Title: Parameters Affecting the Axial Load Response of Ultra High Performance Concrete (UHPC) Columns
Author(s): Hyun-Oh Shin, Hassan Aoude and Denis Mitchell
Publication: Symposium Paper
Appears on pages(s): 48-70
Keywords: UHPC; Fibers; Columns; Axial loading; Seismic detailing; Confinement
Ultra-high-performance concrete (UHPC) is an innovative material that exhibits high compressive and tensile strength as well as excellent durability. The provision of fibers in UHPC results in improved ductility and increased toughness when compared to conventional high-strength concrete. These properties make UHPC well-adapted for use in the columns of high-rise buildings and heavily-loaded bridges. This paper summarizes the results from a database of tests examining the effects of various design parameters on the axial load performance
of UHPC columns. Experimental results illustrating the effects of concrete type (UHPC vs. high-strength and ultra-high-strength concrete), UHPC compressive strength and transverse reinforcement detailing are presented. The results show that the use of UHPC in columns resulted in increased load carrying capacity and post peak ductility when compared to conventional high-strength or ultra-high-strength concrete due to the ability of steel fibers to delay cover spalling. However, greater amounts of confinement reinforcement were required to achieve
the same level of axial load performance as the UHPC compressive strength was increased from 150 to 180 MPa. The results also showed that the amount, spacing, and configuration of transverse reinforcement, as well as their interaction significantly affected the axial load response of UHPC columns. However, increasing the amount of transverse reinforcement had the most pronounced effect on post-peak behavior. The effect of the confinement provisions in current codes (CSA A23.3-14 and ACI-318-14) on the ductility of the UHPC columns was also investigated. Based on the results, an alternative confinement expression for achieving ductile behavior in UHPC columns was proposed.