• Journal of the Korea Institute of Building Construction
• /
• v.23 no.1
• /
• pp.11-22
• /
• 2023

In this work, a depth-by-depth evaluation on the deterioration of concrete is suggested by utilizing disk shaped concrete specimens. Dynamic elastic modulus of cylindrical concrete was measured using a free-free resonance column method and compared with dynamic elastic modulus of disk-shaped concrete measured by impulse excitation technique(IET) and impact resonance(IR). According to the results of the experiment, both IET and IR methods showed a smaller difference in dynamic elastic modulus with smaller deviation in data when thickness of the disk specimen was increased. This trend was more evident from dynamic elastic modulus measured by IR method compared to that measured by IET. Variation in data was also smaller with the IR result. To increase the accuracy of the data, it is recommended to use the IR method for disk specimen with a diameter of 100mm and a thickness of 25mm.

• Journal of the Korea Concrete Institute
• /
• v.22 no.5
• /
• pp.625-632
• /
• 2010

The moduli of concrete has been determined by various testing methods. The impact resonance (IR) method has been shown to be truly a simple nondestructive testing method which produces consistent results. It is possible to determine not only the modulus but also damping ratio from the IR test. However, the values of elastic modulus and damping ratio of concrete from the test is known to be affected by various test conditions including, specimen support condition, impact steel ball size and sampling rate. In this study, the optimum IR test conditions are suggested and validated experimentally. The test results showed that the recommended test conditions yielded a variation of resonant frequency within ${\pm}0.3%$ and damping ratio ${\pm}10.0%$. In addition, the modulus from the IR test was comparable to that from a static test when the effect of strain amplitude was properly taken into account.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.3
• /
• pp.221-230
• /
• 2000

The usefulness and limitations of the impact-resonance method, which is a nondestructive evaluation (NDE) method for concrete, are studied by both experimental and theoretical methods. For the experimental study, several concrete slab specimens with various inclusions embedded were fabricated, and tested by the impact-resonance method. Some of the inclusions have been detected and accurately located, but some have not. The reasons for the failure in the latter cases have been investigated theoretically by using finite element analyses, from which the primary factors determining the success of the method have also been identified. This study will serve to enhance the understanding of the underlying physics and to improve the usefulness of the impact-resonance method as applied to concrete NDE.

• Tunnel and Underground Space
• /
• v.17 no.2 s.67
• /
• pp.83-89
• /
• 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.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.5
• /
• pp.42-48
• /
• 2017

When concrete structures expose to fire, the structures were damaged accompanied with degradation of material properties of concrete. In order to determine the reuse of fire-damaged concrete structures, it is needed a careful determination considering conditions of fire damage, such as exposure temperature and exposure time, and also potential to restore fire damage. This study investigates on the evaluation of residual material properties of fire-damaged concrete under different post-fire curing regimes. An experimental study was performed on concrete samples to measure the dynamic elastic modulus by the impact resonance vibration method. Upon the experimental results, the evidence of restoration of material properties was confirmed on specific post-fire curing regimes, higher humidity conditions. Additionally, a correlation analysis was performed on the dynamic elastic modulus with the tensile strength for identifying the effects of post-fire curing regimes on both material properties of fire-damaged concrete.

• International Journal of Highway Engineering
• /
• v.9 no.4
• /
• pp.55-63
• /
• 2007

Deformational characteristics of subgrade soils are important properties in the mechanistic analysis and design of pavement system. In this study, to evaluate the effect of specimen construction methods on deformational characteristics of subgrade soils in Korea, resonant column tests were performed for specimens constructed by various methods. Specimen construction method affected to the modulus value but the variation in the normalized modulus reduction curve was almost identical. The effects of specimen construction method on modulus are decreased with increasing confining pressure. The average maximum variation in the modulus value with different specimen construction methods was estimated as 16.8%. The differences in the modulus value of the specimens with same water content and dry density conditions that made by gyratory compaction and impact compaction were very small within 5.2%. The impact compaction method was proposed as a specimen construction method for determining the design input parameter testing considering that impact compaction method is much simpler and require less expensive specimen construction equipment and setup than gyratory compaction method.

