Cold-formed Steel C-sections Research Articles

The Performance of Cold-Formed Steel Beam-Column Connections with Screw Configuration

Cold-formed steel is being used as a viable substitute for traditional steel and building materials due to its performance, affordability, convenience, lightweight, and environmental friendliness. The major purpose of this current research is for a reaction to force-deformation at the connection level to be delivered, which is proper for typical cold-formed steel (CFS) screwed beam-column assembly CFS C-section, and to show the influence of the behavior of CFS under bending test. An inner plate, double angle plate, and self-drilling screws are used by a basic beam-column frame idealized CFS to join the beam-column. Fixed support was implemented at the column base, whereas the beam end had free support. A 0.75 mm cold-formed steel C-section with 80mm height and 30mm width was utilized in this study and assembled into an "I" and "box" configuration. 3d and 4d were used to compute screw spacing for self-drilling screws with 4 mm heads and 2 mm bodies. The first type was each angle plate (top and seat angle) screwed with eight screws, whereas the second involves four screws. The CFS section’s thinness led to the use of screw connections, which are essential to their ability to withstand connection failures, to anticipate the failure mode of the connection segment. Numerical simulation by ABAQUS Student Edition and analytical studies have been conducted by AS/NZS 4600:2018 to investigate the capacity of CFS under bending. Quantity and the arrangement of the screws determine the displacement ductility with tighter spacing enhancing performance and reinforcing global and local buckling resistance.

Effects of Lip Length and Inside Radius-to-Thickness Ratio on Buckling Behavior of Cold-Formed Steel C-Sections

Cold-formed steel (CFS) sections constructed with high-strength steel have gained prominence in construction owing to their advantages, including a high strength-to-weight ratio, shape flexibility, availability in long spans, portability, cost-effectiveness, and design versatility. However, the thin thickness of CFS members makes them susceptible to various forms of buckling. This study focuses on addressing and mitigating different types of buckling in columns and beams by manipulating the lip length (d) and the ratio of inside radius to thickness (Ri/t) in CFS C-sections. To achieve this objective, a comprehensive analysis involving 176 models was conducted through the Finite Element Method (FEM). The findings reveal that an increase in lip length leads to a corresponding increase in critical elastic buckling load and moment (Pcrl, Pcrd, Pcre, Mcrl, Mcrd, and Mcre). It is recommended to utilize a lip length greater than or equal to 15 mm for both columns and beams to mitigate various buckling types effectively. Conversely, an increase in the ratio of inside radius to thickness (Ri/t) results in an increase in critical elastic local buckling load (Pcrl) and moment (Mcrl). Thus, lip length (d) significantly influences column and beam buckling, whereas Ri/t exhibits a relatively impactful effect. Subsequently, the experimental test results were used to verify finite element models. These insights contribute significant knowledge for optimizing the design and performance of CFS C-sections in structural applications.

Testing, numerical modelling and design of G550 high strength cold-formed steel built-up section columns

This paper investigates the buckling behaviour and load-carrying capacity of G550 high strength cold-formed steel built-up section columns under axial compression through experiments and numerical simulations. Two types of built-up sectional profiles were formed, which were defined as built-up OI-section and built-up CB-section. Each built-up OI-section member is formed by connecting two cold-formed steel C-section members in a back-to-back manner using self-drilling screws, while each built-up CB-section member consists of a cold-formed steel C-section member and a cold-formed steel U-section member, which are connected in a face-to-face manner by self-drilling screws. The experimental programme included tensile coupon tests, initial geometric imperfection measurements and 20 pin-ended column compression tests. In the numerical modelling programme, finite element models were developed and validated against the experimental results, and then used for parametric analyses to generate a total of 250 numerical data with different cross-section dimensions and member lengths. Based on the experimental and numerical data, the accuracy of both the effective width method and the direct strength method for predicting the strengths of G550 high strength cold-formed steel built-up section columns, as set out in the American Specification, was evaluated. The evaluation results indicated that both the effective width method and direct strength method provided accurate and consistent failure load predictions for G550 high strength cold-formed steel built-up OI-section columns on average, but with some unsafe failure load predictions, while the predicted failure loads were inaccurate, scattered and conservative for G550 high strength cold-formed steel built-up CB-section columns. Moreover, the effective width method and direct strength method yielded a similar level of design consistency for G550 cold-formed steel built-up section columns, but the direct strength method resulted in more accurate and less conservative failure load predictions than the effective width method. The modifications to the codified DSM equations were proposed for G550 high strength cold-formed steel built-up section columns and shown to provide improved predictions of failure load over the design codes.

