Cyclic damage constitutive behavior of UHPC under uniaxial tension

The uniaxial behavior of UHPC under cyclic tension is experimentally investigated for two different fiber volume fractions (V_f = 1.5 % and 2.0 %) with a full incursion in compression. The tension coupons are loaded and then fully unloaded (hence incurring compression) under two types of cyclic loading regimes (one and two cycles per displacement increment). Displacement increments include cycles prior to and post attaining the localization strain. The experimental results show that strength and stiffness degradation under cyclic loading is not substantial until the strains exceed the localization strain and that the compression incursions have no effect on the tensile response for the applied loading regime. It is also observed that increasing the steel fiber volume fraction mildly inhibits the stiffness degradation process. An analytical elastoplastic stress-strain relationship considering damage with only two calibration parameters is introduced and calibrated to express the cyclic stress-strain relationship of UHPC under tension. The proposed relationship is reasonably robust in capturing the hysteretic tensile response of UHPC and is therefore suitable for finite element simulation of UHPC structures under cyclic loading.