Concrete elements degrade due to the continuous application of compressive fatigue loads. The irreversible deformation or induced compressive strains evolve; hence, the progressive stress redistribution between concrete and embedded steel reinforcing bars should be accounted for in fatigue analysis of…
Concrete elements degrade due to the continuous application of compressive fatigue loads. The irreversible deformation or induced compressive strains evolve; hence, the progressive stress redistribution between concrete and embedded steel reinforcing bars should be accounted for in fatigue analysis of concrete structures. Experimental investigations were conducted to study the behavior of four small-scale reinforced concrete deep beams with shear-span to effective-depth ratio of 1.25. The principal compressive strain evolutions from the beam struts were obtained from the strain transformation analysis of LVDT data, and compared with the predicted principal strain evolutions. Each predicted strain evolution was obtained by substituting the initial strut compressive stress estimated from the static analysis of the fatigue load into a strain evolution model from the literature. The comparison between the measured compressive strain evolution from the experiments and the predicted strain evolutions indicated that the design approach in the literature is overly conservative for concrete. However, this is generally attributed to the neglect of the contribution of the tensile strength of concrete in fatigue resistance. The strut-and tie method was used for the fatigue resistance verification of deep beams by modifying the constitutive models and effectiveness factor of concrete with fatigue damage models. The irreversible compressive strain is considered as a pseudo-load, and the progressive crack growth of steel reinforcement resulting from the evolving stresses is accounted for using an equivalent cycle concept with the Paris crack growth model. Within the developed algorithm, failure will occur when one of the evolving stresses in either the concrete strut or steel reinforcement approaches the corresponding residual strength.