Effect of using different configurations of NSM-CFRP strips on the flexural strength of RC beams

The main objective of this research is to study, experimentally, the flexural strength of lightweight reinforced concrete (LWRC) beams strengthened using the near-surface mounted carbon fiber reinforced polymer technique (NSM-CFRP). Four simply supported beams with a rectangular cross-section are strengthened with NSM-CFRP strips and subjected to a monotonic four-point bending test up to failure. The parameters studied in this paper are using: (1) Two horizontal strips at the middle half of the beams span; (2) Two horizontal strips at full beam span length; and (3) One horizontal strip at beam full span length. The failure mode, ultimate capacity, deflection, and crack pattern were evaluated. The results showed that using two horizontal strips at the middle half of the beams span increased the ultimate load by 7.14%; while using two horizontal strips at full beam span length increased the ultimate load by 12.55%; and using one horizontal strip at beam full span length increased the ultimate load by 9.35% compared to the control beam. The mode of failure for all beams was pure flexure, concrete crushing and epoxy-concrete interfacial de-bonding. Accordingly, it can be considered that using two horizontal strips at full beam span length is the best configuration to enhance the flexural strength.