Use of Synthetic Aperture Focusing Technique to Detect the Defects in Concrete Specimen with Single Void and Single Layer∕ Double Layers Rebars

• Main Authors: JHANG, YOU-BIN, 張祐賓
• Other Authors: Liao, Shu-Tao
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/48896472840613747925

碩士 === 中華大學 === 土木工程學系碩士班 === 100 === The testing constraints and the capability of using the Synthetic Aperture Focusing Technique (SAFT) to detect void defects embedded in concrete block subjected to different introduced stress wave lengths and rebars are studied in this paper. This study first used the numerical simulation of finite elements to study the effects of the sizes of the impacting steel balls, the rebars and the layers of rebars on the testing responses. The testing results were processed with the Synthetic Aperture Focusing Technique and presented in images so that the direct effects of various kinds of parameters can be assessed. The study also cast concrete specimen with single void and single layer and double layers of rebars. Impact-response tests were carried out and the results were compared with those from numerical simulation. The results from the numerical simulation and experiments revealed that the sizes of the impacting steel balls would directly affect the resolution of the images from the SAFT. It was also found that the effect of existing rebars on the testing signals can be neglected when the wave length of the introduced stress waves is larger than eight to ten times of the size of the rebars. In this condition, the specimen can be regarded as uniform material and thus the results of evaluating the void defects would not be affected by the size of aggregates. Through this study, it is hoped that the capability of application of the SAFT can be enhanced in scanning and detecting the defects embedded in concrete structures.