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標題: 以敲擊式繞射波傳輸時間法量測淺裂縫之研究
Study of Determining Shallow Crack by the Impact Time-of-Flight Diffraction Techniques
作者: 張年浩
關鍵字: Time-of-Flight Diffraction Techniques;敲擊式繞射波傳輸時間法;Crack;stress waves;裂縫;應力波
出版社: 土木工程學系
在混凝土結構物的安全評估中,裂縫之狀況一直是不容忽視的項目,敲擊式繞射波傳輸時間法提供了一種直接以應力波動行為量測裂縫深度方法,以應力波動方法測定混凝土結構物表面裂縫之開裂深度時,裂縫深度以及波速的量測計算全賴時間領域的位移波形正確判讀,若無法充分掌握應力波形的變化將使得量測工作耗時費力,而為了使檢測人員在現場施測時,有效了解應力波動行為,本文內容針對現場可能遭遇到的淺裂縫進行研究,期能提供日後之參考。本文研究方法係採用數值模擬分析及實際試體試驗研究,將應力波導入測試模型內部,利用置於表面裂縫另一側之接收器,來監測應力波動所產生之訊號,藉由控制敲擊接觸時間以及敲擊能量,來瞭解試驗配置以及深度變化所造成的波形改變,使用敲擊式繞射波傳輸時間法,經由實際試體試驗結果,與數值模擬分析所得之結果亦相當符合,模擬裂縫深度增加為20.7 mm以上時,從波形圖上已經無法辨別出的表面R波,但是經由裂縫底部尖端繞射所產生的向上位移反應逐漸增強,有利於裂縫深度檢測。此外,依試驗所需配置適當之儀器,並討論配置距離狀況對量測誤差之影響;由試驗可知對點定位H0產生之誤差,對淺裂縫深度量測之結果有很大影響。

In the safety evaluation of concrete constructions, cracking is always one of the conditions that can't be neglected. The Time-of-Flight Diffraction Technique offers a direct way of stress wave propagation to determining the depths of surface opening cracks; while applying stress wave propagation method to determining the surface crack depths on the concrete constructions, the depths of cracks and measurement of wave speeds all rely on the accurate analysis of displacement waveform in time domain. If one can't effectively control the variations of stress waves, then the surface crack depths determining work will become more time and effort consuming. To let examiners effectively understand stress wave propagation while carrying out the experiment in place, the content of this thesis specifically describes the different shallow surface crack depths that were confronted in the experiments, hoping to provide references to following researchers on this related field. The research methods applied here are numerical analysis and laboratory studies experiment research. The stress wave was generated by impact, with the receiver equipped on the other side of the surface, one can monitor the stress wave propagation information. Through the control of the impact contact time and energy, one can have a comprehension on the allocation of the experiment and the wave variations caused from different surface crack depths. It is found out that the outcome experiment result are very consistent with those obtained from numerical analysis. When the depth of simulated cracks is more than 20.7mm, it becomes difficult for us to differentiate surface R wave from the wave figure. However, the upward movement tendency caused by the bottom part crack wave is highly increased and this kind of reflection adds the advantages to the examining work. Furthermore, according to the equipments needed in the experiment, error analysis was performed to investigate the influence of equipment allocation errors. From the experimental result, it is shown that the position error form H0 has profound influence on the result of crack depth measurement.
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