• 한국지반환경공학회 논문집
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• 제15권12호
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• pp.71-77
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• 2014

집중호우는 사면의 붕괴와 사회 기반시설물의 파괴 등을 포함하는 다수의 재해를 유발한다. 이러한 관점에서 강우재현 원심모형실험은 지반구조물의 안정성을 평가하기 위한 합리적인 수단이 될 수 있다. 원심모형실험에서 모형의 변위를 취득하기 위하여 일반적으로 LVDT 또는 레이저 변위계가 사용된다. 그러나 강우모사 시 LVDT는 모형지반으로의 과다 침윤의 문제가 있으며, 레이저 변위계는 레이저의 산란에 의해 계측치의 정확성이 저하된다. 따라서 본 연구에서는 강우재현 원심모형실험에 적용하기 위한 수평변위 계측장치를 개발하였다. 본 연구를 통하여 탄성의 박철판과 스트레인 게이지를 이용하여 제작된 본 장치는 관입을 위한 말단부를 고정시켜 수행한 검정 결과로부터 정확한 변위-변형률 관계를 나타냄을 확인하였다.

• 한국농공학회논문집
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• 제55권2호
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• pp.87-95
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• 2013

The aim of this study is to examine the behavior of reservoir fill dam with the water level raising by use of the centrifugal model test and the numerical simulation. In this study, LIQCA2D-SF based on the cyclic elasto-plastic constitutive model proposed by Oka et al. (1999) is applied for numerical simulation. In order to investigate the displacements and the pore water pressures in the fill dam due to the water level raising velocity, three model tests in centrifugal field of 50g for fill dams were conducted. A comparison between the test result and the simulation result has provided the influence on the displacement and the pore water pressure of the fill dam with increasing up of the water level.

• 한국농공학회논문집
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• 제58권3호
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• pp.91-100
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• 2016

Recently, lots of damages have been lost because large magnitude earthquakes were occurred in the world. It has been increased the number of earthquakes in Korea. It needs improvement required for the repair of deteriorated reservoirs, reinforcement and raised reservoir coping with climate change and earthquake. This study aims to investigate the seismic behavior of deterioration reservoir levee using dynamic centrifugal model test. Therefore, two case tests in centrifugal field of 60 g, the result has provided the influence on the acceleration response, displacement, settlement and the pore water pressure of the reservoir with earthquakes. From the results larger displacement and acceleration response at the front side of reservoir embankment with poor-fabricated core in seismic condition may degrade overall stability. Reasonable reinforcement method of the raised reservoir embankment is required for ensuring long-term stability on earthquake.

• 한국안전학회지
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• 제12권3호
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• pp.139-146
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• 1997

In this study, centrifugal model tests were performed to investigate the behavior of excavated earth retaining wall with the depth of excavation and different types of wall(aluminum, steel panel). Jumunjin standard sand was used for foundation soil. The raining method was adopted to form the required relative density of the model ground. The lateral earth pressure measured from tests were compared with estimated active earth pressure by Rankine's theory. The test results have shown that the earth pressure acting on the retaining wall and the rotation displacement of the wall are influenced by the depth of excavation and the type of wall. It was found from the test results that the deformation of the wall increases with the depth of excavation.

• 한국유체기계학회 논문집
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• 제19권1호
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• pp.37-44
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• 2016

In this study, a parametric study of a centrifugal pump with double volute has been performed numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport model was selected as turbulence closure through turbulence model test. The finite volume method and unstructured grid system were used for the numerical analysis. The optimal grid system in the computational domain was determined through a grid dependency test. The expansion coefficient, circumferential and radial starting positions and length of divider were selected as the geometric parameters to be tested. And, the hydraulic efficiency and the radial thrust coefficient were considered as performance parameters. It was found that the radial thrust and hydrualic efficiency are more sensitive to the expansion angle and circumferential starting position of the divider than the other geometrical parameters.

