Experimental Study On Debonding Failure In FRP Strengthened Concrete Beams

Since the reform and opening up,China has witnessed the rapid development in economy and great progress in the infrastructure construction.In order to meet the transportation requirements in new era,the task for maintaining and reinforcing the structures of existing buildings and bridges has become increasingly heavy with ever-growing demands.Carbon fiber material has been widely adopted in the maintenance and reinforcement of existing structures for its high strength,excellent durability and so on.Moreover,the application of prestressed carbon fiber reinforcement technology can make advantage of high strength in carbon fiber material,improve the mechanical performance of structure in usage stage and enhance the ultimate bearing capacity.However,whether it is non-prestressed or prestressed carbon fiber reinforcement,whether the beam end takes the additional anchorage measures or not,reinforced beams are likely to suffer from early stripping damage.What's worse,early stripping damage will reduce the ultimate load capacity of reinforced beams and have a negative effect on the safety of reinforced components,leaving huge hidden danger on carbon fiber reinforcement technology.The paper covers the bending static load experiment on six concrete beams,the comparison in operation performances like cracking load,ultimate load,span deflection,the beam top concrete strain and ultimate failure mode between different carbon fiber reinforced beam and unreinforced beam and analysis on the effect of the end anchorage measures and the initial pre-stressing strength of the carbon fiber sheet on these mechanical properties.This paper expatiates on the peeling failure of the concrete protective layer at the end of the carbon fiber board reinforced concrete beam and the peeling failure caused by the intermediate crack and makes an analysis on the mechanism of each stripping failure mode and the corresponding peel strength model.The experimental results were compared with the calculated values of the strength model,which helped to find out the relatively ideal model of stripping failure strength of the protective layer.The experimental study shows that the inadequate shear strength of the reinforced beam tends to cause peeling damage due to the shear fracture.Therefore,adequate shear bearing capacity should be ensured on the reinforced concrete beam in the carbon fiber bending reinforcement design of the concrete beam.