Investigation of the structural behavior of hybrid FRP–steel reinforced concrete beams

In the presented thesis, the behavior of hybrid CFRP-steel reinforced concrete beams was examined. In the study, a total of five beams were prepared. One of them was reinforced concrete beam with CFRP bars, two beams were hybrid CFRP-steel reinforced concrete beams and two beams were hybrid CFRP-steel reinforced steel fiber concrete beams. The beam specimens were 150×200 mm in cross section sizes and 1500 mm in length. The prepared beams were designed as over-reinforced. The beams were tested under four-point loading to determine the flexural behavior. In the experimental study, an electronic data acquisition system was set and the applied load and the corresponding deflections and strains were recorded in a computer at an interval time. In the beam tests, cracks, crack developments, applied load, deflections and strains in the beams were observed. The ultimate loads, load-deflection curves of the beams were attained. It was observed that the tested beams were failed as over-reinforced in consistent with design. In the experiments, it was found that steel fibers restricted the crack widths and improved the ductility of the beams. In addition, a theoretical procedure was taken into consideration to analyse the plain and steel fibers reinforced concrete beams with hybrid FRP-steel bars in the study. In the theoretical method, the nonlinear stress-strain relationships of plain and steel fiber concrete were considered. The tested beams were analysed for load-deflection curves and load capacities. The analytical results were compared with the test results and obtained in good agreement. It was determined that the stress-strain models for plain and steel fiber concrete assumed in the theoretical method provided reasonable results for the predicting the behavior of hybrid CFRP-steel reinforced concrete beams.