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.