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Title:Nondestructive damage characterization of concrete and concrete-steel composites using contactless ultrasonic scanning
Author(s):Song, Homin
Director of Research:Popovics, John S.
Doctoral Committee Chair(s):Popovics, John S.
Doctoral Committee Member(s):Duarte, Carlos Armando; Weaver, Richard L.; Ruzzene, Massimo
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Nondestructive evaluation
Contactless ultrasonic wavefield imaging
Full wavefield data processing
Compressed sensing
Concrete materials
Steel-clad concrete
Distributed cracks
Steel-concrete interface disbond
Abstract:Concrete is a widely used construction material for critical infrastructure systems such as bridges and nuclear power plants. During its service life, concrete and concrete-steel composite structures are subject to various deterioration mechanisms including freezing/thawing cycles, alkali-silica reaction (ASR) and sulfate attack. Prolonged and repeated exposure to the mechanisms can lead to the initiation of surface and internal damage that grows during the remaining service life of structure unless appropriately repaired. To repair and retrofit damaged structures effectively, damage needs to be detected and characterized early on in the process. Although existing nondestructive evaluation (NDE) approaches have shown potential for detecting and characterizing some type and extents of damage in concrete and concrete-steel composites, the wide range and size of damage types and natural heterogeneity and material variability of the concrete itself limit the effectiveness of existing NDE methods. In this dissertation, new NDE techniques are developed based on contactless ultrasonic scanning measurements and are applied to detect and characterize specific types of damage in concrete and concrete-steel composite structures that are not well addressed with existing NDE technology. For the case of distributed cracking damage in concrete, contactless ultrasonic wavefield imaging hardware and data processing method is studied. The developed wavefield imaging hardware consists of a multi-channel MEMS ultrasonic microphone array with a signal conditioning circuit and an automated mechanical scanner that enables rapid ultrasonic wavefield data acquisition with high signal-to-noise ratio (SNR). To further accelerate the wavefield data acquisition, a compressed sensing approach is also proposed. Then, a series of analyses, numerical simulations and laboratory-scale experiments are carried out to understand the interaction between incident ultrasonic waves and distributed sub-wavelength cracks. A wavefield data processing technique is developed to extract non-propagating oscillatory fields that are sensitive to sub-wavelength cracks. The developed NDE technique is evaluated through application to large-scale concrete block samples under realistic ASR environments. The experimental results demonstrate that the developed contactless wavefield imaging hardware enables rapid acquisition of high-quality ultrasonic wavefield data and that the proposed wavefield data processing technique successfully detects and characterizes distributed cracking damage in concrete. In a separate effort to develop an NDE technique to characterize interface bonding conditions of concrete-steel composite structures, a contactless ultrasonic scanning approach using the attenuation characteristics of guided waves is developed. Based on an understanding of guided wave propagation in multi-layered media through analytical modeling and numerical simulations, a signal processing technique is proposed to extract an attenuation-related wave feature that is sensitive to steel-concrete interface bonding conditions. The feasibility of the developed NDE approach is then established by experiments on steel-clad concrete specimens with varying interface bond quality. The results demonstrate that steel-concrete interface bonding conditions are quantitatively evaluated using the proposed approach while the technique remains unaffected by variations of test conditions such as transmitter lift-off distances and sensor-specimen coupling.
Issue Date:2019-04-18
Rights Information:Copyright 2019 Homin Song
Date Available in IDEALS:2019-08-23
Date Deposited:2019-05

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