Investigation of innovatively strengthening reinforced concrete beams with insufficient shear capacity using carbon fiber strands

In this thesis, the effect of strengthening of reinforced concrete beams with insufficient shear capacity with carbon fiber bundles/strands in different configurations on the beam behavior was experimentally investigated. Within the scope of the study, a total of twelve reinforced concrete beams were tested under vertical load. Two of them were used as reference specimens and the remaining ten beams were strengthened with variable parameters such as different types of strands, strand spacings and the use of epoxy. The reference specimens failed due to diagonal tension failure. Beams strengthened with specially produced carbon fiber strands and epoxy showed an increase of up to 92% in load carrying capacity. It was also observed that shear cracks were confined and more ductile behavior was exhibited. When the effect of strand spacing is analyzed, beams strengthened with d/4 spacing have higher load carrying capacity and ductility compared to d/3 and d/2. In addition, it was determined that the specimens strengthened with specially produced strands exhibited a more rigid behavior than the specimens strengthened with carbon fiber bundles or strands. During the test, no rupture was observed in the specimens strengthened with specially produced strands. These findings indicate that the 6 mm diameter specially produced strand preferred in the experiments was sufficient. In the specimens strengthened with carbon fiber bundles or strands, it was concluded that the strand diameter should be appropriately increased to prevent rupture. The use of epoxy was found to be highly effective in improving the energy dissipation capacity of the specimens. A notable finding is the up to 128-fold increase in plastic energy dissipation capacity observed in the epoxy-strengthened specimens. As a result, the findings demonstrate that this strengthening application with an innovative technique is effective and feasible for increasing the load-carrying capacity and ductility of reinforced concrete beams with insufficient shear capacity, while providing valuable insights for future research.