Strengthening of Square Concrete-Filled Steel Tube Column with Steel Bars Under Uni-Axial Load

Abstract

The aim of this research report the experimental results on the structural responses and modes of failure of square concrete-filled steel tube (CFST) column strengthened with steel bars under axial compressive load. A total of eighteen specimens included: two CFST columns (reference CFST columns) and sixteen CFST columns strengthened with steel bars. The nominal dimension of the square specimens are 150 mm in width and 750 mm in height. The main parameters used in this research, including 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 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 inside center of tube (pattern 1) showed higher increase in ductility performance as compared with the CFST columns strengthened with steel bars at the inside corners of the tube (pattern 2).