Fire performance of axially restrained steel reinforced concrete columns

In order to investigate the fire resistance of axially restrained steel reinforced concrete columns, fire tests on seven axially restrained steel reinforced concrete columns were carried out considering load ratio, load eccentricity and steel ratio as the varying parameters. The test adopted a constant load heating mode, and through the experiments, the temperature distribution, displacement, deformation, fire resistance and failure mode of the restrained steel reinforced concrete columns under fire were studied. The test results show that the vertical load on the top of the axial compression columns is larger than that of the eccentric compressed columns with the same load ratio. The concentrically compressed columns expand slowly at first and then shorten gradually at high temperature. Because the axial restraint shares the vertical load of the column, the compression deformation varies mildly with fire duration, and the axial restraint prolongs the fire resistance of the column. For eccentrically compressed columns, the expansion deformation at high temperature is greater than that of the concentrically compressed columns, and the expansion deformation first increases and then decreases. The axial restraint increases the vertical load of the column and shortens the fire resistance of the column. The load ratio has a significant influence on the fire resistance of the axially restrained steel reinforced concrete columns. The fire resistance decreases with the load ratio. When the load ratio is not larger than 0.5, the fire resistance increases with the eccentricity ratio of the axial load. The fire resistance increases with the steel ratio to a certain extent. © 2022, Editorial Office of Journal of Building Structures. All right reserved.