Research On Theory And Method Of Bond-slip Monitoring Of Reinforced Concrete

The good bond behavior between steel and concrete is the key to the bearing performance of the structure.The bond-slip degration of steel-concrete affects the mechanical properties and duratility,which has a degree of influence on the energy dissipation mechanism of the whole structure.The bond properties of concrete-steel bars with different fly ash content were studied by using electrochemical impedance spectroscopy and acoustic emission.The experimental results were verified by finite element analysis software.The failure mechanism of reinforced concrete interface was studied.The calculation of bond-slip between concrete and steel was analyzed from various aspects.The average tensile stress was approximated by the tensile stress of the steel.The stress distribution is calculated based on the matrix theory.The stress state analysis of the intercostal concrete was based on the mechanical model.Based on the energy principle and elastic mechanics theory,the energy release is analyzed during the bond damage process.The extrusion experiment block and the four-point bending beam was formed by the concrete with different fly ash content.Combined with acoustic emission technology and electrochemical impedance spectroscopy technology,the changes of electrochemical impedance spectroscopy parameters and acoustic emission parameters during the loading process of each test block were studied.The changes of resistance and capacitance in ac impedance spectrum test results,as well as the change trend of energy and damage location in acoustic emission were mainly explored.The research shows that the reinforced concrete interface capacitance increases and the electrical resistance decreases with the increase of the degree of bond damage.The bond performance of the interface can improve with the fly ash content of about 20%.The energy spectrum of acoustic emission can intuitively reflect the damage resistance of steel-concrete interface,and the damage location map can show the development course of damage.Based on the above theoretical analysis results and experimental research,the ANSYS software was used to simulate the extrusion test and the four-point bending test.The reinforcement of the steel-concrete was simulated by the spring element and the contact element.For different test pieces with different fly ash content,different strength grades of concrete are used instead.The simulation results of extrusion experiment show that the relationship between slip and load can be divided into two stages.The turning point can be regarded as splitting load.The influence of fly ash content on the interface transition zone can be indirectly analyzed by the stress distribution of steel bar,and the simulated results are consistent with the acoustic emission results.Before the macro crack occurred,the simulation results of four-point bending show that the slip of the reinforced concrete beam is significantly larger than that of the mid-span.In the pure bending section,the slip of reinforcement does not change obviously.The compressive stress on the bonding surface is positively symmetrical along the mid-span.The surface shear stress of the steel bar is antisymmetric along the mid-span interface.Combined with the theoretical analysis,experimental research and numerical simulation,the bonding properties of concrete and steel bars with different fly ash content are analyzed,and the bonding slip characteristics of reinforced concrete are investigated comprehensively.It provides a reference for further research on the bond-slip of the reinforced concrete interface.