ABSTRACT
This paper presents an experimental investigation on 12 circular steel tube confined Ultra High Performance Concrete (UHPC) stub and intermediate columns under axial loading. The UHPC using steel fibers of 0%, 1% and 2% by volume were produced for filling in the steel tube. The test results show that a significant improvement in the strength and ductility of the columns is achieved by the composite action between the UHPC core and the steel tube. However, there is no noticeable increase in the strength enhancement and the ductility with incorporation of steel fibers. The ultimate load obtained from the test results were compared with the predictions by the codes EC4, AISC and AIJ. The comparisons reveal that the AIJ gave the best predictions, while EC4 can be safely extended for concrete with compressive strength up to 200 MPa if the confinement effect is not considered.