Local-distortional interactive behavior and design of cold-formed steel C-sections with & without slotted holes

Local-distortional interactive behavior and design of cold-formed steel C-sections with & without slotted holes

Web crippling resistances of cold-formed stainless steel sections: A proposal for EN 1993-1-4

The current EN 1993-1-4 does not have supplementary web crippling design provision for cold-formed stainless steel sections under local transverse forces. Therefore, designers are generally referring to the guidance in EN 1993-1-3 for cold-formed carbon steel sections. Over the past decades, quite a substantial number of tests have been carried out worldwide to study the behaviour of cold-formed stainless steel sections undergoing web crippling, among which the majority of the data were focused on C-sections as well as square and rectangular hollow sections (SHS and RHS). To this end, tailor-made design provisions for these stainless steel sections can be developed. In this study, up-to-date web crippling test data on cold-formed stainless steel C-sections and SHS/RHS were firstly collected. The applicability of the web crippling design provisions as per the new version of EN 1993-1-3 to stainless steel sections was assessed. New design provisions for cold-formed stainless steel unstiffened C-sections (unlipped channels), stiffened C-sections (lipped channels) as well as SHS and RHS under local transverse forces are proposed in this study. The newly developed web crippling design provisions for C-sections and SHS/RHS were derived based upon reliability requirements as regulated in EN 1990 using available experimental data reported on austenitic, ferritic and duplex stainless steel types of various grades. The proposed design provisions for stainless steel sections have been made in line with the development of the new version of EN 1993-1-3 provisions and therefore are recommended to EN 1993-1-4 for calculating web crippling resistances under local transverse forces.

Stiffening Performance of Cold-Formed C-Section Beam Filled with Lightweight-Recycled Concrete Mixture.

The aim of this paper is to investigate the flexural performance of a new steel–concrete composite beam system, which is required to carry higher loads when applied in flooring systems with less self-weight and cost compared with conventional composite beams. This new composite member is prepared by filling a single cold-formed steel C-section with concrete material that has varied lightweight-recycled aggregates. In addition, varied stiffening scenarios are suggested to improve the composite behavior of this member, since these cold-formed C-sections are of a slender cross-section and more likely to buckle and twist under high bending loads than those of hot-rolled C-sections. The influence of using four different lightweight-recycled aggregates that combine together in the infill concrete material was investigated. These recycled aggregates are recycled concrete aggregate (RCA), expanded polystyrene (EPS) beads, crumb rubber aggregates (CRA) and fine glass aggregates (FGA). For this purpose, 14 samples of cold-formed galvanized steel C-purlin were filled with concrete material (containing 0 to 100% recycled aggregates) which are experimentally tested under pure bending load, and 1 additional sample was tested without the filling material. Further numerical models were prepared and analyzed using finite element analysis software to investigate the effects of additional parameters that were not experimentally examined. Generally, the results confirm that filling the C-sections with concrete material that contains varied percentages of recycled aggregates offer significantly improved the flexural stiffness, bending capacity, and ductility performances. For example, using infill concrete materials with 0% and 100% recycled aggregate replacement increased the bending capacity of hollow C-section by about 11.4 and 8.6 times, respectively. Furthermore, stiffening of the concrete-filled C-sections with steel strips or screw connectors eventually improved the composite behavior of the specimens which led to an increase in their bending capacities accordingly, and this improvement enhanced more with an increased number of these strips and connectors.

Simplified design method of cold-formed steel columns with built-up box sections

The built-up box section members in this paper consist of single cold-formed steel (CFS) C-section and U-section basic components, which are connected by self-drilling screws at the flanges. This study incorporates experimental and theoretical research on the buckling behavior and ultimate strength of axially loaded pin-ended CFS built-up box section columns as affected by local and local-flexural interactive buckling modes. In total, 28 specimens were prepared and tested under axial compression. The test results revealed visible local buckling or local-flexural interactive buckling for specimens. Thereafter, finite element models were established by the ABAQUS software and validated with the structural behavior of the test specimens. The effects of the slenderness ratio, web depth-to-thickness ratio and screw spacing on the ultimate strength of the built-up columns were investigated based on the numerical analysis. Finally, based on the test results of this research as well as previous works in the literature, a simplified design method was proposed to predict the ultimate strength of built-up box section columns. By comparing the predicted results against the test results, the proposed method was subsequently validated.

