• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.5
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• pp.395-411
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• 2011

This paper presents a new supporting system using steel ribs. In order to perform this research, experimental and numerical studies were performed. In the experimental study, the scaled model tests for the new supporting system consisting of the steel ribs and rock bolts were carried and compared with the conventional existing supporting system. The numerical simulation was carried out to evaluate the new supporting system to verify the experimental results. It was found that the new tunnel supporting system will reduce the tunnel damage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3423-3428
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• 2014

Numerical studies were performed to evaluate the structural safety of a greenhouse under both snow and wind loads. In the case of a wind load, fluid-structure interaction (FSI) method was used to consider the local pressure distributions on the greenhouse-induced by aerodynamic characteristics. The results showed that the maximum stress and deformation occur near the junction of pipe supports and rafters of the roof, where connecting clips are installed. Moreover, the wind load is a more severe condition than a snow load. Overall, these results will be used to design a prefabricated connecting clip with easy installation and low maintenance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1303-1313
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• 2013

In this study, the reference values for the internal forces of the rail supports caused by a wheel load, a unit vertical displacement, a unit end rotation in examination of the serviceability of concrete slab track bridge were obtained. In analysis, the analysis models of which the rail was continuously and discretely supported by elastic springs were used. The internal forces of the rail supports from the analysis were compared with the results provided in the DS 804 regulations and agreed with well. In addition, the effects of the space between the rail supports and the stiffness of fastener on the internal forces of the rail supports were investigated.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.6
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• pp.523-528
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• 2015

As the sizes of mobile phones and watch phones decrease, the joining bolt for the products should also be decreased to a miniature size. However, the miniature-sized bolt has to support sufficient joining and anti-releasing torque to keep the product fastened. In this study, the thread shapes are designed to improve anti-releasing performance of bolts. Especially, when bolt materials is stronger than nut materials, the design of thread shapes is needed, like bolt for wood, to improve the fastening capability. Through the joining and releasing analyses of bolts, the thread shapes for SUS302 bolt and Mg alloy nut are newly designed. It was shown that the newly designed bolt has 20 % higher anti-releasing torque and 35% lower torque loosening slope compared to the standard bolt.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1995.06a
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• pp.54-64
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• 1995

대표적인 대형 베어링인 일체형 볼 베어링과 와기어 레이스형 볼 또는 로울러 베어링의 마찰 특성을 비성형 유한요소 프로그램인 MARC를 사용하여 상호간의 마찰형상에 대한 접촉응력과 마찰력 특성을 비교 해석하였다. 특히 와이어 레이스식 슬루잉 링 베어링은 우수한 마찰특성 때문에 건설기계, 하역기계, 광산기계나 탱크와 같은 국방무기 등에서 널리 사용되고 있다. 접촉면의 변형에 따른 일체형의 볼 베어링은 마찰력과 기울기면에서 와이어 레이스식 베어링에 비하여 크고, 같은 와이어 레이스식 베어링에서는 마찰력의 경우 볼 타입이 로울러 탕입에 비하여 약간 크게 나타났다. 이들의 계산결과를 종합하면 와이어 레이스식 베어링이 일체형 베어링에 비하여 마찰특성이 우수하고, 특히 와이어 레이스 베어링중에서 로울러 타입은 마찰 토오크면에서 균일하기 때문에 베어링을 사용한 제어기능 설계에서 특히 우수한 결과를 제공할 수 있다. 유한요소 해석결과는 기존의 실험결과와 잘 일치하고 있어서 슬루잉 링 베어링의 최적설계에 유한요소 해석의 유용함을 확인하였다. 또한 상부 구조물과 하부 구조물을 연결하기 위한 체결볼트의 구멍은 하중조건에 따라서 구조적 불안정성을 야기할 수 있음도 확인하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.79-84
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• 2003

Cold expansion of fastener holes is a mechanical process widely used in the aerospace industry. This treatment leads to an improvement of fatigue behavior due to the developed compressive residual stresses on the hole surface. Despite its importance to aerospace industries, little attention has been devoted to the accurate modeling of the process. This study is devoted to the modeling and simulation of the residual stress resulting from the cold expansion of two adjacent fastener holes. Simultaneous cold expansion of two adjacent holes lead to much higher compressive residual stress than sequential cold expansion.

