Investigation of RC Beams Strengthened with Prestressed NSM CFRP Laminates

Abstract

In this research, concrete beams were strengthened with carbon-fiber-reinforced polymer (CFRP) laminate strips that were placed in precut grooves on the concrete surface. Five simple-span RC beams were tested. Among these specimens, one served as a reference beam and was not strengthened, one was tested after being strengthened with nonprestressed near-surface-mounted (NSM) CFRP laminates, and the remaining three were strengthened with NSM CFRP laminates that had been prestressed to 5, 20, and 30% of the nominal ultimate strain of the strips. The test results indicate that the prestressed beams more effectively improved the cracking and yielding loads than the nonprestressed strengthened specimen. In addition to a higher cracking load, the prestressed strengthened specimens had cracks with a more limited distribution and width. Furthermore, the prestressed strengthened beams had up to a 15% higher ultimate load-carrying capacity than the nonprestressed specimen, and their failures corresponded to lower deflections.