservative by 8% on average for columns failed through local buckling. [ABSTRACT FROM AUTHOR]

The paper develops a detailed finite-element model for the reliable nonlinear collapse analysis of built-up cold-formed steel columns with discrete fastener connections. First, the main components of the computational model are discussed, including their available options and comparison between their results, followed by a rational justification for the options chosen in this study. Specifically, a detailed theoretical background is provided with conclusive comparisons of the options for enforcing end support conditions, applying contact conditions between the constituent plates, selecting connection elements for representing intermediate screw fasteners, and finally, the incremental load stepping and nonlinear solution schemes. The accuracy and performance of the proposed FE modelling strategy are verified against the experimental data, contributing to the calibration of the influencing parameters. The predictions of the proposed methodology are shown to be in excellent agreement with the test data in terms of the failure mode and the inelastic capacity curve up to ultimate capacity and beyond. Upon its successful calibration, the FE model is utilised to perform extensive parametric studies into the effects of various design parameters on the ultimate strength of built-up columns. This includes practical variations of cross-section dimensions, sectional slenderness, built-up section geometry, and fastener spacing. The parametric study results suggest a meaningful dependency of the ultimate capacity of built-up sections on the fastener spacing ratio, the critical buckling half-wavelength of the built-up section and the relative number of restrained components in the built-up configuration undergoing sectional buckling. • Numerical study of built-up sections with more than two component sections. • Influence on strength and failure mode of contact and connection modelling. • Determination of relevant design parameters for built-up sections via parametric studies. [ABSTRACT FROM AUTHOR]

Stainless steel is now widely used in construction as structural members in recognition to its unique beneficial properties such as corrosion resistance, higher strength, ductility, and negligible maintenance cost. Recent research on stainless steel has led to the evolution of a deformation based design rule, the Continuous Strength Method (CSM), which has been shown to perform well in predicting cross-sectional resistances but still requires considerable research to be used in predicting member resistances. The current paper proposes a new design method for lateral-torsional buckling (LTB) behaviour of welded stainless steel I-sections combining CSM design philosophy and traditional Perry-type concept used for column buckling. As part of the numerical study presented herein, nonlinear finite element (FE) models were developed and validated using available test results. Once the FE modelling technique was validated, a large number of reliable numerical results were generated to investigate effects of various factors on the resistance of members subjected to LTB. Obtained results showed that the cross-section slenderness λ ¯ p and the non-dimensional proof stress e have significant influences on LTB resistance. Effects of e was appropriately incorporated by introducing a correction factor to modify λ ¯ p . As LTB curves were mostly affected by λ ¯ p , it was included in the equation for calculating imperfection parameter η csm,LT , which is a key parameter to include member imperfections in Perry-type design equations. This new approach ensures appropriate utilization of strain hardening for stocky cross-sections and allows to avoid the complex process of calculating effective geometric properties for slender sections. All available test and generated numerical results were used to assess the performance the current European, the Australian and the proposed CSM based design rules for LTB. Comparisons clearly showed that the proposed approach performed significantly well in predicting the LTB response of stainless steel I-sections. [ABSTRACT FROM AUTHOR]

Fastener pre-tension is commonly used in the practical cases of aluminium alloy bearing-type connections with friction provided by treated surfaces. However, research on the effect of friction on the ultimate resistance is currently limited. In this paper, a numerical investigation on the structural performance and design of aluminium alloy double shear connections fastened by preloaded stainless steel swage-locking pins is presented. Finite element (FE) models were developed using Abaqus explicit dynamic packages and validated against the tests conducted previously. Prior to the numerical modelling of shear connections, the framework of aluminium alloy material properties has been studied. In order to simulate the full-range stress–strain relations and the failure of the tested aluminium alloys, two damage models were evaluated. The adopted model was then used to simulate the fracture occurred at the peak load or the post-peak stage in the double shear connection tests, and investigate their failure mechanism of bearing, shear-out and end-splitting. Upon validation, an extensive parametric study of 330 shear connections was conducted to investigate the effect of friction and pin configuration on the structural performance of shear connections made of different aluminium alloy grades. The values of the friction and pin hole resistance at the ultimate loads were comprehensively discussed. The numerically derived ultimate resistances were also compared with the current design equations, which were shown to provide conservative and scattered results due to the lack of consideration of the friction effect. A new design method was proposed with the friction effect incorporated, resulting in accurate predictions of ultimate resistance for aluminium alloy shear connections with preloaded stainless steel swage-locking pins. • Finite element models of aluminium alloy double shear connections fastened by preloaded swage-locking pins developed. • Ductile damage models in Abaqus calibrated. • Parametric study of 330 shear connections conducted. • Effects of friction on connection resistance analysed. • Design equations of predictions of ultimate resistance for aluminium alloy shear connections proposed. [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]

