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標題: 以應力波檢測混凝土內部鋼筋保護層厚度之研究
Measurement of the Cover Thickness of Reinforcing Bars in Concrete Structures by the Stress Wave Propagation
作者: 蕭家孟
Hsiao, Chiamen
關鍵字: Cover Thickness
Reinforcing Bars
Stress Wave
Impact-Echo Method
出版社: 土木工程學系
摘要: 本論文之主要目的在開發新的非破壞檢測技術,以測定混凝土結構內部鋼筋之保護層厚度。目前市售之鋼筋檢測儀器大多採用電磁波,當鋼筋間距較小時,由於電磁波受了相鄰鋼筋彼此之干擾互制作用,造成檢測訊號判讀不易而失敗。本文所欲開發的鋼筋新檢測技術,將突破傳統不以電磁波,而改採應力波動原理,其主要研究構想源自於應力波在鋼筋內之傳動速度比在混凝土內來得快,只要藉由適當的給予應力波動激發源及儀器配置,即可測得應力波在混凝土內部經由鋼筋傳動的應力波訊號,進而精確的測定出鋼筋保護層厚度;由於檢測所得應力波引起之訊號處理,皆以最短波動路徑為依據,故檢測結果直接與檢測點下方鋼筋有關,並不受相鄰鋼筋存在與否之影響,將可適用於鋼筋排列緊密處檢測之需,以彌補目前採用電磁波法之不足。本論文分別以數值分析及實驗室試驗,確認所有相關之檢測參數及其對檢測結果之影響。研究結果顯示,為檢測混凝土結構內部鋼筋之保護層厚度,敲擊源與接收器之配置距離須足夠使應力波能以全折射方式經鋼筋傳播,並首先到達接收器,由量得之混凝土波速、監測到應力波經鋼筋傳播之傳動時間及已知之傳播路徑條件下,即可測得鋼筋保護層之厚度。
The objective of this thesis is to develop a new nondestructive technique for determining the cover thickness of reinforcing bars in concrete structures. Currently, the available equipment for detecting reinforcing bars is based on the electromagnetic methods. When the spacing between reinforcing bars is small, the interaction of electromagnetic field between adjacent reinforcing bars results in detection failure due to difficult interpretation of signals. The new technique proposed in this thesis for detection of reinforcing bars makes use of stress waves instead of electromagnetic waves. The idea is derived from the fact that stress waves have a faster wave speed in steel bars than that in concrete. Because the propagation of stress waves follows the shortest travel path, the measured signal is mainly influenced by the reinforcing bar directly beneath the test point and has nothing to do with adjacent reinforcing bars. This is the reason why the stress wave technique can satisfy the need for detecting reinforcing bars in the areas containing congested bars. This thesis presents both numerical and experimental studies to investigate all the related parameters and their influences on measuring accuracy. The results obtained from these studies show that the distance between the impactor and the receiving transducer must be enough to make the P-wave incident on and refracted from a reinforcing bar with a critical angle and ensure its first arrival at the receiver. Consequently, the cover thickness of the reinforcing bar can be determined by knowing the transit time and the travel path of the P-wave through the reinforcing bar together with the measured P-wave speed of concrete.
Appears in Collections:土木工程學系所



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