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• Performance of CFS composite beams with profiled steel sheeting is numerically studied. • 3D FE model of CFS composite beam specimens comprising cold-formed double-lipped channel section, profiled steel sheeting, concrete slab and bolted shear connector is developed. • Of particular interests are the geometric characteristics, material nonlinearities, and loading procedures. • Effects of different parameters including compressive strength of concrete, thickness of concrete slab, height and grade of cold-formed steel section, thickness of profiled steel sheeting, number and diameter of shear connectors are investigated. Cold-formed steel composite beams are known for their unique advantages, like being lightweight and ease of installation. The use of profiled steel sheeting in cold-formed composite beams reduces construction time and costs by acting as a permanent formwork in the composite beams. The current study presents a 3D finite element model of cold-formed steel composite beam specimens comprising a cold-formed double-lipped channel section, profiled steel sheeting, concrete slab, and bolted shear connector. Employing bolted shear connectors, structural components can be deconstructed and replaced after their service life expires or if they are damaged. The characteristics of the materials obtained from an experimental program were assigned to the finite element model. Geometric characteristics, material nonlinearities, and loading procedures were attentively simulated, and a dynamic explicit procedure was employed for the numerical analyses. A comparison of the results obtained from the finite element models and the available experimental results validated the precision of the models. Then, numerical studies were conducted to investigate the effects of various parameters, including compressive strength of concrete, thickness of concrete slab, height and grade of cold-formed steel section, thickness of profiled steel sheeting, number and diameter of shear connectors, on the behavior of the composite beam. The results showed that the height and grade of the cold-formed steel section and compressive strength and thickness of the concrete slab have a significant effect on increasing the capacity of the composite beam. [ABSTRACT FROM AUTHOR]

This paper presents a detailed investigation of the lateral characteristics of cold-formed steel truss structures used in electric power substations. Five full-scale specimens were tested, and their responses were recorded under monotonic and cyclic loading regimes. Of particular interest were the specimens' maximum lateral load capacities and deformation behaviours. A rational estimation of the seismic response modification factor, R, of the truss structures is also provided. In addition, different types of stiffened sections were employed in order to examine the impact of the presence of stiffeners and lips on seismic behaviour, as well as on the lateral resistance of the structure. Detailed comparisons between relevant code methods, finite element modelling and an experimental study were then conducted to suggest an appropriate value for the R factor. A financial evaluation was also performed, to highlight the advantages of employing cold-formed steel trusses in the electric power substation industry. The results show that the cold-formed steel structural system is a reasonable alternative to the currently used hot-rolled steel structures, and that its use decreases the cost of the structures by almost 50%. [ABSTRACT FROM AUTHOR]

