Fire performance and design of light gauge steel frame wall systems made of hollow flange sections

This study investigated the fire performance of load-bearing LSF walls made of innovative hollow flange section studs. Firstly full scale tests were performed to determine the reliable fire-resistance rating of the LSF walls where both the uninsulated and cavity insulated walls were tested with varying load ratios from 0.2 to 0.6. The test results proved the superior fire performance of LSF walls made of hollow flange section studs. The effects of load ratio and plasterboard joint on the fire performance of LSF walls and temperature distribution across the stud cross-sections were identified. Improved plasterboard joints were also proposed. Elevated temperature mechanical property tests were also performed.

Thereafter, thermal and structural finite element models were developed and validated using the test results. Following this, a detailed finite element analysis based study was conducted to investigate the effects of stud dimensions such as web depths and thicknesses, elevated temperature mechanical properties, types of wall configuration, stud section profiles, plasterboards to stud connections and realistic design fire curves on the fire performance of LSF walls. It was also shown that the commonly used critical temperature method is not appropriate in determining the FRR of LSF walls.

Currently available effective width based design rules were modified to improve their accuracy to predict the structural capacity of hollow flange section studs subjected to non-uniform temperature distributions caused by fire on one side. New direct Strength method based design rules were then established and they also predicted the FRR of LSF walls made of hollow flange section studs accurately. Finally, spread sheet based design tools were developed based on the proposed design rules.