• Title/Summary/Keyword: 충격-반향기법

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Theoretical Considerations in the Application of Impact Echo and Impulse Response Techniques to Integrity Tests on Drilled Shafts (I) (현장타설말뚝의 비검측공 건전도시험법에 관한 해석적 고찰 (I))

  • 이병식;이원구
    • Journal of the Korean Geotechnical Society
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    • v.17 no.5
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    • pp.97-105
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    • 2001
  • 현장타설말뚝의 건전도 평가에서 충격반향, 충격응답기법과 같은 비검측공 시험법을 적용하는 사례가 점차로 증가되는 추세에 있다. 비검측공시험법의 적용성을 체계적으로 평가하기 위해 수행된 일련의 연구결과 중에서 본 논문에서는 시험법의 결함탐지 능력을 평가하기 위해 수행된 해석적 연구결과에 관해 논한다. 이 연구에서는 시험법의 결함탐지능력에 대한 제반 영향인자 중에서 결함의 유형, 위치 및 크기의 영향을 평가하고자 하였다. 이를 위해서 여러 가지 조건에서 말뚝머리에 작용하는 충격하중에 대한 흙-말뚝 구조의 동적응답을 ABAQUS를 이용한 유한요소법으로 해석하였다. 이로부터 얻은 신호를 충격반향 혹은 충격응답기법으로 처리.분석하여 각 시험법의 결함탐지 능력을 평가해 보았다. 연구결과 이들 두 기법 모두 결함의 위치와 유형은 비교적 정확하게 탐지하는 것으로 나타났다. 그러나 충격응답기법을 이용하여 추정한 결함 크기는 신뢰도가 매우 낮았다. 이 문제를 해소하여 시험법의 적용성을 향상시키기 위해서는 측정된 동적응답신호를 이용하여 적절한 역계산 기법을 개발하여 적용할 필요가 있다는 결론을 얻었다.

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Investigation on Impact-echo Testing Method for Rock Specimens (암석 시편의 충격반향(공진주) 시험에 관한 고찰)

  • Cho, Jung-Woo;Lim, Bo-Sung;Cho, Ho-Bum;Jeon, Seok-Won;Ha, Hee-Sang
    • Tunnel and Underground Space
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    • v.17 no.2 s.67
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    • pp.83-89
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    • 2007
  • Impact-echo test is a non-destructive testing method to determine dynamic properties of a material. This presentation introduces the experimental set-up and procedure of the test for rock specimens. In addition, the test results of domestic rocks collected in 5 different areas, a cement mortar and aluminium alloy are presented. The test results include resonance frequencies of P- and S-wave as well as damping ratios of the described 7 different materials. The differences between dynamic and static values of elastic moduli are about 10%, while the dynamic Poisson's ratios are greater than the static Poisson's ratios by at least 0.07. The damping ratio is dependent on the joint density and degree of weathering of a rock specimen.

Integrity Evaluation of Deep Foundations by Using Impact Echo Method(Numerical Study) (충격반향기법을 이용한 깊은 기초의 건전도 평가(수치해석))

  • 김동수;박연홍
    • Journal of the Korean Geotechnical Society
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    • v.15 no.2
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    • pp.139-152
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    • 1999
  • These days we broadly apply drilled shafts for deep foundations to build infrastructures. The defects of the deep foundations cause the decrease of their support load capacity and the increase of settlement, and the subsequent damage of the super-structures. In consequence, non-destructive testings techniques of concrete piles are important for their integrity evaluation. To improve understanding and reliable application of the impact echo method for the integrity evaluation of the drilled concrete piles, numerical studies of the impact response of concrete piles by using axi-symmetric three-dimensional finite element method are peformed for (a) sound piles: (b) piles containing necks, voids and layers of low-quality concrete: and (c) piles in soil and/or above rock. The results of these studies show that the finite element method is effective for evaluating the impact response of drilled concrete piles.

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Non-contact Impact-Echo Based Detection of Damages in Concrete Slabs Using Low Cost Air Pressure Sensors (저비용 음압센서를 이용한 콘크리트 구조물에서의 비접촉 Impact-Echo 기반 손상 탐지)

  • Kim, Jeong-Su;Lee, Chang Joon;Shin, Sung Woo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.3
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    • pp.171-177
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    • 2011
  • The feasibility of using low cost, unpowered, unshielded dynamic microphones is investigated for cost effective contactless sensing of impact-echo signals in concrete structures. Impact-echo tests on a delaminated concrete slab specimen were conducted and the results were used to assess the damage detection capability of the low cost system. Results showed that the dynamic microphone successfully captured impact-echo signals with a contactless manner and the delaminations in concrete structures were clearly detected as good as expensive high-end air pressure sensor based non-contact impact-echo testing.

