Behaviour and design of CFS stud walls under both sides fire exposure

Cold-formed steel (CFS) stud wall systems fabricated using CFS channel studs, tracks and fire-rated sheathing materials are increasingly used in Australia, New Zealand, Europe and North America. Although a large number of research studies has focused on the behaviour of load-bearing CFS stud wall systems at ambient temperature and in fire, the knowledge related to the behaviour as well as suitable design methods of these wall systems exposed to fire on both sides is very limited. Recently, the safety of CFS stud walls under both sides fire exposure has become a concern to fire engineers. In this study, detailed investigations of load-bearing CFS stud walls under both sides fire exposure were undertaken using thermal and sequentially coupled structural finite element (FE) models. These models were validated against the standard fire test results of CFS stud walls under one side fire exposure available in the literature. Using the thermal and sequentially coupled structural FE analysis results, the effects of cavity insulation, thickness of gypsum plasterboards and both sides fire exposure on the behaviour and fire resistance level (FRL) of CFS stud walls were investigated and the results were compared with those for CFS stud walls under one side fire exposure. These results highlighted the major differences between the CFS stud walls under one side and both sides fire exposures in terms of their thermal and structural behaviour and FRL. Finally, appropriate design guidelines using the direct strength method in the CFS design standards are proposed.