運用數位影像法及羅吉斯迴歸探討鹼-骨材反應引致之裂縫行為

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题名:	運用數位影像法及羅吉斯迴歸探討鹼-骨材反應引致之裂縫行為
作者:	李忠祐;Li, Chung-Yu
贡献者:	土木工程學系
关键词:	鹼-骨材反應;數位影像法;最大概似法;羅吉斯迴歸;ROC曲線
日期:	2020-01-22
上传时间:	2020-06-05 16:28:19 (UTC+8)
出版者:	國立中央大學
摘要:	鹼-骨材反應(AAR)是一種對混凝土建築物有害的化學反應，反應會形成膠體並膨脹造成混凝土的開裂，因此在量測膨脹量是一個重要的工作。傳統的AAR之膨脹量量測只能得知兩測點間的平均應變，但混凝土建築內含有骨材、水泥砂漿以及孔隙，並非均質材料且由AAR引致之應變亦非均勻，而應變與裂縫發生之機制也有待建立。本文透過製作兩組試體將其放入ASTM C1293養護環境以及室溫中，利用掃描器掃描影像改善了以傳統相機拍攝造成的問題，並透過數位影像法量測分析試體內部全域應變場及應變不變量，以探討AAR引致應變與裂縫發生之機制。探討的主題包括：(1)AAR引致裂縫之發展過程、(2)裂縫延伸方向與主應變方向之關係、(3)以最大概似法建立羅吉斯迴歸曲線探討裂縫發生之機率與應變大小之關係以及(4)利用ROC曲線找出最佳分界點探討由早期應變預測裂縫發生之可行性。結果顯示由早期的應變建立之裂縫預測圖與晚期實際裂縫圖做比對兩者吻合度頗高。 ;AAR is one of dangerous chemical reaction in concrete building. The reaction will form the basoid which will expand and make the crack. So it is important to measure the expansion. In the past, the tranditional method of measurement in AAR only can get the average expansion between two observed points. But the concrete building contain aggregate, mortar and pore. It is nonhomogeneous material and the strain which is induced by AAR is not uniform. The mechanism is not established between strain and crack. In this study, we made two concrete sample and placed into curing of environment with specification and room temperature. The images was scanned by scanner to improve the image which is taken by trainditional camera. We can get the strain filed by digital image correlation and take this to explore the mechanism which is induced by AAR between strain and crack. The discussion of topic include: (1) the crack development process which is induced by AAR; (2) the relationship between the direction of ceack and the direction of maximum major strain; (3) establish the logistic regression cureve with maximum likelihood estimation method to explore the relationship between the probability of crack occurrence and the magnitude of strain; (4) getting the best breakpoint by ROC curve to explore the feasibility of predicting the occurrence of crack from early strain. The result show that the comparison between the crack prediction established by the early strain and the actual crack in the late stage is quite high.
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