The concurrent use of concrete slab, and cold-formed steel section as a composite beam improves strength and stiffness, thus preventing local and lateral buckling of the beam. The composite action could be fulfilled by suitable shear connectors, though the codes do not prescribe any equation to determine the shear capacity, and design rule of these connectors. The friction-grip bolted shear connectors were introduced and their mechanical performance was studied via the experimental tests and finite element modeling. At first, ANSYS software was used for the 3D finite element modeling of these connections. The obtained results were verified by experimental results. It can be shown that the proposed model can estimate the behavior of friction-grip bolted shear connectors in composite beams with cold-formed steel section. Then, extensive parametric studies with 72 specimens were carried out and the effect of diameter and strength of the bolts, thickness and strength of cold-formed steel sections, clearance between the bolt and concrete hole and pretension force on the behavior of these connectors were evaluated. The effect of each parameter on the shear capacity of the connection was evaluated. Some equations were proposed for figuring out the shear capacity and load–slip curve of these connections based on the experimental and 3D finite element results. • A new friction-grip bolted shear connector in composite beam comprising concrete slab and CFS section is introduced. • Mechanical performance of the proposed shear connector is investigated through experimental tests and numerical modeling. • The proposed numerical model can well estimate the shear connectors in the composite beams. • Parametric studies including 72 specimens are carried out and the effect of structural characteristics are evaluated. • Some equations for determining the shear capacity and load–slip curve of the connection are proposed. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the behaviour of cold formed steel truss connections. Eighteen full scale cold-formed steel truss connections were tested. Of particular interests are the specimens maximum load capacity and the load-deformation behaviour. The study also looks at the failure modes of the connections. The behaviours exhibited by the connections are discussed and the design capacities calculated from the current CFS design standards are compared to the experimental results of the connections. This study investigates the main factors contributing to the ductile response of the CFS truss connections in order to suggest recommendations for connection designs, and improvements so that the connections respond plastically with a significant drift and without any risk of brittle failure. Also, a number of alternative fasteners are chosen and investigated for comparison with those that are currently specified for trusses' connections. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study of cold formed steel frames sheathed by fibre-cement boards (FCB) under cyclic lateral loading. Four full scale fibre-cement shear walls were tested. Of particular interests are the specimens maximum lateral load capacity and the load–deformation behaviour as well as a rational estimation of the seismic response modification factor, R factor. The study also looks at the failure modes of the systems and investigates the main factors contributing to the ductile response of the CFS shear walls in order to suggest improvements so that the FCB sheathed walls respond plastically with a significant drift and without any risk of brittle failure such as connection failure or fibre-cement board fracture. Both double-sided and single-sided FCB shear panels as well as a new proposed configuration were studied. The study shows that while the overall performance of the currently in-use FCB sheathed lateral resistant system under cyclic loads is not satisfactory with a small average R factor of 2.5, the proposed FCB lateral resistant system can be considered as a reliable system with a much higher value of R factor of 5. [ABSTRACT FROM AUTHOR]

The use of concrete slab in cold-formed steel (CFS) beams can not only increase the ultimate resistance, but also can prevent their lateral buckling. Since the formation of composite action in this type of beams requires the use of appropriate shear connectors, in this paper, an extensive numerical study was conducted to investigate the behavior of 8.8 grade bolted connectors in CFS composite beams. For this purpose, at the first, advanced numerical models of concrete-CFS section connections were developed. Geometric details, material nonlinearities, material damage models and loading protocols were carefully simulated. Next, the results obtained from the numerical models were validated in detail against the experimental results. It was proved that the developed models have the ability to simulate the behavior of the 8.8 grade bolted connectors in these connections. At the end, an extensive parametric numerical study consisting of 216 connections was conducted. The examined parameters included CFS thickness, CFS ultimate strength, concrete compressive strength, embedded bolt's height and bolt diameter. Consequently, the effect of each of these parameters on the ultimate strength, ductility as well as the failure modes of the bolted shear connectors was carefully investigated. • Structural performance of CFS-concrete composite beams is investigated. • Numerical study was conducted to study the CFS composite beams. • 216 connections were studied. • Geometric details, material nonlinearities, and loading protocols were simulated. [ABSTRACT FROM AUTHOR]

Abstract: Experimental investigations were conducted to evaluate the lateral seismic characteristics of light-weight knee-braced cold-formed steel structures. In all, four full-scale 2.4×2.4m2 specimens with different configurations were tested under a standard cyclic loading regime. This paper focuses on the specimens'' maximum lateral load capacity and deformation behavior and provides a rational estimate of the seismic response modification factor, R, of knee-braced walls. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of CFS walls. That is in order to suggest improvements so that the shear steel walls respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling. A discussion on the calculated response factors in comparison to those suggested in the relevant codes of practice is also presented. [Copyright &y& Elsevier]

Abstract: Non-linear finite element analyses were carried out to evaluate and optimize the seismic characteristics of knee-braced cold formed steel shear walls using software ANSYS. Different structural characteristics including: material nonlinearity, geometric imperfection, residual stresses and perforations are taken into account. The numerical models were verified based on experimental tests. Agreement of the numerical simulations and the test results showed that finite element analysis can be used effectively to predict the ultimate capacity of knee-braced CFS shear panels. A total of 12 models with a various ranges of knee-elements'' lengths were investigated. Of particular interests were the specimens'' maximum lateral load capacity and deformation behavior in addition to a rational estimation of the seismic response modification factor. Preliminary conclusions presented in this paper, refer to the optimum seismic characteristics of knee-braced CFS shear walls and the corresponding dimensions and configuration. [Copyright &y& Elsevier]

