Fire performance of load bearing LSF wall systems made of low strength steel studs

Light gauge steel frame (LSF) walls are commonly used in single and two storey residential and commercial buildings and modular based mid-rise building construction. They are lined with single or two layers of gypsum plasterboards and used with or without cavity insulation or noggings. This paper presents the details of a series of standard fire tests of load bearing LSF walls used in low-rise building construction to investigate the effects of using low strength steel studs, noggings and cavity insulation. The presence of cavity insulation significantly reduced the fire resistance level (FRL) of load bearing walls while the use of noggings increased the FRL, and these findings are considered valid for both low and high strength steel stud walls. Structural finite element models of fire tested walls were then developed using appropriate elevated temperature mechanical properties, validated using the fire test results and used in a parametric study of LSF walls made of both low and high strength steel studs. The results showed that FRL of low strength steel stud walls is reduced by about 25% in the common load ratio range in comparison with high strength steel stud walls, while their critical hot flange temperatures are reduced. These differences are due to the variations in their elevated temperature mechanical properties caused by the material composition. Reliable fire performance results of both low and high strength steel stud walls from finite element analyses and fire tests are presented and compared in this paper. This study has highlighted the importance of using accurate elevated temperature mechanical property reduction factors in numerical analyses and design of LSF walls.