Experimental Investigation On Fire Resistance Of Composite Cross-shaped Column Reinforced By Inner High-strength Concrete-filled Steel Tubular Core Column

The composite special-shaped column reinforced by inner high-strengthconcrete-filled steel tubular core column is to configure a high-strength concrete-filledsteel tubular core column in the normal reinforced concrete special-shaped column. Dueto the configuration of the high-strength concrete-filled steel tubular core column, themechanical behavior and fire resistance of the composite special-shaped column bothimproved effectively.In this paper, six full size composite cross-shaped columns reinforced by innerhigh-strength concrete-filled steel tubular core column were experimental tested on fireresistance under different fire conditions. Two composite cross-shaped columns wereexperimentally tested under ISO834standard fire to get their fire resistance, threecomposite cross-shaped columns were experimentally tested under ISO834standard firewith different heating time and then they were texted under axial compression after fire,one composite cross-shaped column was texted under axial compression at normaltemperature. The test focused on the effects of high-strength concrete-filled steel tubularcore column, stirrup spacing and heating time on the failure mode, axial deformationand axial bearing capacity of the composite cross-shaped columns under different fireconditions.The damage conditions, temperature field, axial deformation-time curve, lateraldeformation-time curve and post-fire residual load bearing capacity of the specimenswere obtained by the experiment. Depending on the results, the fire resistance of thecomposite cross-shaped column was analyzed. It is found that the fire resistance of the composite cross-shaped column is much better than that of the normal reinforcedconcrete cross-shaped column. The inner high-strength concrete-filled steel tubular corecolumn can greatly improved the fire resistance and axial bearing capacity of thecomposite cross-shaped column. The composite cross-shaped column has goodmechanical behavior and fire resistance.According to the experiment results, the factors which influence the post-fireresidual load bearing capacity of the composite cross-shaped column have beenanalyzed in this paper. At last, the residual load bearing capacity calculation formula ofthe composite cross-shaped column is established. And the calculation results are wellmatched with the tests data.