• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2011.04a
• /
• pp.660-663
• /
• 2011

폭발하중은 매우 짧은 시간 내에 순간적인 높은 압력으로 발생된다. 따라서 폭발하중을 받는 구조물은 매우 복잡한 순간 동역학적 손상 거동을 나타낸다. 이러한 외부 하중에 대한 실험적 연구는 큰 비용, 시설, 그리고 군사적 보안 문제가 요구되기 때문에, 고성능 컴퓨팅 기술을 이용한 수치적 기법을 통해 구조물의 동적 비선형 해석을 수행하였다. 수치해석의 정확성을 높이기 위해 폭풍파와 같은 대기전파의 경우 Euler 기법, 콘크리트 재료의 경우 Lagrange 기법을 적용한 복합적 수치해석 (multi-solver coupling) 기법이 적용되었다. 제안된 수치해석 기법은 explicit 유한요소해석 프로그램인 AUTODYN을 이용하여 수행되었다. 그리고 클러스터 (cluster) 내 병렬 알고리즘 (parallel algorithm)을 이용하여 수치해석의 효율성을 높였다. RC 구조물의 수치해석 결과, 기존 실험 결과와 비교하여 잘 일치되었다. 또한 영역분할 개수가 증가할수록 수행시간은 감소되었고 Speed-up과 효율성은 높아졌다.

• Journal of the KSME
• /
• v.22 no.1
• /
• pp.9-14
• /
• 1982

복합재료를 이용하여 부품제작을 한 후 어떠한 결합방법을 채택할 것인가를 결정할 때 고려해 야할 점을 기계적 결합법과 접착결합법을 비교하여 검토하였다. 기계적 결합은 하중을 많이 받고 분해 및 결합이 자주 예상되는 부품에 채택해야 할 것이며 복합재료의 특성을 고려하여 보강 시에 부착하는 평판의 섬유방향은 가급적 드릴구멍주위를 부드럽게 하여 응력집중을 낮출 수 있으며 하중의 종류에 따라 적층의 섬유방향을 조절함으로서 응력집중을 조절할 수 있다. 드릴 구멍 주위인 파손은 평판의 폭과 구멍의 직경등이 크게 작용함으로 강도해석을 할 경우에 응력 해석을 한 후 허용응력등을 결정해야할 것이다. 접착졀합법은 작업이 간단하나 신뢰도가 떨어지 므로 하중을 많이 받는 구조물에의 사용에 주의를 요하며 설계방법도 매우 다양하게 제안되어 있어 선택함에 있어 하중 환경조건등을 점검해야할 것이다. 접착결합법은 드릴구멍같은 불연속 성을 갖지 않기 때문에 응력집중이 생기지 않으나 접착층의 길이등 기하학적 형상에 따라 다르게 나타남으로 잡착층의 분리가 일어나지 않도록 설계되어야 한다. 특히 복합재료의 이방성인 성 질을 감안하여 접착층에 이웃하는 피접착층의 섬유방향에 주의해야 하며 층간응력이 파손에 미 치는 영향을 고려하여 설계에 임해야 한다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.18 no.5
• /
• pp.499-509
• /
• 2016

In recent years, the use of underground spaces becomes more frequent and the demands for urban tunnels are rapidly increasing. The urban tunnels constructed in the ground with a shallow and soft cover might be deformed in various forms on the face, which would lead, the tunnels to behavior 3-dimensionally, which may have a great impact on the longitudinal load transfer. The tunnel face might deform in various forms depending on the construction method, overburden and the heterogeneity of the ground. And accordingly, the type and size of the distribution of the load transferred to the ground adjacent to the tunnel face as well as the form of the loosened ground may appear in various ways depending on the deformation form of the tunnel face. Therefore, in this study was conducted model tests by idealizing the deformation behavior of the tunnel face, that were constant deformation, the maximum deformation on the top and the maximum deformation on the bottom. And the test results were analyzed focusing on the deformation of the face and the longitudinal load transfer at the ground above the tunnel. As results, it turned out that the size and the distribution type of the load, which was transferred to the tunnel as well as the earth pressure on the face were affected by the deformation type of the face. The largest load was transferred to the tunnel when the deformation was in a constant form. Less load was transferred when the maximum deformation on the bottom, and the least load was transferred when the maximum deformation on the top. In addition, it turned out that, if the cover became more shallow, a longitudinal load transfer in the tunnel would limited to the region close to the face; however, if the cover became higher than a certain value, the area of the load transfer would become wider.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.33 no.1
• /
• pp.1-7
• /
• 2020

