| Structural damage identification technology and modal parameter identification technology from the date of birth,is to solve the problems in practical engineering,so it has a high practical value and realistic engineering background.Modal parameter identification and structural damage identification technology are more and more applied to the damage diagnosis and health monitoring of structures,and are paid more and more attention,and gradually become a hot topic in engineering research field.In civil engineering,the bond between the concrete and the reinforcement produced by the degradation of structural cracks,are generally caused by the corrosion of steel bars.The study on changes of the dynamic characteristics of reinforced concrete structures before and after steel corrosion of steel bars can provide a scientific basis for the detection of damages to reinforced concrete structures in engineering.This paper,according to the experimental principle of steel electrochemistry accelerating corrosion,obtained 6 reinforced concrete beams suffering from steel corrosion by manually controlling the corrosive area and degree of steel.In this experiment,steel corrosion rate is divided into such 4 degrees as 0%,5%,10%and 15%.The paper has studied the impacts of steel corrosion on the damping ratio and the natural frequency of reinforced concrete structure,and thereby made the experiment more systematic and comprehensive.The paper mainly covers the following aspects:1)Design and placing a batch of reinforced concrete T-shaped beam samples;design the corrosive steel device and use electrochemistry to accelerate corrosion of the sample steel;calculate the current density,magnitude of current and conduction time according to Faraday’s law and thereby control the corrosion rate of the steel;control the corrosion area and degree manually by processing the sample.2)Make use of the fading characteristic of the free vibration of cantilever beam;apply the method of vibration test to conduct mode test on cantilever beam when the corrosion rate is 0%,5%,10%and 15%respectively;conduct Fourier transformation against the response signal of the structure to obtain the damping ratio and the natural frequency of the reinforced concrete structure in each stage.3)Pick out corroded steels,and clean and weigh them.It is found that the actual corrosion rate of the steel during the experiment is around the theoretical value,which means that the corrosion degree of steel is successfully controlled.What’s more,through visual inspection,it is also found that the method of controlling corrosion area of steel manually is also effective and feasible.4)By processing and analyzing the data obtained from experiment,the paper found that the damping ratio of the reinforced concrete beams would increase with the deepening of the corrosion degree of steel,while the natural frequency of the reinforced concrete beams would decrease as the corrosion degree of steel deepens.The result has shown that steel corrosion has huge influence on the dynamic characteristics of the reinforced concrete beams.5)Use ANSYS modeling software and apply finite element program to conduct numerical analog computation against the dynamic characteristics of the reinforced concrete structure under different corrosion degree,and analyze and compare the result of numerical analog computation with the result of the experiment.It is found that the natural frequency calculated through numerical analog computation is approximate to the numerical frequency obtained in experiment.This paper has demonstrated the significant influence of steel corrosion on the reinforced concrete beams.It has made use of the fading characteristic of the free vibration of cantilever beam and applied the method of vibration test to obtain the damping rate and the natural frequency of the reinforced concrete structure,which can be used as a diagnose index of damage identification to identify the corrosion damage of engineering structures. |
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