• The Journal of the Acoustical Society of Korea
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• v.16 no.5
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• pp.36-42
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• 1997

This paper purposes the measurement method of vibration intensity in building structure which is a method of measuring the intensity and the flow of vibration energy. We derived basic theory and measuring theory for a simple beam, and comparison of the experimental results with calculated results. As a result, according to the calculated value from acceleration distribution and the measurement result from the method of vibration intensity under the condition except near field of measurement zone. The measured results, show that this method is useful for measuring the vibration energy flow in building structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.574-577
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• 2007

본 논문에서는 실 시공 중인 PSC 교량에 대하여 풍하중에 의한 상시 진동 계측 자료을 기반으로, 교량의 동특성(고유진동수, 모드형상)을 추정하였으며, 이를 바탕으로 대상 교량의 탄성계수를 추정하여 정적 계측을 통한 탄성계수 결과와 비교하였다. 본 논문에서 사용한 동특성 추정 기법은, 대표적인 주파수 영역 해석 방법인 Frequency Domain Decomposition(FDD) 방법과 시간영역 해석 방법인 Stochastic Subspace Identification(SSI) 방법을 이용하였다. 탄성계수 추정은 유한요소모델과 계측 결과를 이용하여 두 개의 결과 차이가 수렴하도록 하는 반복 계산을 통해 탄성계수를 추정하였다. 우선, 탄성계수 추정 기법의 검증을 위해, 수치 해석을 통하여 그 기법을 검증하였으며, 해석 결과 정확한 탄성계수값을 추정하였으며, 이를 통해 본 논문에서 적용한 탄성계수 추정법에 대한 신뢰도를 확인하였다. 이를 바탕으로 사용된 추정 기법을 실 교량에 적용하기 위해 실제 상시 진동 계측 값을 바탕으로 실교량의 동특성 및 탄성계수를 추정하였다. FDD 및 SSI 기법을 통한 모드 해석 결과, 두 기법 모두 유사한 결과를 나타내어 FDD 및 SSI 두 방법에 대한 결과의 신뢰도를 확인 할 수 있었다. 추정 탄성계수 값은 거더 단면내 설치한 응력계 및 변형률계를 통한 계측 결과값의 범위 내에 있음을 확인하였다. 따라서 본 논문에서 적용한 교량의 상시 진동 데이터를 바탕으로 한동특성 및 탄성계수 추정법이 구조물의 대략적인 탄성계수 및 이에 따른 구조물의 전체적인 건전도를 파악하는데 도움이 되리라 생각된다.

• Journal of Korean Society of Steel Construction
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• v.22 no.5
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• pp.445-453
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• 2010

Recently, the remodeling projects of old low-rise buildings were launched in Korea. However, most of them were not satisfied with the value set forth by the KBC2005. Even though there are some research studies on how to improve the seismic performance of such buildings as newly constructed buildings, there is little research in measuring the actual vibrations on low old buildings to prove the effect of retrofit. There also has not been any in-depth research on the dynamic characteristics of full-scale structures using vibration measurements of the building that was damaged to failure. Using an actuator, the dynamic characteristics of reinforced three-storey concrete buildings were evaluated before and after they were damaged. After an 80-mm horizontal displacement by the actuator, frequency in the long and short directions were reduced to 20.85% and 5.77% respectively ; damping ratio was also reduced to 53.9% and 23.15% respectively.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.173-188
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• 2002

In General, the measured loads and load-time function suggested by Bachmann iota walking are used for vibration analysis of structures subjected to footstep loads. It is not easy to measure walking loads because they we influenced by various parameters. Therefore, it is needed to model the walking loads that can be applied to structure analysis. Parameter study is used for the walking loads having various walking frequency for vibration analysis of structures under walking loads. In this study, walking loads were measured directly by using a force plate within two load cells, and the parameters of the walking loads were analyzed. The measured walking loads are decomposed into harmonic loads by using the Fouler series. Functional relationship between the walking frequency and the Fourier coefficients can be derived from the coefficients of harmonic loads obtained by the decomposition process, and the walking loads were formulated. It is possible to apply the venerated walking loads easily or conveniently by the proposed equation to the analysis of a structure subjected to walking loads.

• 한국IT서비스학회:학술대회논문집
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• 2007.05a
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• pp.549-553
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• 2007

국가적으로 전체 터널의 수는 대폭 증가하는 추세이며, 시공 및 유지관리 단계에서 체계적이고 장기적인 계측을 통한 관리가 필수적이다. 그러나 제한적인 계측만을 수행하고 있으며, 계측된 데이터가 체계적으로 관리되지 않아 유지관리 등 시공 이후의 단계에서 기초 정보로 활용하지 못하고 있는 실정이다. 이러한 상태의 주요한 원인 중 한 가지는 기존의 유선 계측기가 터널현장의 복잡하고, 다양한 장비들이 운용되는 상황에서 설치 및 유지관리에 어려움이 있기 때문이다. 또한 고가의 로거의 필요성은 경제성 면에서도 장애가 된다. 따라서 터널의 효율적인 계측 및 관리를 위해서는 경제성이 확보된 무선의 효율적인 계측기의 개발이 선결되어야 하며, 본 연구에서는 지그비(Zigbee) 기술을 활용하여 기존 터널 계측기의 70% 이상을 차지하는 진동현 계측기를 무선화 할 수 있는 모듈의 프로토타입을 개발하였다. 본 고에서는 이와 관련된 다음의 내용을 기술하고자 한다. - 지그비 기술을 활용한 진동현 계측기 무선화 모듈 프로토타입 개발 내용 - 현장 실험 방법 및 결과

