Cold-formed Members Research Articles

Nonlinear response of high-strength cold-formed steel built-up members subject to cyclic compression

Nonlinear response of high-strength cold-formed steel built-up members subject to cyclic compression

Study on Mechanical Properties of Partially Concrete-encased Cold-formed Thin-walled C-section Steel Compression-bending Members

Abstract Cold-formed thin-walled C-section steel is prone to localized strength deficiencies. To address this issue, partially encased concrete (PEC) columns have been integrated into the steel to form partially encased concrete cold-formed thin-walled c-section steel compression-bending members. In this study, a finite element model of 36 PEC composite columns is developed using ABAQUS finite element software. The impact of various factors, including PEC column section size, eccentric distance, batten plate spacing, and concrete strength, on the eccentric compression behavior of these members is investigated. The results of the analysis show that both the ultimate bearing capacity and initial stiffness of PEC columns increase with the section size, while they decrease with the increase in eccentric distance. The batten plate spacing has minimal effect on the ultimate bearing capacity and initial stiffness of PEC columns under eccentric compression. Additionally, concrete strength plays a role in the ultimate bearing capacity of PEC columns, with higher concrete strength leading to a higher ultimate bearing capacity.

Testing and numerical modelling of web-stiffened cold-formed steel channel section compression members with web perforations and batten reinforcements

Testing and numerical modelling of web-stiffened cold-formed steel channel section compression members with web perforations and batten reinforcements

Analysis and Design of Pre-Engineered Building Structure Using Staad.Pro

Abstract – This paper presents a comprehensive analysis and design study of a Pre-Engineered Building (PEB) structure using STAAD.Pro, a structural analysis and design software widely used in civil engineering. PEBs have gained significant traction in modern construction due to their modularity, faster erection time, and cost-effectiveness compared to conventional steel structures. The objective of this study is to evaluate the feasibility, material optimization, and structural performance of a PEB industrial shed located in Chennai, India. The structure was modeled and analyzed under various loading conditions including dead load, live load, wind load, seismic load, and collateral load, following IS 800:2007, IS 875 (Parts 1–3), and IS 1893:2016. The design incorporated tapered sections for the primary frames and cold-formed members for purlins and girts. Seismic and wind loads were particularly critical due to the site's location in Zone III and a basic wind speed of 50 m/s. The final STAAD.Pro output confirmed that the structure remains within permissible deflection limits and achieves material economy through optimization. This paper demonstrates that PEBs provide a viable, efficient, and sustainable alternative for industrial infrastructure development. Key words: Pre-Engineered Building, Deflection, Optimization, STAAD PRO, etc.

Fire-Induced Thermal Gradients in Cold-Formed Steel Flexural Members: A Numerical Parametric Study for Structural Application

Fire-Induced Thermal Gradients in Cold-Formed Steel Flexural Members: A Numerical Parametric Study for Structural Application

Local-distortional-global buckling interaction os lipped channel steel cold-formed columns

It is well-established that axially loaded thin-walled steel cold-formed members are susceptible to elastic buckling. This has been a focal point of numerous research studies, leading to insights into various buckling interaction cases, including local-global (LG), local-distortional (LD), distortional-global (DG), and local-distortional-global (LDG) interactions. This investigation specifically focuses on the triple buckling interaction LDG, building upon the authors' previously proposed design solution for LD buckling interaction. The study was conducted using experimental and finite element method (FEM) column results, creating a comprehensive database to validate the proposed solutions. The first research step involved verifying the accuracy of the shell FEM model by calibrating with experimental results of lipped channel (LC) columns developing the LDG buckling. Once the FEM model's accuracy was confirmed, a parametric study was conducted to support the development of the proposed LDG design solution for LC columns. The proposed design equations adhere to the core principle of the direct strength method, capable of incorporating all single buckling modes (L, D, and G) and their combinations (LG, LD, and LDG). Comparisons were made using LRFD-based reliability analysis, which confirmed that the proposed solution is reliable, easy to apply, and aligns with the usual design principles and parameters found in current codes and standards for steel cold-formed structures. Additionally, DG and LDG design approaches from other authors are mentioned and discussed in the context of the findings of the present investigation.

