Fatigue fracture of fibre reinforced concrete in flexure

An experimental study on the behaviour of fibre reinforced concrete under flexure is presented, where pre-cracked notched beams were tested under cyclic loading for concrete with different dosages of hooked-ended steel fibres. The fatigue crack growth and stiffness degradation during the cycles are discussed in term of the rate of evolution of crack opening, and the critical crack opening is identified, beyond which the crack growth becomes unstable. S–N curves have been proposed with respect to the critical crack opening as these would be more relevant to design avoiding sudden failure. It is evident that higher dosages of fibres improve the fatigue life of cracked concrete only when the magnitudes of the cyclic loading are high, and that the effect of dosage is insignificant at lower magnitudes. For the fibre concretes considered here, the endurance limit seems to be about 50% of the pre-crack load in the post-peak regime.