Flexural properties of new cold-formed thin-walled steel and concrete composite slabs

This paper presents a new type of steel and concrete composite slab, which is composed of cold-formed thin-walled steel C-sections, bars, concrete and polystyrene foam panels. Considering different filling quantities of the foam panel in the slab, two specimens (one three-hole slab and one two-hole slab) are made for flexural testing. Aimed at studying the bending performance and failure mode of the composite slab, the specimens are analyzed with respect to their flexural capacity, ductility ratio, concrete strain, reinforcement strain and C-section strain. Results show that the composite slab fails in a normal section of flexure while it has good bearing capacity and ductility in the test. The strain of concrete in the slabs is linearly distributed along the section height, which conforms to the plane section assumption. Mechanical performance of the three-hole slab is better than that of the two-hole slab. Together with finite element simulations, the numerical results of flexural capacity are compared to the test results; the comparison indicates that they are in good agreement, which lays a foundation for the subsequent parametric analysis.

Experimental Analysis of Cold-Formed Steel C-Sections with the Notch Subjected to Axial Compression

Studies on the use of cold-formed steel (CFS) C-section, which is a civil engineering material, in building and civil engineering work are still on-going. The advantages of the CFS C-section are becoming so interesting that it is often being used as a roof truss system, storage rack, and wall framing. In order to have a roof truss system with a strong, safe, and stable condition, a study on truss member was carried out using the cut-curving process. Before the CFS C-section was curved, the process started by cutting the section in a proper way. A parametric study was conducted to determine the suitability of the cut pattern which recognised as a notch in the section and find out whether or not the notch depth would affect the ultimate load of the CFS C-section column. The study of CFS C-section was separated into two parts; firstly, to investigate the mechanical behaviour of the column in different notch depths and secondly, to investigate the behaviour in different column height with fixed notch depth. The notch width of 3 mm and notch spacing of 100 mm for both parts were fixed. Total specimen for both parts were 15 specimens. The results of the study showed that the reduction of the ultimate load was about 56–65% of the variation of notch depth section when compared with the normal section. Therefore, the ultimate load of the section with the notch decreased when the notch depth increased. In addition, the study illustrated that the reduction of the ultimate load was 64–82% of the variation of column height between 100 mm to 500 mm. Finally, the average percentage of the column height was 72% which can use in the modification of CFS C-section without notch to CFS C-section with notch calculation.

Experimental Evaluation of Composite Beam-to-Column Joint Using Cold-Formed Steel Sections

This paper is focusing on the experimental investigation of composite beam-to-column joint formed by a composite concrete slab and two lipped cold-formed steel C-sections placed back-to-back as beam and column. As the bare joint of cold-formed sections might not have higher moment resistant, a composite action from the composite concrete slab is utilized and expected to enhance the load carrying capacity of the joint. Two specimens namely the composite joint and non-composite joint are constructed and tested until failure under a point load at a certain eccentricity from the face of the column to induce moment to the joint. All components which are the decking, hot rolled plate, bolts and reinforcement bar used were the same for both specimens except the arrangement of the longitudinal bars. The relationship between the load and deflection, and subsequently, the moment and rotation of the joints are obtained specifically, the ultimate load and the respective moment resistance. It is found out that the composite joint yields higher ultimate load and moment resistance compare to the non-composite joint. The results also indicate that a composite joint has credible rotation and moment resistance, and the fracture of the joint occurs after substantial rotational deformation has been achieved.

