Temperature field of intumescent coating protected concrete-filled steel tubular columns under fire

Abstract

In the fire protection design for concrete-filled steel tubular (CFST) structures, the analysis of temperature field usually acts as a preceding step to further study the mechanical performance in fire. However, there is still a lack of systematic research on the temperature field of CFST sections with intumescent fire coating (IFC). In this study, fire tests of four hollow steel tubular specimens and twenty CFST specimens lasted for 180 min ∼240 min were carried out under ISO-834 standard fire curve and all the specimens were protected with IFC. A technical process to determine the equivalent thermal conductivity of IFC applied to CFST columns was proposed. A verified finite element analysis (FEA) model to predict temperature field of IFC protected CFST section was established and the size effects of CFST sections on the temperature field were studied. It was found that the intumescent coating can reliably work together with CFST specimens without overall crumbling during the long-time fire exposure up to 240 min. The temperature rise of the steel tube of CFST column can be significantly delayed with the effective insulation of IFC together with the heat absorption of the core concrete. The main factors affecting temperature rise of the IFC protected CFST section under fire are the core concrete, dry film thickness (DFT) of IFC and sectional diameter.