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Use of the Impactor with Sensing Device for Measuring Cracks in Concrete and the Thickness of Concrete
本文針對不同曲率之曲面版塊進行厚度檢測，採用傳統雙探頭及內裝設感應元件之可感測敲擊時間原點裝置進行檢測，可知含曲率之曲面版與未含曲率之平版依ASTM C1383之檢測方法檢測波速並無太大的差異，而所得的厚度頻率更是一致。具有曲率之版塊與平版在對應於厚度上之反應﹐所分析得到之敲擊反應仍主要由P波來回於版厚方向的重覆反射所主導，與是否具有曲率無關。所以將將ASTM C1383之混凝土版厚之量測方法應用在隧道襯砌厚度量測實為一個可行之方法。最後以現場厚度之檢測，更進一步確定所開發儀器之適用性。
The objective of this thesis was to develop a new device for tracing the start time of impact when using the impact-generated stress wave technique to evaluate the quality of concrete structures. The device is to embed piezoelectric material in the steel sphere. With the new device, stress waves are generated and the start time of impact is traced so that the evaluation work only needs a single receiver. Thus, the cost and work of evaluation and signal analysis can be reduced, which largely enhances the evaluation efficiency.
The device with an embedded piezoelectric material in the steel sphere can directly monitor the force-time response during impact. This is because the stress induced by impacting the steel sphere on the concrete surface generates voltage response in the piezoelectric material due to the natural interchange between stress and electric charge. The experimental results show that the time of the initial output from the device is the time when the steel sphere strikes on the concrete surface. This means that there is no time difference between the initial signal output from the device and the start time of the impact. Therefore, the device can be used directly to trace the start time of the impact without calibration. Experimental results show that the new device can be applied successfully to crack evaluation and plate thickness measurement with good accuracy.
Finally, numerical and experimental studies were performed to investigate the feasibility of using the impact-echo method for measuring the thickness of concrete liners. Numerical and experimental results show that the curvature of a liner does not have any influence on the impact-echo response. The thickness frequency is still generated by multiple wave reflections between the two bonded surfaces. Therefore, the thickness measurement procedures proposed in ASTM C 1383 are still applicable to concrete liners in contact with materials having acoustic impedance much less than concrete.
|Appears in Collections:||土木工程學系所|
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