Search Results (101)

Cold-formed steel (CFS) channel beams are increasingly used as primary structural elements in modern construction due to their lightweight and high-strength characteristics. To accommodate building services, these members often feature perforations—typically circular and unstiffened—produced by punching. Recent studies indicate that adding edge stiffeners, particularly around circular web openings, can improve flexural strength. Extending this idea, attention has shifted to hexagonal web perforations; however, limited research exists on the bending performance of hexagonal cold-formed steel channel beams (HCFSBs). This study presents a detailed nonlinear finite element (FE) analysis to evaluate and compare the flexural behaviour of HCFSBs with unstiffened (HUH) and edge-stiffened (HEH) hexagonal openings. The FE models were validated against experimental results and expanded to include a comprehensive parametric study with 810 simulations. Results show that HEH beams achieve, on average, a 10% increase in moment capacity compared to HUH beams. However, when evaluated using current Direct Strength Method (DSM) provisions, moment capacities were underestimated by up to 47%, particularly in cases governed by lateral–torsional or distortional buckling. A reliability analysis confirmed that the proposed design equations yield accurate and dependable strength predictions. Full article

Concrete-filled steel columns are increasingly recognised for their enhanced structural performance. This study investigates an innovative shear connector design with screw connectors as an alternative to conventional connection types. From push-out testing, the shear capacity of screw connectors in composite columns comprising cold-formed steel sigma sections and concrete infill was evaluated. Experimental push-out testing demonstrated the effectiveness of theoretical equations in estimating the shear strength of screw connections. The comparison indicates that established design methods provide reasonable predictions, supporting their applicability in practical scenarios. Theoretical equations in the literature for estimating shear strength were tested for suitability and gave comparable results. Disassembling of tested specimens showed that a concrete failure was the prominent mode of ultimate condition. Shear screws offer a novel design alternative to conventional shear connection methods. They demonstrate significant potential for structural applications when integrated with advanced composite column sections, such as the four-sigma built-up CFS sections. The study highlights screw connectors as a cost-effective, sustainable, and practical solution for innovative composite column designs, offering significant potential for construction and maintenance efficiency. Full article

This paper focuses on the buckling behavior of circular hollow section (CHS) beam–columns. The literature review highlights the need for further investigations to improve the accuracy of structural performance predictions and optimize the design guidelines for CHS beam–columns. A comprehensive parametric study was conducted using the developed finite element model, which included a total of 1400 simulations, including sections made from cold-formed and hot-finished steel. An assessment of the existing design provisions in Eurocode 3 is presented. Based on the results, a revised buckling design approach is proposed. The existing design provisions in Eurocode 3 provide conservative predictions on the buckling resistance of CHS beam–columns for both cold-formed and hot-finished sections. The proposed design approach demonstrated improved accuracy in predicting the buckling resistance, with mean predicted-to-test ratios and RMSE values of 0.99 and 8.1 kN for Class 1–2 sections, and 1.00 and 6.4 kN for Class 3–4 sections. Finally, a reliability analysis was conducted to assess the safety and reliability of the proposed design approach, resulting in a partial safety factor of 1.12 compared to 1.14 for Eurocode 3, indicating slightly reduced conservatism, while maintaining adequate safety levels. Full article

This paper presents an experimental and numerical investigation of the axial compression behavior of perforated cold-formed steel upright profiles commonly used in pallet racking systems. The primary objective is to examine how slenderness influences the failure modes and load-bearing capacity of these structural elements. Three column lengths, representative of typical vertical spacing in industrial rack systems, were tested under pin-ended boundary conditions. All specimens were fabricated from 2 mm thick S355 steel sheets, incorporating web perforations and a central longitudinal stiffener. Experimental results highlighted three distinct failure mechanisms dependent on slenderness: local buckling for short columns (SS-340), combined distortional–flexural buckling for medium-length columns (MS-990), and global flexural buckling for slender columns (TS-1990). Finite Element Method (FEM) models developed using ANSYS Workbench 2021 R1 software accurately replicated the observed deformation patterns, stress concentrations, and load–displacement curves, with numerical results differing by less than 5% from experimental peak loads. Analytical evaluations performed using the Effective Width Method (EWM) and Direct Strength Method (DSM), following EN 1993-1-3 and AISI S100 specifications, indicated that EWM tends to underestimate the ultimate strength by up to 15%, whereas DSM provided results within 2–7% of experimental values, especially when the entire net cross-sectional area was considered fully effective. The originality of the study is the comprehensive evaluation of full-scale, perforated, stiffened cold-formed steel uprights, supported by robust experimental validation and detailed comparative analyses between FEM, EWM, and DSM methodologies. Findings demonstrate that DSM can be reliably applied to perforated sections with moderate slenderness and adequate web stiffening, without requiring further local reduction in the net cross-sectional area. Full article

