Term of Award

Spring 2023

Degree Name

Master of Science, Civil Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Civil Engineering and Construction

Committee Chair

Saman Hedjazi

Committee Member 1

Hossein Taheri

Committee Member 2

L. Stetson Rowles

Abstract

Nondestructive testing (NDT) is a reliable method for determining the structural integrity of new and old construction and understanding the condition of structural defects. It is widely acknowledged that the interpretation of nondestructive evaluation (NDE) has a significant impact on the reliability and consistency of this technology. However, NDT data acquisition remains subjective and heavily dependent on the operator’s knowledge and expertise. As a result, there are still issues to be resolved regarding the imaging and diagnostic procedures for NDT-based concrete inspection. NDT methods such as ground penetrating radar (GPR), and impact-echo (IE), have been extensively used to inspect concrete bridges for damage and deterioration. In this study, concrete slabs were investigated in a laboratory setting with simulated structural defects such as corrosion, delamination, honeycomb, and voids. To validate the accuracy and robustness of the two NDT methods, defects were embedded closely (ranging from 1 to 5 inches) and superimposed in two different layers for the same specimen. GPR B-scan (line scan) radargrams demonstrated hyperbolic shapes for voids and corroded rebars, whereas delamination was identified by a hollow strip pattern. GPR C-scan (area scan) data was used to calculate the size (length, width, and thickness) of delamination simulated by polystyrene sheets. The results showed an accuracy of 80% in predicting the thickness of delamination. GPR, however, did not detect delamination for objects smaller than 8 inches in size due to the dense meshing. The amplitude data from GPR A-scans (amplitude vs depth) were used to calculate the depth of a defect. Statistical measures exhibit a high degree of agreement between the depth measured by GPR and the actual depth of a defect. The IE method uses elastic waves to propagate through concrete for identifying the embedded defects. The interpretation of IE data involved post-processing of reflected signals in the time-domain and frequency-domain modes. The simulated structural defects did not show any discernible trend in time-domain data. However, defects were detected using IE thickness data from the peak frequency spectrum. The frequency-domain IE data was validated by comparing it to GPR data for similar concrete specimens.

Research Data and Supplementary Material

Yes

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