Earthquake causes wide and severe damage to building structures due to the great ground motion which is also one of inducements of other extreme events such as fire, tsunami and debris flow. The Multi-extreme loads such as earthquake and the subsequent actions could be much more destructive than the earthquake action itself. Regarding the safety of properties and lives, in order to evaluate building structures subjected to post-earthquake actions, it is important to accurately assess the partial damage caused by earthquake on structural components. By using experimental method, two groups of flange-welded/web-bolted steel I-beam-to-hollow-tubular-column connections were investigated under static and cyclic loadings at ambient temperature. The flexibility and strength of the connections are measured, while the damage phenomena and failure modes are explored during the tests. The connection damage was found to be a cumulative process with fracture extending. The increasing damage led to significant gradual degradation of the connection mechanical properties. The quantificational evaluation was also carried out to investigate the connection damage degree according to different loading intensities. Using finite element (FE) modelling, study was carried out and validated by the experimental results while a good agreement was achieved. The test and FE modelling results in this study provided detailed understanding of the performance of the flange-welded/web-bolted steel tubular connection. It can be used for further investigation of the connections subjected to combined actions of extreme loading such as post-earthquake fire. [ABSTRACT FROM AUTHOR]

This paper investigates, for the first time, the behaviour and design of railway double track open timber floor plate girder deck steel bridges under combined buckling modes including web distortional buckling. A 3-D finite element model has been developed for the railway bridges, which accounted for the bridge geometries, initial geometric imperfections, material nonlinearities of the bridge components, bridge boundary conditions, interactions among bridge components and bridge bracing systems. Most of the aforementioned parameters are not incorporated in current design codes of railway bridges, which are credited to this study. The simply supported bridges investigated had a span of 30m, a width of 7.2m and a depth of 3.12m. The bridge components comprising main plate girders, stringers, cross girders, connections, bracing members, stiffeners, bearings, and field splices were designed following the design rules specified in the European Code for steel bridges. The live load acting on the bridge was Load Model 71, which represents the static effect of vertical loading due to normal rail traffic as specified in the European Code. The finite element model of the double track bridge was developed depending on additional finite element models, developed by the author, for small and full-scale plate girder steel bridge tests previously reported in the literature. Ultimate loads, load-mid-span deflection relationships, failure modes, stress contours of the double track bridge as well as of the small and full-scale tests were predicted from the finite element analysis and compared well against test results. Parametric studies were performed on the railway bridges highlighting the effects on the structural behaviour and ultimate loads carried by the bridges owing to the change in the bridge geometries, slenderness and steel strength. The paper presents a complete piece of work regarding the finite element analysis and design of railway steel bridges, which can be used for further parametric studies, finite element analyses and investigations of the bridges under different loading and boundary conditions. The parametric study has shown that the presence of web distortional buckling causes a considerable decrease in the ultimate load of the steel bridges. It is also shown that the use of high strength steel offers a considerable increase in the ultimate loads of less slender steel bridges. The study has also shown that the design rules, loading and recommendations specified in the European Code provide accurate and conservative estimations for the design of railway steel bridges, except for the bridges failing mainly by web distortional buckling [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the influence of manufacturing on the buckling and post-buckling behaviour of thin-walled, columns made from CFRP. Static compression was performed on channel-section profiles with dimensions equal to 80 mm × 38 mm × 240 mm (web × flange × length of profile) composed of an eight-layered symmetric laminate [45/−45/45/−45] and a thickness of 0.92 mm. The samples were manufactured by two distinct methods: 1) conventional lamination of a channel, and 2) by manufacturing a square cross-section and cutting it into two channels. Buckling tests showed that the second method is 2.5 times more material efficient and provides 18 % higher buckling resistance. Moreover, three finite element models were implemented—a​ model that did not include any prestress (residual stresses), and simulations of the channel and square cross sections where residual stresses were included. The conventional channels matched the numerical results of the model which did not include any prestress (nominal error of 1.8%). Whereas the buckling response of the square cross section samples were substantially influenced by the residual stresses (18.1% increase in buckling load). These results have significant implications for the design/production of CFRP channels with enhanced buckling performance. • Buckling analysis of thin-walled, carbon fibre channel cross-section profiles. • Two manufacturing techniques: standard lamination and half square profiles. • Three element models compared with experimental results. • Residual stress from production enhances buckling resistance by 18%. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) weatherboard claddings are popular in industrial and housing applications, and CFS weatherboard claddings with spans of up to 1500 m are now being used in New Zealand. However, there are limited experimental data on their behaviour under uplift and cyclic wind loading. This paper presents a detailed experimental investigation to investigate the wind-uplift capacity of clip-fixed CFS weatherboard cladding. A total of 24 new tests were carried out on a series of weatherboard claddings under static wind uplift and cyclic pressure using a Pressure Loading Actuator (PLA). Two different cladding thicknesses (0.48 mm and 0.55 mm) were considered in the experimental investigation. The material properties of the claddings were determined using tensile coupon tests and the initial geometric imperfections were measured using a laser scanner. Tests revealed that the weatherboard clips are susceptible to local failure in the region of the tek screws where two adjacent cladding sheets are connected, followed by the global failure of the cladding assembly at ultimate wind pressure. The global failure was initiated by the shear failure of the weatherboard clips. A nonlinear finite element model was also developed for weatherboard claddings under static wind uplift pressure, which showed reasonable agreement with the experimental results. The non-linear material properties and initial imperfections were included in the finite element model. A parametric study was conducted comprising 264 finite element models to investigate the effect of thickness, yield stress and cladding span on the wind uplift capacity of such weatherboard claddings. It was found that the width of pan, yield stress and cladding thickness are important factors in influencing the wind-uplift capacity of such weatherboard cladding profiles. The experimental results and the numerical model can be used by the researchers and practising engineers to predict the wind-uplift capacity of such weatherboard claddings under static wind uplift and cyclic wind pressures. • An experimental program was carried out on a series of weatherboard claddings under static wind uplift and cyclic pressure using a Pressure Loading Actuator (PLA). • A total of 24 tests were conducted and reported herein. Two different cladding thicknesses (0.48 mm and 0.55 mm) were considered in the experimental investigation. • A nonlinear finite element model was also developed for weatherboard claddings under static wind uplift pressure, which showed good agreement with the experimental results. • A parametric study was conducted comprising 264 finite element models. • Load-span tables are also proposed for ultimate limit state of failure for weatherboard claddings. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study into the behaviour of rubberised concrete-filled steel tubes (RuCFST), incorporating concrete with relatively high rubber replacements of up to 60% of mineral aggregates by volume. Axial compression, eccentric compression, and three-point bending tests on circular specimens are carried out and the results are used to validate the nonlinear procedures adopted in continuum finite element (FE) models of RuCFST members. A constitutive material model specific for confined rubberised concrete and associated modelling techniques, developed from existing procedures for concrete-filled steel tubes (CFST), is proposed for RuCFST members. The modelling techniques involve different damage definitions including low strength concrete with high rubber replacements in compression and bending. It is shown that the proposed modelling procedures can predict reliably the structural behaviour of circular RuCFST members under combined axial-bending conditions. The numerical procedures are then employed in undertaking a detailed parametric assessment for RuCFST cross-sections. The results are used to appraise current design procedures and to propose modifications that provide improved capacity predictions for a wide range of properties and loading conditions. [ABSTRACT FROM AUTHOR]

