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Cold-formed steel (CFS) is a popular form of construction in New Zealand and the developed world because it can be cost-effective, durable, sustainable, resilient to extreme environmental and seismic loads and easy to install. When used in domestic and medium-rise buildings, T-Stub connection between CFS channel sections is formed by using self-drilling screws which connect the flanges. In the literature, no prior investigation on the tension capacity of such connection has been reported. Therefore, this paper describes a novel test procedure for determining the tension capacity of such CFS T-Stub connection and the associated mechanism of failure. An experimental test program that comprises thirty experimental tests is reported in this paper. Three channel section thicknesses were examined: 0.55 mm, 0.75 mm, and 0.95 mm. All specimens failed as a result of tilting of the screws and bearing failure. Non-linear elasto-plastic finite element (FE) models were developed, and the predictions were validated against the experimental test results. It was adjudged that there was reasonable agreement in terms of connection strength and failure mode prediction. Finally, the design strengths derived from current design standards were compared with the experimental failure loads. It was found that the American Iron and Steel Institute (AISI 2016) and Australian and New Zealand Standard (AS/NZS 2018) are conservative by 6% and unconservative by 10% for the initial and final failure loads of T-Stub CFS connections, respectively. • A novel cold-formed steel T-stub connection was studied experimentally and numerically. • The results of a total of 30 new experimental tests were reported. • Finite element analysis was conducted and validated against the test results. • The prediction accuracy of current design standards was evaluated. [ABSTRACT FROM AUTHOR]

This paper reports laboratory testing and numerical modelling on the cross-sectional behaviour and resistances of press-braked S690 high strength steel slender channel section stub columns under combined compression and minor-axis bending. A testing programme, including initial geometric imperfection measurements and ten minor-axis eccentric compression tests, was firstly conducted. This was accompanied by a numerical modelling programme, including a validation study, where finite element models were developed and validated against test results, and a series of parametric studies, where the validated finite element models were used to generate further numerical data. The obtained test and numerical data were then adopted to evaluate the current codified design interaction curves for press-braked S690 high strength steel slender channel section stub columns under combined compression and minor-axis bending, as provided in the European code, North American specification and Australian/New Zealand standard. The evaluation results revealed that the codified design interaction curves led to conservative and scattered resistance predictions, mainly due to the conservative end points (i.e. the cross-section compression and bending resistances). Finally, a new design interaction curve, anchored to more accurate end points, was proposed and shown to result in a higher level of design accuracy and consistency than the codified design interaction curves. • The behaviour of S690 high strength steel slender channel sections under minor-axis combined loading was studied. • Minor-axis eccentric compression tests were carried out. • FE models were developed and validated against the test results and then used to perform parametric studies. • The codified design interaction curves were evaluated, revealing a high level of conservatism. • A new interaction curve, anchored to the CSM end points, was proposed and shown to yield higher design accuracy. [ABSTRACT FROM AUTHOR]

The concept of seismically low-damage structures was introduced by researchers to decrease the likelihood of irreparable damage as well improving the response of the structure. The need to shift from conventional ductile design to a less ductility (damage) oriented design was emphasised by different researchers in New Zealand and across the world back in the 1990s and 2000s. Damage Avoidance Design (DAD) philosophy introduced in the early 2000s took the idea of low-damage design to another level. Self-centring is the main aspect of a DAD designed. However, the need to change the seismic design philosophy was mostly felt by the community and decisions makers after the considerable financial and social loss resulted from the 2011 Christchurch earthquake. Several damage-avoidance concepts and solutions have been introduced and developed in the past. However, most of these solutions haven't been widely implemented in practice because of the complexity and extra construction costs. This research aims to overcome this gap by introducing a new solution that can be easily adopted by the construction industry without imposing extra complexity and construction costs. This paper presents the development of a new innovative seismic device named as Self-Centring Structural Connector (SSC) as a new self-centring friction damping device. The main purpose of this device is to provide a cost-efficient yet flexible solution to achieve a range of efficient DAD structures in practice. In this paper, the principles of the force-deflection relationship for the SSC is analytically developed and validated through experimental investigation. In addition, the influence of various parameters affecting joint performance are studied through an analytical model. Finally, some possible applications of this device are introduced. As per the findings based on the analytical modelling and experimental investigation, it can be observed that the joint performs well to achieve the design and construction objectives making it a suitable solution for DAD. [ABSTRACT FROM AUTHOR]

