On the mechanical degradation of R/SFRC beams under flexural fatigue loading

Present research brings the analysis of the influence of steel fibers on the mechanical degradation of reinforced concrete beams under flexural fatigue loading. Current experimental work aims to emphasize the fiber capacity in mitigating the mechanical decay of the concrete structures in terms of rebar deformation, crack spacing and other mechanical parameters. The experimental campaign encompassed reinforced concrete beams with low reinforcing ratio of 0.35%. While two beams were produced with plain concrete, the other two were fabricated with the addition of 40 kg/m3 of hooked-end steel fibers. The fatigue tests were load-controlled under a 6 Hz sinusoidal wave under distinct loading level ranges. When comparing the same loading range, steel fiber reinforced concrete structural beams reported much lower strain values along the fatigue test. The fibers showed a very effective capacity to redistribute the stresses in the traction zone and, consequently, reducing the measured strains on the longitudinal reinforcement. Similar mechanical deterioration was observed when it comes to the analysis of deflection and curvature evolution along the fatigue test. The rate of mechanical deterioration is linked to the applied stress levels. The growth of one main crack reveals that the fatigue rupture was controlled by the stress concentrations in the tensile rebars at the crack location.