Title: Structural behavior of reinforced ultrahigh performance concrete under uniaxial loading

Abstract

Ultrahigh performance concrete (UHPC) has recently been promoted for many applications in the construction industry due to its superior mechanical properties including the high compressive strength and the sustained post-cracking tensile strength as well as its pronounced durability. UHPC is mostly preferred to exhibit a strain-hardening tensile response in which multiple micro-cracking characterizes the response until reaching the peak tensile capacity. Such feature results in a large deformation capacity (ductility) and gradual cracking. On a material level, UHPC has been found to demonstrate high ductility and slow failure pattern. However, on a structural level, when combined with rebar reinforcement, the response of UHPC has not been clearly established, and some incidents of quick and brittle collapses have been witnessed, particularly under shear loading where a single macro-crack governs the failure in a very abrupt manner. Hence, the tensile behavior of reinforced UHPC members under tension still requires further research. The tension stiffening effect, the cracking patterns under different fiber content ratios and reinforcement ratios, and the ductility need more elucidation. To this end, this study aims at investigating the behavior of reinforced UHPC under uniaxial loading with regard to the effect of fiber content ratio and reinforcement ratio. The fiber content ratio used in this study was 1, 2, 3.5% in volume, and the reinforcement ratio was 0.97, 1.4, 2.18 and 3.41%. The effects of these parameters on the bearing capacity, ductility and cracking pattern are explored. In addition, an analytical model for describing the response of a UHPC tension member is proposed and simplified expressions for calculating the micro-cracks spacing and macro-crack spacing are provided. The response of UHPC tension members can be extended to describe the response of the tension chords in flexural members.