The wind responses of twin buildings are determined by the characteristics of wind loads and the dynamic characteristics of the structural systems of the buildings. In this study, the characteristics of wind pressure that influence wind responses were identified for two different spacings between the twin buildings using a wind tunnel test and the proper orthogonal decomposition (POD) method. Structural dynamic characteristics were also identified using 3D structural system modeling. The double modal transformation method was utilized to evaluate the characteristics of wind pressure for across-wind and along-wind conditions and the effect of the dynamic characteristics of each structure on the wind responses. The channeling and vortex effects were identified through the POD method. Across-wind loads were significantly affected by the spacings between the twin buildings, whereas along-wind loads were minimally affected. Similarly, while using the double modal transformation method, a significant difference was noticed in case of the cross-participation coefficients in the across-wind direction condition for the different spacings between the buildings; however, the along-wind direction condition showed negligible difference. Therefore, the spacing between the two buildings plays a more important role in across-wind responses compared to along-wind responses.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.25 no.1
• /
• pp.19-26
• /
• 2012

In this study the progressive collapse behavior of a moment frame with infill steel panels is evaluated using nonlinear static pushdown analysis. The analysis model is a two story two span structure designed only for gravity load, and the load-displacement relationship is obtained with the center column removed. To obtain local stress and strain as well as the global structural behavior, finite element analysis is conducted using ABACUS. Through the analysis the effect of the span length and the thickness of the steel plate on the progressive collapse behavior of the structure is investigated, and the effect of the dividing the infill panel using stud columns is also studied. According to the analysis results, the thickness of the panels required to prevent progressive collapse increases as the span length increases, and as the number of panel division increases the progressive collapse resisting capacity increases slightly but the effect is not significant. It is also observed that when the infill panel is installed in only a part of the span the progressive collapse resisting capacity is somewhat increased.

• Journal of the Korea Institute of Building Construction
• /
• v.15 no.3
• /
• pp.273-280
• /
• 2015

In this study, tests were carried out to find out a method to ensure the fire resistance performance of high-performance non-refractory coating CFT columns. For the high performance concrete fabrication with 100MPa, blast furnace slag(BS) and steel and nylon fibers were used. It was found that the partial replacement with BS improved the fire resistance performance of the concrete. Based on the results of lab tests, the large fire test was conducted. For this test, the CFTs with the size of ${\phi}500{\times}4,200mm$ and the reinforcement of SS 400 steel were prepared and they were subjected to a loading condition. It was found that as the level of load increased, the level of fire resistance decreased. For example, In with the loading condition of 2000kN the CFT could resist the fire for over 240 minutes, whereas, with the loading condition of 3,000kN and 4000kN applying to equivalent CFTs, the resisting time against fire were 184 minutes, and 120 minutes, respectively.

