The Specific Properties Research of RC Beams Multiple Strengthened with Near-Surface Mounted Carbon Fiber Reinforced Plastic Bar and Pre-Stressed Helical Rib Bar

Seven concrete beams were constructed with normal reinforcement bars. Grooves were opened on the concrete cover of the tensile region in the concrete beams using different combinations of carbon fiber reinforced plastic (CFRP) and pre-stressed helical rib bar (HRB), CFRP and HRB pre-stressed at different levels were inserted into the grooves and filled with resin. Flexural experimental results indicated that the limit bearing capacity, rigidity, and crack resistance of the beams were strengthened significantly with near-surface mounted two pre-stressed HRB and one CFRP (BF1P2) bar, or near-surface mounted one pre-stressed HRB and two CFRP (BF2P1) bars, in which HRB was pre-stressed at 30%, 45%, and 60% of its limit strength, respectively. Compared with an un-strengthened beam, the crack loads of the BF1P2 beams increased by 86.70% and 133.33%, the yield loads by 32.25% and 72.04%, and the limit bearing capacities by 72.73% and 90%. The crack loads of the BF2P1 beams increased by 50% and 133.33%, the yield loads by 50.54% and 136.56%, and the limit bearing capacities by 72.20% and 173.60%. The BF1P2 beams had better reinforcing results compared to those of the BF2P1 beams. The beam strengthened with HRB pre-stressed at 45% of its limit strength was the best concrete beam.