• Wind and Structures
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• 제18권2호
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• pp.155-180
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• 2014

The safety of road vehicles on the ground in crosswind has been investigated for many years. One of the most important fundamentals in the safety analysis is aerodynamic characteristics of a vehicle in crosswind. The most common way to study the aerodynamic characteristics of a vehicle in crosswind is wind tunnel tests to measure the aerodynamic coefficients and/or pressure coefficients of the vehicle. Due to the complexity of wind tunnel test equipment and procedure, the features of flow field around the vehicle are seldom explored in a wind tunnel, particularly for the vehicle moving on the ground. As a complementary to wind tunnel tests, the numerical method using computational fluid dynamics (CFD) can be employed as an effective tool to explore the aerodynamic characteristics of as well as flow features around the vehicle. This study explores crosswind effects on a high-sided lorry on the ground with and without movement through CFD simulations together with wind tunnel tests. Firstly, the aerodynamic forces on a stationary lorry model are measured in a wind tunnel, and the results are compared with the previous measurement results. The CFD with unsteady RANS method is then employed to simulate wind flow around and wind pressures on the stationary lorry. The numerical aerodynamic forces are compared with the wind tunnel test results. Furthermore, the same CFD method is extended to investigate the moving vehicle on the ground in crosswind. The results show that the CFD results match with wind tunnel test results and the current way using aerodynamic coefficients from a stationary vehicle in crosswind is acceptable. The CFD simulation can provide more insights on flow field and pressure distribution which are difficult to be obtained by wind tunnel tests.

• 한국지반공학회논문집
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• 제20권5호
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• pp.127-134
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• 2004

본 연구는 RAP공법의 구조물 기초로서의 안정성 및 사용성 확보를 위한 기초연구로써, RAP공법이 적용된 지반의 지지력 및 파괴거동을 실내모형토조시험을 통하여 검토한 것이다. 본 연구에서는 RAP 공법을 구조물 기초로서의 파괴거동을 파악하기 위한 실내모형실험을 수행하였다. 사질토 지반에서 상대밀도별(60%, 70%, 90%), 직경 별(45mm, 60mm, 70mm)로 RAP를 설치한 후 깊이별(5cm, 10cm, 15cm, 20cm, 25cm, 30cm)로 토압계를 각각 RAP에 인접한 곳과 RAP 중심에서 1.0D 떨어진 곳에 설치하여 하중재하 실험을 수행하여 RAP의 지지력 및 파괴거동을 검토하였다. 실험 결과 RAP의 파괴거동은 깊이 5∼10cm(1.0D∼2.0D)에서 최대 횡토압을 받아 일반적인 RAP의 파괴 형태인 Bulging 파괴가 발생하는 것으로 판단되었다. 그리고 RAP에 하중을 가하였을 경우 상대밀도가 낮을 경우에는 RAP의 직경변화가 컸으며 상대밀도가 높을 경우에는 RAP의 직경변화가 작음을 알 수 있었다. 깊이별 횡방향 응력 분포도는 상부에서 횡토압의 영향이 크게 나타났으며 하부로 내려갈수록 작아지는 것을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제15권4호
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• pp.136-145
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• 2011

준설매립후 연직배수공법을 적용하여 지반개량을 수행하는 대규모 국가산업단지 조성 프로젝트를 대상으로, 각 심도별 채취된 불교란 시료를 이용하여 물리즉 특성 및 압밀 특성 등을 분석하기 위한 실내시험을 실시하였으며, 수평 압밀계수 및 현장 초기 응력 산정을 위한 콘 관입 및 소산시험을 수행하였다. 지층을 구성하고 있는 하부의 원지반 점토층과 상부의 준설 매립층은 유사한 해성점토로 구성되어 있으나, 초기 간극비와 초기 함수비, 초기 응력상태, 방향별 투수성과 압축성 등의 압밀특성에 있어서는 시간경과에 따른 압밀거동에 있어 매우 큰 차이를 보이는 다층 지반의 특성을 띠고 있다. 압밀과 관련된 응력이력이 다른 두지층의 초기응력을 산정하기 위하여 콘 관입시험 및 소산시험시의 간극수압 측정결과를 분석하였으며, 이를 통해 압밀이 진행중인 하부 원지반 점토층에서의 매립하중과 상부 성토에 의한 각 심도별 과잉간극수압 분포 및 이를 통한 초기응력을 산정할 수 있었다.