• Aerospace Engineering and Technology
• /
• v.1 no.1
• /
• pp.1-7
• /
• 2002

This paper describes the analysis method about the dynamic characteristics and vibratory load through HDS(Helicopter Design Study). To analyze the dynamic characteristics of helicopter rotor blade, the natural frequencies and modes are calculated according to rotor operational speed(Ω). Generally the proximity of rotor natural frequency and N times of rotor operational speed is a dominant component to determine the helicopter vibration. Also we can predict the airframe vibration by calculating the airload of rotating blade exactly. We expect to establish the design procedure of rotor dynamics by describing the two major analysis methods necessary to rotor design.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.1C
• /
• pp.53-63
• /
• 2010

Since the water retention curve is considered as a major parameter to evaluate the unsaturated ground or soils, overburden pressure and clay content on soils underneath ground surface have not been considered for estimating water retention characteristics. Therefore, a need exists that the effect of overburden pressure and clay content on water retention characteristics was assessed in typical weathered soils found in Korea. Soil-Water Characteristic Curve and the unsaturated hydraulic conductivity were estimated using water retention characteristics under the condition of different overburden pressure, clay content, and de-saturation path. Then, these effects are evaluated with the results of SWCC tests from the laboratory. In addition to that, the unsaturated moisture capacity and diffusivity of each case is discussed.

• Proceedings of the ESK Conference
• /
• 1995.04a
• /
• pp.97-105
• /
• 1995

본 연구의 목적은 드는 작업에 있어서 한국 작업자의 적정하중을 구하여 중량물 안전기준을 정하는 것이다. 본 연구에서는 주어진 작업조건하에서 피실험자가 들어올릴 수 있는 적정하중을 결정하기 위 한 기준으로서 피실험자 자신에 의해서 인지되는 스트레스 정도를 이용하는 심리육체적 방법(Psychophysical method), 주어진 작업조건하에서 요추에 가해지는 압력을 이용하는 생체역학적 방법(Biomechanical method), 주어진 작업조건하에서 피실험자의 에너지 소모량을 이용하는 생리학적 접근법등이 이용되었다. 피실험자는 학생(n=3) 두개의 군으로 나뉘어진다. 실험에 들어가기 전에 피실험자에 대한 인체측정과 근력측정을 수행 하였다. 실험은 수직면에서 드는 빈도(1,2, 와 4회/분)와 드는 높이(0-8cm 와 47-102cm)를 조합한 6가지의 작업을 무작위로 선택하여 심리육체적 방법으로 각 작업에 대한 적정하중을 구하였다. 연구결과로서 피실험 자의 신체자료와 근력의 비교로부터 신체조건은 학생이 우수하였으나, 근력은 작업자가 우수하였다. 본 연구 에서 채택된 들기의 빈도가 변함에 따라 최대허용 하중은 변하였다. 작업자군에 대하여는 빈도가 증가할수록 최대허용 하중은 감소하였으며, 학생군에 대하여는 분당 1회와 분당 4회간의 유의한 차이가 있었다. 들기의 시작-종점의 변화에따른 최대허용 하중은 통계적으로 유의하지 않았다. 위의 두 결과는 들기의 빈도가 들기의 시작-종점보다 민감한 변수임을 가리키며 이는 미국 NIOSH의 결과와 일치한다. 심리육체적 방법을 사용하여 우리나라의 젊고 건강한 남성의 대부분(99%)을 고려하여 산출된 최대허용 하중은 미국 NIOSH 안전기준과 큰 차 이가 없음을 발견하였다. 또한 이 최대허용 하중은 인체역학적방법과 생리학적 방법을 사용하여 검토한 결과, 무리가 없는 수준임이 입증되었다. 본 연구의 결과를 토대로우리나라 젊고 건강한 남성에게 적합한 무게상수는 작업자군에 대하여 25.05kg, 학생군에 대하여 20.24kg 으로 나타나 이는 미국 NIOSH 안전기준과 대체로 일치함을 발견하였다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.5
• /
• pp.2403-2407
• /
• 2012

Finite number of pile elements are considered in load transfer method. And section force and movement of each pile element are computed by considering compatibilities between pile displacement and the load transfer along a pile and between displacement and resistance at the tip of the pile. For the conventional load transfer method, large amount of computations due to iterations are needed. Formulation of finite difference equation from the differential equation which depicts pile behavior under axial loading was accomplished in order to simplify the computation for obtaining pile section forces and displacements. By comparing the results between the simplified computation method and the reported data, there was no difference between the two results.