Study On Concrete Structural Damage Identification Method Based On Stack Migration Imaging Technology

Stack migration imaging technology of seismic wave is used in nondestructive test (NDT) of concrete structure. A new type of damage detection method is formed. It makes a necessary theory basic for the structure health monitoring system (SHMS) of civil engineering and supplies the maintenance, reinforcement, reconstruction of concrete structure with theoretical foundation.Firstly, this paper introduces the theory basis of stack migration imaging and several migration methods in common use in geophysical prospecting. Then two digital filtering methods, including 1-D frequency filtering and 2-D apparent velocity filtering are emphatically elaborated by using data process flow. Multi actuator/sensor technology is used to damage identification of concrete structure in inspection of concrete beam with embedded crack. Transducers are the acoustic emission (AE) sensors which adapt to frequency range of the elastic wave propagation in concrete material. The center response frequency of these transducers is 150KHz. According to experimentation and analysis of stacking amplitude curve of different parameters, selective range of such parameters as exciting distance, exciting-receiving distance, receiving distance, arrange length is verified. And the parameters belong to multiple observational systems. A type of data process flow of stack migration imaging of pre-damage concrete beam is presented on the basis of seismic prospecting data handling styles, properties of elastic wave propagation in concrete material and inherent characteristic of concrete damage detecting. Horizontal stacking and diffracting scan prestack migration technologies are adopted in data process. The basis idea is that the same phase amplitudes of reflection wave are stacked and other random interrupt signals are weaken for different phase, which can improve signal noise ratio and pop out reflective interface. Experimental results show that stack migration imaging technology is effectual and accurate for embedded crack concrete. Compared with other methods in common use (Ultrasonic Test), it has unique advantages: The evaluation of damage is visible and compact, while information from this method is more abundant than that from others.These conclusions result from the experiments carried out in the laboratory, and this method needs to be further improved before it is applied to the engineering practice. Combined with more advanced sensor and means or theory for data process, this method can provide a more precise image and a better imaging section.