An Overview of Buckling Behaviour of Cold-Formed Steel Built-Up Members: Connected Face-to-Face and Backto-Back

Cold-formed steel (CFS) is increasingly being used in modern buildings owing to its lightweight, recyclable nature and material usage efficiency aligning with sustainable practices. Built-up CFS sections have garnered significant attention owing to their increasing application in modern construction. These thin-walled CFS sections are prone to low buckling resistance, limiting their application in tall buildings under extreme loading conditions. This paper review comprehensively the buckling behaviour and structural stability of various CFS built-up configurations of face-to-face, back-to-back non-gapped and back-to-back gapped configurations. The findings show that built-up sections enhance structural performance by reducing local, distortional, and global buckling compared with single sections. Fasteners and stiffeners are crucial for improving the performance by optimising the fastener spacing and the inclusion of stiffeners significantly enhances structural stability. These modifications enhance both the structural axial and flexural performances by improving the buckling resistance under extreme loads. Current design standards often inadequately address buckling complexities and necessitate updates to fully leverage CFS’s structural potential. The back-to-back gapped configuration stands out for its superior constructibility particularly in truss systems, owing to its ease of assembly, adaptability to buckling challenges and improved lateral stability. Innovative design improvements and updated guidelines are required to enhance CFS applications in sustainable and resilient structural systems.

Numerical modeling and design of cold-formed stainless steel elliptical hollow section beam-column members

Numerical modeling and design of cold-formed stainless steel elliptical hollow section beam-column members

Structural behaviour of built-up I-shaped CFS columns

The utilization of cold-formed thin-walled members as structural members has gained significant popularity due to their advantages in fabrication, cost-effectiveness, and transportation convenience. However, the reduced thickness of the used sections poses challenges such as global, local, and distortional member buckling, leading to a decrease in their axial strength. This study focuses on addressing these challenges by connecting the channels together using screws as an alternative to welding, considering the cost, time, and ease of implementation. Conducting finite element analysis on structural columns built-up from cold-formed double C steel channels and subjected to axial loads, this paper verifies the numerical models used against experimental tests known from the literature. A comparison of experimental results with nonlinear FEA and AISI & AS/NZ standards reveals commendable agreement, particularly in predicting the buckling behavior of the built-up I-shaped CFS columns. While the results of the finite element analysis show an overestimation of approximately 3.6% compared to the experimental tests, the AISI and AS/NZS standards demonstrate a conservatism of about 3.0%. Furthermore, the current study investigates the influence of screw spacing on axial strength of built-up cold-formed steel columns. The findings are derived from 175 finite element experiments, evaluating seven different cross-sectional profiles with twelve distinct screw spacings. These spacings correspond to the half-wavelength of local, distortional, and global buckling, divided by values ranging from one to four. The screw spacing determined by half the local buckling half-wavelength along the webs’ centerline resulted in enhancements of 22%, 7%, 13%, and 11% in the critical elastic local, distortional, and global column buckling loads, as well as the nominal axial strength, respectively. These increases were even more pronounced for double-lane fasteners with the same spacing, yielding improvements of 25%, 46%, 17%, and 12%, respectively. For economic considerations, it is advisable to utilize single-lane fasteners with a half-wavelength equal to half the local buckling half-wavelength.

Stability of hot-finished and cold-formed steel hollow section columns: A comparative study

A comparative study into the buckling behaviour of hot-finished and cold-formed steel hollow section members subjected to axial compression is presented in this paper. The main differences between hot-finished and cold-formed hollow sections are initially discussed. An experimental programme conducted to investigate the local, global and local-global interactive buckling of hollow section columns is then described. Three S355 normalised hot-finished and three S355/S420 (dual certified) cold-formed profiles, covering circular, square and rectangular hollow sections (CHS, SHS and RHS respectively), were studied. The stress-strain characteristics of the examined materials were obtained through tensile coupon tests. 3D laser scanning was utilised to determine the distribution of geometric imperfections in selected SHS test specimens and a consistent approach to characterise different forms of geometric imperfections from the scan data is put forward. A stub column test was carried out on each cross-section to examine its local buckling behaviour, and a series of long column tests were performed on all test profiles. In total, 21 tensile coupon tests, six stub column tests and 40 long column tests were conducted in this programme. Finite element models were also developed, validated and used for parametric studies to generate supplementary numerical datasets. The obtained test and numerical data, along with the existing experimental results collected from the literature, were used to evaluate the accuracy and reliability of the Eurocode 3 (EC3) stability design provisions for hot-finished and cold-formed hollow section columns; aspects requiring improvements are highlighted to guide future studies.

