Elevated temperature thermal properties of carbon steels used in cold-formed light gauge steel frame systems

Abstract

Fire design of cold-formed Light gauge Steel Frame (LSF) systems requires an accurate assessment of the thermal properties of each component at elevated temperatures. Heat transfer models based on these properties are implemented in order to accurately simulate the thermal behaviour of LSF systems in fire. For all carbon steel components, thermal properties are presented in Eurocode 3 Part 1.2. To verify the accuracy of thermal properties in Eurocode 3 Part 1.2 for the cold-formed steel components used in LSF construction, a series of thermal property tests was conducted based on the ASTM standard test methods. Thermal property tests were conducted to determine the specific heat at constant pressure, relative density, thermal conductivity and thermal diffusivity of three types of carbon steels, namely Grade 500 steel, Grade 300 steel and Grade 140 steel, due to their use in LSF construction. Test results showed the differences between the Eurocode 3 Part 1.2 model for carbon steels and the measured thermal property data for both specific heat and thermal conductivity of all three types of carbon steels due to chemical composition and the influence of carbon content. Hence, new equations were developed for specific heat and thermal conductivity for the selected carbon steels. To verify the effect of the measured thermal property results, 3-D heat transfer models of LSF floor-ceiling systems were developed and analysed. New thermal properties of carbon steels were used as inputs and comparisons made against fire test results for validation purposes. This paper presents the thermal properties of three selected carbon steels, which are commonly used in cold-formed LSF systems and the results.