• 콘크리트학회지
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• 제24권3호
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• pp.29-33
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• 2012

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.249-256
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• 2003

To investigate the safety and stability of the concrete lining, numerous studies have been conducted over the years and several methods have been developed. Most signal processing method of NDT techniques has based on the Fourier analysis. However, the application of Fourier analysis to analyze recorded signal shows results only in frequency domain, it is not enough to analyze transient waves precisely. In this study, a new NDT technique .using the wavelet theory was employed for the analysis of non-stationary wave propagation induced by mechanical impact in the concrete lining. The wavelet transform of transient signals provides a method for mapping the frequency spectrum as a function of time. To verify the availability of wavelet transform as a time- frequency analysis tool, model experiments have been conducted on the concrete lining model. From this study, it was found that the contour map by Wavelet transform provides more distinct results than the power spectrum by Fourier transform and it was concluded that Wavelet transform was an effective tool for the experimental analysis of dispersive waves in concrete structures.

• International Journal of Concrete Structures and Materials
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• 제3권1호
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• pp.25-32
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• 2009

A non-destructive testing (NDT) method for evaluating physical properties of concrete including the compressive strength is highly desirable. This paper presents such an NDT method based on measurement of electromagnetic (EM) properties of the material. Experiments are carried out on cement mortar with different water/cement (W/C) ratios. Their EM properties including the conductivity and the dielectric constant are measured at different exposure conditions and curing periods over a wide frequency range of the EM wave. The compressive strength of these specimens is also tested. It is found that both the conductivity and the dielectric constant increase as the W/C ratio decreases and the curing period increases, which lead strength development in the specimens. A linear correlation is observed between the averaged EM properties over the 5 to 20 GHz frequency range and the measured compressive strength, demonstrating the effectiveness of the EM property-based NDT method in evaluating strength of OPC mortar.

• Computers and Concrete
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• 제20권3호
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• pp.257-262
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• 2017

This study aims to develop a signal processing scheme to accurately predict the thickness of concrete slab using air-coupled impact-echo. Air-coupled impact-echo has been applied to concrete non-destructive tests (NDT); however, it is often difficult to obtain thickness mode frequency due to noise components. Furthermore, apparent velocity in concrete is a usually unknown parameter in the field and the thickness of the concrete slab often cannot be accurately measured. This study proposes a signal processing scheme using guided wave analysis, wherein dispersion curves are drawn in both frequency-wave number (f-k) and phase velocity-frequency ($V_{cp}-f$) domains. The theoretical and experimental results demonstrate that thickness mode frequency and apparent velocity in concrete are clearly obtained from the f-k and $V_{cp}-f$ domains, respectively. The proposed method has great potential with regard to the application of air-coupled impact-echo in the field.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.24-25
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• 2016

Concrete has been recognized as a material which is resistant to high temperatures, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. So, concrete at high temperature is evaluated mechanical properties for safety inspection. However, research of ultrasonic method is not much. Therefore, the purpose of this study is to NDT(non-destructive test) of 30, 70, 110MPa concrete exposed high temperature using ultrasonic pulse velocity and amplitude.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.1021-1024
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• 2008

콘크리트의 내부 공극을 검출로 열화상기법 적용시 일반적으로 쓰이는 열원인 자연광, 할로겐램프, 열풍과 달리 본 논문에서는 근적외선 히터를 이용하였다. 이 기법에 의한 실험 결과를 각 공극 깊이와 공극 크기별로 무차원 상대 온도로 나타내어 콘크리트 내부 공극의 식별 가능 여부를 조사하였다. 본 실험의 결과, 할로겐램프나 원적외선램프 열원에 비하여 대상 물체를 단시간 내에 가열하여 콘크리트 내부 공극 검출 시간이 상대적으로 짧은 것으로 확인되었다.

• 비파괴검사학회지
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• 제30권3호
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• pp.282-289
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• 2010

Most nondestructive testing techniques require good contact between the sensor and tested concrete surface to obtain reliable data. But the surface preparation is often very time and labor consuming due to the rough surface or limited access of concrete structures. One approach to speed up the data collection process is to eliminate the need for physical contact between the sensor and tested structure. Non-contact air-coupled sensing technique can be a good solution to this problem. An obvious advantage of the non-contact air-coupled sensing technique is which can greatly speed up the data collection in field and thus the damage detection process can be completed very rapidly. In this article, recent developments in non-contact air-coupled sensing technique for rapid detection of damages in concrete structures are summarized to evoke interest, discussion and further developments on this technique to a NDT research community in Korea. It is worth noting that the works in this article have been published in the types of thesis, proceedings, and journals. All published sources are cited in the text and listed in reference.

• 레미콘
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• 7호통권36호
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• pp.23-37
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• 1993

• Advances in nano research
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• 제12권1호
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• pp.1-23
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• 2022

To date, nondestructive tests (NDT) applications and advances in detecting the dispersion and defections of the nano concrete (NC) materials fields are very limited. The current paper provides a review of the dispersion efficiency of nanomaterials in cement-based materials and how NDT can be efficiently used in detecting and visualizing the defections and dispersions of NC. The review identifies the characteristics of different types of nanoparticles used in NC. Nanomaterials influences on concrete characteristics and their dispersion degree are presented and discussed. The main aim of this article is to present and compare the common NDT that can be used for detecting and visualizing the defections and dispersions of different kinds of nanomaterials utilized in NC. The different microscopy and X-ray methods are explicitly reviewed and compared. Based on the collected data, it can be concluded that the fully detecting and visualizing of NC defections and dispersions have not been fully discovered and that needs further investigations. So, the distinction of this paper lies in defining NDT that can be employed for detecting and/or visualizing NC defections and dispersions.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.1029-1032
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• 2008

최근 각 분야에서 연구 및 개발하고 있는 IT 및 자동화 경향이 건설 유지관리에도 전파됨에 따라 유지관리 로봇의 개발과 함께 개발될 비파괴 시스템의 장착이 각광 받을 것으로 예상되고 있다. 토목 구조물의 경우, 이러한 첨단기술의 발전과 더불어 유지관리 측면에서 이러한 첨단기술을 사용하는 것이 적극적으로 고려되고 있다. 그 중 NDT 비파괴 검사방법이 토목구조물의 효율적인 유지관리를 해 적합한 방법으로 사료되고 있다. 본 연구에서는 콘크리트 구조물의 내부결함 탐상을 위해서 초음파 및 레이더 장비가 적용되었으며, 이를 활용하여 실험실 및 현장실험을 통하여 그 적용성을 실험적으로 분석하였다. 실험결과, 초음파 및 레이더 장비는 콘크리트 구조물의 내부결함을 탐상하는데 효과적임으로 분석되었다. 또한 본 연구에서는 실험결과를 바탕으로, 초음파 및 레이더 장비를 적용한 콘크리트 구조물의 유지관리를 위한 알고리즘을 개발 및 제안하였다.