The influence of interaction between NSM and internal reinforcements on the structural behavior of upgrading RC beams

In this paper, the effect of interaction between near surface mounted (NSM) strips and internal reinforcement on the structural behavior of upgrading RC beams has been studied. The position, arrangement and area of NSM glass fiber reinforced polymer (GFRP) strips have been examined experimentally. Six strengthened beams in addition to one control beam were tested in flexural until failure. The load carrying capacity, deflections and the mode of failure of strengthened beams were recorded. The experimental results showed that the installed NSM GFRP side by side has a lower interfacial stress than those installed separated. This improvement is more obvious in the case of NSM strips installed near the internal reinforcement. Furthermore, the installed NSM strips in deep groove experienced higher load carrying capacity than those installed in shallow groove for both patterns. The installation of the NSM GFRP strips in deep grooves using epoxy may be delay or prevent the peeling/debonding failure. The ultimate load of the beam upgraded with one NSM strip adjacent to the stirrups (in deeper groove) is about 1.5 times that of one NSM strip installed near the bottom surface of the beam. This ratio decreased with increasing the area of NSM GFRP strips.