The Continuous Strength Method (CSM) is a recently developed strain based design technique that produces accurate predictions for cross-section resistances for stocky sections against individual and combined actions. This paper numerically investigates the behaviour slender stainless steel cross-sections subjected to combined loading i.e. compression plus bending. Generated numerical results and available test results were used to develop CSM formulations to tackle the conservatism shown by the current international codes in predicting resistances of slender sections. Keeping the basic design philosophy in line with the current CSM design technique, interaction equations are re-calibrated herein for slender stainless steel hollow sections. [ABSTRACT FROM AUTHOR]

The behaviour of cold-formed normal- and high-strength steel columns with square and rectangular hollow sections (SHSs and RHSs) at elevated temperatures was investigated numerically in this paper. A finite element model was developed and validated against experimental results for the cold-formed steel SHS and RHS stub and long columns tested at ambient and elevated temperatures. Parametric studies were subsequently conduced on cold-formed normal- and high-strength steel SHS and RHS columns with various cross-section slenderness and member slenderness at elevated temperatures ranging from ambient to 800 °C. Based on the numerical results and experimental results reported in literature, the applicability of existing design approaches in European and North American standards to the columns at elevated temperatures was evaluated. The evaluation shows that the approaches in standards provide quite conservative strength predictions for the cold-formed normal- and high-strength steel SHS and RHS columns at elevated temperatures except for the overestimation of cross-sectional resistance obtained based on the North American standard. Modified design approaches were proposed to improve the accuracy of strength predictions and can be safely applied to generate designs for the columns under various elevated temperatures. • Cold-formed SHS and RHS columns under elevated temperatures were investigated. • A FE model was validated for accurately predicting the structural behaviour. • Results of FE parametric studies and experiments were used to assess design methods. • Accuracy of design methods was discussed. • Modified design methods for more accurate strength predictions are developed. [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]

Comprehensive experimental and numerical investigations on mechanical properties of Q690 and Q460 high strength steel (HSS) sections and stub column behaviour of the 14 hybrid HSS welded T-section stub column specimens are presented in this paper. A total of six coupon specimens were longitudinally and transversely machined from HSS Q690 and Q460 steel parent plates respectively. Furthermore, initial local geometric imperfections measurements were also carried out. In parallel with the experimental investigation on stub column behaviour, extensive numerical studies were carried out by developing finite element (FE) models to replicate the experimental tests results. The validation of the FE models was confirmed against the obtained experimental data. To supplement the experimental data, validated FE models were used in the parametric studies, by which numerical specimens with a larger range of cross-section dimensions can be generated. Subsequently, cross-section classification slenderness limits for outstand plate elements under compressive load set out in structural steel design codes of EN 1993-1-12, ANSI/AISC 360-16, AS 4100 were evaluated against the experimental and numerical data. In addition to the design codes, design methods such as direct strength method (DSM) and continuous strength method (CSM) were also assessed to evaluate the applicability and suitability for hybrid HSS welded T-section stub columns. It was found that the current codified slenderness limits in EN 1993-1-12, ANSI/AISC 360-16 as well as AS 4100 for slender/non-slender outstand flat elements can generally be adopted for hybrid HSS welded T-section under compression. CSM provide under-estimated compressive resistance in comparison to the design codes and DSM for slender sections. • 14 experimental tests of hybrid HSS welded T-section stub columns have been performed. • Numerical models for hybrid HSS welded T-section stub columns have been developed. • Extensive parametric studies have been carried out. • Design codes as well as design approaches of DSM and CSM have been assessed. [ABSTRACT FROM AUTHOR]