• 한국지반환경공학회 논문집
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• 제4권4호
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• pp.17-23
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• 2003

플라스틱보드드레인(PBD)공법에 의해 개량된 연약점토지반의 압밀특성은 아직 충분히 밝혀져 있지 않기 때문에 개량지반의 압밀거동을 정확히 예측하기는 어려운 실정이다. PBD공법에 사용되는 배수재의 형상은 개량지반의 압밀특성에 영향을 미치는 중요한 인자중의 하나로 알려져 있다. 본 연구에서는PBD공법에 의해 개량된 연약지반의 압밀특성에 미치는 배수재의 폭과 재하중 상태의 영향을 고찰하기 위하여 일련의 실내모형실험을 실시하였다. 모형실험의 결과로부터 모형지반의 침하 및 과잉간극수압의 소산거동과, 모형지반내의 함수비 분포형상을 파악할 수 있었다. 그리고 모형실험결과에 미친 모형지반 상부의 배수조건의 영향을 검토하기 위해서 Barron의 이론해에 의한 압밀거동과 비교, 고찰하였다. 그 결과 모형실험에 의한 압밀거동은 방사방향의 배수조건 뿐만 아니라 연직방향 배수조건으로부터도 영향을 받았음을 알 수 있었다.

• Journal of Biosystems Engineering
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• 제10권1호
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• pp.13-23
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• 1985

Spraying method from the paddy-field levee is known to give insufficient penetration of the spray droplets to the rice stem of the densely grown plants, which is generally encountered at the last stage of rice growth. This study was intended to investigate the spraying system to solve this existing problem. As an approach, it was attempted to develop the boom-with-nozzle, between-the-row application system. Several types of nozzles and their different arrangements in the boom were tested in the field to measure the penetration-reaching distance and the uniformity of spray droplet distribution. The results of the study are summarized as follows: 1. Field experiments by the spraying method from the paddy-field levee showed to have practically no penetration of the spray droplets to the portion of the plant stem with the normal flow volume generally applied and thus need for improving present spraying method. 2. It was found that, considering both the uniformity of the spray droplet distribution and performance rate, the most efficient type of nozzle in the between-the-row boom-type spraying system was one that has core-insert hollow-cone with some clearance between the cone and tip. 3. When tested by applying the spraying method of between-the-row, the nozzle pressure did not affect the uniformity of spray droplet distribution. However, the nozzle pressure had a positive effect on the penetrating-reaching distance of the facing side of the rice stem and did not affect much on that of the opposite face of the stem. It was also found that the maximum pressure to affect the penetration-reaching distance was about $10kg/cm^2$. 4. The uniformity of the spray droplet distribution in the between-the-row system was greatly affected by the height and orientation of the nozzles in the boom. Based on experimental work for the different type of the boom-with-nozzle arrangements, it is recommended that the position of nozzle is set at about 0.45 m above the ground and two nozzles in the boom are oriented to be faced with each other with some angle such that the droplet stream from the nozzle would not directly face with each other.

• 디자인학연구
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• 제14권3호
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• pp.211-220
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• 2001

노인의 일반적 보행특성은 대학생들과는 달리 보행속도가 느려지며 보폭의 길이나 보행주기 또한 감소한다. 그럼에도 불구하고, 노인신발제작을 위한 보행특성분석에 대한 연구는 매우 부족한 실정이다. 이에 본 연구는 압력분포기를 이용하여 노인의 보행시 발바닥에 걸리는 압력을 대학생과 비교하였고, 그 특성을 고찰하였다. 분석결과 노인은 보행시 지면접촉시간이 길고, 보행시 발전체면적에 걸리는 최대 힘은 대학생에 비해 남자노인의 경우 1.12배, 여자노인의 경우 1.20배 정도 많이 걸린다. 노인의 지면 접촉시간은 중족골 아치부분에서 접촉시간이 길다 이러한 분석의 결과를 토대로 노인신발의 디자인시 고려해야할 설계지침을 제시하였다. 본 연구는 인간공학적 노인신발을 디자인 하는데 기초자료로 활용될 수 있다.

