Fire design of LSF wall systems made of web-stiffened lipped channel studs

Abstract

Cold-formed steel stud sections are commonly used as compression members in fire rated load-bearing light gauge steel frame (LSF) wall systems. Although conventional lipped channel section (LCS) studs are commonly used in LSF wall systems, there is a growing interest in developing innovative stud sections to increase the load carrying capacities when used in fire rated LSF wall systems. One such section is the web-stiffened section (WSS), which has increased load carrying capacities as well as enhanced acoustic properties. However, the applicability of the existing structural fire design rules has not been investigated for the WSS stud sections while the advantages of using such sections have not been demonstrated. Therefore, the structural behaviour of WSS stud sections was investigated under ambient and fire conditions using finite element analyses and their capacities were compared with those of conventional LCS studs. Three different LSF wall configurations and three stud thicknesses were considered for both stud sections. The applicability of existing structural fire design rules for LCS and WSS studs used in fire rated LSF wall systems was then investigated based on finite element analyses, effective width method and direct strength method. The results show that WSS studs have much higher load carrying capacities than LCS studs under ambient and fire conditions and that direct strength method based design rules are simpler to use than the effective width based design rules for the structural fire design of LSF wall systems made of both LCS and WSS studs. This paper presents the details of this investigation and the results.