Development of lightweight CFS composite built-up beams: Tests and flexural response

• Published in: Journal of constructional steel research 2023-10, Vol.209, p.108041, Article 108041
• Main Authors: Dar, Mohammad Adil, Ghowsi, Ahmad Fayeq, Dar, A.R., Salam, Shahid Ul, Anbarasu, M., Vivek, K.S., Hajirasouliha, Iman
• Format: Article
• Language: English
• Subjects: Built-up beam; Capacity; Cold-formed steel; GFRP; Stiffness; Timber
• ISSN: 0143-974X; 1873-5983
• DOI: 10.1016/j.jcsr.2023.108041

Although previous attempts for enhancing the buckling resistance of cold-formed steel (CFS) built-up beams through intermittent stiffening, external stiffening and adoption of concrete as composite sections were successful, they may compromise the lightweight constructional feature of these elements. This paper presents a test program aimed at developing CFS composite built-up beams with superior buckling performance and low self-weight for ensuring lightweight construction. Unlike concrete, lightweight stiff boards of timber and glass fibre reinforced polymer (GFRP) were sandwiched between the CFS channels in the web and flange region to construct the lightweight composite beams. All of the beam specimens were subjected to four-point bending with simply supported boundary conditions. Peak strength, load-deformation curves, initial stiffness, strength-to-weight ratios, failure modes and the normalized yield and plastic moment strengths were compared. This study established the structural feasibility of developing lightweight CFS composite built-up beams from timber and GFRP boards, indicating that the flexural strength and stiffness are significantly improved by 150% and 80%, respectively, as compared to the unstiffened CFS built-up beams. Moreover, the studied composite beams were shown to attain their full yield moment capacities, and in some cases more than 90% of their plastic moment capacity, resulting in built-up members with a higher structural efficiency. •A new CFS GFRP-timber composite lightweight beam system was developed.•The efficiency of different combinations of GFRP and timber packing were explored.•Feasibility to adopt GFRP & timber to form CFS composite beams is demonstrated.•Large improvement in strength, stiffness & strength-to-weight ratio was achieved.•Proposed system exhibited around 100% & 90% of its nominal yield & plastic capacity.