• Computers and Concrete
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• 제31권6호
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• pp.561-570
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• 2023

In this paper, the structural performance of RC and HPFRCC slabs exposed to a TNT explosion were numerically investigated. A finite element model was established using the MM-ALE method in the LS-DYNA program to simulate a near-ground TNT explosion at a scaled distance of 1.08 m/kg³. The K&C model was calibrated to exactly reflect the material properties of HPFRCCs that were developed in KICT and KNU. Numerical and experimental results were compared for the damage distribution and failure shape of the slabs. Based on the verified numerical model, a parametric study was carried out to demonstrate the effects of compressive strength and thickness of the slab on the blast resistance. In particular, the spallation failure on the back side of the slab is greatly dependent on the thickness. Finally, additional numerical simulations were conducted to explore the variation in blast pressure characteristics according to the scaled distance and explosive shape. It was confirmed that the pressure induced by cubic TNT was more destructive to the slab than cylindrical and spherical TNT in a nearfield explosion.

• 한국해안·해양공학회논문집
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• 제22권2호
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• pp.88-94
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• 2010

외부안정성을 다룬 동반논문과 차별화하여, 이 논문에서는 심층혼합처리지반에 설치된 안벽의 내부안정성에 대한 정량적 위험도 평가를 위한 신뢰성해석 방법을 제안하였다. 내부안정성 위험도 평가를 위해 개량지반의 단지압, 전단강도 그리고 무개량토의 압출 파괴모드에 대해 MVFOSM, FORM 그리고 MCS를 적용하여 안정성을 검토하고 비교하였다. 심층혼합처리지반상 안벽의 내부안정성에 대한 신뢰성해석 결과, 흙-시멘트 개량체 압축강도의 변동성과 분포형태가 파괴확률에 큰 영향을 미치는 것으로 나타났으며 다른 확률변수들의 영향은 상대적으로 미미했다. 그러므로 흙-시멘트 개량체의 현장 압축강도에 대한 통계적 특성을 합리적이고 정확하게 결정하는 것이 중요하다.

• Geomechanics and Engineering
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• 제6권1호
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• pp.17-31
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• 2014

This paper investigates the development of failure surfaces induced by an embankment on soft marine clay deposits and the characteristics of such surfaces through numerical simulations and its comparative study with monitoring results. It is well known that the factor of safety of embankment slopes is closely related to the vertical loading, including the height of the embankment. That is, an increase in the embankment height reduces the factor of safety. However, few studies have examined the relationship between the lateral movement of soft soil beneath the embankment and the factor of safety. In addition, no study has investigated the distribution of the pore pressure coefficient B value along the failure surface. This paper conducts a continuum analysis using finite difference methods to characterize the development of failure surfaces during embankment construction on soft marine clay deposits. The results of the continuum analysis for failure surfaces, stress, displacement, and the factor of safety can be used for the management of embankment construction. In failure mechanism, it has been validated that a large shear displacement causes change of stress and pore pressure along the failure surface. In addition, the pore pressure coefficient B value decreases along the failure surface as the embankment height increases. This means that the rate of change in stress is higher than that in pore pressure.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.365-372
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• 1999

The plane deformation and spatial seepage(PDSS) analysis was developed to consider 3D flow of excess pore water as well as plane deformation of ground. Here is newly developed an equivalent model for PDSS analysis, which was the purpose to reduce number of finite elements and to take the effects of smear and well resistance into consideration. As the result of PDSS analysis with applying the new model, it is showed that the settlement-tin e relationship by PDSS agrees well with those of Plane strain(PS) and axisymmetric analyses, irrespective of existence of untreated layer. And the excess pore pressure distribution by PDSS is relatively agreed with that of axisymmetric analysis, not with that of PS.