Study On The Bond Behavior Between Non-uniform Corrosion Steel Bar And Concrete Under Sustained Load

Good bond behavior is the prerequisite for the joint work of steel bar and concrete,and the guarantee of the mechanical performance of reinforced concrete member.The corrosion of steel bar in reinforced concrete structures under the influence of external corrosive environments is an important factor affecting the bond behavior.The corrosion of steel bar will change the properties of the bond interface,and even cause cracking,spalling,and delamination of the concrete cover,which will cause problems such as deterioration of the bond behavior.Reinforced concrete members always bear long-term external loads during the service period.Therefore,the research on the corrosion of steel bar under external loads has more practical engineering significance.Aiming at the problem of the bond behavior between steel bar and concrete,this paper takes the corrosion rate of steel bar and the sustained load level as factors,and conducts a systematic research on the corrosion shape of steel bar,time-dependent slip law,corrosion cracking damage,and bond slip relationship.The main research contents are as follows:(1)Based on the Faraday’s law,a simulation analysis of the corrosion shape of steel bar under different auxiliary electrode placement positions in the electrification accelerates corrosion.Calculate the non-uniform distribution of the steel bar corrosion layer,and compare it with the corrosion of the steel bar in the natural environment in other documents,and the accelerated corrosion method is selected to be close to the natural corrosion of the steel bar.The simulation results are verified by the electrification accelerates corrosion test to prove its effectiveness.The calculation method and control scheme of steel bar corrosion distribution are proposed.(2)Through the steel bar corrosion test during the loading period,the relative slip change between the steel bar and the concrete during the sustained load and the corrosion development period is recorded,and the influence of the corrosion and the sustained load level on the time-dependent slip is analyzed.Analyze the rate of time-dependent slip of the specimen,and judge the change trend of slip over time.(3)Based on elastic mechanics theory,calculate the maximum corrosion depth of non-uniform corrosion of steel bar when concrete cover cracks.According to the filling of the cracks by the corrosion product after the concrete cracked,the formula of the relationship between the corrosion degree of the steel bar and the width of the cracks on the surface of the concrete was deduced,and it is verified with the experimental data in the existing literature.Draw the crack distribution diagram of the corrosion cracking specimen under sustained load,and study the influence of the load on the corrosion crack distribution law.(4)Through the bond test of the beam under bending,the load and slip data of each test piece are recorded,and the bond stress-slip curve is drawn,the influence of the sustained load level and the corrosion rate on the bond slip curve is analyzed.Through the analysis of the ultimate bond strength and slip at the peak bond stress,the characteristics of the bond slip curve are studied.Calculate the bonding failure energy and analyze the degradation of bond behavior from the energy concept.