Assessment of fatigue resistance of concrete: S-N curves to the Paris’ law curves

Fatigue behaviour of concrete materials is often investigated on un-notched specimens under the compressive or bending loads. In this experimental study, a notched three-point bending (TPB) specimen is used in high-cycle fatigue experiments to obtain the Wohler’s curve. Based on this approach, a novel, yet relatively simple transition from the traditional Wohler’s curve to the Paris’ law curve is proposed. Such a methodology allows one to obtain the Paris’ law material constants, which are used to determine the fatigue failure of the structure or a component. The constants of the experimentally determined material, measured in four different concrete mixtures, have been verified by recalculating the number of cycles until the fatigue failure Nf by the integration of the Paris’ law equation. The back-calculated number of cycles and the approximation of the S-N curve allowed for a comparison with the experimental data. Furthermore, the initial notch tip was extended in this approximation by the value of the critical distance. Such an extension allowed us to cover a wide range of the experimental data and provided a better prediction of fatigue life. The proposed method was verified on all four studied materials and showed satisfactory results