Study On Seismic Performance Of Reinforced Concrete Cylindrical Pier Exposed To Chloride Ion

The cracking process of reinforced concrete piers induced by chloride ion erosion is a key problem in bridge engineering design.It is a systematic process to evaluate the stability of cylindrical reinforced concrete piers exposed to chloride ion.Firstly,the time correlation between electrochemical accelerated corrosion and the corrosion degree of reinforced concrete piers exposed to natural environment is clarified,and the erosion degradation model of piers is established.Then,the influence of reinforcement spacing and diameter on the internal crack mechanism and spalling mode of cylindrical reinforced concrete piers is investigated,and the damage zone model of piers concrete is proposed.Finally,the earthquake resistant behaviors of cylindrical reinforced concrete piers with different reinforcement ratios after erosion are studied.The research content provides reference for the reinforcement design of cylindrical reinforced concrete piers with different reinforcement ratios under earthquake action in chloride ion.(1)In order to clarify the time correlation between electrochemical accelerated corrosion and the deterioration degree of cylindrical reinforced concrete piers in natural environment,the electrochemical accelerated corrosion test was carried out with the corrosion amount of reinforcement as the evaluation index and different applied voltages and chloride ion concentrations as the control variables.The test results show that the longitudinal cracks parallel to the steel bar and transverse penetration cracks appear at the height of 1/3 to 1/2 under different voltages and chloride ion concentrations.Based on Faraday's law and the Arrhenius time equivalence theory,the accelerating factors of electrochemical accelerating corrosion with different applied voltages and different chloride ion concentrations were deduced.It provides time scale calibration for the subsequent experimental research in this paper,and prepares for the proposed erosion degradation model of piers.(2)In order to explore the internal crack mechanism of cylindrical reinforced concrete piers with different reinforcement forms under the action of chloride ion,it is emphasized to analyze the process of concrete protective layer peeling caused by increasing corrosion products.Based on the extended finite element method,the crack propagation path,propagation rate and cracking Angle of cylindrical reinforced concrete piers are obtained by taking the number of reinforcement,diameter of reinforcement and diameter of pier as variables.The stress superposition caused by the corrosion of adjacent steel bars is the main factor affecting the corrosion crack growth rate.The ratio of the reinforcement spacing to the diameter of the reinforcement and the ratio of the reinforcement spacing to the thickness of the concrete protective layer affect the crack propagation path,which leads to different patterns of spalling(local spalling and layer cracking)of the concrete protective layer.The thresholds of the two peeling modes are 3.17 and 2.22.By comparing the advantages and disadvantages of different spalling modes,the BD model of pier concrete damage zone is proposed to correct the damage zone of protective layer concrete.(3)To clarify the seismic performance of cylindrical reinforced concrete piers after chloride ion erosion.The influence of chloride ion erosion on the physical and mechanical properties of cylindrical reinforced pier column materials was analyzed.Considering the degradation characteristics of the material parameters such as the section of reinforcement,strength,concrete strength and reinforced concrete bonding strength,the erosion degradation model of pier column in this paper was proposed,and the BD model was used to correct the damage area of concrete protective layer.The reliability of the finite element model was calibrated by large scale quasi-static test after electrochemical accelerated corrosion.Based on M-Park-Ang model,the seismic damage factors corresponding to piers with different reinforcement ratios were analyzed,and the optimal reinforcement ratio range was 2.72%-3.42%.The time-varying seismic damage characteristics and damage degree of cylindrical reinforced concrete piers are analyzed and predicted.