• Performance of U-shaped shear connectors in CFS-concrete composite beam is studied. • 10 full scale push-out tests are conducted to study the U-shaped shear connectors. • Four types of shear connectors were considered.· Two types of CFS beams with thickness of 1 and 2 mm are taken into account. • Ductility of the shear connectors is examined according to EC4 code. Since few studies have focused on the shear connectors in the composite cold-formed steel beams so far, this paper studies the behavior of the U-shaped shear connectors which can be used in the composite beams comprising cold-formed steel beam and concrete slab. Accordingly, ten full scale push-out tests were conducted to investigate the ultimate load, failure modes, ductility and stiffness of the U-shaped shear connectors. For this purpose, four types of shear connectors by different screw diameters and orientation of U-shaped shear connectors with respect to the direction of the load were considered; and utilized by two types of cold-formed steel beams with thickness of 1 and 2 mm. The results have shown that change of the screws' diameter from 4.8 to 6.3 mm, leads to an increase of the ultimate load about 25% and 40% for 1 mm and 2 mm thick specimens, respectively. It is also concluded that transverse shear connectors have a better performance than longitudinal ones considering both ultimate load and ductility. The main observed failure mode of all specimens was tilting and bearing in shear connectors except for two specimens which was incorporated with pull-over mode. Moreover, ductility of the shear connectors was examined according to EC4 code. The results show that except for two specimens, the other U-shaped shear connectors used in this study can be accounted ductile. [ABSTRACT FROM AUTHOR]

Composite beams comprised of steel sections and concrete slabs, are one of the most widely used beams due to their advantages such as improving stiffness and strength compared to bare steel or reinforced concrete beams. Moreover, another important advantage of such beams is to prevent buckling of steel section by placing it under tension, which is especially important for low-thickness steel sections such as cold-formed steel (CFS) sections. Although the use of CFS sections in combination with concrete slabs can increase the efficiency of such sections, their low thickness makes it difficult to weld traditional studs as shear connectors on their top flanges. The current paper presents an experimental investigation about the behavior of bolted shear connectors in the composite cold-formed steel beams as a suitable alternative to welded shear studs. To do so, three main parameters including thickness of CFS sections, and size and strength of bolts were taken into account. Fifteen full-scale push-out specimens were constructed and tested. The ultimate load, ductility, stiffness and failure mode of all specimens were then assessed; and their results were reported and precisely discussed. Based on the results, depending on the size and strength of bolts, the ultimate load per shear connector for 1 mm thick CFS sections' specimens is found between 6.2 and 8.6 KN, while this value for specimens by 2 mm thick CFS sections, is found between 15.6 and 26.8 KN. Moreover, based on EC4, the ductility of shear connectors was examined; the results indicate that all bolted shear connectors in this study can be assumed ductile and can be used in partial shear connections. • Structural performance of CFS-concrete composite beams is investigated. • 15 full scale push-out tests are conducted. • The failure modes, ductility and stiffness of the composite sections are studied. • Thickness of CFS sections, size and strength of bolts were taken into account. [ABSTRACT FROM AUTHOR]