• Computational Structural Engineering
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• v.11 no.1
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• pp.161-170
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• 1998

A general formulation of the long cylinder tolerance design for the joint structure is here presented. The aim of this paper is to calculate the tolerance of joint by defining tolerance as a kind of uncertainty and to obtain the robustness of the joint structure. It is formulated on the bases of the minimum sensitivity theorem. The objective function is the tolerance sensitivity for the Von-Mises stress. It also took into full account the stress, displacement and weight constraints. PLBA(Pshenichny-Lim-Belegundu-Arora) algorithm is used to solve the constrained nonlinear optimization problem. The finite element analysis is performed with CST(Constant-Strain-Triangle) axisymmetric element. Sensitivities for design variables are calculated by the direct differentiation method. The numerical result is presented for the cylindrical structure where the joint tolerance is treated as random variables.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.471-478
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• 2000

For many decades, the railway was constructed using tracks with jointed rails of relatively short lengths. The joints cause many drawbacks in the track and lead to signeficant maintenance cost. so, railroad engineers became interested in eliminating joints. Continuous welded rail(CWR) track has many advantages over the conventional jointed-rail track. but, in the case of the elimination of rail joints, it may cause the track to be suddenly buckled laterally by thermal loads. In this paper, firstly, 3-D CWR track model and CWRB program exactly considering the influence of tie are developed far linear static and buckling analysis using finite element method. Characteristics of CWR track model are using 7-dofs beam element as rail, Offset technic exactly considering centroid axies difference of track components(rail, rail-pad-fastener, tie), and Thermal gradient considering thermal difference of top flange and bottom flange in rail section.. second,, Through the static and linear buckling analysis by CWRB, Influences of various track components (rail, ballast, fastener, tie and so on..) on CWR track behavior and stability was characterized.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.37-45
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• 2018

A two-axis gimbal-type antenna for a Compact Advanced Satellite (CAS) is used to efficiently transmit high resolution image data to a ground station. In this study, we designed the structure of a two-axis gimbal-type antenna while applying a launch lock device to secure its structural safety under a launch environment. To validate the effectiveness of the structural design, a structural analysis of the antenna was performed. First, a modal analysis was performed to investigate the dynamic responses of the antenna with and without the mechanical constraints of the launch lock device. In addition, a quasi-static analysis was performed to confirm the structural safety of the antenna structure and bolt I/Fs between the antenna base and the satellite. The suitable range of constraint force on the launch lock device was also determined to ensure the structural safety and mechanical gapping of the ball & socket interfaces, which places multi-constraints on the azimuth and elevation stage of the antenna.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.2
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• pp.74-85
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• 2016

Seismic design of modular structures is usually carried out under the assumption that their load-carrying mechanism is similar to that of traditional steel moment-resisting frames(SMRFs). However, the load carry mechanism of modular structures would be different with that of traditional SMRFs because of their overlapped structural elements and complicated details of connections for the assembly of the unit-modules. In this study, nonlinear static analyses of 3 and 5-story prototype modular structures have been carried out with four different analytical models, which are established in consideration for the effects of overlapped elements and the hysteretic behavior of connections. Prototype structures present different lateral stiffness and strength depending on the modeling of overlapped elements and the rotational behavior of connections. For modular structures designed under assumption that overlapped structural elements are fully composite each other and connections between unit-modules are fixed, their lateral strength and stiffness can be over-estimated. Furthermore, it is known from the analysis results that modular structures with more than 3-stories would possess relatively low overstrength compared to traditional SMRFs.