Shear behaviour and design of doubly symmetric hollow flange beam with web openings

Abstract

Cold-Formed Steel (CFS) sections are extensively used in structural engineering applications replacing the conventional hot-rolled sections due to their inherent advantages. Web openings are generally placed in CFS floor joists and bearers to accommodate the building services, which leads the reduction of floor height. The web openings significantly influence the shear behaviour and reduce the shear capacity. However, very limited research studies have been conducted on hollow flange CFS beams with web openings under shear load. Therefore, this study presents a detailed Finite Element (FE) investigation of the shear behaviour of CFS doubly symmetric Rectangular Hollow Flange Beams (RHFBs) with unreinforced circular web openings. Non-linear FE models were created and validated using the laboratory shear test results. A detailed parametric study was then carried out by extending the validated FE models for doubly symmetric RHFBs with circular web openings. In total,126 FE models were investigated with different geometric parameters including section depth, thickness, material strength and web opening sizes to observe their behaviour on shear strength. The results showed that the existing shear strength design equations are either unsafe or conservative for doubly symmetric RHFBs with unreinforced circular web openings. Therefore, new Direct Strength Method (DSM) based shear design rules are proposed to estimate the shear strength of doubly symmetric RHFBs with unreinforced circular web openings in conjunction with proposed shear reduction factor (qs).