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Research on Fatigue Bending Stiffness Degradation of Prestressed Concrete Beams Considering Size Effect

Based on the fatigue damage development law and damage model of concrete, considering the crack propagation of ordinary steel bars and prestressed reinforcement under fatigue load, the residual useful section area of reinforcement was used to reflect the fatigue damage of steel bars. Further, we considered the correction coefficient of the size effect of concrete and steel bars and derived the formula for calculating the section stiffness of prestressed concrete beams of different sizes after fatigue damage. A multi-stage variable amplitude fatigue load test was carried out on prestressed concrete beams. The test results were analyzed, and the accuracy of the equation was verified based on experimental data. The results show that the stiffness degradation of prestressed concrete beams and the development of concrete damage under the multi-stage variable amplitude fatigue loading test have similar laws. According to the theoretical derivation formula, the deviation between the calculated results and the experimental results is small, which has reference value for the study of the fatigue bending stiffness degradation of prestressed beams considering the effect of size effect.