• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.128-135
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• 2001

본 논문에서는 지반-구조물 상호작용계의 입력하중과 강성에 관련된 물성값들을 구조물에서 계측된 지진응답만을 사용하여 효과적으로 추정할 수 있는 새로운 방법을 제안하였는데, 제안된 방법은 비지계수 추정을 위한 목적함수가 입력하중에 독립적이기 때문에 구조물에서 계측된 지진응답만으로 미지계수의 추정이 가능하도록 되어있다. 본 연구에서 제안된 방법의 검증은 국제공동 연구의 일환으로 최근 대만의 화련에 건설된 대형지진시험 구조물에서 계측된 지진 응답을 사용하여 수행하였다. 추정된 입력하중과 지반과 구조물의 강성에 관련된 물성값들을 사용하여 계산된 지진응답의 계측치와 매우 잘 일치하여, 추정결과의 타당성을 검증할 수 있었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.2
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• pp.23-31
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• 2001

지반 위에 세워진 구조물의 지진응답해석시 지반-구조물 상호작용 영향은 지반으 선형특성을 고려하여 간주되었는데 최근 연구결과에 의하면 구조물 지진해석에서 연약지반의 비선형 특성이 중요한 요소로서 인식되었다. 하지만 지반-구조물계의 복잡한 비선형 특성 때문에 내진설계 기준에서 비선형 지반특성을 고려하기에는 아직도 어려움이 많다. 이 논문에서는 UBC 지반종류 $S_{D}$ 지반 위에 놓인 중규모의 얕은 온통기초와 묻힌 온통기초위에 세워진 건물에 대한 단자유도계 선형 지진해석을 연약지반의 비선형성을 고려하여 최대가속도가 0.17g 과 0.36g 인 Taft E-W 및 El Centro N-S 지진기록을 사용하여 수행하였다. 비선형 지진해석을 결과를 선형해석 결과와 비교하였을 때, 비선형 응답스펙트럼의 최대가속도가 지반의 비선형성 때문에 상당히 줄어드는 것으로 나타나 지반의 비선형성을 고려한 더효율적인 내진설계의 가능성을 보여준다.

• Geophysics and Geophysical Exploration
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• v.19 no.2
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• pp.84-90
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• 2016

The validation of performance test for newly developed or old-used sensor is very important in the earthquake monitoring and seismology using earthquake data. Especially the frequency response of the sensor is mainly used to correct the earthquake data. The technique of the calculation of phase and amplitude with Hilbert transformation for earthquake data that is filtered with band limited frequency in time domain is applied to calculate the frequency response of the sensor. This technique was tested for the acceleration sensors, CMG-5T of 1g and 2g installed on the vibration table at the laboratory and we could obtain satisfactory result. Tohoku large earthquake in 2011 observed at the station SNU that has accelerometer, ES-T and seismometer, STS-2 operated by KIGAM was also used to test the field data applicability. We could successfully get the low frequency response of broad band sensor, STS-2. The technique by using band limited frequency filter and Hilbert transformation showed the superior frequency response to the frequency spectrum ratio method for noisy part in data.

• Journal of the Earthquake Engineering Society of Korea
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• v.4 no.2
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• pp.99-108
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• 2000

구조물의 능동제어 시스템에서 제어기 설계에 사용되는 구조계의 모델과 실구조계의 차이는 시스템의 성능저하 및 불안정성을 유발할 수 있다 이연구에서는 무시된 고차모우드와 같이 주파수영역에서 표현되는 비구조적 불확실성에 대하여 시스템의 안정성을 보장하도록 강인성을 가지는 LQG/LTR제어이론을 사용하여 구조물의 지진응답제어에 효과적으로 사용할 수 있는 제어기 설계방법을 제시한다 특히 고층건물이나 교탑과 같은 구조물의 지진응답 제어에 적용할 수 있도록 각층의 절대 가속도를 측정변수로 층간상대변위를 제어변수로 설정하여 최적제어기를 구성한다 El Centro 지진압력을 받는 6자유도 전단빌딩모델에 대하여 제어기를 설계하거 수치모사를 수행하여 제시한 제어기가 안정도-강인성을 가지고 지진응답제어에 효과적임을 보인다.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.185-201
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• 2018

Nuclear power plants(NPP) are constructed and operated to ensure safety against natural disasters and man-made disasters in all processes including site selection, site survey, design, construction, and operation. This paper will introduce a series of efforts conducted in Korea Hydro and Nuclear Power Co. Ltd., to assure the safety of nuclear power plant against earthquakes and other natural hazards. In particular, the present status of the earthquake, fault, and slope safety monitoring system for nuclear power plants is introduced. A earthquake observatory network for the NPP sites has been built up for nuclear safety and providing adequate seismic design standards for NPP sites by monitoring seismicity in and around NPPs since 1999. The Eupcheon Fault Monitoring System, composed of a strainmeter, seismometer, creepmeter, Global Positioning System, and groundwater meter, was installed to assess the safety of the Wolsung Nuclear Power Plant against earthquakes by monitoring the short- and long-term behavioral characteristics of the Eupcheon fault. Through the analysis of measured data, it was verified that the Eupcheon fault is a relatively stable fault that is not affected by earthquakes occurring around the southeastern part of the Korean peninsula. In addition, it was confirmed that the fault monitoring system could be very useful for seismic safety analysis and earthquake prediction study on the fault. K-SLOPE System for systematic slope monitoring was successfully developed for monitoring of the slope at nuclear power plants. Several kinds of monitoring devices including an inclinometer, tiltmeter, tension-wire, and precipitation gauge were installed on the NPP slope. A macro deformation analysis using terrestrial LiDAR (Light Detection And Ranging) was performed for overall slope deformation evaluation.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1995.10a
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• pp.160-163
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• 1995