Composite structures are increasingly being utilized in modern construction. This computational analysis focuses on the structural performance of composite beams formed by thin-walled, cold-formed steel channel sections strengthened with concrete. The primary objective of this research was to enhance the strength and stability of composite cold-formed steel beams. In this study, back-to-back C-channel sections and concrete slabs with various stiffener configurations were analyzed. The key parameters considered include stiffener spacing, type, and thickness. Additionally, different beam cross-sections, such as C-channel and sigma sections, were investigated. A finite element analysis was conducted using the ABAQUS program, incorporating both geometric and material nonlinearities. The developed models were validated against experimental results from previous research and existing design guidelines. Three beam specimens were examined in this study to assess their structural behavior under static loading conditions. A novel aspect of this research is the investigation of composite cold-formed steel beams under a combination of ultra-high-performance concrete (UHPC) and negative moment effects. The load–deflection behavior of all beam specimens was analyzed, considering variations in cross-sectional dimensions and span lengths. Additionally, the study highlights key material properties, including the maximum compressive strength of concrete, the yield strength of cold-formed steel channels, and the cross-sectional area of the steel components for each beam specimen. This research provides valuable insights for structural engineers, contributing to the optimization of composite cold-formed steel beam design for enhanced performance in practical applications. Full article

This study investigates the buckling performance of built-up cold-formed steel (CFS) columns, with a focus on how different thermal exposures and cooling strategies influence their susceptibility to various failure mechanisms. Addressing the gap in the literature on the fire behavior of mild steel (MS)-based CFS columns, the research aims to provide new insights. Compression tests were conducted on MS-based CFS column specimens after they were exposed to fire, to assess their post-fire buckling strength. The columns were subjected to controlled fire conditions following standardized protocols and then allowed to cool to room temperature. The study examined axial load-bearing capacity and deformation characteristics under elevated temperatures. To improve fire resistance, protective coatings—gypsum, perlite, and vermiculite—were applied to certain specimens before testing, and their performance was compared to that of uncoated specimens. A comprehensive finite element analysis (FEA) was also performed to model the structural response under different thermal and cooling scenarios, providing a detailed comparison of the coating effectiveness, which was validated against experimental results. The findings revealed significant variations in axial strength and failure mechanisms based on the type of fire-resistant coating used, as well as the heating and cooling durations. Among the coated specimens, those treated with perlite showed the best performance. For example, the air-cooled perlite-coated column (MBC2AC) retained a load capacity of 277.9 kN after 60 min of heating, a reduction of only 6.0% compared to the unheated reference section (MBREF). This performance was superior to that of the gypsum-coated (MBC1AC) and vermiculite-coated (MBC3AC) specimens, which showed reductions of 3.6% and 7.9% more, respectively. These results highlight the potential of perlite coatings to enhance the fire resistance of CFS columns, offering valuable insights for structural fire design. Full article

This paper presents a novel design of prefabricated steel–EPS foam concrete composite wall panels, which can solve issues such as long curing times, decreased impermeability and durability, easy corrosion of steel reinforcement, and difficult construction under the cold climate conditions in Northeast China. A parametric analysis of the composite wallboard was carried out using the finite-element analysis software ABAQUS 6.12. In-depth exploration was conducted on the contributions of parameters such as the density of foam concrete, the strength of cold-formed thin-walled C-section steel, and the cross-sectional height of cold-formed thin-walled C-section steel compared to the overall flexural bearing capacity of the composite wallboard as well as the impacts of these parameters on the failure modes. The mechanical properties of the composite wallboard were verified through four-point bending tests. The bearing capacity of this composite wallboard can reach up to 100.58 kN at most, and its flexural bearing capacity can reach 30.44 kN·m. Meanwhile, its ductility coefficient of 2.9 is also within the optimal range. The research results confirm the superior mechanical properties of the designed composite wallboard, providing beneficial references for the research on similar composite material structures. Full article

