Experimental Research On The Bond Performance Of CFRP-Concrete Interface

The need for upgrading, strengthening, retrofitting, and rehabilitating existing structures, or damaged ones, is one of the most important problems that structural engineers face. Recently, an advanced composite material named Carbon Fiber Reinforced Plastic (CFRP) is becoming increasingly popular in the construction industry for strengthening purposes as an alternative to traditional strengthening material. Because of it's several attractive properties such as high tensile strength and modulus of elasticity, light weight, corrosion resistance and simple construction make, it is widely used in strengthening field. The success of concrete members strengthened with continuous CFRP depends on the interface properties between CFRP and concrete member, so the research to bond performance of CFRP strengthening concrete structures is an important problem to many researchers and engineers today in the world. In the paper, the behavior between CFRP and concrete interface is explored primarily by using experimental method and theory analysis method.The experiment of bond performance in the interface of concrete members strengthened with continuous CFRP is designed in the paper. By using the orthogonal test method, 24 test specimens are designed to be studied. The influences on average bond strength are researched by 4-point bending experiments of reinforced concrete member strengthened with continuous CFRP with different parameters of concrete compressive strength, CFRP length, layer of CFRP, and width of CFRP. Moreover, 27 small cube concretes are investigated to the bond strength per area.In the progress of experiments, the strain of CFRP along the bond direction, the failure mode of limit of bearing capacity, etc. are observed. The curves of bond shearing stress variation with the different load level are plotted and the results of experiments are analyzed. The different concrete strength, layer of CFRP, bond length and failure mode are compared and the value of bond strength per area is acquired. It's more valuable to experience of engineering.According to the results of the tests, the main achievements and contents are as follows:First, A layer-structure-model is put forward in the field of substantial microstructure and used to explain the bond mechanism based on the experimental study and fracture mechanics.Second, the mechanism of stress transformation and the process of debonding failuremechanism are researched by the interface bending experiments designed by myself. The process of bond and failure in the interface of CFRP and concrete are analyzed and summarized through using the Fracture Mechanics Theory.Third, according to the bond-slip theory, the limitation of the existing bond-slip mode (x-8 mode) is analyzed based on the results of experiment and failure mechanism. So a new bond -slip mode between the CFRP and concrete interface is put forward, the theory formula is established by using the new bond -slip, and the calculation formula of effective bond length is also brought forward.Forth, through summarizing the results and the analysis of theory, the prospect of application of my thesis is envisioned and some suggestions and presumptions are provided for the further study in the field.