Thermal Performance of Load Bearing Cold-formed Steel Walls under Fire Conditions using Numerical Studies

Abstract

Cold-formed Light gauge Steel Frame (LSF) wall systems are increasingly used in lowrise and multi-storey buildings and hence their fire safety has become important in the design of buildings. A composite LSF wall panel system was developed recently, where a thin insulation was sandwiched between two plasterboards to improve the fire performance of LSF walls. Many experimental and numerical studies have been undertaken to investigate the fire performance of non-load bearing LSF wall under standard conditions. However, only limited research has been undertaken to investigate the fire performance of load bearing LSF walls under standard and realistic design fire conditions. Therefore in this research, finite element thermal models of both the conventional load bearing LSF wall panels with cavity insulation and the innovative LSF composite wall panel were developed to simulate their thermal behaviour under standard and realistic design fire conditions. Suitable thermal properties were proposed for plasterboards and insulations based on laboratory tests and available literature. The developed models were then validated by comparing their results with available fire test results of load bearing LSF wall. This paper presents the details of the developed finite element models of load bearing LSF wall panels and the thermal analysis results. It shows that finite element models can be used to simulate the thermal behaviour of load bearing LSF walls with varying configurations of insulations and plasterboards. Failure times of load bearing LSF walls were also predicted based on the results from finite element thermal analyses. Finite element analysis results show that the use of cavity insulation was detrimental to the fire rating of LSF walls while the use of external insulation offered superior thermal protection to them. Effects of realistic design fire conditions are also presented in this paper.

Thermal performance of load‐bearing walls made of cold‐formed hollow flange channel sections in fire

“…The proposed apparent thermal conductivity values are different from those of Keerthan and Mahendran . As seen in Table , the complete plasterboard fall‐off temperature was 1150 °C in this study, while it was 1000 °C in Keerthan and Mahendran's study.…”

“…The proposed apparent thermal conductivity values are different from those of Keerthan and Mahendran . As seen in Table , the complete plasterboard fall‐off temperature was 1150 °C in this study, while it was 1000 °C in Keerthan and Mahendran's study. This might be due to the improved plasterboard quality resulting in less cracking at elevated temperatures and the improved connectivity between LSB studs and plasterboards, where screws penetrate through both the inner and outer flanges (Figure ).…”

“…Previous researchers stated that although steel is a highly conductive material, the influence of steel studs on the thermal heat transfer process in LSF walls is less significant as they are made of thin steel. Previous researchers used the thermal properties given in Eurocode 3 part 1.2 .…”

“…In the past, Feng et al , Thomas , Keerthan and Mahendran and Shahbazian and Wang have successfully used finite element analyses to predict the thermal performance of LSF walls. However, their studies were limited to LSF walls made of open conventional LCS studs.…”

Thermal Modelling of Load Bearing Cold-Formed Steel Frame Walls Under Realistic Design Fire Conditions

“…A good agreement was obtained with fire test results (time-temperature curves) for LSF walls exposed to a standard fire curve, considering the complexity of gypsum plasterboard behaviour affected by processes such as ablation of plasterboards and migration of moisture into the cavity. These processes were taken into account by considering suitable values for the thermal conductivity of gypsum plasterboard [19]. Details of this process and the proposed values for specific heat, thermal conductivity and mass loss (relative density) are reported in [13,15,16].…”