Experimental Study on the Flexural Behavior of Large-Scale Reinforced Concrete Beams Strengthened with Prestressed CFRP Plates

Abstract Carbon fiber–reinforced polymer (CFRP) systems have been widely used to strengthen concrete structures. To further study the flexural strengthening of concrete beams with prestressed CFRP plates, flexural tests of large-scale reinforced concrete beams were performed, and a tensioning and anchorage system suitable for engineering applications was used in this study. The effects of the prestressing level, strengthening amount, type, and bonding position of the prestressed CFRP plate on the flexural behavior were investigated. The test results showed that the cracking load, yielding load, and ultimate load of all prestressed strengthened beams could reach 2.25–3.38 times, 1.27–1.53 times, and 1.24–1.61 times those of the unstrengthened beam, respectively. The postcracking stiffness, cracking load, and yielding load could be increased by increasing the prestressing level and strengthening the amount of the prestressed CFRP plate. However, a high prestressing level of 50% could lead to a premature intermediate debonding of the CFRP plate before yielding of the steel reinforcements and a reduction in the ultimate load. The use of a low-strength prestressed CFRP plate could achieve a strengthening efficacy similar to that of a high-strength CFRP plate before yielding of the steel reinforcements, whereas the low-strength CFRP plate reduced the ultimate load by 25 kN compared with the high-strength one. The prestressed CFRP plate bonded on the two sides provided a lower flexural strengthening efficacy than that bonded on the bottom of the beam owing to the shorter force arm and the nonuniform stress of the side-bonded CFRP plate.