Corrosion Damage Distribution Based On Acoustic Emission And Its Effect On Bonding Property Of Corroded Of Reinforced Concrete

The influence of the corrosion distribution is usually not considered in the study on bond-slip constitutive relation of corroded reinforced concrete domestic and abroad.However,there is different degrees of damage in the cross section of re-bar when it is corroded,and the initial damage distribution is sure to affect the load-displacement relationship of the re-bar in pull-out process.So,it is the precondition of performance evaluation of damaged structure correctly to carry out the concrete bonding performance study with the different corrosion distribution,and to set up the bond-slip constitutive relation between concrete and re-bar base on the distribution of corrosion.How to obtain distribution of corrosion is a difficult problem on the durability of corroded reinforced concrete.In order to obtain the distribution of corrosion damage after corrosion,and evaluate the weakening effect of the corrosion on the reinforced concrete bond correctly.The bond-slip constitutive relation considering the distribution was set up with the acoustic emission technique which is used to determine the distribution of corrosion.The main research work and conclusions are as follows:(1)The poll-out test specimens of corroded reinforce concrete were design with the orthogonal method,and the monitoring scheme of accelerated corrosion was developed with the corrosion monitoring purpose.The relationship was established between the normalized of corrosion ratio and acoustic emission event with the corrosion acoustic emission signal analysis.Comparing the energy linear positioning results and actual corrosion ratio,the correlation between the energy and corrosion was illuminated.The results show that the corrosion rate is consistent with the acoustic emission event count.The acoustic emission pattern can reflect the distribution of corrosion damage of reinforced concrete,and the damage can be well characterized by the Gaussian function.(2)For the reason that the parameters of reinforced concrete corroded is stochastic distribution,the longitudinal characteristic of re-bar is simulated with Gaussian function based on the corroded characteristic analysis of re-bar.The distribution model of corrosion damage of steel bars was established with the distribution reclassifying of energy.The results show that the fitting result of the longitudinal corrosion damage distribution function of the steel is more consistent with the actual energy distribution with the increase of the number of the specimen.It is shown that it is feasible to simulate the corrosion damage distribution of corroded reinforced concrete by using the acoustic acoustic emission signal parameters.(3)The bond properties test was carried on corroded reinforced concrete specimens.The development law of re-bar strain was analyzed along the anchorage position according the strain of measured bar and the slip of load and free end under different load.The results show that the maximum slip value of the loading end and the free end increases with the increase of the corrosion rate after the corrosion ratio increases to a certain value.(4)With the distribution function of corrosion along the anchorage position,the slip value of each anchorage position and the average bond stress of the corroded member were calculated under different loads,and the relationship was plotted between the slip and the anchoring position,the variation of the slip value was analyzed along the anchorage position.The constitutive equation is established between the average bond stress and slip,and the relationship was established between the bond stress and the slip at different bonding positions based on the experimental results of each specimen.The position function of the bond was established by calculating the bond stress in the same position at the different slip value.According to the influence of different corrosion on the position function,the position function was analyzed considering the influence of corrosion,and the bond slip constitutive relation was established with different corrosion distribution,and then the finite element simulation was carried out to verified the bond slip constitutive relation.The results show that the simulation results are in good agreement with the experimental results.The main innovations are as follows:(1)The influence on accuracy of the theoretical corrosion calculation was analyzed with the different corrosion ratio specimens by using the orthogonal design,analyzing the corrosion ratio of the specimen,the amount of NaCl in the specimen and the current strength when accelerating the corrosion.(2)The relationship was analyzed between the acoustic emission pattern of corroded specimen and the actual situation of corrosion.The Gaussian distribution model of corrosion damage of steel bars was established,and the influence of corrosion ratio on Gaussian distribution model was analyzed.(3)Based on the distribution function of corrosion damage,the stress position function on the distribution of the corrosion damage was solved,and the bond-slip constitutive relation considering the distribution of corrosion damage was established with the Interpolated comparative analysis of the stress position function of different corrosion specimens.