Abstract:
In recent years, carbon fiber reinforced polymers (CFRP) have gained increasing interest in the strengthening of structural members. This trend is due to the specific properties of CFRP, which contribute significantly to the strength and ductility of the reinforced elements. However, debonding results in the loss of the bond between the CFRP laminates and the concrete substrate at an early stage, leading to brittle failure at limited load levels and would prevent the composite materials from reaching their full strength capacity. The phenomenon of premature debonding of FRPs has been proven and confirmed by several researchers and is the main drawback of the EBR (Externally Bonded Reinforcement) technique. In this research work, we opted to use a new technique for strengthening of reinforced concrete beams with composite materials, namely the NSM (Near Surface Mounted) technique. The NSM technique consists of inserting strips of carbon fiber reinforced polymer (CFRP) laminate into slots previously made in the concrete cover of the elements to be strengthened. First, an experimental study was performed on reinforced concrete beams strengthened with CFRP using the
NSM and EBR techniques for comparison. Several parameters were taken into consideration, including the rate of reinforcement, the anchorage length, the surface condition of the CFRPs, the type of reinforcement, the reinforcement technique and the hybrid reinforcement configuration. The experimental results showed the effectiveness of carbon fiber reinforced polymers in improving the structural behavior of the beams, a clear improvement of the bearing capacity was observed. Subsequently, a numerical study was investigated in depth to fully understand the behavior of reinforced
concrete beams strengthened by NSM-CFRP. The computational code used in this study for the numerical modeling is the ATENA 2D finite element software. The results of the numerical models developed have a good agreement with the experimental results. At this stage, the validated numerical models can be used for a parametric study. At the end, this research work was concluded with a parametric study through several strengthening simulations with different parameters influencing the behavior of reinforced concrete beams strengthened by the NSM technique. The parametric study also gave interesting results regarding the effectiveness of the NSM strengthening technique using composite materials.
