Understanding the performance of cold-formed steel frame wall systems in fires to design for superior fire resistance

Overview

This project investigates the structural and thermal performance of Light gauge Steel Frame (LSF) wall systems in collaboration with Knauf Metal, formerly known as Peer Industries Ltd to develop design methods and predict their Fire Resistance Levels (FRL).

In the last decade the use of cold-formed steel frames has expanded rapidly into mid-rise buildings (3 to 9 storeys) as load bearing structural members with applications in hotels, apartments, etc. Robust structural performance, lightweight, as well as ease, efficiency and economy in using cold-formed steel construction are all favourable attributes for mid-rise lightweight construction. However, their fire performance is not well understood. Many design codes do not have any fire provisions for light gauge steel structures, some of them have conservative approach based on limiting temperatures. Thus current designs are restricted to using over-prescriptive FRL tables of only fire tested wall configurations by the manufacturers and professional opinions from experts in this field. This does not facilitate safe or cost effective designs.

Research Activities

This project addresses the significant challenge in current building construction research and explores the development concepts and design rules for LSF wall systems. The behaviour of LSF walls under fire conditions is a complex phenomenon involving degradation of thermal and mechanical properties of both steel and wall lining materials, thermal bowing deflections and their magnification effects due to loss of steel stiffness, associated load eccentricity and shift in stud’s neutral axis, local and global bucking effects, ablation, degradation and plasterboard fall-off, all of which are to be considered in the design of LSF walls under fire conditions.

Full Scale Fire Tests (3 m x 3 m) of both non-load bearing and load bearing wall panels were conducted using the gas furnace at QUT Wind and Fire Lab. Fire tests were performed for a range of stud sections and lined with gypsum plasterboards and MgO boards with and without cavity insulations. Three-dimensional Finite Element models for both thermal and structural performances have been developed for LSF walls under fire conditions using Finite Element program ABAQUS. Thermal properties of a range of gypsum plasterboards and MgO boards used in Australia and New Zealand have been determined from a series of experiments conducted up to 1200 deg celsius and predictive models have been developed. Elevated temperature mechanical properties of steels used in studs have also been measured.

Expected Findings

Using the results from experimental and numerical studies, new design methods are being developed to allow for use by building designers, builders, manufacturers and contractors to ensure the construction of fire safe light gauge steel frame buildings. Specific findings include;

  • Determination of thermal properties of currently available gypsum plasterboards and MgO boards at elevated temperatures.
  • Determining the thermal and structural fire performance of gypsum plasterboard and MgO board lined wall panels using full scale fire tests.
  • Development of validated thermal and structural finite element models to predict the failure times (FRLs) of wall panels.
  • Development of a thermal and structural fire performance database with the failure times (FRLs) of various wall configurations.
  • Accurate and safe design tools/methods to predict the axial compression capacity of steel studs in load bearing wall configurations.

Funding / Grants

  • Australian Research Council (ARC) Linkage Project

Other Team Members

Mohamed Rusthi PhD researcher

Partners

Other Partners

Knauf Metal (formerly known as Peer Industries)