Experimental study of corroded RC beams strengthened with HB-FRP

This paper presents a new method for strengthening corroded RC(reinforced concrete) beams with hybrid bonded fiber reinforced polymers (HB-FRP) and presents the results of experimental research on the flexural performance of corroded concrete beams reinforced with HB-FRP. A total of 5 corroded concrete beams were tested and compared with 2 uncorroded concrete beams reported in previous studies. The variable parameters, including the anchor mode, anchor spacing and anchor depth, were discussed, and their effects on the debonding performance of the two weak interfaces (concrete cover interface and the FRP-to-concrete interface) were analyzed. The results suggest that the ultimate load of the HB-FRP-reinforced corroded beams significantly increased by 31.2-80.6 % compared with that of the EB-FRP-reinforced corroded beams. An inflection point was observed at the load-deflection curve, indicating that the tensile steel bar yielded. The concrete cover cracked after the steel bar yielded to make a concrete tooth with the two adjacent vertical cracks. A theoretical cantilever beam model under the constraint of an anchor was proposed to calculate the FRP stress at the concrete cover cracks. The cracking load of concrete cover increases with the increase of bolt torque. If the concrete tooth is completely cracked, the anchoring effect is lost, and the double interface fails. When the anchor depth exceeds the thickness of the concrete cover and the anchor spacing is small, the debonding of both interfaces is prevented.