Detecting flaws in T-beam concrete structures using the Impact-Echo method.

摘要

The objective of this research was to study the response of reinforced concrete T-beams tested using the Impact Echo method and to determine how the response is affected by the presence of anomalies. Developing the basis for using this nondestructive testing technique (the Impact Echo method) for evaluation and monitoring of concrete T-beams was the main objective of this study. The Impact Echo method involves introducing a transient stress pulse (wave) into a test object by mechanical impact and monitoring the surface displacements caused by the arrival of reflections of the wave from internal defects and external boundaries.; Two-dimensional finite element models of T-beams were used to determine the transient impact response. It is shown that this response is similar to that of plate-like, bar-like structures' behavior, or both. The response depends on the aspect ratio of T-beam component under investigation and the location of the test point along the component. A number of resonant frequencies caused by cross sectional modes of vibration were present at the stem, stem/flange junction and at test locations in proximity to the free boundaries. The individual modes and their corresponding natural frequencies were determined using plane-strain, eigen value finite element models of eight different T-beam cross sections. To verify the results obtained from the numerical studies, experimental studies were performed on three full scale reinforced concrete T-beams. Good agreement was obtained between the numerical and experimental results.; The feasibility of using the Impact Echo method for finding anomalies in concrete T-beams was examined. Finite element studies were performed to gain an understanding of the Impact Echo response for concrete T-beams containing voids, shallow cracks, honeycombing, and inclined cracks. The effect of the presence of reinforcing steel bars on the response was also studied. To verify the numerical results and determine the feasibility of using the Impact Echo method for anomaly detection and monitoring in concrete T-beams, experimental studies were carried out. Results obtained from these studies demonstrate the feasibility of using the Impact Echo method for detecting and monitoring anomalies within reinforced concrete T-beams.; Finally, a detailed test procedure for reinforced concrete T-beams has been recommended in this study.