• Journal of Korean Association for Spatial Structures
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• v.6 no.2 s.20
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• pp.85-92
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• 2006

Precast large panel structures have various connection system such as the horizontal slab-to-wall connection, the vertical wall to wall connection, horizontal slab-to-slab connection, etc. Horizontal connection is connected by vertical tie bars, and vertical joint is connected loop bars and shear keys. The basic function is equalized deformations on later forces and the entire wall panel assembly acts as monolithic actions. Under lateral load some slip occurs in almost vertical connections. The shape and detail of precast connections are very important to the monolithic behavior of overall structures. The paper is a study on the design method and new elasto-plastic analysis of the connections by rigid-bodies spring model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1169-1173
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• 2000

최근에 미국에서는 실선에 대한 충격파 실험의 제약으로 인하여 수치시뮬레이션의 필요성이 더욱 야기되어 1996년도부터 수상함에 대한 실험대체용 수치계산의 가능성에 대한 연구가 시작되었다. 잠수함등과 같이 잠겨진 구조물에 대한 연구는 활발히 이루어졌으나 수상함에 대한 연구는 단순구조물을 대상으로 한 제한적 연구가 이루어져 왔다. 특히 본 연구에서는 아주 복잡한 수상함 구조물을 최대한 정확히 유한요소법으로 모델링하였다. 이러한 실선 충격연구는 실제 실선에 마운트되는 주요 장비의 안정성평가에 아주 중요한 자료를 제공하여주므로 시급한 과제이다. 하지만 수상함의 경우 유체-구조물 상호작용, 자유표면, cavitation등과 같은 해석상의 어려움과 복잡한 구조물의 모델링시 나타나는 현 단계에서의 계산상의 한계 등등 여러 가지 난제가 존재하고 있는 것도 사실이다. 본 논문에서는 수상함 내충격 수치해석의 현기술을 알아보고 수치계산의 발전방향을 제시보고자 한다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.177-184
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• 2002

The concrete median barriers are the most popular safety appurtenances that can be installed on narrow medians and are effective in keeping uncontrolled vehicles from crossing into opposing lanes of traffic. It is necessary to install and maintain median barriers because it is very difficult to reserve enough room required for medians in KOREA. And concrete median barriers are accepted as the actual alternatives for median barriers, mostly because they require almost no maintenance even after serious collisions. Typical concrete median barriers are 810mm high and have 596mm high glare screens on top of them. But we have experienced a number of “climb” and “roll-over” accidents of heavy vehicles until now, and most of all, there have been some serious accidents caused by the part of broken glare screens. We have performed many computer simulations for the evaluation of the crashworthiness of concrete median barriers, and through the simulations we have tried to find a proper type of concrete median barrier.

• Computational Structural Engineering
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• v.10 no.4
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• pp.12-21
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• 1997

차량충돌에 대하여 운전자의 안전확보를 위하여 새로 개발한 철재 중앙분리대에 대한 안전성 분석을 위하여 인체모형을 탑재한 실물차량 충돌실험을 실시하였다. 인체모형의 두부와 흉부, 대퇴부 및 차량의 무게중심점에서 가속도와 충격하중을 계측하여 철재 중앙분리대 방호울타리에 차량충돌시 운전자의 안전성을 검증한 결과 다음과 같은 결론을 도출하였다. 1) 철재 중앙분리대 방호울타리는 콘크리트 중앙분리대 방호울타리에 비해 운전자의 신체 상해치와 차량파괴 등에 있어서 뛰어난 충격흡수성능을 보여주었다. 2) 철재 중앙분리대 방호울타리는 콘크리트 중앙분리대 방호울타리의 경우 빈번히 발생하는 차량전복과 같은 2차사고의 유발 가능성이 전혀 없는 구조적 안정성을 보여주었다. 3) 경량의 차량충돌에 대하여 자체 탄성영역내에서 충격을 흡수하여 유지보수 측면에서 유리함을 나타냈다. 4) 충돌 수 충돌차량에 대한 차량유도성능이 뛰어났으며, 차량의 충돌후 이탈각도는 충돌각도의 60% 이내로 나타났다. 5) 철재 중앙분리대 방호울타리로부터 분리된 파편이 거의 없어 도로소통에 지장을 초래하지 않는다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.37-37
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• 2008

