• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1623-1629
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• 2008

The purpose of this research is to assess the application of recycled-aggregate that is gained from construction wastes as the material of compaction pile method. At the same time, the development of the new technique rectifies defects of the existing compaction pile method for soft ground improvement. In this research, model tests were conducted for analyzing the effect of the soft ground improvement by porous concrete pile using recycled aggregate. Through the results of the model tests, the behavior of settlement on composition ground with surcharge pressure were elucidated.

• 산업기술연구
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• 제27권B호
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• pp.209-214
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• 2007

This paper is the research result about centrifuge model experiments of investigating the behavior of bridge abutment on the sloped ground. Ground condition of the studied site was the bridge abutment with pile foundation adjacent to the slope. The pile foundations was supported on the soft rocks covered with the embankment. Evaluating the behavior of such a complicate ground and structure conditions was not easy so that the centrifuge modelling was performed to find the overall behavior of them. Layout of centrifuge model experiment was simplified to simulate easily the actual behavior of very complicate site condition. Construction process in field such as ground excavation for footing foundation, installation of piles, placement of footing and bridge abutment, backfilling and surcharge loading eas duplicated in the centrifuge model experiment. Consequently, the stability of the piled bridge abutment adjacent to the slope of embankment was evaluated throughout centrifuge modelling.

• 전기학회논문지
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• 제58권10호
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• pp.1861-1868
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• 2009

A ground electrode subjected to lightning surge current shows the transient impedance behaviors. The ground electrode for protection against lightning should be evaluated in view of the transient grounding impedance and conventional grounding impedance, not ground resistance. The transient impedance characteristics of ground electrodes are influenced by the shape of ground electrode and the soil characteristics, as well as the waveform of lightning surge current. In order to propose a simulation method of analyzing the transient impedance characteristics of the grounding system in practical use, this paper suggests a theoretical analysis method of distributed parameter circuit model to simulate the transient impedance characteristics of counterpoise subjected to lightning surge current. EMTP and Matlab programs were employed to compute the transient grounding impedances of three counterpoises with different lengths. As a consequence, the simulated results using the proposed distributed parameter circuit model are in good agreement with the measured results.

• 한국군사과학기술학회지
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• 제15권2호
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• pp.155-160
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• 2012

In this paper, a strip modeling method is developed for the acquisition of target positions in remote area and validated using the imagery of SPOT satellite. This method utilizes the parameters given in header files and constructs a camera model without ground control points. In most cases, the root mean squared error of check points is less than pixel size with one ground control point. The model error of reference image is evaluated using ground control points and used to remove the model error of target images acquired along the same satellite orbit, which enables one to calculate target positions in remote area where no ground control points are available.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1426-1433
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• 2005

In this paper, reliability analysis of surface settlement by ground water drawdown is performed using a reliability-groundwater flow numerical model. The result is compared with that of the deterministic model to evaluate the influence of the uncertainty from hydraulic conductivity in the soft ground as well as to determine the range of hydraulic conductivity of grouted ground. From the analyses, it was found that probability of failure to exceed the tolerable settlement was very high, if the hydraulic conductivity of grouted ground is decided from the deterministic flow model only. Reliability analysis which evaluates variance of hydraulic conductivity should be used together with the deterministic model for grouting design of tunnels to prevent ground water drawdown.

• Earthquakes and Structures
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• 제19권6호
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• pp.445-457
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• 2020

An ultra-high voltage (UHV) transmission system has the advantages of low circuitry loss, high bulk capacity and long-distance transmission capabilities over conventional transmission systems, but it is easier for this system to cross fault rupture zones and become damaged during earthquakes. This paper experimentally and numerically investigates the seismic responses and collapse failure of a UHV transmission tower-line system crossing a fault. A 1:25 reduced-scale model is constructed and tested by using shaking tables to evaluate the influence of the forward-directivity and fling-step effects on the responses of suspension-type towers. Furthermore, the collapse failure tests of the system under specific cross-fault scenarios are carried out. The corresponding finite element (FE) model is established in ABAQUS software and verified based on the Tian-Ma-Qu material model. The results reveal that the seismic responses of the transmission system under the cross-fault scenario are larger than those under the near-fault scenario, and the permanent ground displacements in the fling-step ground motions tend to magnify the seismic responses of the fault-crossing transmission system. The critical collapse peak ground acceleration (PGA), failure mode and weak position determined by the model experiment and numerical simulation are in relatively good agreement. The sequential failure of the members in Segments 4 and 5 leads to the collapse of the entire model, whereas other segments basically remain in the intact state.

