Full-scale tests of load-bearing LSF walls made of built-up CFS channel sections under fire conditions

Built-up cold-formed steel (CFS) studs, such as back-to-back channels (BC) and nested channels (NC) are used in light gauge steel framed (LSF) wall systems instead of the conventional channel studs for improving their load-bearing capacity. However, the knowledge and understanding of their behaviour under fire conditions is limited. In this study, the behaviour of load-bearing LSF walls made of BC and NC studs under fire conditions was investigated using four full-scale standard fire tests. The obtained fire test results were evaluated in terms of both thermal and structural behavioural characteristics and fire resistance level (FRL), and were used in the comparison with those for conventional LSF walls made of single channel studs. The test results showed that (1) without cavity insulation, the thermal and structural behavioural characteristics of the LSF walls made of BC and NC studs are very similar to those of LSF walls made of channel studs, and their FRLs can be taken as the same for the same load ratio (2) LSF walls made of BC and NC studs with two layers of 16 mm thick gypsum plasterboards on each side and without cavity insulation have an FRL of 120 min for a load ratio of 0.4, and (3) the use of cavity insulation reduces the FRL of LSF walls made of NC studs. This paper presents the details of this research study and its outcomes.