EXPERIMENT ON COLD-FORMED STEEL C-SECTION JOINT WITH SCREW AND ADHESIVE MATERIAL

Experiments were performed on the cold-formed steel C-section (CFS-CS) joints using the screw and adhesive material as the main subject of the study to assess the tensile stress-strain capacity. Since the connection has become the foremost aspect of the CFS-CS structure, a number of studies have been focusing to provide a better understanding with regard to the behavior of the connection. Even more so, further studies have also been carried out focusing on alternate solutions to improve the connection capacity. Considering all the above, this paper discusses the influence of varying types of connection on the tensile behavior of CFS-CS elements with particular using the self-drilling screw and 3M Scotch-weld DP810 as an adhesive material. The configurations of the screw(s) used in this study were 1, 2, and 3, while the percentages of adhesive material being used were 50%, 75%, and 100%. The results showed that the use of a higher amount of adhesive does not significantly increase the load capacity, but alleviate the failure condition. The results also showed that all test specimens satisfy the minimum requirement according to design specifications. Article DOI: https://dx.doi.org/10.20319/mijst.2017.32.5163 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Behaviour and design of cold-formed steel C-sections with cover plates under bending

This paper presents an experimental, analytical and numerical investigation on the correlation between non-dimensional slenderness and pure bending strength of stiffened cold-formed steel as a construction material. Cover plates with three different thicknesses (1.6, 2 and 4 mm) were incorporated to evaluate the slenderness effects on flexural performance of C-sections installed at top flanges only as it would be the predicted location for local and distortional buckling. The lateral supports were provided to prevent lateral torsional buckling in the experiment investigation. Application of the Direct Strength Method led to an extensive parametric study to investigate the moment capacity and buckling modes of specimens with different cover plate thicknesses. A nonlinear finite element model was developed and verified against the test results in terms of failure buckling modes. Moreover, a newly recommended non-dimensional slenderness of DSM in order to address the plastic strength for stocky sections was proposed in this paper. The results explicitly showed that the cover plate reduced the non-dimensional slenderness which resulted in improved buckling capacity. Also, it was concluded that the design strengths predicted by the current DSM in accordance with the American specification guideline, AISI, was conservative for sturdy sections as these sections can develop plastic moment.

Buckling Behavior of Cold-Formed Studs with Thermal Perforations

Studies have shown that the optimal structural scheme for low-rise buildings that meets all regulatory requirements is a frame system. In this connection, thin-walled cold-formed steel (CFS) profiles seem to be the best material for constructing light steel framed (LSF) walls. The framework of LSF walls is usually constructed from CFS C-shaped profiles. To increase the thermal effectiveness of a wall, CFS profiles usually have thermal perforations and thus are called thermoprofiles. However, these openings have a negative impact on bearing capacity of profiles and require accurate evaluation. In this article a relatively new reticular-stretched thermoprofile with diamond-shaped openings is considered. The article deals with the buckling analysis of perforated CFS C-sections subjected to compression.

General distortional buckling formulae for both fixed-ended and pinned-ended C-section columns

This paper presents general explicit analytical formulae to provide distortional critical stress estimates for cold-formed steel C-section columns subjected to uniform compression. These formulae are derived by employing the Lau and Hancock model and by introducing a new factor for considering the web rotational restraint reduced by web bending. The results obtained from the general explicit analytical formulae are compared with the numerical results obtained from the computer programs CUFSM or/and GBTUL. For pinned-ended columns, these values are also compared with those yielded by the formulae developed by Lau and Hancock, Schafer, and Silvestre and Camotim. In particular, the distortional critical stress of fixed-ended C-section columns is validated by comparing the corresponding ultimate load based on Schafer’s DSM expressions with numerical results from the research literature. The formulae derived here are validated and their application, accuracy and capabilities are illustrated by these comparisons and validations.

Parametric Study of Compound Cold-Formed Steel Sections as Flexural Members

This paper presents a parametric study on compound cold-formed steel sections as flexural members. The compound members are used to sustain higher load and solve the problems of local buckling and lateral torsional buckling. The aim of this study is to investigate the strength of compound cold-formed steel section subjected to pure bending. Moment capacity of the compound section is calculated in accordance to Eurocode 3. The compound cold-formed steel sections proposed in this study are made up of two cold-formed steel C-section and hot-rolled plates. Steel plates with thickness of 3 mm to 8 mm are added to the cold-formed double C-section with the purpose to increase the bending capacity. From the comparison, moment capacity of compound sections give higher value as compared to cold-formed steel C-section with the comparison ratios range between 1.15 and 3.30. Results from the study show that compound cold-formed steel sections able to enhance the strength in resisting pure bending by adding steel plate at the flanges and web of the section. On the other hand, finite element modeling using ANSYS is carried out on two of the selected compound cold-formed steel sections and the results show good agreement with analytical results.

