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標題: 應用可感測敲擊時間原點之敲擊鋼珠量測混凝土裂縫及厚度
Use of the Impactor with Sensing Device for Measuring Cracks in Concrete and the Thickness of Concrete
作者: 李盈萩
Li, Ying-Chiu
關鍵字: ASTM C1383
出版社: 土木工程學系
摘要: 本文研究開發利用敲擊器內裝設感應元件之可感測敲擊時間原點裝置,可感測敲擊時間原點之裝置能將原本敲擊回音法之儀器設備,由配置雙接收器的混凝土檢測工作之波速及裂縫深度量測,簡化成只需單一接收器即可完成,可降低儀器設備成本與檢測人力需求。 利用鋼珠內裝設感應元件之可感測敲擊時間原點裝置乃於鋼珠內裝設壓電材料,由於壓電材料之應力場與電場耦合特性,當有應力作用時,壓電材料會產生極化電荷,在於敲擊測試物體時,由碰撞所造成之應力作用可同時使壓電材激發出電位差,以求得敲擊時間原點。由研究之結果可以發現鋼珠內裝設感應元件裝置之激發時間與敲擊時間原點相同,於波速檢測時不需做任何的率定工作。 將上述之可感測敲擊時間原點裝置運用於裂縫檢測及平版厚度檢測,皆得到相當好的精度,具有高度之實務應用性。 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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