• The Journal of the Acoustical Society of Korea
• /
• v.14 no.4
• /
• pp.12-20
• /
• 1995

This paper describes principles and experimental results in conjunction with examining the possibility of the detection of effects from a cylindrical objects. Cylindrical objects have its own resonance frequency. The frequency varies according to the diameter, length etc. And acoustic sound, whose frequency and the harmonic components corresponding to resonance frequency, is radiated from the object. When an object have defect in itself, the radiated acoustic sound is different from normal one. So we can detect its defect by analysing frequency components of acoustic sound. We proved that detection of defective objects by acoustic signal analysis is possible automatically. Also the result can be applied to other kinds of objects.

• Journal of the Korean earth science society
• /
• v.32 no.1
• /
• pp.1-11
• /
• 2011

The impact echo and impulse response methods were applied to the safety inspection of concrete structure, which has the rear cavity. The concrete structure model used in this study was divided into four sections, pure concrete, concrete+cavity, reinforced concrete with iron bar, and reinforced concrete+cavity, respectively. Previous study performed by authors have showed a possibility of success to use these method for detection of the rear cavity of concrete structure. Therefore, we tried to get more enhanced result with IE and IR methods through this study. Especially, IE and IR methods are relatively accurate to map the point of measurement, which makes it possible to interpret the depth of the concrete bed and effect by rear cavity with confidence. Followings were revealed from the results; the IE method shows some small peak zones probably indicating the rear cavity in the frequency lower than the resonance frequency and the changes of mobility and dynamic stiffness in the IR method indicate the weak zones. The proposed methods can be used to delineate the weak zones of the concrete structure.

• 한국방재학회:학술대회논문집
• /
• 2011.02a
• /
• pp.162-162
• /
• 2011

표면파 속도 측정은 근래 토목분야에서는 비파괴 지반조사기법으로 활용되고 있다. 최근에는 디지털 신호처리기술의 발달과 함께, 더욱 정확해진 자료분석 알고리즘을 통하여 표면파 탐사관련 기술이 향상되어 3차원의 공간연속적인 시험이 가능해졌다. 본 연구는 표면파의 분산 특성을 이용하여 콘크리트 구조물의 깊이별 강성평가를 하는 SASW(Spectral Analysis of Surface Waves)기법과 STFT(Short time Fourier Transform)과 HWT(Harmonic Wavelet Transform)를 이용한 주파수영역에서의 공진주파수를 통한 부재평가 기법인 IE(Impact Echo)기법을 이용하여 대상부재의 강도평가를 수행하기 위한 시제품 개발을 수행하였다. 시제품은 메인프레임과 2개의 센서로 이루어져 측정을 수행하며 측정장치와 DAQ장치 및 S/W로 구성되어 있다. 메인프레임의 진동특성영향을 제거하기 위하여 2개의 센서는 프레임과 띄움구조로 설계하였고 센싱하는 위치는 대상 재료의 밀착되어 계측할 수 있도록 설계하였다. 탄성파를 계측하여 대상 재료의 깊이별 측정된 표면파의 속도를 계측하며 개발된 시제품의 구조물별 적용성 평가를 위한 실험을 수행하였고 평균 표면파 속도를 통해 추정한 콘크리트 두께와 결함 및 강도 추정의 적용성을 평가하였다. 시제품을 이용해 시험콘크리트 표면파를 측정한 결과 SASW기법을 이용하여 깊이에 대한 위상속도 분포와 IE기법의 결과로 개발된 시제품의 합리적 적용성이 평가되었다. 그러나 재료의 강도추정에 있어서는 각각 알고리즘의 주파수분석 요소들에 의해 변동되는 경향을 보여 추후 많은 테스트를 통해 속도-강도 추정의 회귀곡선식을 S/W에 탑재시키고 다양한 방법으로 조합하는 알고리즘으로 신뢰성있는 강도추정을 위한 알고리즘을 개발하여야 한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• v.y2005m4
• /
• pp.281-287
• /
• 2005

Nonlinear behaviors such as steep-fronted wave motions and a finite amplitude limit cycle often accompanying combustion instabilities have been numerically investigated using a characteristic-based approximate Riemann solver and the well-known ${\eta}-{\tau}$ model. A resonant pipe initially subjected to a harmonic pressure disturbance described the natural steepening process that leads to a shocked N-wave. For a linearly unstable regime, pressure oscillations reach a limit cycle which is independent of the characteristics of the initial disturbances and depends only on combustion parameters and operating conditions. For the 1.5 MW gas generator under development in KARI, the numerical results show good agreement with experimental data from hot-firing tests.