Post-fire behavior of composite column-column connections

The Columns made of Concrete-Filled Steel Tubes (CFST) Connections have proved to be a cost-effective method of composite construction because they enable structures to be dismantled during their service life. Although the behavior of CFST column connections under many different loading scenarios has been well detailed, the postfire resistance of CFST column connections is not proposed in the literature yet. This study shows the possibility to use CFST columns with a bolted-flange connection to advance their post-fire resistance. To this end, CFST columns with and without stiffeners were subjected to standard fire exposure. To address their post-fire performance. The samples are classified into two groups: group 1, stiffener-free connection, and group 2, in which stiffeners are included. Three thicknesses of the bolted-flange were used such as 2, 4, and 6 mm. The results indicated that the different thicknesses of bolted-flanges in group 1 samples the axial stiffness value had some effect and in group 2 samples this effect had been doubled. The stiffeners played a significant role in the toughness value and it was reduced with the reducing of stiffeners thickness. Also, the ductility improvement was notable in stiffened samples. Accordingly, it can understand that the bolted-flange connection of the CFST column have a significant role in fire resistance without adding any external protection materials.