Abstract
Prestressed concrete (PSC) is widely used for the construction of bridges. The collapse of several bridges with PSC has been reported, and insufficient grout and tendon corrosion were found inside the ducts of these bridges. Therefore, non-destructive testing (NDT) technology is important for identifying defects inside ducts in PSC structures. Electromagnetic (EM) waves have limited detection of internal defects in ducts due to strong reflections from the surface of the steel ducts. Spectral analysis of the existing impact echo (IE) method is limited to specific conditions. Moreover, the flexural mode in upper defects of ducts located at a shallow depth and delamination defects inside ducts are not considered. In this study, the applicability of the elastic wave of IE was analyzed, and multichannel analysis of surface, EM, and shear waves was employed to evaluate six types of PSC structures. A procedure using EM waves, IE, and principal component analysis (PCA) was proposed for a more accurate classification of defect types inside ducts. The proposed procedure was effective in classifying upper, internal, and delamination defects of ducts under 100 mm in thickness, and it could be utilized up to 200 mm in the case of duct defect limitations.
Highlights
Because it is not possible to quantify the degree to which the major frequency that theoretically occurs in the impact echo (IE) spectrum is shifted by type, Principal component analysis (PCA) was used in this study to derive the main components for ft, ff, and a certain range of features appearing in the IE spectrum for the duct and delamination defects
EM waves were used to locate steel ducts, and puncture by sampling and drilling was performed to evaluate the lack of grout
The IE method applied thereafter evaluated the state through the occurrence of a theoretical peak in the spectrum, but this method was difficult to be applied for state evaluation because the degree of shift of the frequency depending on the conditions was not clear
Summary
Research Institute for Engineering and Technology, Incheon National University, Incheon 22012, Korea
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