• 한국지반환경공학회 논문집
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• 제19권4호
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• pp.27-32
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• 2018

제한된 토지의 효율적인 활용을 위해 과거로부터 지하공간 개발에 따라 수많은 지반굴착 공사가 이루어져 왔다. 지반굴착은 굴착면 주변지반의 응력변화와 변위를 수반함에 따라 굴착면의 안정성에 영향을 미치게 되어 지반거동에 대한 영향을 예측하는 것이 매우 중요한 문제이다. 이러한 영향 예측을 위한 방법으로 수치해석방법이 주로 이용되며, 최근 컴퓨터 성능 향상과 더불어 수치해석 프로그램의 발달로 매우 복잡한 문제도 적용이 가능해졌다. 그러나 일부 특수해석을 제외하고 대부분 해석모델을 산정 및 적용이 간편한 Mohr-Coulomb 해석모델을 적용함에 따라 굴착면 바닥부에서 실제보다 큰 변위가 발생하는 것으로 예측되어 필요 이상의 보강이 이루어지는 문제점이 발생한다. 본 연구에서는 지반굴착 과정을 모사하여 수치해석을 수행하였으며, 해석모델로 Mohr-Coulomb, Modified Mohr-Coulomb, Duncan-Chang, Hardening Soil 해석모델을 적용하여 그 결과를 비교분석하였다. 본 연구는 수치해석을 통한 지반굴착 문제해결 시 다양한 지반굴착 조건별로 적합한 해석모델 선정을 위한 기초자료로 활용될 것으로 기대된다.

• KIEE International Transactions on Electrophysics and Applications
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• 제4C권5호
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• pp.207-214
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• 2004

This paper presents the characteristics of transient and effective impulse impedances for deeply driven grounding electrodes used in soil with high resistivity or in downtown areas. The laboratory test associated with the time domain performance of grounding piles subjected to a lightning stroke current has been carried out using an actual-sized model grounding system. The ground impedances of the deeply driven ground rods and grounding pile under impulse currents showed inductive characteristics, and the effective impulse ground impedance owing to the inductive component is higher than the power frequency ground impedance. Both power frequency ground impedance and effective impulse ground impedance decrease upon increasing the length of the model grounding electrodes. Furthermore, the effective impulse ground impedances of the deeply driven grounding electrodes are significantly amplified in impulse currents with a rapid rise time. The reduction of the power frequency ground impedance is decisive to improve the impulse impedance characteristics of grounding systems.

• 자원환경지질
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• 제40권3호
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• pp.295-306
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• 2007

본 연구에서는 확률기법인 빈도비 모델 (frequency ratio model) 및 지리정보시스템 (Geographic Information System: GIS)의 공간분석기법을 이용하여 강원도 삼척지역 폐탄광 주변의 지반침하 발생 취약지역을 예측하였다. 지반침하에 영향을 주는 요인들을 추출하기 위해 지형도, 지질도, 갱내도, 토지특성도, 시추공 자료, 기 관측된 침하지 자료 등으로부터 공간자료를 구축하였다. GIS 공간분석과 확률기법을 이용하여 지반침하의 주 요인이 되는 8개의 인자를 추출하였고 관측된 침하지역과 8개 인자와의 연관성을 알아보기 위하여 각각의 결정계수($R^2$)를 계산하였다. 빈도비 모델을 적용하여 각인자의 등급별 가중치를 결정한 후, 이를 중첩 분석하여 지반침하 위험 예측도를 작성하였다. 지반침하 위험 예측도를 기존 침하지 위치와 비교 검증한 결과 96.05%의 높은 예측정확도를 나타냈다. 이를 통해 폐탄광 지역에서 GIS와 빈도비 모델을 이용하여 지반침하 위험지역을 정량적으로 예측하는 것이 가능하다고 판단된다.

• Steel and Composite Structures
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• 제22권5호
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• pp.1001-1018
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• 2016

The purpose of this paper is to compare the structural responses obtained from the stochastic analysis of a suspension bridge subjected to uniform and partially correlated seismic ground motions, using different spatial correlation functions commonly used in the earthquake engineering. The spatial correlation function employed in this study consists of a term that characterizes the loss of coherency. To account for the spatial variability of ground motions, the widely used four loss of coherency models in the literature has been taken into account in this study. Because each of these models has its own characteristics, it is intended to determine the sensitivity of a suspension bridge due to these losses of coherency models which represent the spatial variability of ground motions. Bosporus Suspension Bridge connects Europe to Asia in Istanbul is selected as a numerical example. The bridge has steel towers that are flexible, inclined hangers and a steel box-deck of 1074 m main span, with side spans of 231 and 255 m on the European and Asian sides, respectively. For the ground motion the filtered white noise model is considered and applied in the vertical direction, the intensity parameter of this model is obtained by using the S16E component of Pacoima Dam record of 1971 San Fernando earthquake. An analytically simple model called as filtered white noise ground motion model is chosen to represent the earthquake ground motion. When compared with the uniform ground motion case, the results obtained from the spatial variability models with partial correlation outline the necessity to include the spatial variability of ground motions in the stochastic dynamic analysis of suspension bridges. It is observed that while the largest response values are obtained for the model proposed by Harichandran and Vanmarcke, the model proposed by Uscinski produces the smallest responses among the considered partially correlated ground motion models. The response values obtained from the uniform ground motion case are usually smaller than those of the responses obtained from the partially correlated ground motion cases. While the response values at the flexible parts of the bridge are totally dominated by the dynamic component, the pseudo-static component also has significant contributions for the response values at the rigid parts of the bridge. The results also show the consistency of the spatial variability models, which have different characteristics, considered in this study.