• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.123-129
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• 2002

본 논문에서는 다목적실용위성 1호 개발 과정 중에 수행했던 연성 하중 해석에 대하여 소개하였다. 먼저 일반적인 연성 하중 해석 과정과 다목적실용위성 개발시 수행한 실제의 과정을 비교하였다. 그리고, 다목적실용위성 1호의 유한요소모델과 본 해석에 관련된 각 기관들의 역할을 설명하였다. 준비행모델의 진동 시험 결과를 이용한 유한요소모델의 조정에 대하여 설명하고, 또한, 해석에 입력으로 사용되는 외력함수에 해당하는 하중들에 대하여 설명하였다. 대표적인 해석 결과들을 제시하여 위성이 발사하중에 대하여 안전하다는 것이 예측되었음을 보여 주었다.

• Tunnel and Underground Space
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• v.10 no.1
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• pp.33-44
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• 2000

In order to investigate the effect of progressive collapse of underground circular opening on surface subsidence, laboratory model tests were performed. The modelling materials were sand which has been used as KS standard. Six test models which had respectively different depths of openings were produced. Surface subsidence and horizontal displacements were measured according to progressive collapse of underground opening. Some subsidence prediction method such as NCB method, profile function method and influence function method were considered to predict the subsidence of sand models. The profile function method approximated by Gaussian error function was finally suggested as the most appropriate to sand models.

• Journal of Korean Society of Transportation
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• v.6 no.2
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• pp.21-33
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• 1988

부적정한 도로포장 구조물의 설정 및 유지보수의 적정관리 미흡으로 표면의 피해와 소성변형이 장기간 발생된다. 이로 인한 가요성 통제 구조물의 파괴 원인은 일반적으로 포 장재료의 동질성, 선형탄성 상태의 가정 하에서 분석되었다. 그러나 아스팔트 재료의 특성은 엄밀히 분석해서 완전한 선형탄성이라고는 볼 수 없음은 잘 알려져 있다. 따라서 근본적으 로 포장체의 수명과 파양 예측에 오류 발생가능성이 높다 하겠다. 금번 연구는 이와 같은 종전의 경험적인 선형탄성 방법이 아닌 탄성일소성 상태하의 격자(mechano-lattice) 이론이란 새로운 기법을 도입하였다. 특히 마이너(Miner's Law) 이론의 누적손실과 확률을 적용하여 포장체의 피노수명과 손실을 예측할 수 있다. 금번 이론은 실제로 호주 빅토리아주의 멜보른(Melbourne)시 일부 지역구간을 모형으 로 선정되었다. 분석결과 가장 최적화된 도로포장 각층의 두께와 재료 선정을 하기 위하여 일정기간의 교통량, 상대적 손실지수와 잔여응력 및 표면 변위, 대기온도 그리고 습도의 영 향을 종합적으로 고려하여야 한다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.6
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• pp.1193-1202
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• 1989

본 논문에서는 발전소의 소재로 많이 쓰이고 있는 304 스테인리스강(앞으로는 304SS로 표기함)과 316스테인리스강(앞으로는 316SS로 표기함)의 크립 균열 발생 거동 을 각각 600.deg. C와 625.deg. C에서 조사한다. 이 온도는 발전소의 반응기(reactor)에 사용 되는 304SS와 316SS이 받는 온도이다. 즉 304SS와 316SS의 크립 균열 발생을 지배 하는 파괴 매개변수가 무엇인지가 크립 파괴 실험을 통하여 조사된다. 실험 결과는 이미 제안되어 있는 크립 균열 발생 모델에서 예측된 결과와 비교된다. 특히 304SS 와 316SS은 고온에서의 연성도가 변형률 속도에 따라 변하는 것으로 알려져 있다. 본 연구에서는 '변형률 속도에 따른 재료의 연성도의 변화에 근거한 균열 발생 모델' 을 제안하고, 그 모델에서 예측된 크립 발생 거동을 실험 결과와 비교한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2094-2097
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• 2007

본 연구에서는 사석경사제의 전면부에 불투과성 수중방파제를 설치하여, 불규칙파의 반사에 대한 수치모의와 수리모형실험을 수행하였다. 수치해석 모형에는 Reynolds Averaged Navier-stokes (RANS) 방정식을 지배방정식으로 사용하였고, 난류해석을 위하여 $\kappa-\varepsilon$ 방정식을 사용하였다. 자유수면변위의 정확한 예측을 위하여 VOF 기법을 적용하였다. 수리모형실험은 한양대학교 수리실험실의 조파수로에서 수행되었다. 본 연구에서는 입사파랑으로 불규칙파를 조파하였으며, Bretsch neider-Mistuyasu 스펙트럼을 목표스펙트럼으로 하여 재현하였다. 반사율의 산정에서 입사파와 반사파를 분리하기 위하여 수치모형실험에서는 3점법을 사용하였고, 수리모형실험에서는 2점법을 사용하였다. 수치모의를 통하여 예측된 반사율과 수리모형실험에서 관측한 결과는 서로 잘 일치하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.5
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• pp.51-60
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• 2009