This paper presents an extensive experimental investigation of the circular recycled aggregate concrete filled steel tubes (RACFST) stub columns under to axial compression to assess their cross-section behaviour. Recycled aggregate concrete is a sustainable concrete produced with recycled coarse aggregate (RAC) from demolition wastes generally used to fabricate non-structural elements. When compared with natural coarse aggregate (NCA), the recycled coarse aggregate presents lower mechanical properties due to physical and chemical changes that occurred during the recycling process, and thus the resulting RAC possess lower strength than the conventional natural aggregate concrete. However, the confinement provided by the circular steel tube can increase the strength and ductility of RAC in recycled aggregate concrete filled steel tubes (RACFST) columns. The test programme presented in this paper comprised twenty-three composite columns with replacement ratios (the mass percentages of the NCA replaced by RCA in concrete) corresponding to 0% (nature coarse aggregate), 30 and 50% (recycled aggregate concrete), plus four steel columns used for comparison. The experiments have shown that, as anticipated, the concrete core enhances the composite section load-carrying capacity. However, the control over the contents of this concrete core influences the composite section's ductility. If the fill material presents a brittle behaviour, stress redistributions occur in both steel and concrete to compensate for this effect. Since the behaviour of natural aggregate concrete filled steel tubes (NACFST) and RACFST columns are similar, the present paper starts from a study based on a comparative assessment of the recommendations presented in ABNT NBR 8800, ABNT NBR 16239, AISC 360–16, Eurocode 4 and Australian/New Zealand AS/NZS 2327 design standards. These design recommendations proved to be consistent and in line with the performed experiments. Additionally, the results indicated that the cross-section slenderness ratio (D/t) and the confinement ratio directly influence the composite section response. [Display omitted] • An experimental programme was carried out comprising recycled aggregate concrete-filled steel tubular (RACFST) columns. • Different replacement ratios of the nature coarse aggregate replaced by recycled aggregate concrete were assessed. • The steel tubes were produced using a high-frequency induction welding process minimizing the residual stress effects. • The RACFST stub columns presented similar resistances with NACFST stub columns due to confinement contribution. • EC4 and AS/NZS 2327 predictions provide a good approach to be used to RACFST stub columns' design. • NBR 8800 and AISC 360-16 presented very conservative predictions for the columns' strength. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study of eccentrically loaded circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. The testing programme was conducted on twelve specimens designed with different stainless steel tube section sizes and recycled coarse aggregate replacement ratios, and included tensile coupon tests, concrete cylinder tests and eccentric compression tests. The test results, including the failure loads and modes, load–mid-height lateral deflection curves and evolution of neutral axis, were reported and discussed. Following the testing programme, a numerical modelling programme was conducted, with finite element models developed and validated against the test results and then employed to perform parametric studies to generate further numerical data. The confinement effects were analysed based on the numerical data. The relevant design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were assessed for their applicability to circular RACFSST stub columns under combined compression and bending. On the basis of the quantitative and graphical assessments, it has been found that (i) each set of codified design interaction curve leads to similar assessment results for eccentrically loaded circular RACFSST stub columns with different recycled coarse aggregate replacement ratios and (ii) the failure load predictions from the codified design interaction curves are conservative. • The structural behaviour and resistance of circular RACFSST stub columns under combined loading are investigated. • Twelve eccentric compression tests are conducted. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The confinement effects of different types of RACFSST composite sections are discussed. • The applicability of the relevant codified N–M interaction curves is evaluated. [ABSTRACT FROM AUTHOR]

This paper reports an experimental and numerical investigation into the cross-section behaviour and resistances of press-braked stainless steel channel sections under combined compression and major-axis bending moment. A testing programme was firstly conducted, including initial local geometric imperfection measurements and major-axis eccentric compression tests on ten press-braked stainless steel channel section stub column specimens. Following the testing programme, a numerical modelling programme was performed, where finite element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and initial loading eccentricities. Based on the obtained test and numerical data, the existing design interaction curves, as given in the European code, American specification and Australian/New Zealand standard, were assessed and shown to result in conservative cross-section resistance predictions for press-braked stainless steel channel sections under major-axis combined loading. The conservatism of the codified design interaction curves stems from the conservative end points (i.e. cross-section resistances under pure compression and pure bending), which are determined without considering the effect of material strain hardening, and the inefficient linear shape, which ignores the effect of stress redistribution. Improved design interaction curves were proposed through the adoption of (i) more accurate end points, which are calculated with a rational exploitation of material strain hardening by continuous strength method and (ii) more efficient nonlinear shape, which allows for the stress redistribution. The proposed design interaction curves were shown to result in substantially more accurate resistance predictions for press-braked stainless steel channel sections under major-axis combined loading than their codified counterparts. The reliability of the proposed design interaction curves was confirmed by means of statistical analyses. [Display omitted] • Press-braked stainless steel channel sections under combined loading were studied. • Ten major-axis eccentric compression tests were conducted. • FE models were developed and validated and then used to perform parametric studies. • The codified design interaction curves were assessed, revealing conservatism. • New design interaction curves were proposed and shown to yield higher accuracy. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) Tab connections are popular due to their rapid fastening and ease of installation, and their applications have increased recently in Pacific countries, including Australia and New Zealand. This type of connection consists of a Tab plate formed from the web of the supporting beam and is screwed to the joist web, providing a dependable load path from the joist to the galvanized C-section supporting beam. However, no studies have been reported in the literature for the shear capacity of such connections. This paper presents a shear test program designed to determine the shear capacity of CFS Tab connections and to identify their failure mechanism. The experimental program included three different beam sizes, C-150, C-190 and C-240. Each test was repeated three times, resulting in nine tests in total. All the specimens failed in plate yielding and plate tearing, which occurred on the tension side of the plate (top region). Nonlinear finite element (FE) models were then developed and verified against the test results. The FE results showed good agreement with the test results in terms of connection stiffness, connection strength and failure modes. Finally, it was shown that the design equations given in the Australia/New Zealand standard (AS/NZS 4600) and American Iron and Steel Institute (AISI S100) for predicting the combined bending and shear capacity could predict the ultimate shear capacity of CFS Tab connections investigated in this study. • The results of monotonic shear tests of a novel CFS Tab connection are reported. • CFS Tab connections failed in plate yeailding and tearing. • A nonlinear FE model is developed. Results showed good agreement with the test results. • A design procedure is proposed for predicting the shear capacity of CFS Tab connections. [ABSTRACT FROM AUTHOR]