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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]

The majority of the existing literature on the lateral stability of castellated beams deals with experimental and/or numerical studies. This paper presents a comprehensive analytical study of the lateral-torsional buckling of simply supported castellated beams subject to pure bending and/or a uniformly distributed load. Using the principle of total potential energy, analytical expressions for the critical buckling moments and loads are derived and applied for various beam lengths. The three different locations of the applied load are used: At the top flange, shear center and bottom flange. The results show that the influence of web openings on the critical buckling moments and loads are mainly due to the reduction of the torsional constant caused by the web openings. Web shear effects and web shear buckling become important only when the beam is short and the flange is wide. The critical moments and loads will be overestimated or underestimated if the full or reduced section properties are used. The accurate critical moment or load should be calculated based on the average torsional constant of the full and reduced sections rather than simply taking the average of the critical moments or loads calculated from the full and reduced section properties. The present analytical solutions are verified using 3D finite element analysis results. [ABSTRACT FROM AUTHOR]

Abstract: The majority of the existing literature on castellated members is focused on beams. Very little work has been done on the stability of castellated columns although they have been increasingly used in buildings in recent years. This paper presents a new analytical solution for calculating the critical buckling load of simply supported castellated columns when they buckle about the major axis. This analytical solution takes into account the influence of web shear deformations on the buckling of castellated columns and is derived using the stationary principle of potential energy. The formula derived for calculating the critical buckling load is demonstrated for a wide range of section dimensions using the data obtained from finite element analyses published by others. It was found that the influence of web shear deformations on the critical buckling loads of castellated columns increased with the cross-sectional area of a tee section and the depth of web opening, but decreased with the length and the web thickness of the column. It is shown that the inclusion of web shear deformations significantly reduces the buckling resistance of castellated columns. Neglecting the web shear deformations could overestimate the critical buckling load by up to 25%, even if a reduced second moment of area is used. [Copyright &y& Elsevier]

Abstract: In this paper an analytical model is presented to describe the lateral–torsional buckling behaviour of steel web tapered tee-section cantilevers when subjected to a uniformly distributed load and/or a concentrated load at the free end. To validate the present analytical solutions finite element analyses using ANSYS software are also presented. Good agreement between the analytical and numerical solutions is demonstrated. Using the present analytical solutions, the interactive buckling of the tip point and uniformly distributed loads is investigated and a parametric study is carried out to examine the influence of section dimensions on the critical buckling loads. It is found that web tapering can increase or decrease the critical lateral–torsional buckling loads, depending on the flange width of the beam. For a beam with a wide flange (width/depth=0.96) the critical buckling load is increased by 2% by web tapering, whereas for a beam with a narrow flange (width/depth=0.19) web tapering reduces the buckling load up to10% and 6% for the tip point loading and the uniformly distributed load respectively. [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]

This article investigates experimentally and numerically the thermal performance of a new type of structural insulated panel (SIP) termed 'UWall'. The panel core consists of an ad-hoc waffle skeleton of Expanded Polystyrene (EPS), EPS beads mixed with cement mortar (Portland cement type I and recycled concrete aggregate), and two external water-proof cement boards. The experimental programme examined the panels in three Phases. In Phase 1, 200×200×100 mm block specimens were exposed to a temperature of 70°C for 12 hrs. It was found that the new UWall specimens had a better thermal performance (by up to 20%) over other types of walls typically used in house construction in Southeast Asia such as Mon block wall. In Phase 2, five scaled-down house units (1.5×1.5×2.8 m) were built in Thailand. Temperature and relative humidity outside/inside the units were continuously monitored for 7 days during the summer season. It was found that the new UWall has a good thermal resistance, reducing temperatures by up to 4°C compared to mon-block wall material. The house units were subsequently modelled in Abaqus® software, and the modelling approach proved accurate (within 10%) at simulating the thermal performance of the house units. UWall panels were also tested in bending to determine their structural capacity. It was found that the panels can be safely used as load-bearing walls for single-storey houses. Design charts are then proposed and used to design and build a full-scale house in Phase 3. In Phase 3, a 10×7 m full-scale single-storey house was built using the new UWall panels. Based on results from bioclimatic charts, it was found that daytime temperature and humidity in the full-scale house were deemed as uncomfortable. However, if air movement was provided, the house remained within the comfortable zone at all times. New design charts for full-scale houses with UWall are proposed to meet a desired user-comfort level. This study is expected to promote the use of SIPs in house construction in tropical climates, which in turn is envisaged to save energy and make construction more sustainable. • A new UWall made of recycled aggregate concrete, expanded polystyrene, and cement boards is proposed • Thermal and structural behaviour of new SIP UWall are tested using five scaled-down units and a full-scale house in Thailand • The UWall reduced indoor temperature in the full-scale house by 3–5°C compared to conventional walls • As finite element models of the houses matched well the test results (accuracy <10%), a parametric analysis was performed • New design charts to meet specific structural or thermal performances in full-scale houses are proposed [ABSTRACT FROM AUTHOR]

This article investigates the shear behaviour of Recycled Aggregate Concrete (RAC) Z push-off specimens. Fifteen specimens with different replacement levels of recycled concrete aggregate (RCA = 0 %, 25 %, 50 %, 75 % and 100 %) were tested. It is shown that a 100 % RCA replacement level reduces shear strength by 17.3 %. The shear behaviour of the specimens was further analysed using nonlinear finite element analysis (FEA). The results show that the shear strength results from the FEA and Digital Image Correlation measurements agree well (within 5 %) with the experimental results. This study proposes a new semi-empirical equation to calculate the shear strength of specimens with different RCA replacement levels. The new equation adopts a fracture mechanics approach, and it explicitly considers the shear slip deformation and crack opening. Compared to existing models, the new equation fits better the experimental data in this study, as well as test results from an extensive database obtained from the literature. [ABSTRACT FROM AUTHOR]