Effect of steel fiber on the behavior of circular steel tube confined UHPC columns under axial loading

Abstract

This paper is aimed at presenting an experimental investigation on a total of 12 circular ultra high performance (UHPC) concrete filled steel tube short and intermediate columns under axial loading on only the concrete core. The influence of steel fibers with 1% and 2% by volume was examined by means of some performance indices including the strength and strain enhancement index (SI and SE), the ductility index (DI) and the strength ratio (SR). It was found that the use of steel tube as a confinement method for UHPC columns provides a significant improvement in both terms of the strength and the ductility, thereby restricting the extremely brittle failure of UHPC. In addition, there is no noticeable influence of steel fibers on the strength and ductility of test columns. However, the presence of steel fibers affects to the failure mode and slightly increases the ductility of the intermediate columns.