Abstract: An experimental study on stiffened plates subjected to combined action of in-plane load and lateral pressure is described in the paper. Details of the experiments and finite element analyses of the specimens tested are presented along with the results. Measurements of initial imperfection in the specimens have been made and included in the analyses. Results show that lateral load carrying capacity of stiffened plate drops with increase in axial load and vice-versa. It is found that plate slenderness ratio has significant influence on the ultimate load capacity of stiffened plates subjected to both in-plane load and lateral pressure. Increase of plate slenderness ratio results in a decrease of ultimate load capacity of stiffened plate. The accuracy of the finite element modelling is established by comparing the results with the corresponding experimental values. [Copyright &y& Elsevier]

Abstract: Experimental and numerical investigation of cold-formed lean duplex stainless steel flexural members is presented in this paper. The test specimens were cold-rolled from flat plates of lean duplex stainless steel with the nominal 0.2% proof stress of 450MPa. Specimens of square and rectangular hollow sections subjected to both major and minor axes bending were tested. A finite element model has been created and verified against the test results using the material properties obtained from coupon tests. It is shown that the model can accurately predict the behaviour of lean duplex stainless steel flexural members. An extensive parametric study was carried out using the verified finite element model. The test and numerical results as well as the available data on lean duplex beams are compared with design strengths predicted by various existing design rules, such as the American Specification, Australian/New Zealand Standard, European Code and direct strength method for cold-formed stainless steel. Reliability analysis was performed to evaluate the reliability of the design rules. It is shown that these current design rules provide conservative predictions to the design strengths of lean duplex stainless steel flexural members. In this study, modified design rules on the American Specification, Australian/New Zealand Standard, European Code and direct strength method are proposed, which are shown to improve the accuracy of these design rules in a reliable manner. [Copyright &y& Elsevier]

Abstract: Trapezoidal sheeting of thin-walled steel is applied frequently for roofing and cladding. As such, it is loaded by a concentrated load (at the support) and a bending moment. A recently developed model to predict the sheeting's failure behaviour leaves the question open whether mode jumping (the phenomenon where a plate dynamically changes its buckling mode during an increasing load) should be taken into account in the model. This article presents the analytical and finite element modelling of square and long plates, which, depending on the boundary conditions, may represent the compressed flange of trapezoidal sheeting. The analytical modelling is based on the combination of several displacement functions and using the principle of minimal potential energy. Hereafter the stability of each part of the resulting equilibrium curves is determined. A spin-off of the analytical model is an analytical expression for a current curve-fitted based prediction formula for the post/pre-buckling stiffness ratio by Rhodes. Furthermore, the accuracy range of a solution by Williams and Walker for the far-post buckling behaviour can be confirmed. The finite element modelling has been carried out by implicit dynamic, and explicit (dynamic) simulations. Both for the load levels and the buckling mode sequences, the analytical and finite element models give equivalent results. It is concluded that for the specific boundary conditions that represent the situation of a compressed flange for trapezoidal sheeting, it is very likely that mode jumping will not occur. [Copyright &y& Elsevier]

Experimental and numerical studies on the buckling behaviour of stiffened panels under four point bending during creep age forming (CAF) have been carried out in this study for the first time. The experimental programme comprised buckling tests of five different sizes of stiffened panels of aluminium alloy 7050 at room temperature and buckling tests with different loading degrees in CAF including the loading, heating and creep-ageing stages. The buckling mode, the strain distribution and the strain evolution of the stiffened panel were obtained from the experiments, using digital image correlation (DIC) for the room temperature tests and strain gauges for the CAF tests. The effect of stiffener height and stiffener thickness and the effect of the heating and creep-ageing stages in CAF on the buckling behaviour have been investigated and discussed. It was found that buckling mode varied from one half-wave cosine mode in the elastic loading to three half-wave cosine mode with the increase of buckling stress from elastic to plastic region, and during CAF buckling mainly occurred and grew in the heating process. The corresponding non-linear finite element (FE) simulations of stiffened panels at room temperature and ageing temperature (160 °C) have also been carried out, and the FE results of buckling strain and buckling mode shape show a good agreement with experimental results. The non-linear FE method can provide accurate results of buckling strain and formability limits for cold forming and CAF processes, which can be used to guide the structural design of stiffened panels. • First buckling experiments of stiffened panels under bending in creep age forming. • Buckling mode changes from one half-wave in elastic region to three in plastic region. • During creep age forming, buckling begins and grows mainly in the heating stage. • Non-linear FE results of buckling mode and strain match experimental results well. • Ageing temperature has significant effects on buckling stress but little on strain. [ABSTRACT FROM AUTHOR]

Abstract: In the present work, a set of finite element analyses (FEA) was carried out, using Abaqus to reproduce the mechanical behaviour of integrally stiffened panels when subject to longitudinal compression. Since most fabrication processes, such as welding, introduce distortions and affect the material properties, the sensitivity to these defects was assessed. Different shapes and magnitudes of the initial geometrical imperfections were tested and a high sensitivity was observed to both factors on the ultimate load. The existence of a heat affected material showed no influence on the ultimate strength of the tested panels. [Copyright &y& Elsevier]

