Compressive behavior and strength model of reinforced UHPC short columns

The compressive behavior of reinforced UHPC short columns was investigated in this study. Twelve UHPC columns were tested, with the experimental variables including the coarse aggregate, transverse reinforcement, and fiber content. The compressive behavior of the columns was extensively evaluated in terms of the failure pattern, axial load-deformation relationship, dilatation, steel reinforcement strain, and toughness. The experimental results indicated that the inclusion of coarse aggregate enhanced the axial stiffness of the UHPC columns, and that the addition of steel fibers with a volume fraction of 0.75% or more increased the axial capacity of the UHPC columns by restraining early damage. Furthermore, the results showed that the inclusion of a 1.5% volume fraction of steel fibers in the UHPC columns was able to replace a half of the code-required transverse reinforcement and simplify the seismic hooks for crossties while preventing premature buckling of steel reinforcing bars under axial loading. In addition to the experimental investigation, strength models that were capable of reasonably estimating the peak and post-peak compressive strengths of reinforced UHPC short columns were suggested.