الخلاصة:
Multiple research have made the use of composite materials based on Fiber Reinforced Polymer (FRP ) in several forms ( sheets , laminated or stem) , a way of strengthening and repair external reinforced concrete structures or structural elements EBR (external bonded reinforcement ) . The application of this technique has shown an interesting alternative to strengthening and repair conventional methods. Nowadays, there are several design codes
dealing the strengthening of structural elements.
The magnitude of the increase in the flexural capacity for strengthening structural elements is not very mastered and needs to be explored both theoretically and experimentally. A theoretical model based on the concept of the general theory is further proposed an expanded experimental program was conducted and involved testing a simple bending of reinforced concrete elements in full scale. A comparative study was conducted between the
experimental results, predictions of the proposed model, these different national codes and those of previous work.
The experimental investigation focuses on strengthening reinforced concrete beams by CFRP (carbon fiber reinforced polymers) plates and sheets; submitted a simple four-point bending.
The test specimens are considered as a real size (scale) beams, with a ratio a / d = 1.5 which allows to classify them as deep beams. The effects of various parameters influencing the behavior of these structural elements have been examined such as the rate of tension reinforcement (ρs), the characteristic concrete strength (fck), the rate and type of CFRP, and the damage degree of the element.
This study found that the contribution of strengthening resulted in increased stiffness, and an increase of about 67% for the flexural capacity compared to control beams. Damaged and repaired beams had an almost similar to that of undamaged beams and strengthened behavior. As for ductility, it suffered a huge drop and this seems to be due to the failure mode by peeling.
Finally, the comparison between the experimental results and the model predictions and those codes revealed the importance of longitudinal reinforcement rates. It was the same model was applied to experimental results in the literature. There have been overestimated for the relatively low rate and underestimated for the relatively high rates. Also it was revealed that for the 2.1% rate of the reinforcement becomes ineffective.