This study investigates the toughness and load capacity of various innovative beam configurations of cold-formed steel beams (CFSB) using both ordinary concrete slabs and engineered cementitious composite (ECC) slabs. A finite element analysis with ABAQUS 20 was conducted on double-channel, sigma, G, and omega sections, both with and without inverted lips, as well as the effects of L, channel, and trapezoidal stiffeners and length-to-depth ratios. The double-omega section with ordinary concrete achieved the highest first peak load of 365.2 kN and a toughness increase of 181.1%. Inverted lips enhanced toughness in the double-G and sigma sections, with increases of 156.9% and 158.3%, respectively. Among ECC configurations, the double-omega section with ECC3 slab reached 387.4 kN and a toughness increase of 199.5%. Thinner ordinary concrete sections (70 mm and 90 mm) negatively impacted toughness, emphasizing the need for adequate thickness. Trapezoidal stiffeners also improved toughness. These findings highlight the importance of geometrical design and material selection in optimizing CFSB performance, offering valuable insights for future design practices. Full article

Cold-formed steel (CFS) unsymmetrical angles are increasingly used in structural applications such as portal frames, roof trusses, and transmission towers. However, research on built-up face-to-face unsymmetrical CFS angle columns (FFUACs) with stiffeners remains limited. This study addresses this gap by presenting the findings from six experimental investigations on intermediate FFUACs connected using intermittent screw fasteners. The results offer insights into failure deformation patterns and load-axial shortening behaviour. A nonlinear finite element (FE) model was developed to account for material and geometric nonlinearity, with experimental results used for validation. This study contributes 166 new data points, including six experimental tests under concentric compression and 160 finite element analysis (FEA) results focused on the compressive strength of FFUACs. Additionally, this study evaluates the performance of existing design guidelines based on the direct strength method (DSM). The DSM strength predictions were found to be less conservative for stub FFUAC specimens that failed due to local buckling and more conservative for short FFUAC specimens that failed due to a combination of local and flexural buckling. A revised DSM methodology is proposed to address these discrepancies. Full article

The article provides information about strengthening cold-formed thin-walled steel beams made of the sigma profile. An innovative concept for sectional transverse strengthening of thin-walled beams subjected to concentrated forces was investigated. The proposed solution’s novelty lies in attaching the sectional transverse strengthening to the beam’s cross-section, employing a point crimping technique. This technique requires a specific modification of the cross-section edges, necessitating double-lipped flanges. This strengthening method is innovative, as it has not been previously applied to cold-formed structures. Typically, strengthening is achieved using other cold-formed elements or materials, such as timber, lightweight concrete, or CFRP tapes. The laboratory experimentally validated the proposed method using short- and medium-length beams. The experimental results were then compared with the results of the numerical analyses and the conventional design approach described in EC3. The results demonstrated the feasibility of implementing this type of strengthening, its reliability under load, and the confirmation of an increase in the load-bearing capacity of the experimental samples by 11–24%. Full article

This study conducted experiments to investigate the flexural behavior of steel–concrete composite beams with U-shaped sections, utilizing cold-formed lipped channels as web components. To enhance both flexural and shear performance, trapezoidal plates were added to the lower sides of the composite beams. A total of ten specimens were fabricated, with variables defined according to the following criteria: presence of bottom tension reinforcement and bottom studs, thickness of the trapezoidal side plates (6 mm and 8 mm), and the welding method. Four-point bending tests were conducted, and all specimens exhibited typical flexural failure at the ultimate state. Specimens with bottom tension reinforcement, specifically those in the H5-T6 and H5-T8 series, demonstrated increases in ultimate load of 28.8% and 33.5%, respectively, compared to specimens without tension reinforcement. The use of lipped channels enabled full composite action between the concrete and the steel web components, eliminating the need for stud anchors. Additionally, it was confirmed that the plastic neutral axis, reflecting the material test strengths, was located within the concrete slab as intended. This study also compared the design flexural strengths, calculated using the yield stress distribution method from structural steel design standards such as AISC 360 and KDS 14, with the experimental flexural strengths. The comparison was used to evaluate the applicability of current design standards. Full article

