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Perforated cold-formed steel (PCFS) beams are increasingly used in constructional industry and become popular due to their advantages and economic benefit. Apart from the light weight, the openings in PCFS beams can also be used for services such as pipe utilities to release more building space. However, beams with web perforations may collapse as the result of web-distortional buckling or flange/web distortional buckling due to the web weakness caused by perforations. In this paper a study on the flange/web distortional buckling of PCFS beams is presented. An analytical solution to determine the critical stress of flange/web distortional buckling of PCFS beams is derived by using energy method. To demonstrate the analytical solution, finite element analysis is also carried out. The finite element analysis results show that the analytical solution provided can give good and reliable prediction for the flange/web distortional buckling of PCFS beams. [ABSTRACT FROM AUTHOR]

Abstract Circular holes can be commonly found in the web of cold-formed steel beams to accommodate services such as electric wires and pipelines. The presence of holes will reduce the critical buckling stress of the beams. Hancock proposed solution for determining the distortional critical stress of channel section beams, but limited to the sections without holes. This paper presents an analytical study on the distortional buckling of cold-formed steel channel-section beams with circular holes in the web. Hancock's solution has been modified to derive a simple formulation for approximating the elastic critical stress and moment of distortional buckling of the channel-section beams with circular holes in the web, which are compared with those from the finite element buckling analysis using ANSYS. Finally, the influence of multiple holes on the distortional buckling behaviour and corresponding elastic buckling stress of beams in bending is discussed. Highlights • The distortional buckling behaviour of perforated cold-formed beams is studied. • An analytical model is developed for calculating critical moment. • Finite element analyses are used to simulate the distortional buckling behaviour. • The proposed approach shows good agreement with finite element analyses. • Comparison is made with the method available in the literature. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an analytical study of the flexural buckling and lateral–torsional buckling of cold-formed steel channel section beams subject to combined compression and bending about their major and minor axes. For channel section beams a bending about the minor axis creates a non-symmetric pre-buckling stress distribution, which has a significant influence on the lateral–torsional buckling of the beams. This kind of feature has not been discussed in the existing literature. The focus of this present study is the interaction between the compression load and the bending moments about the major and minor axes. It has been found that for a section subject to combined compression and the major-axis bending the bending moment will decrease the critical compression load, although the critical value of the largest compressive stress in the section actually increases with the applied bending moment. However, for a section subject to combined compression and the minor-axis bending the effect of the bending moment on the critical compression load depends on the direction of bending applied. For bending that creates a compressive stress in the lips the bending moment will reduce the critical compression load. However, for bending that creates a compressive stress in the web the bending moment has almost no influence on the critical compression load. [Copyright &y& Elsevier]

Thin-walled channel beams are easily punched with circular holes on the web to allow the access for services such as plumbing pipes and electric wires. The presence of the holes can alter the stress distribution in the member and reduce the cross-sectional property. Consequently, it changes its buckling mode. Since perforated cold-formed steel beams are usually placed between main structural frame and corrugated roof, the most common loading case is the uniformly distributed transverse load. Recent work by Chen and Li has given the solution for distortional buckling of channel-, zed- and sigma-sections subject to the uniformly distributed transverse load. This paper is an extension of Chen and Li's research to explore the distortional buckling behaviour of perforated cold-formed steel beams with holes. The effect of perforations on the critical stress is evaluated. A new model is deduced to predict the critical stress of distortional buckling by reducing the stiffness of the vertical spring. The Rayleigh-Ritz method is used to solve eigenvalue problems. In order to validate the analytical model, finite element analyses have been performed by using ANSYS. When the beam is longer than 3500 mm, the critical stress computed from the analytical model matches well with the critical stress acquired from the finite element analyses. • The distortional buckling of perforated beams under uniformly distributed transverse loads is studied. • The analytical solution is presented for calculating the critical stress. • The finite element model is used to simulate the elastic buckling of beams. • The stress gradient has a significant effect on the critical load of distortional buckling. • The analytical approach is compared against the results of finite element analyses. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation on the buckling behaviour of plasterboard protected CFS channel-section beams subjected to uniformly distributed loads when exposed to fire on its one side. The work involves three phases, namely heat transfer analysis, pre-buckling analysis and buckling analysis. The heat transfer analysis is accomplished using two-dimensional finite element analysis methods, from which the temperature fields of the channel-section beams are obtained. The pre-buckling analysis is completed using the Bernoulli bending theory of beams with considering the effects of temperature on strain and mechanical properties. The buckling analysis is performed using combined finite strip analysis and classical Fourier series solutions, in which the mechanical properties are considered to be temperature dependent. The results show that there are significant temperature variations in web, fire exposed flange and lip. Also, it is found that the buckling behaviour of the beam with temperature variation in its section is quite different from that of the beam with a constant uniform temperature in its section. [ABSTRACT FROM AUTHOR]