• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.693-696
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• 2011

본 논문에서는 레벨셋 방법을 이용하여, 소음을 차단하기 위한 음향 구조물의 형상 최적 설계를 수행하였다. 음향 결정 구조에서는 음향이 흩어져 있는 결정 구조에 의해서 굴절되기 때문에 결정 모양을 조정함으로써, 음향 거동을 제어 할 수 있다. 형상 최적 설계의 목적은 특정한 각도와 각속도로 입사되는 입사파에 대해서 음향 투과율(acoustic transmittance)이 최소가 되도록 음향 결정의 형상(inclusion shape)을 결정하는 것이다. 음향 압력(acoustic pressure)은 주기성을 갖는 음향 결정에 대해서 헬몰츠(Helmoltz)형태의 지배 방정식을 풀어서 얻을 수 있다. 본 연구에서는 음향 구조물로 결정이 수평 방향으로는 주기적으로 무한히 분포하고 수직방향으로는 유한한 층간 구조를 가지고 있는 소음 방어벽 (Noise barrier)을 고려한다. 결정의 위치는 고정되어 있고, 결정의 형상을 설계 변수로서 음파의 거동을 제어할 수 있도록 하였다. 주기적 구조물을 고려하기 때문에 결정의 좌와 우에 Bloch 이론을 적용해 주기적 경계조건을 부과하였고, 소음 방어벽 위와 아래에는 임피던스 행렬(impedance matrix)를 이용하여, 무한 균질 영역과 소음 방어벽사이의 음파 투과를 모사하였다. 복잡한 형상 변화를 표현하기 위해 임시적 경계를 이용한 레벨셋 방법을 사용하였다. 설계 민감도 해석을 통해 목적함수가 감소하는 방향으로 경계에서의 수직 벡터를 계산하고, 이를 헤밀턴-자코비(Hamilton-Jacob) 방정식에 대입하여, 최적의 형상을 나타내는 레벨셋 함수를 구하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.23-32
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• 2012

Research on steel plate concrete (SC) structures for the modularization of nuclear power plants have been performed recently in Korea. In this study, the seismic capacity and stiffness characteristics of unstiffened SC shear walls under the effects of earthquakes were investigated through static pushover tests. Failure modes, sectional strength, and stiffness characteristics of SC structures under lateral loads were inspected by analyzing the experimental results. The strengths obtained by the experiments were also compared with those derived by the design code of the SC structures. One of the main failures of unstiffened SC shear walls was found to be the type of bending shear failure due to the debonding of the steel plate at the concrete interface. The ductility capacity of SC structures was also confirmed to be improved, which is considered to be a confining effect on steel plates in the longitudinal behavior of SC structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.145-152
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• 2011

Current Bridge Specification for Highway Bridges adopts a simplified method to determine sectional forces of abutment wing by dividing its area into four sections. This simplified method was developed in Japan when numerical analysis was not mature and computer resources were expensive. This simplified method has been with us without modification. This study evaluates the problem of current design practice to improve the design guideline for abutment wing. In this study, a finite element model of abutment wing based on shell elements was developed to obtain accurate sectional force. In addition, foreign design specifications regarding abutment wing were thoroughly examined. It has been observed that sectional forces obtained from the simplified method produce inaccurate results under various geometric shapes. Thus, it is recommended that two dimensional plate analyses should be adopted for future design of abutment wing wall.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.17-26
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• 2010

This study presents a decision making process for installation of wind barrier which is used to reduce the wind acting on running vehicle on expressway. At the first stage of this study, the lateral deviations of running vehicles under side winds were computed from the commercial softwares, CarSim and TruckSim, and then the critical wind speeds for car accident were evaluated from predefined risk index. To determine whether it is needed to install wind barrier or not, cost and benefit from wind barrier are calculated during lifetime. In obtaining car accidental risk, probabilistic distribution of wind speed, daily traffic volume, mixture ratio in the volume, and duration time for wind speed range are considered. It is recommended to install wind barrier if benefit from the barrier installation exceed construction cost. In the numerical examples, case studies were shown for risk and benefit calculation and main risky regions on Korean highway were all evaluated to identify the number of installation sites.

