Nondestructive evaluation of concrete structures using surface and ultrasonic waves = 표면파 및 초음파를 이용한 콘크리트 구조물의 비파괴평가

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This thesis reviews in situ nondestructive evaluation of concrete structures. The surface-wave method for in-service inspection and the ultrasonic wave reflection method for early-age concrete are recommended. The first investigation is carried on with simulation of impact-generated surface waves. Numerical matching for the measured surface waveforms requires sophisticated technology including feature extraction and artificial intelligence algorithm. The proposed principal wavelet-component analysis extracts the feature pulse having the maximum energy density. Artificial neural networks with the extracted pulse estimate simulation parameters and then finite element method simulates the surface waveform. The principal wavelet-component analysis is also adopted to determine the Rayleigh wave velocity, where the extracted Gaus1-wavelet pulse uses early-arrived components without reflection and spurious oscillation. The proposed technique determines the representative Rayleigh wave velocity with short deviation and obtains the reasonable dispersion curve of Rayleigh waves. While the phase of Rayleigh wave is utilized for measuring the wave velocity for evaluating the stiffness, its amplitude determines the Rayleigh wave transmission characterizing damage of concrete. The proposed self-compensating frequency response function evaluates the Rayleigh wave transmission excluding noise and sensor response. The proposed procedure measures the surface-breaking cracks having the depth of 50 to 150 mm, where the resolution seems to be the order of 10 mm. On the other hand, the ultrasonic wave reflection method is satisfactory to measure the properties of early-age concrete inside formwork. The compressive strength of concrete can be estimated with the wave reflection since the measured properties of hydrates govern the failure of materials.
Kwak, Hyo-Gyoungresearcher곽효경researcher
한국과학기술원 : 건설및환경공학과,
Issue Date
303523/325007  / 020045817

학위논문(박사) - 한국과학기술원 : 건설및환경공학과, 2008. 8., [ [vi], 161 p. ]


nondestructive testing; ultrasonic wave; surface wave; concrete; crack; 비파괴검사; 초음파; 표면파; 콘크리트; 균열; nondestructive testing; ultrasonic wave; surface wave; concrete; crack; 비파괴검사; 초음파; 표면파; 콘크리트; 균열

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