Experiments on Cold-Formed Steel Lipped Channel Beams with Complex Edge Stiffeners and Web Holes

This paper presents an experimental investigation and a numerical analysis on the bending strength and behavior of cold-formed steel C-section and ∑-section beams with complex edge stiffeners and web holes. Local buckling, distortional buckling and interaction between local and distortional buckling were observed in the tests. The experimental results show that the stiffened web has great influence on member's bending strength. Compared with C-section specimens, the stiffness of the web stiffeners of ∑-section specimens reduced the influence of the holes. The finite element analysis results show good agreement with the experimental results in terms of bending strength and buckling mode.

Experiments on Cold-Formed Steel C-Section Joists with Unstiffened Web Holes

AbstractExperiments were conducted on cold-formed steel C-section joists with rectangular unstiffened web holes. The presence of holes decreased joist capacity and amplified distortional buckling deformation. Distortional buckling was accompanied by unstiffened strip buckling of the compressed web. When hole depth approached the web depth, sudden buckling of the compressed flange and web above the hole was observed. Critical elastic buckling moments for local, distortional, and global buckling were calculated for each specimen including the influence of holes with recently introduced engineering expressions and finite strip analysis. Forthcoming direct strength method equations for cold-formed steel joists with holes were demonstrated to be viable predictors of flexural capacity for the specimens considered in the experimental program.

Strength and behaviour of cold-formed steel offset trusses

Thirteen full-scale truss specimens fabricated with cold-formed steel C-sections were tested to study various practical strengthening techniques in order to achieve a desired behaviour and an increased capacity. Specimens were subjected to concentrated panel point loading simulating the realistic loading condition of a roof truss. Results revealed that local buckling of the top chord (LBTC) adjacent to the heel plate was the predominant failure mechanism. In instances where the heel plate was not adequately stiffened, the distortion or crippling of the plate occurred at failure. For the investigated pitches, an increase in specimen pitch resulted in an increase in the capacity. Strengthening both the top chord adjacent to the heel plate and the heel connection with both a shallow member and a heel plate stiffener resulted in the most significant increase in the capacity compared with the original truss configuration. Beam–column analysis of the top chords in the failure region was performed using both the conventional interaction design equations and the direct strength method as suggested in CSA S136-07.

Flexural behaviour and capacity of composite panels of light gage steel and concrete

Eight panel specimens were tested in one-way bending to study the behaviour and capacity of composite slab joists consisting of cold-formed steel C-sections and concrete. Various shear transfer mechanisms were implemented on the C-section flange embedded in the concrete to provide the longitudinal shear resistance. Results showed that all specimens reached serviceability limit state while in elastic range and failure was ductile. Shear transfer achieved for all specimens ranged from 42 to 99% of a full transfer while specimens employed with shear transfer enhancements showed a greater percentage and therefore a higher strength compared with those relying only on surface bond to resist shear. The implementation of pre-drilled holes on the embedded flange of the steel C-section was shown to be most effective. The correlation study between the push-out and panel specimens indicated that the calculated moment capacity based on shear transfer resistance obtained from push-out tests was, on average, 10% lower than the experimental ultimate capacity of the panel specimen.

Experimental and numerical investigation on cold-formed steel C-section flexural members

This paper presents an experimental and numerical investigation on the bending strength and behavior of cold-formed steel C-section flexural members with upright, inclined and complex edge stiffeners. A total of 24 specimens that divided into 12 tests including 6 pure bending tests and 6 non-pure bending tests have been conducted. Local buckling, distortional buckling and interaction between local and distortional buckling were observed in the tests. The experimental results show that the edge stiffener and buckling mode have great influence on member’s bending strength. Comparison of the bending strengths under the two bending states show that the bending strength under non-pure bending is higher than which under pure bending, but the increased magnitude is related to the buckling modes. Moment gradient effect has only a minor influence on local buckling, but has great influence on distortional buckling. The tests were simulated by finite element program of ANSYS and the simulated results show good agreement with the experimental results in terms of bending strength and buckling mode.