Temperature rise distribution of circular concrete-filled steel tubular cross-sections with intumescent coating

Abstract

Although concrete-filled steel tubular (CFST) columns exhibit exceptional fire resistance, they might not satisfy the required fire rating of 3 h without additional protection particularly when subjected to high load level. Intumescent fire retardant coating (IFC) provides an efficient way to enhance the fire safety of structural steel members. Temperature rise analysis usually acts as a preceding step when determining the mechanical performance of structures in fire. To understand the effect of IFC and the fire performance of CFST columns, the temperature rise of IFC protected CFST columns was investigated in this study. A series of IFC protected CFST columns were tested in ISO-834 standard fire for 180 min. The test parameters included the diameter of CFST cross-sections and the net dry film thickness (DFT) of IFC. The temperature data was reported and analysed. The results showed that IFC provided efficient fire protection for CFST columns and maintained its integrity throughout the 180 min of fire exposure. For tested specimen (outer diameter = 325 mm) with no coating, 1.16 mm thickness and 3.40 mm thickness of IFC, the temperature of steel surface at 180 min were 1056 °C, 592 °C and 418 °C, respectively. No crack or crumbling was observed in the expanded IFC after the tests. Physical changes and chemical reactions in intumescent coating were deemed to occur from 10 min to 90–140 min depending on thickness of IFC and cross-sectional size. The obtained equivalent thermal conductivity of the IFC attained the minimum values of 1.46 × 10−3 to 4.38 × 10−3 W/(m·oC) at temperature range of 513 to 672 °C.