Fire tests of cold-formed steel walls made of hollow section studs

Abstract

Light gauge steel frame (LSF) walls as primary load-bearing components have been increasingly used in the construction of cold-formed steel (CFS) buildings. Their fire safety has thus become an important consideration for designers. Currently, LSF walls made of lipped channel section (LCS) studs are commonly used in low-rise buildings, but with the expansion of CFS applications to mid-rise buildings, cold-formed steel square and rectangular hollow section (SHS/RHS) studs are being used to meet the higher load capacity demands. However, the fire resistance of LSF walls made of SHS/RHS studs has not been investigated yet, so their fire resistance levels (FRLs) are unknown, restricting their use in mid-rise buildings. Four full-scale load-bearing standard fire tests were therefore conducted to investigate the performance of cold-formed steel SHS/RHS stud walls exposed to fire. The test results showed that CFS SHS/RHS stud walls achieved a higher FRL due to the superior elevated temperature mechanical properties of CFS SHS/RHS, while the temperature development exhibited good similarity with uninsulated LCS stud walls of the same wall configuration. However, a different thermal behaviour was observed when SHS/RHS studs were used in cavity insulated walls, as the hollow cavity reduced the temperature difference between the stud hot and cold flanges. This eliminated the fire resistance reduction caused by thermal bowing deformations and provided an improved fire performance than cavity insulated LCS stud walls. This paper presents the details of the fire tests and the results.