Load bearing cold-formed steel clip angles are one of the commonly used connectors in lightweight cold-formed steel structures. These connectors may fail at their screw connections due to pull-out failure when the screw pulls out of the plate under tension loading conditions. These localized connection failures can cause undesirable failures by dislocating both clip angle and sub-plates. Therefore, a detailed experimental study was carried out to investigate the pull-out failures of load bearing cold-formed steel clip angles considering different parameters such as clip angle configuration, clip angle thickness, screw diameter size, screw thread pitch, number of screws and screw location. This paper presents the test results conducted in this study and compares them with existing pull-out design standard equations. Also, a design equation with a resistance reduction factor is developed and suggested in order to accurately determine the pull-out strength of the cold-formed steel clip angles. • Pull-out failures of load bearing cold-formed steel clip angles are investigated. • 82 full scale CFS clip angles are tested to determine the effects of critical parameters on the pull-out failure loads • Effects of geometrical parameters and configurations are studied. • A design equation is developed for determination of pull-out strength of CFS clip angles. • The new equation is compared with standards' prescribed equations. [ABSTRACT FROM AUTHOR]

• Cyclic behaviour of steel-concrete composite connection is experimentally investigated. • Steel-concrete composite connections have high ductility and energy dissipating capacity. • Three different modes of failure were observed in the steel-concrete composite connections. • The strength deterioration in cyclic loading is much higher than that in monotonic loading. • Increasing the diameter and strength of the shear connector resulted in an increase in the hysteretic loop area. An experimental study of the cyclic behaviour of steel-concrete composite connections using mechanical shear connectors subjected to a low-cycle high-amplitude loading regime is presented in this study. The ductility, strength degradation and absorbed energy which characterise the performance of a mechanical shear connector under cyclic loading conditions in steel-concrete composite connections are assessed. Nine steel-concrete composite connection specimens were designed and tested in order to investigate the cyclic behaviour of the proposed composite connections, and to elucidate the structural behaviour of the demountable bolt shear connectors between the precast concrete panels and steel beams. In addition, three monotonic tests on steel-concrete composite connection were conducted to evaluate the yield slip, yield load, ultimate slip, and ultimate shear strength capacity. The size of the bolted shear connector and the strength of the bolted shear connectors are the main variables in this study. The preparation and construction of the specimens, the testing procedure, the test set-up, and the instrumentation used are described and the results of the monotonic and cyclic tests are reported in detail. [ABSTRACT FROM AUTHOR]

Although cold-formed steel (CFS) members have been widely used in structures, their application is limited due to the buckling and instability of these members. To enhance their strength and stiffness, they are often combined with other materials like concrete or timber. One of the main challenges in composite structures is ensuring proper connection between different components to facilitate safe shear load transfer. This is achieved through various types of shear connectors. Bolted shear connections are preferred over headed shear studs because they offer greater strength and can be easily dismantled. Headed shear studs welded onto a steel section are unsuitable for CFS members due to their low thickness. In this paper, we propose a novel demountable composite connection specifically designed for prefabricated CFS structures. The behavior of this connection was evaluated through fifteen push-out test specimens, with key variables including CFS section thickness and bolt diameter/strength. The ultimate load, stiffness, ductility, and failure modes of all specimens were determined. The results revealed that specimens with a higher thickness of CFS members experienced bolt fracture, exhibiting superior effective stiffness, strength, and ductility. Conversely, specimens with a lower thickness of CFS members failed due to distortional buckling of the CFS members. The test results underscore the importance of carefully designing and providing a proportionate CFS section thickness to ensure shear connectors fracture before the CFS members. This significantly improves the shear strength capacity of the composite connection with CFS sections and precast concrete slabs. Furthermore, the deconstructability of the connection at the end of its service life was investigated. The steel–concrete composite connection with precast concrete slabs and demountable bolted shear connections was also modeled using a 3D finite element method. The numerical model's accuracy in simulating the observed structural behavior was confirmed against experimental data. Finally, appropriate and straightforward formulations for predicting the ultimate load of the CFS-concrete composite connection were proposed. It was concluded that the predictions of ultimate shear load capacity values by EC4, AISC, and AISI provisions for this composite connection are significantly less accurate. • Structural performance of a novel CFS-concrete composite connection is investigated. • The failure modes, ductility and stiffness of the composite connection are studied. • Thickness of CFS sections, size and strength of bolts were taken into account. • Validity of several existing methods for predicting the ultimate shear load are evaluated. • 15 full scale push-out tests are conducted to study the novel shear connectors. [ABSTRACT FROM AUTHOR]

