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Nowadays, the codified procedure for design of centrically compressed cold-formed stainless steel (CFSS) built-up members is absent in Europe. Besides, there are no published research information and experimental data in this structural area. This paper focuses on a comprehensive experimental investigation of closely spaced CFSS built-up columns and addresses their flexural buckling capacity about the minor principal axis. Two series with a total of 36 built-up members were assembled, each formed by two discontinuously and directly connected channel chords oriented back-to-back to form an I-section. The chords were press-braked from flat strips of austenitic stainless steel EN 1.4301 as non-slender channel sections. The chords were uniformly interconnected by bolts or by welds. To identify the effects of interconnection spacing on chords' composite action, the overall and chord slenderness ratios were varied. Material properties, cross-section response and initial imperfections were quantified before testing. As a result, the overall flexural buckling without any local-overall interactions was observed as the dominant failure mode. All findings were used in the accompanying paper [1] to establish qualitative data base through numerical simulations of flexural buckling tests. Additionally, a quantitative accuracy assessment of the design methods for carbon steel built-up columns provided in Eurocode and American Specification was reported on the basis of their ability to predict flexural buckling resistances of the tested columns. This enabled numerical parametric studies and proposing design rules for CFSS built-up columns with non-slender sections that capture interconnection shear stiffness, overall and chord slenderness ratio and strain hardening effects. [ABSTRACT FROM AUTHOR]

Abstract: Prefabrication of concrete slabs reduces construction time for composite steel–concrete buildings and bridges. Different alternatives for shear connectors (bolts and headed studs) are analysed here to gain better insight in failure modes of shear connector in order to improve competiveness of prefabricated composite structures. Casting of high strength bolted shear connectors in prefabricated concrete slabs offers the higher level of prefabrication comparing to a standard method of grouting welded headed studs in envisaged pockets of concrete slabs. In addition, bolted shear connectors can easily be dismantled together with the concrete slab thus allowing the improved sustainability of the construction, simpler maintenance, and development of modular structural systems. Bolted shear connectors have been rarely used in construction, actually just for rehabilitation works, because there is a lack of design recommendation. The first step towards the design recommendation is to understand the difference between the headed shear studs and the bolted shear connectors in a push-out test. Push-out tests, according to EN1994-1-1, using 4M16 — grade 8.8 bolts with embedded nut in the same layout and test set-up as for previously investigated headed studs were performed. Finite element models for both shear connectors were created, and good match with experimental data was obtained. Basic shear connector properties such as: shear resistance, stiffness, ductility and failure modes have been compared and discussed in detail by using experimental and FE results. Parametric FE analyses of shear connector's height are carried out and shear resistance reduction factor has been proposed for bolted shear connectors. [Copyright &y& Elsevier]

Headed stud shear connectors are commonly implemented in steel-concrete composite floors for connecting the concrete slab to the steel beam and providing composite action between those two elements. The orientation of profiled sheeting is usually transverse or parallel to the supporting beam, and for those cases, design codes provide specific detailing requests and relations for obtaining headed stud resistance. Nevertheless, design codes do not recognise specific configurations when the angle between profiled sheeting ribs and the beam is in the range between 0° and 90°, which is characteristic of irregular-shaped floor structures. Due to the lack of design recommendations for headed stud resistance in these cases, investigations of the effect of the rib-to-beam angle on headed stud shear performance were conducted and presented in this paper. Experimental work included push-out tests conducted on specimens with rib-to-beam angles of 45° and 60°, as well as control specimens with ribs transverse to the beam. The influence of varied rib-to-beam angles on shear connector properties such as shear resistance, stiffness, ductility, and failure mode was discussed. According to experimental research, finite element models of push-out tests were created and verified. The parametric numerical analysis covered key parameters such as concrete class, headed stud height and diameter, and rib-to-beam angle. According to the results, an analytical relation for obtaining headed stud resistance in profiled steel sheeting with a rib-to-beam angle between 30° and 90° was proposed. • Rib-to-beam angles between 0° and 90° in steel-concrete composite beams. • Experimental push-out tests on headed studs with rib-to-beam angles of 45° and 60°. • Development of finite element numerical models. • Parametric study for different rib-to-beam angles, concrete classes and stud geometry. • Analytical relation for stud resistance for varied rib-to-beam angles. [ABSTRACT FROM AUTHOR]

