Axial compressive performance of UHPC filled steel tube stub columns containing steel-polypropylene hybrid fiber

Abstract

This paper presents an experimental investigation of axial compressive performance of ultra-high performance concrete filled steel tube (UHPCFST) stub columns containing steel-polypropylene hybrid fiber. A total of 42 UHPCFST specimens are tested. The main variables considered involve the steel tube thickness and the fiber characteristic parameters regarding the volume fraction and the aspect ratio. The axial load – axial strain responses are captured and the distinctive failure modes are analyzed. The results indicate that an increase in the steel tube thickness significantly improves the mechanical performance of UHPCFST in terms of stiffness, ultimate load and post-peak behavior. The incorporation of hybrid fiber can be beneficial to further improve the axial compressive performance of UHPCFST. Particularly, a favorable contribution is observed as the steel tube thickness is of 5.5 mm. It is noticed that hybrid fiber could delay and prolong the composite action between the outer steel tube and the core UHPC. Finally, the applicability of current international codes on estimating the ultimate bearing capacity of UHPCFST stub columns is verified. The research outcomes pave the way to boost the practical application of UHPCFST.