Experimental Research On The Bond Behavior Between Cfrp And Corroded Reinforced Concrete

The durability problem of reinforced concrete structures has become increasingly serious and has attracted the attention of countries in the world.A large number of engineering examples show that the corrosion of steel bars is one of the major causes of damage and failure of reinforced concrete structures.At present,the externally bonding FRP reinforcing technology has been widely used in these degraded reinforced concrete structures.This field has always been a research hotspot in the field of civil engineering.However,the research results on the effect of reinforcing steel corrosion on the FRP bond performance of RC components are limited.Many experiments have shown that the effect of FRP-reinforced concrete members mainly depends on whether the stress at the bonding interface between FRP and concrete is effectively transmitted,while the rust effect of reinforcing steel tends to affect the bonding properties between FRP sheet and concrete.Therefore,76 concrete specimens externally bonding FRP strip are prepared for research.A single shear test method is used to investigate the affect of corrosion-deteriorated concrete on FRP bond stress transfer system under different bar diameters and different corrosion gradients.The main research results of this dissertation are as follows:(1)All the specimens were energized to accelerate steel corrosion.The testing results show that the corrosion cracking process and characteristics of the specimens with different corrosion rates and different steel bar diameters.Furthermore,the relationship between the width of the corrosion crack and the corrosion degree is obtained.(2)To observe and analyze the phenomenon during loading process and the mode of debonding failure by single-shear test,and then analyzing the test results to get the influence of different corrosion degree on the ultimate bond capacity of the interface.Based on the above investigation,the load-slip relationship of the bonded interface and the stress-strain distribution of FRP sheets are obtained and compared.(3)Through the projective covering method of fractal theory what are observed are the fractal features and differences between the peeled surface of concrete protective layer and the rust-cracking surface.Then the fractal characterization of corroded concrete cracks under different corrosion degree is conducted by pixel point method.Then the relationship between different corrosion degree and fractal dimension is analyzed and calculated,and a new method of rapidly predicting the corrosion degree of steel concrete structure is proposed.(4)The FRP paste criteria for FRP-concrete interface is established: the three most accurate bond capacity models and the experimental values in this dissertation contribute to deduce the critical corrosion rate formula.In addition,a calculation model for the ultimate bond strength of FRP under the action of corroded steel is established which can provide a theoretical basis for the research on the performance of FRP shear reinforcement and reinforcement methods for subsequent corroded reinforced concrete beams.