In parallel with an experimental investigation of the flexural buckling behaviour of built-up stainless steel columns presented in the accompanying paper (Dobrić et al., submitted for publication), a detailed Finite Element Analysis (FEA) has been performed to simulate the experiment and identify the key factors affecting the buckling response. The FEA entailed realistic geometry, measured geometric imperfections and material properties of the specimens. Very good agreement was obtained between the experiment and FEA, which proved the capability of the computational approach to replicate experimental results and predict ultimate buckling loads. In the absence of explicit design rules for flexural buckling resistance of stainless steel closely spaced built-up members, the experimental results were compared with design predictions according to the existing European Standard and American Specification for carbon steel structures. The findings indicate that the mentioned design standards may be very conservative regarding the buckling resistance of stainless steel built-up members; this under-prediction may be associated with the impact assessment of chord slenderness and interconnection stiffness on the buckling response. The main purpose of this research is to establish a qualitative data base reliable for the further quantitative numerical parameter analysis and for the development of new design rules for compressed stainless steel cold-formed built-up members. [ABSTRACT FROM AUTHOR]

This paper describes an experimental and numerical investigation of stainless steel material response and behaviour of press-braked channel sections under pure axial compression. A material test programme that covers austenitic stainless steel EN 1.4301 was carried out to study the nonlinear stress–strain relationship and changes of basic mechanical properties due to the press-braking processes. The key experimental results were used to estimate the appropriateness of existing analytical material models and to determinate strain-hardening exponents. The validation of recently proposed models for predicting the strength enhancements in cold-formed sections was also performed. Additionally, corresponding Finite Element (FE) models were built for flat and corner coupons to match the tensile test results and to establish the parameters of a ductile damage model in Abaqus. The susceptibility to local buckling of the channel section was determined by stub column tests. The FE model, calibrated and validated against the experiments, was used to perform a parametric study over a wide range of section slenderness. This allowed the quantitative assessments of design procedures stated in Eurocode 3 and American Specifications, and the Continuous Strength Method (CSM). The comparisons between generated data and predicted strengths reveal the conservatism of the Eurocode 3 design method for both non-slender and slender channels. In contrast, the CSM reflects significantly better the nonlinear buckling behaviour of non-slender channels. Although this method gives more accurate results comparing to effective with method employed in Eurocode 3, the slight unsafe predictions were found for slender channels in the intermediate cross-section slenderness. [ABSTRACT FROM AUTHOR]

In this paper, the structural stability and compressive capacity of pin-ended cold-formed stainless steel angle columns with different slenderness were experimentally investigated. The experimental programme was performed on press-braked lean duplex stainless steel equal-leg angle sections with nominal dimensions of 80 × 80 × 4 mm, and involved material testing, initial imperfection measurements and 11 column tests. The test setup and procedure, together with the key experimental results, axial load vs. lateral deflections, axial load vs. torsional rotations and characterised failure modes, were fully reported and analysed. The experimental observations reveal that the failure mode type, including local/torsional, flexural-torsional and flexural effects, is highly dependent on the column's slenderness and initial imperfections. The measured compressive strengths were compared with the resistance predictions determined according to European and Australia/New Zealand codified design procedures. It was found that experimentally obtained ultimate capacities are significantly higher than those calculated according to the specifications. However, the database of test results is still quite limited, and a further research is needed to amplify the data needed to enable a more precise assessment of the codified procedures. • Eleven pin-ended cold-formed stainless steel equal-leg angle columns were tested. • Different buckling failure modes were systematically investigated. • Failure loads conservatively predicted by European and Australian design procedures. [ABSTRACT FROM AUTHOR]

One of the most important acceptance issues regarding the implementation of small-scale wind turbines in urban environments is related to human comfort. Turbine-induced vibrations can have a large influence on small-scale turbine implementation for urban wind harvesting. A typical five-storey steel-framed office building with a roof-mounted, horizontal-axis wind turbine was numerically analysed. The aim of the work was to investigate the increase in vibration after the installation of the turbine. A comparison was made between floor vibrations caused by wind action on the building only and by wind action on the building and turbine combined. The results were then compared with requirements given in various design codes. The main outcome of the analysis is that the installation of the turbine did not compromise the building's serviceability. [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]