EXPERIMENTAL INVESTIGATION ON HIGH-STRENGTH SELF-STRESSING AND SELF-COMPACTING CONCRETE FILLED STEEL TUBE COLUMNS SUBJECTED TO UNIAXIAL COMPRESSION

To improve the compactness and reduce the shrinkage of core concrete in concrete filled steel tube (CFST) columns, and to ensure a synergic action between steel and concrete to better fit practical needs, this paper deals with the mechanical behavior of high-strength self-stressing and self-compacting CFST columns under uniaxial compression. 17 column specimens were tested for different confining factors, self-stress levels and concrete strengths. The test results showed that the use of high-strength self-stressing and self-compacting concrete in CFST columns effectively compensated the shrinkage of core concrete, and the lateral constraints from steel tubes alleviated the brittleness of high strength concrete. In addition, the bearing capacity of the column was increased from 13% to 21% as the confining factor varied from 0.548 to 0.846, and was increased by 5% to 12% when the concrete strength upgraded from C60 to C80. The distribution of the self-stress versus the bearing capacity of the column followed a second-degree parabola. Based on the test result, analytical equations for the bearing capacity of the high-strength self-stressing and self-compacting CFST columns was developed, which is expected to serve as a reference for practical engineering applications.