Numerical and Experimental Study on applying Synthetic Aperture Focusing Technique to Test Cracks and Defects in Reinforced Concrete

• Main Authors: Sung-Lin Liu, 劉松林
• Other Authors: Shu-Tao Liao
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/17512009468205965826

碩士 === 中華大學 === 土木工程學系碩士班 === 102 === In this paper the capability of the Synthetic Aperture Focusing Technique (SAFT) in detecting and imaging the cracks in plain concrete and the voids in reinforced concrete were studied. This research first utilized the Finite Element models to simulate the response of the stress wave propagation of a plain concrete with horizontal and tilted cracks and of a reinforced concrete with void subjected to impacting forces. The response signals were analyzed with SAFT and the resultant images were presented so that the feasibility of applying this technique on scanning and revealing the cracks and voids embedded in reinforced concrete can be studied. Two experimental specimens are then constructed in this research to be impacted by steel balls of different sizes and analysis was conducted with SAFT imaging procedure. Finally the results from experiments and from numerical simulation were compared for the purpose of verification. It was revealed from numerical simulation and experimental verification that the resolution of the images would be affected by the wave length of the stress waves introduced by the impacts of different steel balls. If the wave length of the introduced stress waves is short, fine cracks in the specimen can be revealed, whereas if the wave length is long, the interfering of reinforced bars can be reduced so that the defective voids can be scanned and revealed. Finally the feasibility of rotating the surfaces for impacting tests for testing and revealing defects was studied.