Characteristics of Elastic Wave in Fire damaged High Strength Concrete using Impact-echo Method (충격반향기법을 이용한 화해를 입은 고강도 콘크리트의 탄성파 특성)

  • Lee, Jun Cheol;Lee, Chang Joon;Kim, Wha Jung;Lee, Ji Hee
    • Fire Science and Engineering
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    • v.29 no.1
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    • pp.1-6
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    • 2015
  • In this study, the damages of high strength concrete exposed to high temperature have been evaluated by the impact echo method. Elastic wave velocity and dynamic modulus of elasticity were measured by the impact echo method, and the compressive strength and the static modulus of elasticity were measured by the compression testing method after exposure to high temperature. The results showed that elastic wave velocity has a linear correlation with the compressive strength and dynamic modulus of elasticity has a linear correlation with static modulus of elasticity. Based on results, it is concluded that the impact echo method can be effectively applied to evaluate the mechanical properties of fire damaged high strength concrete.

Residual Echo Cancellation for Hands-Free Telephony (핸즈프리 전화통신을 위한 잔여반향제거)

  • Park Seon Joon;Cho Chom Kun;Lee Ji Ha;Cha Il Whan;Youn Dae Hee
    • Proceedings of the Acoustical Society of Korea Conference
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    • spring
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    • pp.169-172
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    • 2000
  • 본 논문에서는 차량 환경에서 핸즈프리 단말기를 위한 잔향반향제거 방법을 제안한다. 제안된 방법은 기존의 음향반향제거와 잡음제거의 결합구조에 근거하며, 음성신호의 스펙트럼 특성을 배경잡음화함으로써 잔여 반향제거 성능을 향상시킨다. 일반적으로 음향반향제거에서 실제 충격응답보다 적은 차수의 적응필터를 이용할 경우 잔여반향의 전력이 증가하며, 잡음제거기법을 적용하여 잔여반향성분을 줄일 수 있다. 음성신호가 입력되는 음향반향제거기의 잔여반향을 효과적으로 제거하기 위해 음성신호의 AR 스펙트럼에 따른 역필터링을 수행함으로써 잡음제거기에 의한 잔여반향제거 성능을 향상시킬 수 있다. 제안된 기법은 현재 상용화되고 있는 이동통신용 음성부호화기에 포함된 잡음제거기법과 결합하여 사용할 경우 매우 적은 부가 계산량만으로 구현할 수 있다.

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A study on a Integrated analysis for survey of the cavity behind the Concrete (콘크리트 배면 공동탐사를 위한 복합적 해석 연구)

  • Noh, Myung-Gun;Oh, Seok-Hoon;Suh, Baek-Soo
    • 한국지구물리탐사학회:학술대회논문집
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    • 2009.10a
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    • pp.185-189
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    • 2009
  • Integrated analysis of GPR, impact echo and impulse response for detection of the rear cavity of concrete was performed on the test-bed which was made in the same scale and component ratio to the real concrete structure. GPR survey may roughly delineate the location of the cavity, but applying the IE and IR technique to the test-bed, the location was clearly identified.

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Comparison of Longitudinal Wave Velocity in Concrete by Ultrasonic Pulse Velocity Method and Impact-Echo Method (초음파 속도법과 충격반향기법에 의한 콘크리트의 종파 속도 비교)

  • Lee, Hoi-Keun;Lee, Kwang-Myong;Kim, Young-H.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.23 no.2
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    • pp.98-106
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    • 2003
  • Nondestructive test (NDT) provides much information on concrete without damage of structural functions. Of NDT methods, elastic wave propagation methods, such as ultrasonic pulse velocity (UPV) method and impact-echo (IE) method, have been successfully used to estimate the strength, elastic modulus, and Poisson's ratio of concrete as well as to detect the internal microstructural change and defects. In this study, the concretes with water-binder ratio ranging from 0.27 to 0.50 and fly ash content of 20% were made and then their longitudinal wave velocities were measured by UPV and IE method, respectively. Test results showed that the UPV is greater than the longitudinal wave velocity measured by the If method, i.e., rod-wave velocity obtained from the same concrete cylinder. It was found that the difference between the two types of velocities decreased with increasing the ages of concrete and strength level. Moreover, for the empirical formula, the dynamic Poisson's ratio, static and dynamic moduli of elasticity, and velocity-strength relationship were determined. It was observed that the Poisson's ratio and the modulus of elasticity determined by the dynamic method are greater than those determined by the static test. Consequently, for the more accurate estimation of concrete properties using the elastic wave velocities, the characteristics of these velocities should be understood.

Estimation of the thickness of refractory ceramics using the impact-echo method (충격반향기법을 이용한 내화물 두께 추정)

  • Lee, Seongmin;Shin, Namho;Roh, Yongrae
    • The Journal of the Acoustical Society of Korea
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    • v.36 no.4
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    • pp.247-253
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    • 2017
  • Generally, the vibration characteristics of refractory ceramics are identified by assuming them as isotropic materials. However, in practice, refractory ceramics exhibit anisotropic properties as they are manufactured by pressing ceramic powders along a particular direction. Therefore, in this research, the frequency responses of a refractory ceramic brick along its width, length, and height directions were acquired using finite element analysis by assuming that the ceramics had tetragonal symmetry in their material properties. The validity of the numerical analysis results was verified by comparing them with those from experimental measurements. Based on the frequency response, the thicknesses of the refractory brick along three different directions were estimated using the impact-echo technique. The maximum difference between the estimated and actual thicknesses was observed to be less than 5 %. This result confirms the effectiveness of the impact-echo technique along with anisotropic property characterization to evaluate the thickness of the refractory ceramic.