Abstract: Cold-formed profiled steel roof sheeting can be directly connected to the top chord of a steel truss through powder-actuated shot nails or self-tapping screws. The lap shear behaviours of both shot nailed and screwed connections are studied in this paper using both testing and FE analysis at ambient and elevated temperatures. The studies for screwed connections show that four components of loading capacity, including bearing force between thin sheet and screw shank, frictional force between washer and thin sheet, frictional force between thin sheet and thick plate, and the bearing force by the tilting of thin sheet are identified and quantified. The studies for shot nailed connections show strong interactions among washer, shot nail, thin sheet and supporting plate. The protuberance feature developed during the nail driving process, which causes material in thick plate flowing upward, has a significant positive contribution to the loading capacity of the connection. [Copyright &y& Elsevier]

Abstract: This paper discusses the nonlinear analysis of normal and high strength cellular steel beams under combined buckling modes. A nonlinear 3-D finite element model has been developed, which accounted for the initial geometric imperfection, residual stresses and material nonlinearities of flange and web portions of cellular steel beams. The nonlinear finite element model was verified against tests on cellular steel beams having different lengths, different cross-sections, different loading conditions and different failure modes. Failure loads, load–mid-span deflection relationships and failure modes of cellular steel beams were predicted from the finite element analysis. An extensive parametric study involving one hundred and twenty cellular steel beams was performed using the verified finite element model to study the effects of the change in cross-section geometries, beam length and steel strength on the strength and buckling behaviour of cellular steel beams. The results of the parametric study has shown that cellular steel beams failing due to combined web distortional and web-post buckling modes exhibited a considerable decrease in the failure loads. It is also shown that the use of high strength steel offers a considerable increase in the failure loads of less slender cellular steel beams. The failure loads predicted from the finite element model were compared with that predicted from Australian Standards for steel beams under lateral torsional buckling. It is shown that the Specification predictions are generally conservative for normal strength cellular steel beams failing by lateral torsional buckling, unconservative for cellular steel beams failing by combined web distortional and web-post buckling and quite conservative for high strength cellular steel beams failing by lateral torsional buckling. [Copyright &y& Elsevier]

Abstract: Cold-formed profiled steel roof sheeting can be directly connected to the top chord of a steel roof truss through self-tapping screws. At ambient temperatures, neither EN 1993-1-8 nor EN 1993-1-3 can be used directly for this type of connection. Besides, no design rules are available in EN 1993-1-2 for designing screwed connections in fire. A 3D Finite Element (FE) model for a single-lap shear screwed connection is developed using ABAQUS software. After the validation by tests, the model is used to predict the ultimate resistance of connections at both ambient and elevated temperatures. Further, the effects of edge and end distances on the connection resistance are investigated. Based on the analyses results, revised design equations for predicting the connection resistance are proposed. The design resistance is calibrated by testing and FE analyses results according to the procedure given in EN 1990 and the partial safety factor is derived. [Copyright &y& Elsevier]

The stability and design of steel equal-leg angle section members subjected to uniaxial bending are studied herein. An experimental investigation, comprising material testing, initial geometric imperfection measurements and physical tests on hot-rolled steel equal-leg angle section beams is first presented. The test results, in combination with existing experimental data on steel equal-leg angle section beams collected from the literature, are then used for the validation of numerical (shell finite element) models, developed within the commercial package ABAQUS. Next, a numerical parametric study is presented considering both hot-rolled and cold-formed steel angle section beams with a wide range of slenderness values. In major-axis bending, both lateral-torsional and local buckling were observed, with the former characterised by lateral deflection and twist of the cross-section along the member length but no cross-section deformation and the latter by relative twist and transverse bending of the outstands. In minor-axis bending, lateral-torsional buckling and Brazier flattening were observed, with the latter characterised by splaying of the outstands. Note that, for equal-leg angles under minor-axis bending, lateral-torsional buckling is dominant when the cross-section tips are in compression, while Brazier flattening is more influential when the cross-section tips are in tension. When designing for major-axis bending according to Eurocode 3, both local and lateral-torsional buckling are considered; it is shown herein that equal-leg angle section beams under major-axis bending can be designed using a normalised slenderness based on the minimum of the local and lateral-torsional elastic buckling moments, while also considering the ratio of the local to the lateral-torsional elastic buckling moments. For minor-axis bending, Eurocode 3 only requires cross-section checks; this is found to result in unsafe predictions in some cases. It is shown that both safer and more accurate resistance predictions can be achieved when lateral-torsional buckling and Brazier flattening are accounted for in the design of equal-leg angle section beams under minor-axis bending, using a normalised slenderness, based on the minimum of the lateral-torsional and Brazier flattening critical buckling moments. Finally, new design proposals for steel equal-leg angle section beams, covering both major- and minor-axis bending, are developed and verified against the experimental and numerical results. The proposed design rules are shown to offer substantially more accurate and consistent resistance predictions compared to existing codified design rules. The reliability of the new design provisions, with a recommended partial safety factor γ M1 = 1. 0 , is verified following the EN 1990 procedure. • Critical buckling behaviour of equal-leg angles under uniform bending is described. • Experiments on hot-rolled steel equal-leg angle section beams are presented. • Numerical parametric study considering steel angle section beams is described. • Experimental and numerical results are used to develop a new design approach. • Accuracy and reliability of the new proposals is verified in accordance with EN 1990. [ABSTRACT FROM AUTHOR]

