• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.493-502
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• 2001

This paper describes a seismic design procedure for rib-reinforced RBS(Reduced Beam Section) steel moment connections. Engineers often use rib plates to enhance seismic performance of steel moment connections. thinking that the 2nd moment of inertia is increased so that the tensile stress in the beam flange groove weld is reduced However the force transfer mechanism in the rib connections is completely different from that as predicted by the classical beam theory ; a clear diagonal strut action is present in the rib. By treating the rib as a strut the writer has recently proposed an equivalent strut model that could be used as the basis of a practical design procedure. In this paper the proposed equivalent strut model is briefly presented first. A step-by-step design procedure is then recommended based on the proposed model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.3
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• pp.267-275
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• 2009

This paper presents the p-convergent coupling element on the basis of the ESSE(equivalent single layer shell element) and the PLLE(partial-linear layerwise element) to analyze laminated composite plates. The ESSE is formulated by the degenerated shell theory, on the other hand, the assumption of the PLLE is piecewise linear variation of the in-plane displacement and a constant value of lateral displacement across the thickness. The proposed finite element model is based on p-convergence approach. The integrals of Legendre polynomials and Gauss-Lobatto technique are chosen to interpolate displacement fields and to implement numerical quadrature, respectively. This study has been focused on the verification of p-convergent element. For this purpose, various finite element multiple models associated with the combination of ESSE and PLLE elements are tested to show numerical stability. The simple examples such as a cantilever beam subjected vertical load and a plate with tension are adopted to evaluate the performance of proposed element.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.8
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• pp.961-966
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• 2013

A coupled governing equation of thermoelectric materials can be converted into an uncoupled form to predict the effective Seebeck coefficient of thermoelectric composites, where modified Eshelby model is adopted. The predicted results by the present approach for serial- and parallel-connected composites and composite with spherical inclusions are compared with theoretical and experimental results from literatures to be justified. It is shown that the predictions by the theoretical approaches coincide exactly and show in good agreement with the experiments.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.6-21
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• 2008

We have investigated the effect of the forward and reverse ESD pulse accumulation on the development of the oxide VCSEL's electrical and optical characteristics. The forward ESD-induced degradation is complicated, showing three degradation phases with increasing ESD voltage while the reverse ESD-induced degradation is divided by a sudden distinctive change in elecorl-optical characteristics. By comparing the measured L-I-V characteristics and their derivatives with the fitted characteristics using an equivalent circuit model as well as the large signal circuit model, the development of the oxide VCSEL's electro-optical characteristics under forward and reverse ESD conditions has been fully understood.

• Journal of the Korean Society for Railway
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• v.11 no.5
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• pp.465-470
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• 2008

Sound transmission characteristics are investigated on the honeycomb panels used for railway vehicles. Equivalent orthotropic plate model and equivalent mass law are applied to predict the sound transmission loss (STL) of the honeycomb panels. The predicted values of the STL are compared with the measured values. The reliability and the limitation of the prediction models are investigated. Coincidence effect and local resonance effect on STL are considered. The result of the study shows that the equivalent orthotropic plate model can be used as a good prediction model, if the local resonance frequency is properly applied. finally, ways to improve the severe STL drop by local resonance are proposed and the effect on the sound insulation performance is analysed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.153-158
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• 1995

보 및 평판의 진동에 대해서 에너지의 손실은 재료감쇠를 이용한 표면감쇠처리나 지지부에서의 감쇠처리에 의하여 증가될 수 있다. 감쇠재료를 이용한 표면감쇠처리의 예로서 보/평판 표면에 접착되는 감쇠 테이프나 코팅등은 아주 효과적임이 입증되었다. 마찬가지로 지지부 감쇠처리는 점탄성재료의 삽입에 의해서 설명될수 있다[1]. 보/평판의 감쇠에 대한 최근의 많은 연구들은 진동하고 있는 보/평판의 표면에 적용하는 감쇠 테이프 혹은 적층형태의 감쇠 처리방법에 대해서 주로 수행되었다. 일반적으로 표면감쇠처리방법은 진동감소에 아주 효과적이지만 실제 적용상에서 항상 가능한 것은 아니며, 이와 같은 경웨는 지지부 감쇠 처리방법에 의존하게 된다[2]. 감쇠특성을 갖는 점탄성재료를 실제로 적용할 때 보/평판의 유한한 길이가 점탄성재료로 지지되며 점탄성재료의 물성치와 치수에 따라서 계의 모우드 매개변수(고유진동수, 계의 손실계수 그리고 모우드형상)가 크게 달라진다. 그리고 이와 같은 계에 대해서는 지지부의 거동보다는 전체 시스템의 고유진동수와 손실계수 그리고 보 영역에서의 모우드 형상에 더 관심이 있으므로 지지부 영역을 집중매개변수(lumped parameter)로 나타내어 계를 해석할 수 있다. 일반적으로 보와 평판의 경계에서는 병진 및 회전방향의 강성 뿐만 아니라 두 강성사이에 연성효과도 동시에 발생하게 되므로 이 항을 고려하여 계를 모델링해야 한다. 본 연구에서는 우선 점탄성 재료에 의한 지지부영역의 등가 강성계수들을 구하고 경계에 강성행렬을 갖는 보의 등가시스템을 얻는다. 그리고 등가시스템의 주파수방정식으로부터 모우드 매개변수에 대한 지지부의 영향을 살펴본다. 또한 시스템이 비교적 복잡한 사각 평판의 진동에 대해서도 동강성행렬법(dynamic stiffness matrix method)을 이용하여 해석하고자 한다. 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.ive structures utilized in Client/server architecture for distribution and cooperative processing of application between server and client this study presents two different data management methods under the Client/server environment; one is "Remote Data Management Method" which uses file server or database server and. the other is "Distributed Data Management Method" using distributed database management system. The result of this study leads to the conclusion that in the client/server environment although distributed application is assumed, the data could become centralized (in the case of file server or database server) or decentralized (in the case of distributed database system) and the data management method through a distributed database system where complete responsi