Evaluation of the Influence of Bolt Fastener Spacing on the Elastic Critical Load from the Lateral-Torsional Buckling Condition of Built-Up Bending Members.

In an experimental study of two-branched beams bent transversely about the major stiffness axis, the elastic critical load from the lateral-torsional buckling condition was determined. The tests were conducted on simply supported two-branch beam models with a built-up section consisting of two cold-formed channel members (2C) bolted back-to-back. The bolts were located at the mid-height of the built-up cross-section. Five groups of members differing in longitudinal bolt spacing were examined. The models were gravitationally loaded (using ballast) at the centre of the beam span. This approach eliminated the undesirable effect of the lateral support of the beam, e.g., by the actuator head. The critical load, measured by the concentrated transverse force (Pz,cr), was determined using the modified Southwell method. It has been experimentally shown that, in built-up beams, there is an influence of bolt spacing on the elastic critical load from the lateral-torsional buckling condition. The lowest critical load capacity and the most non-linear behaviour of the built-up member were observed in beams bolted with only three bolts (at the supports and in the middle of the span). However, the experimental results obtained in this study show that increasing the number of bolts above a certain level (in the case of the tested models, it was seven bolts) does not result in a further increase in the critical load, which is a surprising result. The obtained values were 15 to 23% lower than the critical load determined numerically by the finite element method (LTBeamN) for an analogous element with a uniform I-section.

Behaviour and design of cold-formed high-strength steel built-up beams

Behaviour and design of cold-formed high-strength steel built-up beams

Energy-based equations for distortional buckling of Zed and rack section columns

Energy-based equations for distortional buckling of Zed and rack section columns

Direct Stiffness–Strength Method: An Alternative Design Approach to AISI for Sheathed Cold-Formed Steel Z-Section Structural Members Subjected to Bending

Direct Stiffness–Strength Method: An Alternative Design Approach to AISI for Sheathed Cold-Formed Steel Z-Section Structural Members Subjected to Bending

Data driven models for capacity prediction of CFS lipped channel flexural members

Data driven models for capacity prediction of CFS lipped channel flexural members

Stability design of cold-formed high and ultra-high strength steel thin-walled box sections using effective stress-strain model

Stability design of cold-formed high and ultra-high strength steel thin-walled box sections using effective stress-strain model

Buckling behavior of cold-formed steel sigma and lipped channel section beam-columns: Experimental and numerical investigation

Buckling behavior of cold-formed steel sigma and lipped channel section beam-columns: Experimental and numerical investigation

Improvement of CSM for high-strength S690 and S960 unlipped channel columns, beams and beam-columns

Improvement of CSM for high-strength S690 and S960 unlipped channel columns, beams and beam-columns

Experimental Study on the Pull-Out Capacity of Blind Rivet Nuts (BRNs) Mounted on Cold-Formed Square Hollow Section Members with Different Wall Thickness

In this study, pull-out tests of blind rivet nuts (BRNs) mounted on cold-formed square hollow section (SHS) webs with 100×100 mm nominal cross-section dimensions and different wall thicknesses (2.0 to 5.0 mm) were performed, and the effect of different wall thicknesses and BRN thread sizes on the test results was experimentally investigated. M10 and M12 stainless steel BRNs were mounted on SHSs using a standard riveter tool, and the test elements were prepared for the experiment. Load–displacement curves and the final damage modes were obtained for each test specimen. The results show that the pull-out capacity depends on both the SHS wall thickness and rivet nut thread size. Although the pull-out capacity increased in both thread sizes with the increase in wall thickness parameters, the effect of thread size is negligible in the case of 2.5, 3.0, and 4.0 wall thickness. In addition, when a connection is created using a BRN, the design should consider the stripped thread strength in addition to the pull-out capacity.

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

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