In recent years, the use of artificial intelligence-based methods in engineering problems has been expanded. In the current study, the method of artificial neural networks (ANN) has been employed to predict the ultimate strength of bolted shear connectors in cold-formed steel (CFS) composite beams. For this purpose, multilayer perceptron (MLP) networks with a hidden layer were used. Three parameters affecting the performance of these networks, including the training algorithm, the activation function in the hidden layer, and the number of neurons in the hidden layer, were examined and the most accurate network was selected. The input and target data for training the network were provided by conducting an extensive numerical study on the behavior of bolted shear connectors in CFS composite beams. Consequently, using ABAQUS software, finite element (FE) models validated with experimental results were first developed. Then, 216 models with different characteristics were analyzed and a reliable database was provided for the development of neural networks. Moreover, in order to prove the high accuracy of the ANN method, the stepwise regression (SR) method was also developed as one of the powerful regression-based methods, and the performances of these two methods were compared. Finally, the most important purpose of this study is to propose an accurate ANN-based formulation in order to predict the ultimate strength of bolted shear connectors in CFS composite beams. Due to the fact that so far no relationship has been proposed to predict the resistance of shear connectors in CFS composite beams, the formula presented in this paper can be helpful in the design process of this type of beams. [ABSTRACT FROM AUTHOR]

Pull-out failures are one of the common failures in load bearing cold-formed steel clip angles causing catastrophic damages, where plate and screw fastener are dislocated. Thus, a detailed experimental study was first conducted to investigate the pull-out failures in cold-formed steel clip angles under tensile loading conditions. Then, since experimental tests are time-consuming and expensive, the ability of finite element modeling in the ABAQUS software environment was used to predict the pull-out behavior of the clip angles. The force–displacement behavior, ultimate strengths, and failure modes were compared with those obtained from experimental tests to validate the finite element models. The results were compared with those obtained from current design equations. Then, new design equations associated with numerical and both numerical and experimental results were provided by considering all geometrical and mechanical parameters to accurately predict the pull-out failure loads of the clip angles. • Pull-out failures of load bearing cold-formed steel clip angles are investigated. • A detailed finite element analysis is conducted using the ABAQUS program. • Finite element models are validated using the test outcomes carried out by authors. • Effects of various mechanical and geometrical parameters are considered. • New pull-out equation is presented based on both numerical and experimental results. [ABSTRACT FROM AUTHOR]

Load bearing cold-formed steel clip angles are commonly used in various connections, subjected to different loading conditions. This numerical parametric study was performed in order to investigate the effect of various parameters on pull-through strength of fasteners on the anchored leg of cold-formed steel clip angles. In this regard, a finite element analysis is conducted, using ABAQUS program, to model the specimens subjected to tension forces. The finite element modeling is verified, using the existing tested clip angles and the ability of the validated finite element models in predicting the pull-through strength of other clip angle cases is evaluated, by comparing the obtained results with the experimental results. This parametric study provides a detailed information on the effect of any effective parameters, such as clip angle geometry, basic mechanical properties, and screw fastener head or washer sizes on the pull-through failures of bearing clip angles. According to the results, although the effects of parameters, such as screw fastener head or washer sizes and mechanical properties, on the pull-through strength are significant, the effect of clip angle geometry can be neglected. Finally, a suitable design equation is proposed to calculate the pull-through failure of load bearing clip angles. Moreover, a new equation is presented to calculate elastic stiffness of cold-formed steel clip angles, using a simple analytical model. The results obtained from this equation are in a proper agreement with the initial slope of force-displacement curves. • Pull-through strength of load bearing cold-formed steel clip angles are investigated. • Effect of various mechanical and geometrical parameters is considered. • New pull-through design equations are presented for clip angles with low and high strength steel. • New initial elastic stiffness equation is presented for cold-formed steel clip angles. • The new stiffness equation can be applied to component-based method of clip angles. [ABSTRACT FROM AUTHOR]