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.5
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• pp.471-485
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• 2014

The monitoring method of geotechnical structures using acoustic emission(AE) and microseismicity(MS) is to detect the microscopic deformation and fracture behavior in the inner structures by measuring induced acoustics and vibrations. It can identify a pre-indication of failure by taking advantage of the characteristics that the amount and occurrence rates of AE and MS increase rapidly prior to large scale destruction of the target structures. The monitoring system consisting of high-quality sensors, high-speed data acquisition device and the operation program is required for the practical application of this method. Recently, the AE and MS monitoring systems have been localized. In particular, the developed operation software which can analyze and interpret the measured signals was demonstrated through a number of applications to domestic fields. This report introduces the configuration and features of developed monitoring system, then the challenges and future direction of AE monitoring in geotechnical structures are discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.21-26
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• 1990

포장도로는 신설된 후 계속적인 차량의 통행과 기후 조건의 변화등으로 시 간이 경과함에 따라서 그 상태가 저하된다. 따라서 포장도로는 일정기간이 지난 후에는 쾌적한 차량의 통행을 보장하기 위하여 유지보수를 실시하여야 한다. 이러한 유지보수를 효율적이고 과학적으로 수행하는 것은 대단히 중요 하다. 미국과 같은 선진국의 경우 도로 신설의 투자비 보다 유지보수에 사용 되는 예산이 더 많아지고 있는데 효율적인 유지관리 시스템의 개발로 투자 비를 적정화하고자 하는 노력이 크게 증가되고 있다. 도로 포장 구조체가 도 로 이용자에게 어느 정도의 안전성, 쾌적성 및 신속성을 제공하고 있는가를 평가하는 것은 포장관리의 중요한 고려사항이며 그 결과는 포장의 공용성 개념으로 표현된다. 포장상태 조사시 포함되는 항목들은 포장유지관리 시스 템을 운용하는 기관마다 약간씩 차이는 있으나 대체로 노면조도, 노면장애, 구조적 능력, 미끄럼저항등이다. 이중 진동계측장비가 많이 사용되는 항목은 노면조도와 구조적 능력평가 부분으로서 이 두 항목에 포함되는 진동 계측 장비와 그 이용방법에 관해서 논하고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5C
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• pp.185-192
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• 2012

The objective of this study is to present and verify a method for evaluating the fundamental period of a rockfill dam using artificially generated vibration from a blasting event. In this study, the artificial blasting vibration tests were carried out at the site adjacent to the existing Seongdeok Dam for the first time in Korea. The artificial vibrations were induced by 4 different types of blasting with the various depths of blasting boreholes and the various explosive charge weight. During the tests, the accelerations time histories were recorded at the crest of the dam. In this acceleration history, only free vibration decay part following the main vibration event was extracted and it was analyzed by frequency domain analysis using Fast Fourier Transform (FFT). From the results of FFT, the fundamental period of the target dam was evaluated. It is found that the effect of different blasting types on the fundamental period of the target dam is negligible and the fundamental period of the target dam can be consistently obtained by blasting vibration tests. Furthermore, it is found that the period of the target dam calculated by the method using blasting vibration test is similar to that obtained by the method of previous researchers using the real earthquake records. Therefore, in case that the earthquake record is not available, the fundamental period of a rockfill dam can be reasonably evaluated if blasting vibration test is allowed at the site adjacent to the dam.

• Journal of Korean Association for Spatial Structures
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• v.11 no.1
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• pp.131-138
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• 2011

For train vibration influence assessment of newly constructed buildings in building design levels, 4 train measured vibration acceleration responses were used to compare with TR theory values and suitability of TR values was proposed. Through this TR method, construction planned grounds located near railroad areas were selected and ground vibration measurement was conducted. Through natural frequency by MIDAS, vertical acceleration response, and ground frequency from measured vibration response, TR was calculated and vibration prediction was conducted. As a result of comparing acceleration response estimate applying TR and measured value of train vibration acceleration response, it was found that it was in 3.61%~37.1% of margin of error. Clear peak of 7.19~10.61Hz in KTX, Gyungeuisun, and cement train were confirmed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.594-603
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• 2018

Recently, according to the development of measurement techniques, it has become possible to take complicated and time-consuming field measurements in a simple and convenient manner. In this background, this study estimated the tension of cables under ambient vibration using minimized measurement and signal processing. The VBDM using video-only by low-cost equipment was used as a minimized measurement. An estimation of the natural frequency using the mirror frequency concept was also proposed to solve the shortage of frequency band in this case. Furthermore, the FDD method was adopted for a natural frequency estimation in the ambient vibration related to field application. Experimental studies using a cable-stayed bridge model were carried out to examine the properties of the mirror frequency and the applicability of FDD with the proposed minimized system. The results showed that FDD for ambient vibration also works properly in an estimation of the natural frequency using the minimized system. In addition, the mirror frequency concept can allow a high natural frequency estimation even in a distorted signal by low-speed recording, which can overcome the limit of the minimized system. Overall, the proposed minimized system can be effective for the tension estimations of a cable under ambient vibration.