The structural behaviour and design of cold-formed steel square and rectangular hollow section (SHS and RHS) beam–columns, made of both normal and high strength steels, are investigated in the present study through a comprehensive numerical modelling programme. Refined finite element (FE) models were first established and calibrated against a collection of existing cold-formed steel member test results from the literature. Following this, an extensive parametric study was undertaken to expand the cold-formed steel beam–column data pool, covering a wider range of steel grades, cross-section geometries, member slendernesses and loading combinations. Results from the parametric study were then used to examine the accuracy of the current codified beam–column design methods, provided in the European Standards EN 1993-1-1 (2005) and EN 1993-1-12 (2007) as well as the American Specification AISC 360-16 (2016). The comparisons revealed that the codified design rules provide varying levels of accuracy in predicting the ultimate resistances of cold-formed steel beam–columns depending on the steel grade. An improved design approach, compatible with current codified design rules in EN 1993-1-1 (2005), is proposed that features (1) recently developed column buckling curves that reflect the increasing normalised column buckling resistance with increasing steel yield strength; (2) bending moment resistances calculated using the Continuous Strength Method (CSM) and (3) new interaction curves for cold-formed steel beam–columns, which are anchored to these more accurate end points. The newly proposed design approach is shown to yield more accurate and consistent resistance predictions over current design provisions for cold-formed steel SHS and RHS beam–columns made of different steel grades, and its reliability has also been statistically verified in accordance with EN 1990. • Numerical study on cold-formed steel SHS and RHS beam–columns was conducted. • Modified EC3 column design approach was extended to columns in steel grades up to S1100. • Bending resistance predictions from CSM were adopted in beam–column design. • New beam–column design approach was developed to account for influence of steel grade. • Current EC3 partial safety factor was shown to be applicable to design proposal. [ABSTRACT FROM AUTHOR]

The design development of new cold roll formed sections can lead to a significant reduction in material costs if the sections are optimised for strength performance considering the effect of shapes and change of material properties by cold working during the manufacturing process. In this paper, the buckling and ultimate strengths of cold roll formed channel and zed sections with intermediate stiffeners under distortional bending were studied using experimentally validated Finite Element (FE) models. The section strength was optimised using FE modelling and optimisation based on Design Of Experiments (DOE) and response surface methodology. A nonlinear FE model was first developed for a referenced section subject to four-point bending tests and the section's dimensions and material properties were defined as geometric parameters using the DOE technique. A response surface was then used to determine the influences of the stiffeners' location, shape, size, and cold working at the section corners and stiffener bends during the manufacturing process. A multi-objective genetic algorithm method was deployed to obtain optimal shapes for the sections with maximum buckling and ultimate strengths while keeping the same amount of material used. The results revealed that the ultimate bending moment capacities could be enhanced up to 17% and 25% for the channel and zed sections, respectively. Including the cold working effect had considerable enhancement in the ultimate moment capacities, with a maximum increase of 5%. The results of this study clearly demonstrated an efficient and effective approach to optimise design for strength performance of cold roll formed sections. • FE simulations of channel and zed sections were established and compared with test results. • FE models accounted for both geometric shapes and change of material properties due to cold working. • Strength of the sections were investigated by FE modelling integrated with design of experiments and response surface. • Optimal sections were achieved by using multi-objective genetic algorithm optimisation. [ABSTRACT FROM AUTHOR]

The cross-sectional behaviour and residual compression resistances of S690 high strength steel welded I-section stub columns after exposure to elevated temperatures up to 950 °C have been investigated, underpinned by testing and numerical modelling, and fully presented in this paper. The testing programme used three S690 high strength steel welded I-sections — I-80 × 60 × 5, I-100 × 100 × 5 and I-140 × 70 × 5, and for each aforementioned I-section, seven geometrically identical stub column specimens were prepared and tested after exposure to different levels of elevated temperature (including 30 °C, 300 °C, 600 °C, 700 °C, 800 °C, 900 °C and 950 °C). This was followed by a numerical modelling programme, where finite element models were developed and validated against the post-fire stub column test results and then adopted to conduct parametric studies to generate further numerical data over a wide range of cross-section dimensions. Given that there are currently no available design standards for high strength steel structures after exposure to elevated temperatures, the relevant ambient temperature design rules, as set out in the European code, American specification and Australian standard, were assessed, using post-fire material properties, for their applicability to S690 high strength steel welded I-section stub columns after exposure to elevated temperatures up to 950 °C. The results of the assessments revealed that (i) all three sets of codified ambient temperature slenderness limits for internal and outstand plate elements in compression are generally accurate when used for cross-section classification of S690 high strength steel welded I-section stub columns after exposure to elevated temperatures and (ii) the ambient temperature local buckling design rules (i.e. slenderness limits in combination with effective width methods), as set out in the three considered design standards, are capable of providing accurate and consistent post-fire compression resistance predictions for S690 high strength steel welded I-section stub columns. • The post-fire behaviour of S690 HSS welded I-section stub columns is investigated. • A total of 21 post-fire stub column tests were performed. • FE modelling and parametric studies were conducted. • The codified ambient temperaure design rules were evaluated, indicating applicability. [ABSTRACT FROM AUTHOR]