고온에서 안정적인 DLC막을 성막하기 위해 PECVD공정에서 실리콘을 첨가하여 제조하였다. 기존의 실리콘첨가 DLC막과는 다르게 고온에서 생성됨으로 마이크로 클러스터 형태의 DLC구조로서 disordered 영역이 넓게 존재하고 있어 I(D)/I(G)비에서의 변화가 있는 것이 관찰되었다. 실리콘 양이 증가할수록 값이 낮아지는 것이 관찰되는데 이는 실리콘량이 증가하면서 수소의 위치에 실리콘이 결합하면서 sp3 단일구조형태의 코팅 막을 만드는 것이 관찰된다. 고온 어닐링효과로 내부구조에서 다량의 sp2구조가 관찰되는 것으로서 DLC막이 어느 정도 흑연화되지만, 실리콘이 SiC에서 SiOx로 $SiO_2$와 SiOH막으로 바뀌는 면서 마찰계수가 낮은 DLC막을 유지할 것으로 기대되며, XPS와 FT-IR분석에 의해 이러한 상들의 존재를 관찰할 수 있었다. 특히 공정상 TMS이 증가하면 첨가된 Si에 의해 형성되는 막이 초기부터 OH기를 다량 포함하고 있는 것을 알 수 있었고, 온도 상승에 의해서 실리콘표층에 더욱 많은 SiOx계열의 물질이 생성되는 것이 명확하게 발견되었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.35-43
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• 2006

In this paper, procedures and research results involved in the development of glass reinforced composite bridge deck of hollow section were presented. Laminate design for the 3 cell deck section was performed. Structural characteristics such as serviceability, strength, failure and stability for DB24 load were analytically studied through the finite element analysis for the composite deck plate girder bridge. Composite deck tube was fabricated with pultrusion and extensive tests such as flexural test, girder-connection test, barrier-connection test, compression fatigue test and flexural fatigue test were carried out to evaluate structural behavior experimentally. Also, field load test was conducted for the demonstration plate girder bridge with composite deck and requirements for the strength and serviceability were reviewed.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.5
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• pp.601-607
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• 2006

This paper proposes a novel balance control scheme of a biped robot to predict the next position of ZMP using Kalman Filter. The mathematical model of the biped robot is generally approximated by 3D-LIPM(3D-Linear Inverted Pendulum Mode), but it cannot completely express the robot's dynamics. The stability of the biped robot depends on whether the ZMP(Zero Moment Point) position is in the stability region or out of. And the internal error between the robot mechanism and its model could affect the stability of a robot. Therefore, the proposed balance control not reduces the internal error, but also timely generates the proper control. The experiment of the proposed balance control is simulated on the virtual workspace where the biped robot may encounter with various difficulties.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.5
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• pp.9-17
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• 2010

In this paper we propose an improved hierarchical routing protocol for wireless hybrid mesh network. The proposed method efficiently manages network topology and reduces overhead traffic for setting routing path by considering link stability. The simulation results show that the proposed method outperforms the HOLSR (hierarchical optimized link state routing) method in aggregate goodput, packet delivery ratio, and end-to-end delay.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.453-460
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• 2016

Offshore wind turbines are divided into an upper wind turbine and a lower support structure. Offshore wind turbine system is required to secure high reliability for a variety of external environmental conditions compared to ground wind turbines because of additional periodic loads due to ocean wave and current effects. In this study, extreme load analyses have been conducted for the designed offshore wind turbine foundation with weight control functionality using computational fluid dynamics (CFD) then structural analyses have been also conducted to investigate the structural design requirement.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.707-716
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• 2006

The optimization of the direct design system of semi-rigid steel frames using advanced analysis and genetic algorithm was presented. Advanced analysis can predict the combined nonlinear effects of connection, geometry, and material on the behavior and strength of semi-rigid frames. Geometric nonlinearity was determined using stability functions. On the other hand, material nonlinearity was determined using the Column Research Council (CRC) tangent modulus and parabolic function. The Kishi-Chen power model was used to describe the nonlinear behavior of semi-rigid connections. The genetic algorithm was used as the optimization technique. The objective function was assumed as the weight of the steel frame, with the constraint functions accounting for load-carrying capacities, deflections, inter-story drifts and ductility requirement. Member sizes determined by the proposed method were compared with those derived using the conventional method.