• Tunnel and Underground Space
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• v.21 no.2
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• pp.117-127
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• 2011

The purpose of this study is to demonstrate the effect of in-situ rock stresses on the deformability and permeability of fractured rocks. Geological data were taken from the site investigation at Forsmark, Sweden, conducted by Swedish Nuclear Fuel and Waste Man-agement Company (SKB). A set of numerical experiments was conducted to determine the equivalent mechanical properties (essentially, elastic moduli and Poisson's ratio) and permeability, using a Discrete Fracture Network-Discrete Element Method (DFN-DEM) approach. The results show that both mechanical properties and permeability are highly dependent on stress because of the hyperbolic nature of the stiffness of fractures, different closure behavior of fractures, and change of fluid pathways caused by deformation. This study shows that proper characterization and consideration of in-situ stress are important not only for boundary conditions of a selected site but also for the understanding of the mechanical and hydraulic behavior of fractured rocks.

• Explosives and Blasting
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• v.38 no.1
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• pp.1-13
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• 2020

Gas explosion accidents are steadily being issued due to increased gas consumption in Korea and foreign countries. To analyze the effects of these gas explosions, a TNT equivalent method is used. In this study, the TNT equivalent was calculated in the event of an explosion due to the volume content in the air of CO, CH₄ and C₂H₄, the typical flammable gases emitted by coal. Also, the peak overpressure and impulse variation with the distance from explosion point were compared and analyzed by gas using the calculated equivalent value of TNT. The upper limit of the TNT equivalent for the three mixed gases is up to five times larger than the other gases mixture. In addition, the peak overpressure and impulse, which are factors of the TNT characteristic curve, are also increasing as the number of gases increases.

• Plant Journal
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• v.9 no.4
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• pp.31-36
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• 2013

In order to extend a hot gas parts replacement cycle of a gas turbine, blade row 1 from low pressure turbine, which has a significant impact on the cycle, has been selected from stored set after one cycle use. Taking into account the status of the first stage moving blade in LP turbine operated more than 27,000 equivalent operating hours(EOH) and the replacement cycle in the same type of gas turbine, the replacement of the high temperature components installed on the GT, a study subject, can be extended from 24,000 to 27,000 EOH.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.2
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• pp.165-171
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• 2013

Due to the difficulty in considering dynamic load in the view point of a computer resource and computing time, it is common that external load is assumed as ideal static loads. However, structural analysis under static load cannot guarantee the safety of design of the structures under dynamic loadings. Recently, the systematic method to construct equivalent static load from the given dynamic load has been proposed. Previous study has calculated equivalent static load through the optimization procedure under displacement constraints. However, previously reported works to distribute equivalent static load were based on ad-hoc methods. Improper selection of equivalent static loading positions may results in unreliable prediction of structural design. The present study proposes the selection method of the proper locations of equivalent static loads to dynamically applied loads when we consider transient dynamic structural problems. Moreover, it is appropriate to take into account the stress constraint as well as displacement constraint condition for the safety design. But the previously reported studies of equivalent static load design methods considered only displacement constraint conditions but not stress constraint conditions. In the present study we consider not only displacement constraint but also stress constraint conditions. Through a few numerical examples, the efficiency and reliability of proposed scheme is verified by comparison of the equivalent stress between equivalent static loading and dynamic loading.