Study On The Interfacial Bonding Property Of FRP Reinforced Concrete

Reinforced concrete structure has been widely used, but huge economic losses have been caused by the corrosion of steel. Therefore, FRP bars are applied gradually, which become the focus of research in the field of civil engineering at home and abroad. By now, the bond performance of FRP tendon and concrete has been studied by lots of experimental research and theoretical analysis, but the numerical research is rare. In numerical model, the spring model is common, while contact model is little. The further numerical research on comparison of load and the vertical displacement of FRP concrete beams and reinforced beams and the distribution of bond strength need to be studied.The research work and conclusions are as follows:1. Based on the existing theoretical calculation formula, the elastic theory is used to analysis the numerical model. With the comparison to the test results, the theory can predict the pull-out load well.2. Using numerical models to simulate pull-out specimens, which are the spring model and the face-face contact model to analysis the influence of different parameters on the bonding properties. Results show that:the bond strength increases when concrete strength increases. Diameters from 6-12mm, the bond strength decreased greatly, diameters from 14-20mm, the bond strength decreased slightly.Diameters from 6-10mm, the best protection layer thickness is 30mm, diameters from 12-20mm, the best protection layer thickness is 40mm. With the increase of bond length, bond strength increases slightly, so the bond length shoulds not be too long according to the actual situation.3. Based on the results of pull-out test, numerical models of FRP beams is conducted by choosing the appropriate thickness of the protective layer and the diameter of FRP bars. Analysis shows that:with loading on FRP beam, there are concrete cracking stage stage and concrete crushing stage. The cracking load of reinforced beam is larger than that of FRP beam. Before cracking, the displacement of FRP beam and reinforced beam differents slightly. Before the yielding of steel, the displacement of reinforced beam is less than that of FRP beam. After the yielding of steel, the displacement of reinforced beam increases rapidly. FRP beam failure is brittle. When the elastic modulus of FRP bars is over 180GPa, displacement is not significantly increased with a larger bearing capacity. Crack has great influence on the bonding strength which causes dropped segments. In the pure bending section which is between 700mm and 1000mm to the end, the bond strength is small.