• Journal of the Korean Vacuum Society
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• v.17 no.6
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• pp.576-581
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• 2008

High-quality double-walled carbon nanotubes (DWNTs) were synthesized without defects and amorphous carbonaceous particles by catalytic decomposition method at $800^{\circ}C$ in high yield. As-synthesized carbon materials almost consist of DWNT bundles with a diameter 12 - 20 nm.. The DWNTs rope have uniform diameter about 2 - 5 um and length up to several tens micrometer. DWNTs is inner tube diameter 0.9 - 1.5 nm and outer tube 1.6 - 2.2 nm. We investigate the crystallinity of DWNTs by TEM and Raman spectroscopy. We also found that the Fe-Mo bimetallic catalyst was active as a very efficient catalyst for the synthesis of DWNTs with the catalyst decomposition method. Our results also indicate that Tetra Hydro Furan (THF) is a very ideal carbon source for the synthesis of DWNTs.

• Explosives and Blasting
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• v.28 no.2
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• pp.76-85
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• 2010

In this paper, we present the result of an analytical investigation concerning the demolition range for the pre-weakening of load-bearing wall in explosive demolition. Pre-weakening of load-bearing wall is usually conducted based on field experience because reliable specifications or guidelines for the design of pre-weakening have not yet been established in Korea. This study is one of the efforts to develop such a reliable specification or guideline for the pre-weakening process. Hence, the focus of the study is on the estimation of pre-weakening range of load-bearing wall. For the purpose, a finite element analysis (FE analysis) was conducted, and a pre-weakening range of load-bearing wall was suggested based on the analysis result.

• Digital Contents
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• no.5 s.48
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• pp.16-17
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• 1997

한국정보보호센터(KISA)가 3월 14일 방화벽 시스템의 평가기준안에 대한 설명회를 개최했다. 국내 방화벽 관련 업체 관계자들이 참석한 이 설명회에서 KISA는 보안기능과 보증에 대한 요구사항을 기본 구조로 평가등급을 7단계로 분류하여 현재 시장에 유통되고 있는 방화벽에 등급을 부여하겠다는 것을 확실히 했다. 이러한 세부적인 평가기준안이 나옴에 따라 그동안 외산방화벽을 수입ㆍ공급해왔던 업체들은 이 평가기준안에 따른 보다 나은 평가등급을 받기 위한 대책마련에 고심하고 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.99-103
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• 1990

도로망의 확충과 교통량의 급속한 증가에 따른 교통소음 증가는 연도주민에 게 생활방해를 심화시키고 있다. 이를 저감시키기 위한 방지대책의 일환으로 전파경로상에 방음벽이 설치되고 있으나, 이의 설치부서가 서로 다르고, 또 한 소음피해지역 주민의 공간분포와 도로구조 및 교통특성등을 정량화하여 종합적으로 반영하지 않고 설계.시공하고 있어 방음벽 효과를 크게 기대할 수 없는 실정이다. 따라서 본고에서는 방음벽의 효과를 제고하고 규격의 통 일성을 기할 수 있는 방안 등에 관하여 살펴보고자 한다.

• Magazine of the Korea Concrete Institute
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• v.5 no.2
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• pp.162-170
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• 1993

축력과 횡력을 받는 전단벽의 휨과 전단 거동을 분리산정하기 위하여 R/C 전단벽에 관한 실험 결과에 대해 System Identification을 행한다. 이를 토대로, 전단벽의 강도 저하 계수 'R'과 극한 회전능력을 구하는 실험식을 제안한다. R/C뼈대구조-전단벽에 대한 비탄성 해석 유한요소 컴퓨터 프로그램(IDARC)을 이용하여 전단벽의 지진 이력 거동을 재현한다. Identification 결과를 Digitize한 실험 결과와의 비교에 의해 검증하고, 총변형으로부터 휨과 전단에 의한 변형요소를 해석적으로 분리 함으로서 비탄성 전단 거동과 강도 저하 계수 'R'의 산정이 가능해진다. 또한 실험 결과에 대한 회귀 분석을 통하여 전단벽의 극한 회전 능력에 대한 실험식이 얻어진다.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.175-176
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• 2010

Current Bridge Specification for Highway Bridges adopts a simplified method to determine sectional forces of abutment wing by diving its area into four sections. This simplified method was developed when numerical analysis was not mature and computer resources were expensive. It has been criticized that the simplified method produces conservative results. This study evaluates the problem of current design practice to improve the design guideline for abutment wing.