Investigation of fatigue behavior in prestressed CFRP reinforced RC beams exposed to natural subtropical environment

This study explores the fatigue behavior of prestressed CFRP-reinforced concrete (RC) beams in subtropical environments, addressing the gap in understanding their long-term performance under natural exposure. Five specimens were subjected to one year of natural exposure under sustained load conditions before fatigue testing. During the exposure period, the strain on the CFRP laminate was monitored, and a decrease of 5.37% in prestress loss after exposing 300 days was observed. The digital image correlation (DIC) method was employed to capture the crack initiation and growth during the fatigue tests, with detailed analyses of crack growth rates, deflection evolution, and failure modes. Experimental results indicated that natural exposure accelerates fatigue crack growth compared to the results of the unexposed RC beams tested by this group. Moreover, the finite element model (FEM) was developed to account for CFRP-concrete interface degradation due to natural exposure and material nonlinearities, allowing for the determination of the J-integral of the main crack. Fatigue life prediction models, based on experimentally obtained crack growth rates and stress intensity factors (SIF) calculated using the J-integral, were derived. The predicted fatigue lives were within a 20% error margin of the experimental results, demonstrating the reliability of the proposed models.