Comparative study on prestress loss and flexural performance of rectangular and T beam strengthened by prestressing CFRP plate

Abstract

Influence of real and small size (laboratory) specimens with different prestress levels on the flexural performance of RC beam has not yet been compared to verify the reliability of experimental research for real applications. In this study, an experiment was designed by casting rectangular (small-scale) and T-section (large-scale) RC beams, which were strengthened by CFRP plates with 0, 20 and 40% prestress levels. The prestress loss and flexural performance was assessed for both scales. The instantaneous and initial 7-day prestress losses of the small-scale specimens were notably higher than those of the large-scale specimens. Thereafter, a four-point bending test was conducted to assess the specimens’ flexural performance. The experimental results showed that the cracking, yield and ultimate moments increased with the prestress level, in which the incremental rate of the ultimate moment of the small-scale specimens was obviously greater than the large-scale specimens. The load–deflection curves of the large-scale specimens suddenly dropped with simultaneous CFRP plate debonding from the plate end, while this phenomenon was not obvious during the small-scale specimen tests. This result indicates that the adhesive bonding benefits the stiffness of the real-size strengthened beams, but this was not observed in the small-size specimen tests.