Effect of Under-Stressing on the Fatigue Strength of RC Beams Rehabilitated with NSM CFRP Reinforcement

Toutanji H., Eljufout T.

10th International Conference on Fibre-Reinforced Polymer (FRP) Composites in Civil Engineering (CICE), İstanbul, Turkey, 8 - 10 December 2021, vol.198, pp.342-350 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 198
  • Doi Number: 10.1007/978-3-030-88166-5_29
  • City: İstanbul
  • Country: Turkey
  • Page Numbers: pp.342-350
  • Keywords: Fatigue, Beam, Under-stressing, CFRP, NSM, BEHAVIOR, LIFE
  • Istanbul Technical University Affiliated: No


Reinforced Concrete (RC) bridges are subjected to a growing traffic load along their service life. The rupture of steel rebars is the most dominant failure mode of RC beams under fatigue loads. Applying cyclic stresses below the fatigue limit improves the fatigue strength of metals, which also known as "under-stressing". This paper investigates the influence of under-stressing on the fatigue performance of RC beams rehabilitated with Near Surface Mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP). The study includes four RC beams with dimensions of 152.4 x 152.4 x 1,521 mm. A strengthened and a non-strengthened specimens were tested under monotonic loading to obtain the flexural static capacity. A strengthened specimen was tested as a reference under constant amplitude cyclic stress without experiencing pre-fatiguing. In contrast, a non-rehabilitated RC beam was pre-fatigued to simulate the conditions of service loading. Later, the specimen was rehabilitated with NSM CFRP reinforcement and tested under the same cyclic load of the reference specimen. The rehabilitated RC beam had an improvement in the fatigue responses when compared to the reference strengthened specimen. Under-stressing had a major role in decelerating the fatigue crack propagation of steel rebars and in extending the fatigue life of the rehabilitated RC beam.