Numerical investigation on the fire resistance of load bearing LSF walls: the effect of the load level

Resumo

This article investigates the fire performance of Light Steel Frame (LSF) walls commonly used in
buildings. Six full-scale LSF tests with different layouts are validated through numerical simulations using
uncoupled thermal and mechanical analyses. The hybrid numerical model incorporates experimental data to
accurately predict the LSF wall temperature, solving the non-linear transient thermal analysis. Three mechanical
simulations are developed: elastic buckling analysis for instability mode, Geometric and Material Non-Linear
Imperfection Analysis (GMNIA) for load-bearing capacity at room temperature, and thermo-mechanical analysis
considering temperature effects under constant load. Model validation compares six experimental tests under room
temperature and fire conditions. The Root Mean Square Error is used for each comparison. Results show that the
fire resistance (R) of LSF walls decreases with the load level. The impact of the cavity insulation is examined,

revealing potential improvements in fire resistance for cavity-insulated LSF hollow stud walls compared to non-
insulated ones. Notably, hollow section studs generally exhibit higher fire resistance than corresponding lipped

section studs when void cavities are used. The investigation proposes a new approach to determine the fire
resistance based on the relationship between the critical temperature of steel studs (Hot flange) and load levels.
This relationship allows us to predict the fire resistance time through a preliminary thermal analysis of LSF walls.