This study deals with the behaviour of duplex stainless steel bolted connections. The aim of the study is to respond to the question if the current stainless steel design specifications are able to predict the behaviour of such connections. Firstly, the net cross-section capacity of duplex stainless steel plates subjected to tensile loading are presented. They were conducted to obtain the stress–strain curves and tensile fracture behaviour used to support the finite element (FE) fracture simulations. Secondly, nonlinear FE models are developed for duplex stainless steel bolted connections subjected to tensile loading. The FE models are validated against experimental data in terms of load–displacement curves, failure modes and ultimate loads. Then, a numerical parametric study that consists of 133 duplex stainless steel grade EN 1.4162 bolted connection specimens is carried out. The failure modes of bolted connections are carefully examined, including combined tear out and bearing, bearing and net section, looking at the influence of parameters such as end distance, edge distance and spacing between the bolts in the connections. The results are compared to the design rules prescribed in the current stainless steel design specifications. Generally, it is found that the Australian/New Zealand (AS/NZS), American (SEI/ASCE) Specification and European codes conservatively predict the ultimate strengths of the bolted connections, whereas the strengths predicted by the AS/NZS and SEI/ASCE specifications are overall more accurate and less scattered. • Net cross-section capacity of duplex stainless steel plates are presented. • Numerical models of duplex stainless steel bolted connections are validated. • Duplex stainless steel bolted connections are parametrically studied. • The current design specifications provide conservative strength predictions. • The current design specifications generally predict the correct failure modes. [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]

Cold-formed steel square and rectangular hollow section (SHS/RHS) studs are often used to replace the conventional lipped channel section studs in light gauge steel frame (LSF) wall systems to meet the required high load demand. To ensure adequate structural fire resistance of SHS/RHS stud walls, four full-scale fire tests were previously completed under standard fire conditions. However, the full-scale fire tests are expensive and time-consuming, while the complex fire performance cannot be adequately explained through test observations and results alone. Hence, a numerical study was undertaken by developing simplified and sheathed stud finite element (FE) models of tested walls. This paper provides the details of the developed models of LSF walls made of SHS/RHS studs at both ambient and elevated temperatures and a comparison with experimental results. The validated models were used to highlight the advantage of using SHS/RHS studs in cavity insulated stud walls and further understand the factors that may affect the fire resistance of LSF walls, such as steel grade and stud depth. In addition to the simplified stud model, advanced modelling techniques were used to explore the effects of sheathing and localised plasterboard fall-off on the wall behaviour in fire. Overall, this paper presents a numerical study of SHS/RHS stud walls and the simplified stud model developed in this paper can be used to predict the fire performance of other SHS/RHS stud walls with similar wall configurations. • Developed simplified & sheathed stud FE models for ambient capacity of stud walls. • Developed transient thermal FE models for time-temperature curves of wall components. • Developed transient thermal-structural coupled models for FRL of SHS/RHS stud walls. • Examined the need to include sheathing and localised board fall-off in wall models. • Investigated the factors affecting the fire resistance and wall behaviour in fire. [ABSTRACT FROM AUTHOR]

This paper explores an attempt to investigate the structural behaviour and design of equal-leg stainless steel angle columns fabricated by the laser-welding of individual hot-rolled plates and by hot-rolling process. The studies cover columns with pin-ended boundary conditions exposed to pure axial compression. An advanced and realistic finite element model able to replicate the buckling features of stainless steel angle columns is developed and validated against available experiments collected in the literature. Employing the validated finite element model, quantitative numerical parametric studies, considering minor-axis flexural buckling, as well as flexural–torsional buckling, are performed. Based on comprehensive benchmark data, the accuracy, safety and applicability of the existing column design procedures provided in the European and North American structural stainless steel codes are assessed. The evaluation results reveal that the North American codified design procedures lead to conservative and scattered resistance predictions, thereby demonstrating a need for their improvement. As a result of conducted studies, the new criteria for design of pin-ended hot-rolled and laser-welded stainless steel equal-leg angle columns are proposed. Their suitability for inclusion in the European structural stainless steel design code is confirmed by statistical reliability analyses in accordance with EN 1990. • Structural response of pin-ended hot-rolled and laser-welded stainless steel angle columns studied. • FE parametric studies including geometric and material nonlinearity carried out. • Accuracy of European and North American codified procedures assessed. • Proposal provided for European buckling curves. • Reliability analysis of proposed design criteria performed. [ABSTRACT FROM AUTHOR]

This paper explores the use of the finite element software package ABAQUS/Explicit to simulate the behaviour and strength of power-actuated fastener (PAF) connections joining cold-formed steel sheet to hot-rolled steel plate subjected to monotonic shear loading. The finite element (FE) models are developed for the simulation of the entire process including both installation and loading stages. The fastener is firstly driven into the steel materials to consider the initial plastic deformations around the contacts between steel plates and fastener caused by dynamic impact. Subsequently, monotonic shear loading is applied to the PAF connections until failure by a displacement control at a low speed. Various aspects of the FE models such as fracture model of the materials, loading rate, mesh sensitivity are calibrated to optimise the computing time and improve the accuracy of the FE models. The simulations are validated against experiments conducted in a separate study by the authors, and good agreement between the test and numerical results is achieved. The accurate and reliable FE models in this study are able to simulate and provide insights into the shear behaviour of the power-actuated fastener connections in terms of initial stiffness, maximum shear capacity, failure modes as observed in the experiments (i.e., bearing, shear fracture, and pull-out of the fastener), ductility, and damage patterns of the connectors. It is demonstrated that FE analysis can therefore be used to extend experimental data in a parametric study and to optimise the design of PAF connections in shear. [Display omitted] • A FE study into shear behaviour of Power-Actuated Fastener connections is conducted. • ABAQUS/Explicit is used to simulate the installation and load application stages. • Three limit states are simulated: pull-out, shear fracture and bearing failures. • The accuracy and robustness of the FE model are validated and optimised. [ABSTRACT FROM AUTHOR]

