Fire design of LSF floors using hollow flange channel joists

• Investigated the behaviour of LSF floors made of hollow flange channel (HFC) joists in fire
• Fire performance data of different LSF floor configurations was used.
• Developed simple fire design rules to predict the moment capacities of HFC floor joists and fire ratings of floor systems
• Load ratio versus time curves for varying LSF floor configurations were predicted.
• Direct Strength Method based fire design rules were also developed.

Predicting the fire performance of commonly used Light gauge Steel Frame (LSF) floor systems is important in designing them for fire situations. In the past, many researchers conducted full scale fire tests and numerical analyses for this purpose. However, some researchers have proposed fire design rules to predict the fire resistance ratings of LSF floor systems to avoid expensive fire tests. Their proposals were developed only for LSF floors made of conventional lipped channel section (LCS) joists. Therefore this research was aimed at developing fire design rules for the new LSF floor systems made of hollow flange channel (HFC) section joists. It used the fire performance data from an extensive parametric study based on validated finite element models of the new floor system with varying floor component configurations. Three different fire design rules were proposed to predict the fire resistance ratings of LSF floors based on the available design equations from past research and current design standards. The proposed design equations were validated by comparing the fire resistance rating predictions with the finite element analysis results obtained from the parametric study. Further a new Direct Strength Method based fire design rule was also developed and validated using finite element analysis results. The fire design rules proposed in this paper can be used to predict the fire resistance ratings of LSF floors made of HFC section joists with varying sizes and steel types, and plasterboard/insulation configurations without the need for further fire testing and numerical analyses.