The bond-slip behavior between cold-formed thin-walled steel (CTS) and foamed concrete (FC) is a critical issue in the mechanical performance of FC-filled CTS composite wall structures. Thus, this study provides experimental and theoretical research on the bond-slip behavior between CTS and FC. A total of eleven specimens were tested using push-out configurations, considering the number of web holes, foamed concrete (FC) strength, anchorage length, and CTS section splice form. A constitutive model for bond-slip was proposed, and the regression formulas for accurately predicting the characteristic bond strength between CTS and foamed concrete were established. A finite element model was developed to investigate the bond-slip mechanism at the interface between CTS and FC. The bond-slip constitutive model accurately fits the experimental and finite element results. The results indicate that the ultimate bond strength of the specimens increases with the number of web holes; when the number of web holes reaches two, the ultimate bond strength is 155.4% of that of the non-perforated specimens. As the concrete strength increases from 3.43 MPa to 11.26 MPa, the ultimate bond strength of specimens with two web holes improves by 23.1%, while non-perforated specimens have a 54.7% enhancement. When the anchorage length is extended from 200 mm to 400 mm, the ultimate bond strength decreases by 29.3%. Additionally, when steel sections are joined in a double-span I form, the bond strength increases by 91.6% and 95.8% compared to the single-span form and the double-span box form, respectively. Full article

Thin-walled channel beams such as cold-formed steel purlins are primarily used to withstand wind forces in the roofing and walling systems of buildings. Traditionally, these types of members are usually designed for bending moments, with the effects of torsion ignored. However, the loading on thin-walled channels can be much more complicated than simple bending actions. Because of the position of the shear centre outside the section, channels can undergo bending and torsion when subjected to vertical load on the top flange. The applied torsion may cause significant stresses in the channel, which may need to be accounted for in design. There appears to be no research on quantifying the effects of torsion on thin-walled channels subjected to a uniformly distributed load acting on the top flange. In this paper, a theoretical solution is derived for calculating the longitudinal stresses in thin-walled channels subjected to torsion caused by a uniformly distributed load acting on the top flange. The theory is validated by modelling the channels in a finite-element analysis. The theoretical results include calculations of the twist rotation, bimoment, sectorial coordinate and longitudinal stresses, while the results from the finite-element analysis include the twist rotation and longitudinal stresses. The results show that the longitudinal stresses caused by torsion can significantly exceed those caused by the bending moment. Practical advice is also given for engineers on how to minimize torsion in cold-formed steel purlins. Full article

In the local building industry of Pakistan, pre-engineered steel building manufacturers mainly employ their own self-developed software and Excel sheets. These systems are based on empirical formulas mentioned in the AISI manual. Under this scenario, a need was found to validate AISI flow charts using commercial software like CUFSM 5.04 and ABAQUS R2019x. This study presents a validation of the CUFSM software and the American Iron and Steel Institute (AISI) Direct Strength Method (DSM) results of channel section flexural members using the non-linear finite element method employing ABAQUS. In this study, eight standard cold-formed channel-section (C-section) steel members were modeled and analyzed using ABAQUS to simulate realistic behavior under four-point loading conditions. The non-linear finite element models incorporated material and geometric non-linearities to capture the actual response of the steel elements. The results obtained from ABAQUS were compared with those predicted by the CUFSM and DSM, focusing on critical parameters such as nominal strength, buckling modes, and deformation patterns. During this study, it was observed that out of the selected sections, the AISI charts predict conservative and even unsafe flexural capacities in some of the cases concerning other methods, with a maximum difference of 14.03%. The differences obtained using DSM and ABAQUS when compared with the results of the AISI charts varies on both the plus and minus sides. This study will not only affect the industry in terms of innovative designs for efficient structures but also the community in regards to low-budget construction. Full article

Cold-formed steel (CFS) sections, increasingly favored in the construction industry due to their numerous advantages over hot-rolled steel, have received limited attention in research concerning the flexural behavior of galvanized iron (GI)-based CFS at elevated temperatures. Understanding how these materials and structures behave under elevated temperatures is crucial for fire safety. The authors have performed experimental studies previously on GI-based CFS under elevated temperatures. In that study, CFS sections made of GI of grade E350 of 1.5 m long and 2 mm thickness were used. Built-up beam sections were tested under two-point loading after heating to 60 and 90 min durations and subsequently cooling them down using air and water. This study aims to uncover the influence of different stiffener configurations on the load carrying capacity of sections under elevated temperature parametrically. With the experimental study results from previous studies as a reference, authors used FEM analysis to comprehensively study the behavior of GI-based CFS sections under fire. Vertical, horizontal, and not providing a stiffener were the configurations selected to study the beams parametrically. Parametric analysis confirmed that different stiffener configurations did not alter the predominant failure mode, which remained distortional buckling across all specimens. Beams with vertical stiffeners demonstrated superior performance compared to those with horizontal stiffeners in parametric analysis. Lateral–torsional buckling was observed in the reference specimen, lacking stiffeners due to inadequate restraint at the supports. Full article