Damage Evaluation Of Concrete Based On Acoustic Emission Technique

It has been over one hundred years since the concrete was born. In the lifetime of structures, the performance of concrete will degrade under the effect of various kinds of external factors. The process of degradation usually accompanies with the development of pores, microfissures and fissures in concrete. Therefore, acquiring the actual status of concrete materials is the necessity of knowing the status of structures. Meanwhile, it provides the necessary evidences for the prevention and maintenance of the concrete structures. Acoustic Emission Technique (AE) is a dynamic non-destructive damage test method. Because their signals are coming directly from the flaws and different flaws will generate different signals of acoustic emission, the properties of flaws by using acoustic emission technique can be evaluated. As soon as the features of signals of acoustic emission are determined, the security monitoring of flaws can be carried out in a long period, which is difficult to fulfill with other non-damage test methods. For the purpose above, this thesis tries to establish the connection between concrete materials'features of acoustic emission on status of single axle compression and concrete's damage, and finally evaluate the concrete's damage in a quantitative way. Sponsored by the project "Structural damage detection based on the combination of pizoelectric sensor and spectral element model updating"(50378041)of National Nature Science Funds of China,the study on evaluation of concrete damage based on acoustic emission technique has been carried out in this thesis. First of all, the fundamental theories on acoustic emission technique and principals of mechanics of concrete damage, which primarily represents AE rate process, are introduced. At the same time, the fundamental parameters in the test of acoustic emission and equipments of acoustic equipments are also presented. Next, based on the Loland damage model, the practical quantified method has been established by using the damage mechanics and the theory of the rate process analysis. For the purpose of verifying test results, Kaiser effect and Felicity effect are adopted and the feature of concrete, and memorization on the stress history are used to assure the final evaluation results. Finally, using this method, the acoustic emission test has been carried out on the concrete samples of Xinyang Shihe Bridge in Henan province under the single-axle compression test, and the experimental data are analyzed and processed to complete the evaluation of the concrete damage in this bridge. The actual damages of concrete are obtained and the varieties of factors, which can affect the test results such as transducer, filter bandwidth, sampling model, are discussed. The experimental results demonstrate that acoustic emission technique is a kind of effective method in the area of concrete damage evaluation.