• 대한기계학회논문집B
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• 제25권12호
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• pp.1730-1738
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• 2001

This paper presents an overview of testing and analyzing field performance of a centrifugal chiller which has a rated capacity of 200 RT(703 kW). Field data of a chiller installed in the cleanroom research building of KIST has been collected far performance analysis. The operating data included start-up, shut-down, and quasi-static state where cooling capacity and compressor power consumption varied cyclically. It was found that the steady-state thermodynamic model could be applied to relate the cooling capacity and COP under quasi-static conditions. The results led to finding the required cooling load pattern and a possible energy saving method. This study provides a method of evaluating performance of a large capacity centrifugal chiller in which field test is necessary.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.201-204
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• 2010

Earthquake load to design a structure has been calculated from a fixed base SDOF model using amplified surface accelerations along soft soil layers. But the method dose not consider a soil-structure interaction. Centrifugal experiments that were consisted of soil, a shallow foundation and a structure were performed to find the effects of soil-structure interaction. The experiments showed that mass and stiffness of the foundation affected a response of the structure and nonlinear behavior of soil near the foundation. And a rocking displacement caused by overturning moment affected the response and increases a damping effect. In this study, the centrifugal experiment was simulated as a two dimensional finite element model. The finite element model was used for nonlinear time domain analysis of the OpenSees program. The numerical model accurately evaluated the behaviors of soil and the foundation, but the rocking effect and the behavior of structure were not described.

• 한국지반공학회논문집
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• 제38권1호
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• pp.35-45
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• 2022

개착공법으로 원형 수직구 건설 시, 가시설 흙막이 벽체는 일정 수준의 변위를 허용하는 연성벽체로 설계된다. 합리적이고 경제적인 연성벽체의 구조 설계를 위해서는 벽체에 작용하는 토압을 정확히 평가할 필요가 있다. 원형 수직구 벽체에 작용하는 토압은 주변 지반의 소성 변형과 밀접하게 연관되어 있으나, 이에 대한 연구는 부족한 상황이다. 본 연구는 원형 수직구의 단계 굴착을 원심모형시험을 통해 모사하고, 원심모형시험 중 촬영된 이미지에 이미지 해석 기법을 적용하여 원형 수직구 굴착 시 주변 지반에 발생하는 변형을 평가하였다.

• 한국지반공학회논문집
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• 제37권6호
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• pp.39-50
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• 2021

최근 국내에 리히터 규모 5.0 이상의 지진의 빈도수가 늘어남에 따라 지진피해가 늘어나면서 내진설계에 대한 많은 연구와 관심이 높아져 가고 있는 실정이다. 최근 발생한 포항지진에 의해 많은 피해가 발생하였고, 항만시설물 또한 피해가 발생하였다. 본 연구에서는 항만구조물 중 외곽시설인 직립식 방파제의 지진 시 발생하는 동적 거동을 원심모형실험을 통해 분석하였다. 이를 위하여 상사법칙을 적용한 직립식 방파제 모형에 포항지진파, 인공지진파 I, II의 총 세 가지 지진파를 적용하고, 지반에 대하여 DCM보강, 사석치환의 두 가지 방식의 보강을 한 경우를 고려하여 원심모형실험을 수행하였다. 그 결과 획득한 지진 시 직립식 방파제의 동적 거동에 대하여 가속도, 수평·수직 변위를 분석하여 내진안정성을 검토하였다. 검토 결과 방파제 기초지반이 DCM보강 및 사석치환을 통해 지지력 및 강성이 높아짐에 따라 가속도 증폭이 억제되는 경향을 나타내었다.

• 설비공학논문집
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• 제27권4호
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• pp.187-194
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• 2015

This paper describes the PI controller design based on a practical transfer function model for centrifugal water chillers. The rotational speed of a compressor and the opening angle of an electronic expansion valve were simultaneously regulated as manipulated variables to maintain temperature reference and to ensure high efficiency of the chiller. The COP according to the change in each variable was investigated by performing some static experiments, and it was reflected in the PI controller design to accomplish the high efficiency control. Especially, the practical transfer function model of the chiller was built based on the dynamic experimental data considering the strong inherent non-linearity and complexity of the chiller system. The validity of the designed PI controller was proven by some experimental results using the test facility and the results were also compared to the conventional evaporating pressure control results.