Fire design rules for LSF walls made of hollow flange channel sections

• Investigated fire performance of LSF walls made of HFC studs subject to non-uniform temperature distributions.
• Developed improved fire design rules based on the effective width method in ambient temperature design codes.
• Developed improved fire design rule based on the direct strength method.
• Design rule predictions agree well with the fire performance data from validated finite element models.
• Predicted load ratio versus failure time curves for different LSF wall configurations made of HFC studs.

Cold-formed Hollow Flange Channel (HFC) sections can be used in Light gauge Steel Frame (LSF) wall systems due to their structural efficiency. Recent experimental and finite element analysis based investigations conducted by the authors have demonstrated the superior fire performance of LSF walls made of welded HFC sections. The authors have developed a wide range of fire performance data of LSF walls through a finite element analysis (FEA) based extensive parametric study. This paper investigates the applicability of the available fire design rules to predict their structural capacities. Since fire design rules were not available for HFC sections, the latest design rules for LCS studs subjected to non-uniform temperature distributions were selected for evaluation from the pool of various design rules given in standards and previous studies. Suitable modifications were then incorporated for simplification and improved accuracy. Two improved design methods based on AS/NZS 4600 and Eurocode 3 were proposed. The structural capacity of HFC section stud found from the design rule predictions was converted into load ratio which is the ratio between the structural capacities under fire and ambient conditions, and the load ratio versus FRR curve were produced for different LSF walls. These were then compared with the FEA results, to verify the accuracy of the proposed design rules. This paper also presents suitable DSM based design method proposed for HFC section studs subject to non-uniform temperature distributions in LSF walls, and verifies its accuracy.