일본 병고현 보부지진은 우리나라는 물론 전세계에 큰 충격을 주었다. 최첨단 과학기술과 경사대국의 재력을 가진 나라들도 이 자연의 무서운 파양역에 아직은 무력함을 이 지진 참사가, 그것을 단적으로 증명해 준다. 지금까지는 한반도이 환태평양 지진대에서 다소 떨어져 있어서 큰 지진이 발생할 염려가 없다는 것이 일반적인 통념이었다. (중략)

• The Journal of Engineering Geology
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• v.29 no.1
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• pp.1-12
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• 2019

Earthquake can change underground stress condition around the hypocenter and affect the fracture systems of the rocks. In Korea, the M5.8 Gyeongju earthquake on September 12, 2016 and M5.4 Pohang earthquake on November 15, 2017 occurred inside the Yangsan fault zone and possibly affected the fracture systems in the Yangsan fault zone and nearby rock masses. In this study, the characteristics of the fracture system (fracture orientation, number of the fractures, fracture spacing and aperture, dip angle, fracture density along depth, and relative rock strength) of the rocks in the low/intermediate level radioactive waste repository site located in the coastal area of the East Sea are analyzed by the impact of the Gyeongju and Pohang earthquakes using acoustic televiewer data taken from the boreholes at the radioactive waste repository site in 2005 and 2018. As a result of acoustic televiewer logging analysis, the fracture numbers, fracture aperture, and fracture density along depth overall increased in 2018 comparing to those in 2005. This increase tendency may be due to changes in the fracture system due to the impact of the earthquakes, or due to weathering of the wall of the boreholes for a long period longer than 10 years after the installation of the boreholes in 2005. In the borehole KB-14, on the whole, the orientation of the fractures and the average fracture spacing are slightly different between 2005 and 2018, while dip angle and relative rock strength in 2005 and 2018 are similar each other.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.1
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• pp.123-132
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• 1999

One of the major difficulties in the seismic analysis of a dam-reservoir system is the treatment of the energy radiation in the upstream direction of the reservoir. In the paper, a new transmitting boundary is presented that can model properly the radiation of energy in the far field direction of a semi-infinite reservoir with constant depth. In the newly developed method, effects of surface wave motion are taken into accounted and the reservoir-foundation interaction is approximately accounted for with an absorbing boundary condition. If a dam has vertical upstream face and the infinitely long reservoir maintains constant depth, then the proposed transmitting boundary can be directly coupled with the model of dam body. In present study, the dam body is assumed to behave elastically and modeled by finite element method. Seismic responses of a dam model are investigated using the newly developed transmitting boundary.

• Economic and Environmental Geology
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• v.40 no.4
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• pp.445-459
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• 2007

Superconducting Gravimeter(SG) was installed and has been successfully operated at MunGyung, Kyungsang province in Korea in March 2005. It was registered as the 21st observatory of the Global Geodynamics Project. Since SG can precisely measure the gravity variations below the 1mHz frequency band, it has the outstanding capability to sense and resolve many different periodic gravity components from each other. From the raw data collected between 18 March 2005 and 21 February 2006 diurnal and semi-diurnal tidal band's residual gravity components were analyzed. During this process, the instrumental noises, air pressure, and ground water corrections were carried out. Values of $-3.18nm/s^2/hPa\;and\;17nm/s^2/m$ were used respectively in the air pressure and groundwater corrections. Hartmann-Wenzel and Whar-Dehant Earth tide models were adopted to compute the residual gravity for Q1, O1, P1, K1, M2, N2, S2, K2 tidal bands. For the ocean loading correction, SCW80, FES952, and FES02 models were used and compared. As a result, FES02 ocean loading model has shown the best match for the data processing at MunGyung SG MunGyung SG gravity was compared with GRACE satellite gravity. The correlation coefficient between the two gravity after groundwater correction was 0.628, which is higher than before ground water correction. To evaluate sensitivity at MunGyung SG gravity statition, the gravity data measured during 2005 Indodesian earthquake was compared with STS-2 broad band seismometer data. The result clearly revealed that the SG could recorded the same period of earthquake with seismometer event and a few after-shock events those were detected by seismometer.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.1
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• pp.25-34
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• 2010

A method is presented for evaluating the seismic failure probability of bridge structures which show a nonlinear hysteretic dynamic behavior. Bridge structures are modeled as a bilinear dynamic system with a single degree of freedom. We regarded that the failure of bridges will occur when the displacement response of a deck level firstly crosses the predefined limit state during a duration of strong motion. For the estimation of the first-crossing probability of a nonlinear structural system excited by earthquake motion, we computed the average frequency of crossings of the limit state. We presented the non-Gaussian closure method for the approximation of the joint probability density function of response and its derivative, which is required for the estimation of the average frequency of crossings. The failure probabilities are estimated according to the various artificial earthquake acceleration sets representing specific seismic characteristics. For the verification of the accuracy and efficiency of presented method, we compared the estimated failure probabilities with the results evaluated from previous methods and the exact values estimated with the crude Monte-Carlo simulation method.