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Title:Evaluation of internal damage in reinforced concrete elements using ultrasonic tomography
Author(s):Choi, Hajin
Director of Research:Popovics, John S.
Doctoral Committee Chair(s):Popovics, John S.
Doctoral Committee Member(s):Do, Minh N.; Golparvar-Fard, Mani; Chao, Shih-Ho
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Damage assessment
Non-destructive evaluation
Abstract:Quality control and quality assurance (QC/QA) of the concrete infrastructure has become an important national issue, especially because construction inaccuracies and invisible internal defects can result in unexpected structural response and failure. In order to evaluate the condition of an existing concrete structure, non-destructive testing (NDT) has been widely used as an assessment tool. Ultrasonic pulse velocity (UPV) is an efficient method to characterize the condition of concrete elements, and tomographic imaging is a powerful tool for visually identifying internal damage. However, the implementation of UPV data within a tomographic imaging scheme for application to full-scale concrete (RC) structures has not been realized to date because of practical and technological restrictions. In this dissertation, some of those barriers are overcome by using contactless air-coupled ultrasonic sensors in a scanning test configuration to acquire large amounts of ultrasonic data to create ultrasonic tomograms of large-scale concrete structures. The development of the testing system is described. The measurements are carried out using an automated robotic scanning frame using new sensing technology. Image reconstruction algorithms, including synthetic aperture focusing technique (SAFT) and algebraic reconstruction technique (ART), are reviewed and evaluated for application to imaging of full-scale RC columns. The performance of the data collection system and selected optimal imaging approach are verified through tests on a RC column test sample containing embedded artificial defects. The obtained tomographic images are compared with those from a commercially available ultrasonic imaging device. A comprehensive visualization scheme to characterize the column test sample, based on fusion of integrated ultrasonic tomography and 3-D computer vision, is presented. Such integrated visualization provides holistic characterization of the test sample. Next, the utility of attenuation tomography for enhanced damage detection is evaluated, both through numerical simulation and experimental studies. Finally, the developed ultrasonic tomographic testing system is applied to full-scale RC columns and slab-beam-column sub-assemblages subjected to simulated earthquake loads. Different concrete types, including normal reinforced concrete and high performance fiber-reinforced concrete, and seismic different loading schemes are considered. Comparisons of ultrasonic tomograms and strain gauge data illustrate the potential for velocity and attenuation tomography to monitor internal damage progression of structural RC elements both at global and local levels.
Issue Date:2016-11-16
Rights Information:Copyright 2016 Hajin Choi
Date Available in IDEALS:2017-03-01
Date Deposited:2016-12

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