Experimental research on flexural behaviors of damaged PRC beams strengthened with NSM CFRP strips

This paper investigates the flexural behaviors of the damaged prestressed reinforced concrete (PRC) beams strengthened with near surface mounted (NSM) carbon fiber-reinforced polymers (CFRP) strips under overloading. A bending test was carried out to evaluate the effects of three variables: the cycle number, overload amplitude and strengthening under loading or unloading. Different damage degrees were mainly controlled by cycle number and overload amplitude. The test results showed that strengthening with NSM CFRP strips could effectively inhibit crack development. Compared with the un-strengthened beam, the flexural load-carrying and stiffness of the strengthened beams were enhanced evidently. With the increase of cycle number and overload amplitude, the yield loads increased. The yield load of strengthened beam under unloading was higher than that of strengthened beams under loading. These three variables had limited influence on the ultimate bearing capacity. The deformations of the strengthened beams were smaller than that of the control beam, and decreased with the increase of cycle number, but increased with the increase of overload amplitude. The deformations of the strengthened beams under loading were slightly greater than that of the strengthened beam under unloading in the early phase but smaller in the later phase. The ductility of strengthened beams was evidently reduced compared with that of the control beam. The displacement ductility factors of the strengthened beams under loading decreased with the increase of cycle number and overload amplitude, and were smaller than that of strengthened beam under unloading.