Unequal-leg angles can be used to provide more efficient design in specific cases, but the behaviour of unequal-leg angles has received much less attention than equal-leg angles. This paper studies the flexural and torsional buckling modal participation and investigates the structural behaviour of aluminium alloy unequal-leg angle columns. The experimental programme, which was carried out on two unequal-leg angle cross-sections, included material coupon tests, initial geometric imperfection measurements and a total of eight column tests. The test setup, procedure and results are fully reported. Following the experimental investigation, numerical models were developed and validated against the test results. Upon validation, a series of parametric studies were carried out to analyse the influence of width-to-thickness ratio and aspect ratio on the flexural and torsional buckling modal participation. The ultimate resistances obtained from simulations were used to assess the accuracy of the current design provisions given in the European standard for aluminium alloy structures. The result comparison shows that the existing design provisions yield inaccurate predictions for unequal-leg angle columns. Considering mode interaction, a more accurate and convenient design method was proposed for unequal-leg angle columns. • Results of tests on aluminium alloy unequal-leg angle columns were presented. • Existing design provisions in EC9 for unequal-leg angle columns were assessed. • Buckling modal participation for unequal-leg angle columns was investigated. • A revised design method with accuracy and convenience was proposed. [ABSTRACT FROM AUTHOR]

The membrane residual stresses and local buckling behaviour of S960 ultra-high strength steel welded I-section stub columns have been investigated through a comprehensive testing and numerical modelling programme. The testing programme included material testing, membrane residual stress measurements, initial local geometric imperfection measurements and sixteen stub column tests. On the basis of the measured data, a membrane residual stress predictive model was developed. Following the testing programme, a numerical modelling programme was conducted, where finite element models were firstly developed and validated against the test results and then adopted to conduct parametric studies to generate further numerical data. The obtained test and numerical data were used to assess the applicability of the relevant design provisions for S700 (or S690) high strength steel welded I-section stub columns, as given in the European code, American specification and Australian standard, to their S960 ultra-high strength steel counterparts. The assessment results generally revealed that (i) all three sets of codified slenderness limits can be accurately and consistently used for cross-section classification of S960 ultra-high strength steel welded I-section stub columns and (ii) the local buckling design provisions in the three design codes also lead to accurate and consistent cross-section compression resistance predictions. • The membrane residual stresses and local buckling of S960 ultra-high strength steel welded I-sections were studied. • Two sets of membrane residual stress measurements and sixteen stub column tests were conducted. • A new membrane residual stress predictive model was proposed. • FE models were developed and validated against the test results and then employed to conduct parametric studies. • The applicability of the codified slenderness limits and effective width methods was assessed. [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]

Steel cylindrical shell structures such as silos and tanks are very sensitive to geometric imperfections and prone to a plastic instability failure known as elephant's foot (EF) buckling. This type of buckling arises under axial compression. The aim of this paper is to explore the plastic collapse response in conical shells with low semi-vertex angle values under compression. In a first step, the initial geometric imperfection shapes that dictate which plastic mechanisms arise were identified using finite element (FE) models. In a second step, a parametric study reported two plastic collapse mechanisms and showed that the elephant's foot plastic collapse mechanism is the most likely to appear in compressed conical shells with low d / t values, followed by the Yoshimura collapse mechanism, more common with larger d / t values. Finally, a practical model in which the parameters have been adjusted from numerical models has been derived for the elephant's foot plastic mechanism. This model provides the load-deformation behaviour of compressed conical shells at the post-collapse region. The load vs. end-shortening curves provided by the model have been validated through comparison with curves given by the FE models. The good agreement between the results proves the efficiency of the practical model to predict the collapse response of conical shells. • Different buckling categories have been obtained for two different thicknesses. • Sensitivity to imperfections has been analysed and different imperfection amplitudes have been considered. • Elephant foot mechanism is the most common failure that arises with small imperfections. • The Yoshimura mechanism mainly appears with large initial imperfections. • A model to define the compressive load vs. end-shortening displacement response for conical shells has been developed. [ABSTRACT FROM AUTHOR]

Currently, there is still no explicit design approach for cold-formed stainless steel columns with equal-leg angle sections in Europe. A comprehensive numerical investigation, validated by the available experiments collected in the literature, has therefore been undertaken to provide benchmark data for the assessment of design procedures for cold-formed stainless steel angle columns currently adopted in European and Australian codes. Minor-axis flexural buckling, as well as flexural-torsional buckling have been considered. In total, 27 different cross-section sizes covering both slender and non-slender sections, and a wide range of column slenderness values have been examined including austenitic, duplex and ferritic grades. On the basis of the experimental and numerical results, new design recommendations for cold-formed stainless steel equal-leg angle columns have been made per family of stainless steel. The suitability of the proposals was confirmed by means of a reliability analysis. • FE parametric studies including geometric and material nonlinearity performed. • Accuracy of European and Australian codified procedures assessed. • Proposal provided for different buckling curves per stainless steel family. • Reliability analysis of existing and proposed design recommendations carried out. [ABSTRACT FROM AUTHOR]