To secure the structural safety of structures and members against earthquakes, the plastic deformation capacity demand of members should be accurately predicted. In the present study, a method for the evaluation of the plastic deformations of members for moment frames was developed. To facilitate the practical use of the proposed method in equivalent seismic design, the plastic deformations of members were evaluated based on the results of elastic analysis, without using nonlinear analysis. The plastic deformation demands of members were formulated as functions of story drift demand, redistributed moment and member stiffness. Story drift demand and moment redistribution were directly determined from elastic analysis. The proposed method was applied to an 8 story-2 bay moment frame, and the predicted plastic deformations were verified using nonlinear analysis. The results showed that the proposed method could be used to accurately predict the member plastic rotations with simple calculations. The proposed method can be applied both to the earthquake design of new structures and to the performance evaluation of existing structures.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.3
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• pp.135-142
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• 2009

The initial free surface profile and energy of a tsunami are closely related to the wave heights of a tsunami in nearshore and can be determined by using the earthquake parameters. Along the Western coast of Japan, the possibility of a tsunami triggering by undersea earthquakes is very high. Many seismologists have attempted to predict the parameters of earthquakes that could occur in these regions, but it is difficult to accurately predict them. As such, several case studies have been conducted involving behaviors of an unexpected tsunami that occurred in this region. If a relationship between the earthquake parameters and the wave heights of a tsunami is found, it would be easier to examine the effects of the tsunami. In this study, several virtual tsunami events have been simulated, and the wave heights of the tsunami are computed by varying the earthquake parameters to examine the relationship between the earthquake parameters and the tsunami wave heights. Numerical simulations have been conducted in virtual topography.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.655-660
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• 2007

A canard-leading edge flap deflection scheduling laws have been established to enhance the maneuverability of the canard type fighter class aircraft. These scheduling laws are the relation of canard-leading edge flap deflections and flight conditions to maximize the lift-drag ratio. For these purposes, the corrected supersonic panel method has been used to predict the lift-drag characteristics due to canard-leading edge flap deflections. In addition, the high speed wind tunnel test has been conducted with 1/20 scale model to validate the predicted scheduling laws. Good agreements have been obtained compared with the results of high speed wind tunnel test. Based on the results obtained from the experimental and numerical studies, the corrected supersonic panel method has shown to be useful to establish the canard-leading edge flap deflection scheduling law for the aerodynamic design of canard type fighter class aircraft.

• Geotechnical Engineering
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• v.14 no.2
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• pp.93-106
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• 1998

The behavior of axially loaded pile was analyzed by two methodologies: one is the finite difference method using load transfer curves recommended by API(1993) , and the other is the numerical analysis using the FLAC program. From both analyses, load-displacement curves and load distributions along the depth were evaluated appropriately for the measured. The analysis using the FLAC could capture the nonlinearity of load-displacement curve even for unloading and reloading cases, since the unloaded stress paths of fill layer elements occurred on the failure envelop. Futhermore, the measured load transfer curves were compared with the API recommendations and with the calculations obtained front the results of the FLAC analysis for the interpretation of the transfer behavior between the soil and the pile under axial loadings. It was concluded that the atrial behavior of open ended piles at Pusan could be evaluated by both the finite difference analysis using API load transfer curves and the numerical analysis using FLAC.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.291-299
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• 2003

The effect of temperature and soil confining stress on geosyntheic creep behaviour was studied by performing the temperature dependent confined creep tests for HDPE geogrid and geomembrane specimen. The visco-elastic creep coefficients of the geosynthetics were evaluated by the test results and it was proposed that the simple expressions for the instantaneous and limit creep strain of geosynthetics was considered as a function of temperature and confining stress on geosynthetics. Based on the time-temperature superposition principle, a master curve has been drawn for extrapolating tensile creep strains to longer time intervals(1$\times$10 $^7$min.∼1$\times$10$^{10}$min.). By using this master curves, the shift factors which can be used in establishing master curve considering confining stress on geosynthetics were carried out. Each tests was performed during 8,000∼12,000 min., with temperature ranging between 5$^{\circ}C$ and 4$0^{\circ}C$ and with confining stress ranging between 0 t/$m^2$ and 9 t/$m^2$.