Seismic Behavior of RC Square Columns Strengthened with Self-Compacting Concrete-Filled CFRP-Steel Tubes

This paper presents an experimental study of the seismic behavior of RC square columns strengthened with self-compacting concrete-filled carbon-fiber-reinforced polymer (CFRP)-steel tubes (CFCSTs). Eleven columns were tested under lateral cyclic load while simultaneously being subjected to constant axial load. The test parameters included the number of CFRP layers, the thickness of the steel tube, and the axial load level. The entire failure process, ultimate lateral load, and deformation capacity were analyzed. The experimental results indicated that the seismic bearing capacity of the RC columns could be improved significantly while the strengthening method was applied, because the ultimate lateral loads of the strengthened columns were 7.36-9.67 times that of the unstrengthened column, and the improvement ratio of ductility parameter reached 42.38-115.56%. The CFRP jacket could effectively delay or even prevent the local buckling of the steel tube, leading to better structural seismic performance. As the number of CFRP layers increased, the ultimate bearing capacity, ductility, and energy-dissipation capacity of the CFCST-strengthened columns increased slightly. The CFCST-strengthened columns under a higher axial load level exhibited better ultimate bearing capacity and energy-dissipation capacity but worse ductility. With the increase of the thickness of the steel tube, all seismic performance indexes significantly improved. The CFCST-strengthened columns were simulated by using the finite-element analysis software Abaqus 6.14-4. The comparison of the analytical results with the experimental results revealed that they are basically consistent with each other.