Strengthening of Reinforced Concrete Cantilever Beams by Using Externally Bonding and Near-Surface Mounting Strengthening Techniques

This research aims to study the efficiency of using different strengthening techniques to strengthen the reinforced concrete cantilever beams. Carbon fiber reinforced polymer (CFRP) strips and laminates with different patterns are used for this purpose. The practical program consisted of casting and testing of nine reinforced concrete cantilever beams (RCC). All these specimens had the same dimensions of (200×300×1250) mm, as well as the same main and secondary reinforcement. One of these beams was considered a reference beam with no strengthening, while the other eight beams were strengthened with the mentioned strengthening techniques. The strengthening variables included the type of CFRP (strips or laminate), the number (or equivalent area) of strips and the laminates, and the strengthening technique (external bonded EB and near surface mounted NSM). All specimens were tested until failure under point load at the free end of the beams. The results showed that all the used strengthening techniques increased the strength of beams for ultimate load and stiffness, with increasing ratios ranging from 37% to 67%. The strengthened tested beams noticeably increased with the CFRP layer (or area) for both types of CFRP (strips and laminates). Also, the CFRP laminate showed a higher effect in the increase in beam strength than the CFRP strips. Related to the strengthening technique, the Near Surface Mounted technique showed a higher effect in increasing beam strength than the External Bonded technique for different strengthening types and amounts.