Load-Deformation Behaviour of Roof Truss System Made with Cold-Formed Steel Hollow Rectangular Section

Abstract

The swift advancement of modern construction has established cold-formed steel (CFS) as a prominent structural option owing to its high strength-to-weight ratio and lightweight properties. However, CFS in open sections such as channel and zee sections is heavily restricted by susceptibility to premature instabilities such as local, distortional, and lateral-torsional buckling. The study examines the structural performance, especially the load-deformation behaviour of closed structural sections, to address and resolve these deficiencies and limitations. The main objective of the study is to experimentally determine the load-deformation behaviour of a full-scale roof truss system fabricated from a CFS hollow rectangular section and to compare it with that of a CFS channel section. A full-scale roof truss measuring 4,900 mm in span and 1,100 mm in height was constructed in a Howe configuration type and assembled using 6 mm self-drilling screws. Static vertical load experimental activity was conducted utilising a 100 kN load cell, a hydraulic jack, five linear variable deformation transducers (LVDTs), and seven strain gauges linked to a data logger to record ultimate load capacity, deformation and localised strain actions. The experimental results indicated that the CFS hollow outperforms the CFS channel section, attaining a 52.42% increase in ultimate load capacity and a 21.66% decrease in vertical mid-span deformation. The CFS channel had premature local and distortional buckling at its top chords, but the CFS hollow successfully mitigated early geometric instabilities. Ultimately, the study concludes that CFS hollow serves as a highly efficient, stiff and structurally stable system that is ideal for lightweight and sustainable long-span roofing applications.