ÖBV Guideline UHPC: Tensile Fatigue Performance of pre-strained UHPFRC

In this paper we present the tensile fatigue performance of UHPFRC that was tested on pre-strained samples. Parameters varied are (a) maximum fatigue stress, (b) pre-applied strain and (c) fiber volume content of the UHPFRC mix. The specimens were loaded displacement controlled until the intended pre-strain, which exceeded the elastic domain, was reached. The fatigue load was then applied force-controlled with constant amplitude and a frequency of 10 Hertz until failure of the specimens or until 2ā10 6 load cycles were reached (run-out). During testing, the strains increased due to incremental damage from fatigue loading. It was found that failure initiated once the strains reached the threshold where the softening branch of the static stress-strain response commences. Higher pre-straining is equivalent to accumulated fatigue damage, thus reducing the load cycles to failure. Based on these findings, an empirical fatigue life model was established to determine the remaining fatigue life of pre-strained UHPFRC.