Flexural Behaviour of optimised cold-formed steel beams with sleeve stiffened web openings

CFS beams are often provided with web openings to accommodate building services. However, the area reduction in the web affects their load-bearing capacities. The reduction of bending capacity can be regained through providing suitable stiffeners in the vicinity of the web openings and through providing the web openings to the optimised CFS beams. Many research studies have been conducted for the former but no research studies have been reported for the latter. This paper presents an investigation on providing reinforced web openings to optimised CFS beams to restore the original flexural capacity. A computational analysis was carried out. The Finite Element (FE) elements were validated against experimental data from the literature and then used in conducting detailed parametric studies (80 FE models). The influence of the rectangular openings with four different sizes (hole height-to-web depth ratios: 0.2, 0.4, 0.6 and 0.8) and four different sleeve stiffening lengths (5, 10, 15 and 20 mm) on the bending capacity subject to distortional buckling was investigated in the parametric study. The results indicated that introducing web openings to the optmised CFS along with sleeve stiffening arrangement is a satisfactory approach to restore the original bending capacity. In addition, the optimum sleeve length was found and updated direct strength-based design equations are proposed to predict the bending capacity of the CFS beams with sleeve stiffened rectangular web openings subject to distortional buckling

Optimised and slotted cold-formed steel channels: a solution for modular buidling systems

The steel construction industry has recently put a lot of effort to better understand Modular Building Systems (MBS) and replaced, where possible, conventional construction methods. MBS claims promising advantages including speed of erection, improved quality, reduced cost, and flexibility. Therefore, research efforts are tuned to the structural, social, and safety evaluations of MBS while it is recognised that there are challenges associated with their use, yet to be addressed. The main challenges are improving structural, fire, and energy performances, need for lightweight materials, more access space during renovation and transportation difficulties. This paper investigates how the use of optimised Cold-Formed Steel (CFS) members with slotted web can address such challenges. The optimisation was performed using Particle Swarm Optimisation (PSO) method and subsequently, slotted perforations were added to enhance the structural, fire and energy performances, respectively. Finite Element (FE) analysis was employed to assess the performance of optimised innovative CFS beams with slotted perforations. As a result, the optimisation and FE analyses resulted in a 30-65% of flexural capacity enhancements along with notable performance improvement in fire and energy performances over conventional Lipped Channel Beam (LCB). Using such optimised innovative sections a conceptual design of a corner-post module was also developed. Hence, the optimised CFS channels with slotted perforations would be a convenient tool to overcome the reported challenges related to MBS, result in more cost-effective and efficient building solutions

Assessment of perforated steel beam-to-column connections subjected to cyclic loading

This paper presents a study of welded perforated beam-to-column connections, forming the so-called RWS systems. The effect of using non-standard novel web opening configurations of variable depths and positions is investigated. The ease of manufacturing process together with the improvements on the structural behaviour foreshadows the enhancements gained using these perforated members. It is concluded that using large perforations is an effective way of improving the behaviour of connections enhancing their ductility and their energy dissipation capacity. The connections with novel openings outperform the conventional ones; hence they can be suitably used in the aseismic design of steel frames

Web crippling behaviour and design of aluminium lipped channel sections under two flange loading conditions

Aluminium alloys have recently drawn significant attention in structural applications due to its outstanding mechanical characteristics. Thin-walled members fabricated by aluminium alloys can be more competitive in construction industries than the conventional cold-formed steel sections, particularly in areas with high humidity and severe environmental conditions. Nevertheless, they are more vulnerable to various types of instability due to their relatively low elastic modulus compared to steel. Applying high concentrated load transversely on thin-walled members can cause critical damage to the web of the cross section called web crippling. Although a large number of studies has been performed to investigate the web crippling mechanisms on different types of sections, the existing studies are primarily of the empirical nature and thus merits further investigations. To fill the research gap, this study was thus performed based on our previously conducted experimental work to further comprehend the web crippling phenomenon of the roll-formed aluminium lipped channel (ALC) sections under the loading conditions of end-two-flange (ETF) and interior-two-flange (ITF). This was done through numerical investigations followed by a parametric study which are reported herein in details. A wide range of roll-formed ALC sections covering web slenderness ratios ranged from 28 to 130, inside bent radii ranging between 2 mm and 8 mm, bearing lengths ranged from 50 mm to 150 mm, and three sheeting aluminium alloy grades (5052-H32, 5052-H36 and 5052-H38) were considered in the parametric study. The acquired web crippling database was then used to assess the consistency and accuracy of the current design rules used in practice. It was found that the web crippling capacity determined by the current international specifications are unsafe and unreliable, whereas the predictions of the recently proposed equations agree very well. Furthermore, a Direct Strength Method (DSM)-based capacity prediction approach was proposed and then validated against the web crippling database acquired here as well as the experimental and numerical data for cold-formed steel lipped channel sections used in the literature

Vierendeel Bending Study of Perforated Steel Beams with Various Novel Web Opening Shapes, through Non-linear Finite Element Analyses

The Vierendeel mechanism is always critical in perforated steel beams with single large web openings, where global shear forces and Vierendeel moments co-exist. Thus far, the main parameters that are known to affect the structural behavior of such beams are the depth of the web opening, the critical opening length of the top tee-section and the web opening area. A comprehensive Finite Element (FE) study of four sizes of perforated steel sections with three different sizes of eleven standard and novel non-standard web opening shapes was undertaken, and their primary structural characteristics presented in detail in order to provide a simple design method for general practice. The different geometric parameters were isolated and studied in order to understand the significance of their effects and in turn advance the knowledge on the performance of perforated steel beams. An elaborate FE model was established, with both material and geometrical non-linearity, allowing load redistribution across the web openings and formation of the Vierendeel mechanism. The reduction of the global shear capacities, due to incorporation of the local Vierendeel moments acting on the top and bottom tee-sections, was obtained directly from the FE analysis. Following that, a comparison of the global shear-moment (V/M) interaction curves of the steel sections with various web opening shapes and sizes was established and empirical generalized V/M interaction curves developed. Moreover, the accurate position of the plastic hinges was determined together with the critical opening length and the Vierendeel parameter. This work has now shown that the shape of the web opening can also significantly affect the structural behavior of perforated beams, as opposed to the equivalent rectangular shape predominately used so far. In addition, the effect of the position of the web opening along the length of the perforated beam was revealed. The importance of the parameters that affect the structural performance of such beams is illustrated. The thorough examination of the computational results has led to useful conclusions and an elliptical form of a web opening is proposed for further study. The outcome of this study is considered as being relevant for practical applications