Abstract:
The aim of this research is to report the experimental results on the structural responses and modes of failure of square concrete-filled steel tube (CFST) column with hybrid cement strengthened by steel bars under axial compressive load. A total of thirty specimens included: six CFST columns (reference CFST columns) and twenty-four CFST columns strengthened with steel bars. The nominal dimension of the square specimens is 150 mm in width and 750 mm in height. The stiffness of steel tubes is 3.0 mm, 4.5 mm, and 6.0 mm. The main parameters used in this research, include the four types of steel bars, which are RB6, RB9, DB12, and DB16, and the two positions of strengthening with steel bars. In total specimens are prepared and loaded concentrically in compression to failure. The results of these tests showed that the CFST columns strengthened with steel bars have a linear elastic behavior up to approximately 80-90% of their maximum compressive load. Then, the behavior of the columns is nonlinear. The mode of failure of the columns is identified as the crushing of the concrete core and local wall buckling of the steel hollow tube. In addition, it is also noted that the CFST columns strengthened with steel bars at the inside center of the tube (pattern 1) showed a higher increase in ductility performance as compared with the CFST columns strengthened with steel bars at the inside corners of the tube (pattern 2).