Flexural Behavior of Reinforced Concrete Beams Strengthened with Near-Surface-Mounted Prestressing Screw-Threaded Steel Bars Using Digital Image Correlation Method

In this paper, the flexural behavior of four reinforced concrete (RC) beam specimens strengthened with near-surface-mounted (NSM) prestressing screw-threaded steel bars (PSBs) were investigated with four-point bending experiments, where the failure mode, load-deflection relationships, ductility, and cracking behavior were examined as key properties. The digital image correlation (DIC) technique was used to perform full-field measurement and provide information on the deformation and failure process of concrete members. The test results indicated that the beams strengthened with NSM PSBs exhibited improved load-bearing capacity and enhanced ductility performance. It was also observed that prestressing the strengthening bar and increasing the NSM reinforcement ratio can significantly enhance the strengthening effect on the beams while controlling the development and propagation of cracks; however, the deformability of the specimen would reduce accordingly. In addition, the emerging optical technique proved to be effective in measuring the full-field deformation and monitoring the cracking evolution of concrete structures.