Effect of Confining Pressure on Compressive Strength and Ductility of Square Section Concrete Filled Tube Column

Abstract

Concrete-filled-tube (CFT) column is developed to become an excellent structural element due to its superior strength and ductility performance contributed by the composite action. However in case of the rectangular section of CFT column, this advantage was less than that of the curricular section due to non-uniform distribution of lateral pressure. This paper aims to develop the performance of the square section of the CFT column using preconfining pressure. The square sections of CFT columns were experimentally investigated for its strength and ductility performance based on its compressive strength and load-deformation characteristics under uni-axial load test. The main parameter investigated was the confining pressure, which various from 0, 2.4, 4.8 and 7.2 MPa corresponding to 0, 11.4, 22.9 and 34.3% of concrete strength. The steel tubes with external dimensions of 98, 98 and 350 mm were used to confine the core concrete having a compressive strength of 20.98 MPa. The confining pressure was applied by preconfining of the steel jacket. During the experiments, load-deformation curves were recorded. Test results showed that increasing of confining pressure of 11.4–34.3% of concrete strength slightly improved the compressive strength of the square section of CFT column by 3.0–19.3% and the more improvement occurs at the preconfining pressure beyond 22.9%. However, it was found that the use of preconfining steel jacket for the square section of CFT column does not enhancing its ductility as well as energy absorbing capacity unlike the circular section.