Structures may be subjected to static and dynamic loads during their service life. When it comes to the dynamic spectrum, wind action, ocean waves and seismic loads are key examples and are responsible for cracking evolution and material degradation along service life. Therefore, the fatigue behavior of cementitious materials has been receiving great attention due to cyclic loading that can be of natural occurrence or induced by human activity lately. This research aims to investigate the effect of dynamic loads on the mechanical degradation of steel fiber reinforced concrete (SFRC) subjected to flexural fatigue. A self-consolidating concrete with a compressive strength of 60 MPa, reinforced with hooked-end steel fibers, was developed. At the material level, pre-cracked prisms were tested. The dynamic properties, natural frequencies, vibration modes, and damping ratios, were evaluated through modal analysis, allowing the detection of damage levels. Changes in these parameters indicated the presence of damage, and the Modal Assurance Criterion (MAC) analysis highlighted the sensitivity of mode shapes to the degradation process. Notably, the reduction in stiffness was substantially greater than the damage detected by dynamic tests. At the structural scale, four-point flexural fatigue tests were conducted on reinforced concrete beams with steel fiber reinforcement. These tests were performed under continuous stress corresponding to 80 percent of the steel s yield strain, with loading frequencies of 6 Hz and 0.35 Hz, and stress ratios of 0.3 and 0.1. The results showed that incorporating steel fibers improved the distribution of tensile stresses, thereby enhancing the fatigue life of the beams. Moreover, lower loading frequencies intensified mechanical degradation due to the higher energy release per cycle. At greater stress amplitudes, stiffness degradation became more pronounced, compromising fatigue performance. To predict this behavior, a generalized model based on moment curvature relationships derived from constitutive models and closed-form equations was proposed, describing the mechanical degradation of beams throughout the fatigue cycles. Experimental tests validated accuracy of the model in predicting both fatigue life and structural performance, confirming its effectiveness for assessing the mechanical degradation of steel fiber–reinforced concrete beams under fatigue loading.