Equivalent Temperature Prediction for Concrete-Filled Cold-Formed Steel (Cf-Cfs) Built-Up Column Sections (Part B)

Innovative concrete-filled cold-formed steel (CF-CFS) built-up column sections subjected to axial compression and elevated temperatures were previously investigated, assessing their structural fire performance in detail. However, the analytical fire resistance methodology presented in the EN1994-1-2 requires advanced heat transfer analysis to compute the temperature evolution of the steel and concrete components of the composite cross-section. This paper presents a set of empirical formulations to predict equivalent temperature for steel and concrete components of CF-CFS built-up column sections. The finite element modeling technique to predict temperature evolution through the CF-CFS built-up column sections was calibrated using a 2-D heat transfer analysis (part A of this study). As a simplification, the concrete-infill was divided into two areas, namely inner and outer core areas. The equivalent temperature of the steel section and the steel embedded area were also considered. The results showed good accuracy of the proposed empirical formulas