Concrete Structural Damage Of Active Ultrasonic Detection Method

Concrete is one of the most important materials in civil engineering. It becomes a significant task to enhance the supervision and control of concrete. As a precondition not to influence the capability to load or other function, the examine means to mensurate some relevant physical value right on the framework or component, and through the relativity of the value and the quality of concrete, the performance of the concrete structure can be speculated. That is, nondestructive testing (NDT) method has become an important direction in structural health monitoring (SHM) field.Took the active ultrasonic testing method in crack propagation in concrete structure as the object of study, the concrete members which have crack damage are detected with active sensing technique based on the ultrasonic wave elementary theory. The analysis and processing of the sensing signal are carried out by the digital signal processing including time domain analysis, spectral analysis and wavelet analysis. To sum up, the main researches in this thesis are listed as follows:1. According to the ultrasonic propagation property in concrete, this thesis discusses the selection of acoustic waveform in the active ultrasonic testing, and studies the principle of time delay estimation by using wavelet transform.2. Active ultrasonic inspection system is designed, which includes ultrasonic transmitting circuit and receiver amplifier. Besides, based on LabVIEW software, the experimental software is built, which contains various functions, such as data acquisition, signal stimulation, interface display and so on.3. Using active ultrasonic technology, the thesis develops an experiment to inspect the crack growth. Through time domain analysis, spectrum analysis and wavelet analysis, the received signals are processed. The experimental results show that the time delay and amplitude of the response signal can be good evidences to distinguish the crack damage in concrete and the main frequency can also be supplementary means.4. The damage features and degree are proposed in amplitude, waveform and energy terms. The wave packet energy is computed by using numerical integration. The test results confirm that it has the good feasibility.