Flexural behavior of large-size RC beams strengthened with side near surface mounted (SNSM) CFRP strips

Taking the reinforcement of monorail guide-way as the background, the effectiveness of SNSM carbon fiber reinforced polymer (CFRP) strengthening technique applied for the large-size reinforced concrete (RC) beams was evaluated. First, considering the effect of curing condition, the single shear pull-out tests of NSM CFRP were carried out to determine proper curing temperature and time. Second, considering the influence of CFRP spacing, prestress level of CFRP and longitudinal reinforcement ratio, the flexural experiments of strengthened beam with SNSM CFRP technique were carried out by four-point loading method. The results showed that the bond behavior between CFRP and concrete represented a negative quadratic curve with curing temperature and a positive arc-tangent curve with curing time. The flexural capacity of strengthened beams was obvious higher than the un-strengthened beam, which were increasing with the improvement of prestress level and the reduction of CFRP spacing. However, the improvement of flexural capacity of strengthened beam with prestressed CFRP was not obvious with the increase of prestress level, and the longitudinal reinforcement ratio had a negative impact on the flexural capacity. Finally, considering above-mentioned factors, a predicted model of flexural capacity and mid-span deflection for the beam strengthened with SNSM CFRP was developed and validated.