• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.571-576
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• 2001

The objective of this study is to assess seismic damage potential and evaluate structural performance of columns in concrete moment frames. For this purpose the results of 3 former studies are compared. Experimental variables considered in these studies are lap-splice of longitudinal reinforcement, axial load level, longitudinal reinforcement ratio, etc. The columns in 1st story of the building are considered in these studies since the columns in 1st story shall resist largest axial force during an earthquake. Based on test results strength, ductility capacities as well as plastic hinge length are compared and discussed.

• 콘크리트학회논문집
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• 제15권5호
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• pp.679-688
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• 2003

종방향 텐던이 경사진 복부에 배치되는 박스 거더의 경우 프리스트레스 힘은 종방향 뿐만 아니라 횡방향 거동에도 영향을 미친다. 본 논문에서는 종방향 프리스트레싱에 의해 유발되는 횡방향 효과를 산정하는 기법을 제안하였다. 박스 거더의 유한요소 정식화 및 종방향 프리스트레싱 해석에 의해 프리스트레스 분포를 산정한 후, 이를 이용하여 횡방향 등가하중을 산정한다. 제안기법에 의한 수치해석결과와 기존의 접판법에 의한 수치해석결과는 유사하며, 이는 본 기법이 합리적임을 나타낸다. 제안기법을 이용하여 박스 거더 슬래브의 횡방향 거동을 분석하였다. 수치분석은 복부경사각, 텐던 편심에 대한 경간 길이비 등과 같은 주요 변수를 통해 수행되었다. 전형적인 단면 조건에서 종방향 프리스트레싱 효과만을 고려할 때, 박스 거더 슬래브의 횡방향 응력은 크지 않은 것으로 나타난다. 그러나, 복부 경사각이 50도 이하로 과도하게 작아지거나 텐던 편심에 대한 경간 길이비가 28이하로 작아지는 경우에는 교량 설계시 횡방향 응력의 크기를 고려할 필요가 있다고 사료된다.

• Journal of Mechanical Science and Technology
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• 제20권12호
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• pp.2105-2114
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• 2006

In this paper, a simplified model is studied to predict analytically the vibration from the helical gear system due to an axial excitation of helical gears. The simplified model describes gear, shaft, bearing, and housing. In order to obtain the axial force of helical gears, the mesh stiffness is calculated in the load deflection relation. The axial force is obtained from the solution of the equation of motion, using the mesh stiffness. It is used as a longitudinal excitation of the shaft, which in turn drives the gear housing through the bearing. In this study, the shaft is modeled as a rod, while the bearing is modeled as a parallel spring and damper only supporting longitudinal forces. The gear housing is modeled as a clamped circular plate with viscous damping. For the modeling of this system, transfer matrices for the rod and bearing are used, using a spectral method with four pole parameters. The model is validated by finite element analysis. Using the model, parameter studies are carried out. As a result, the linearized dynamic shaft force due to the gear excitation in the frequency domain was proposed. Out-of-plan displacement from the forced vibrating circular plate and the renewed mode normalization constant of the circular plate were also proposed. In order to control the axial vibration of the helical gear system, the plate was more important than the shaft and the bearing. Finally, the effect of the dominant design parameters for the gear system can be investigated by this model.

• 동력기계공학회지
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• 제9권3호
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• pp.71-78
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• 2005

A high-pressure hose includes rebar layers of the synthetic fiber such as nylon or a steel wire to control internal pressure. The hose assembly is manufactured through the swaging process to clamp the hose into the metal fittings. Usually, the hose behavior is affected by the resultant of the longitudinal and circumferential forces produced by the internal pressure. The rebar layers can appear the most ideal rebar effect when they are arranged to the same direction as the resultant force. The braid angle applied in the rebar layers is an important factor in determining ultimate burst pressure and overall hose life. Failure can occur on the contacted parts of a hose with the metal fittings under severe operating conditions such as high pressure and temperature of the inner fluid. In this paper, the mechanical behavior between the hose and the metal fittings during the swaging process and the stress variation characteristics of a high-pressure hose under a constant applied pressure are analyzed with respect to the braid angle of steel wire using the finite element method.

• Geomechanics and Engineering
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• 제17권3호
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• pp.237-245
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• 2019

In deep mixed rock strata, a double shield TBM (DS-TBM) is easy to be entrapped by a large force during tunneling. In order to reduce the probability of the entrapment, we need to investigate a favorable driving direction, either driving with or against dip, which mainly associates with the angle between the tunneling axis and strike, ${\theta}$, as well as the dip angle of rock strata, ${\alpha}$. We, therefore, establish a 3DEC model to show the changes of displacements and contact forces in mixed rock strata through LDP (longitudinal displacement profile) and LFP (longitudinal contact force profile) curves at four characteristic points on the surrounding rock. This is followed by a series of numerical models to investigate the favorable driving direction. The computational results indicate driving with dip is the favorable tunneling direction to reduce the probability of DS-TBM entrapment, irrespective of ${\theta}$ and ${\alpha}$, which is not in full agreement with the guidelines proposed in RMR. From the favorable driving direction (i.e., driving with dip), the smallest contact force is found when ${\theta}$ is equal to $90^{\circ}$. The present study is therefore beneficial for route selection and construction design in TBM tunneling.

• 콘크리트학회논문집
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• 제17권5호
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• pp.775-784
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• 2005

본 연구에서는 합리적인 내진설계기준의 정립을 위하여 철근콘크리트 교각의 내진성능에 영향을 미치는 주요 인자에 대하여 분석하였다. 기존 연구 결과에 따르면 한반도와 같은 중약진 지역에서의 철근콘크리트 교각의 심부구속철근비가 과다하게 사용되어 왔다는 결론을 내렸다. 따라서, 본 연구에서는 기존의 실험 결과들을 분석하여 합리적인 심부구속철근비를 제안하였다. 본 연구에서 제안된 심부구속철근비는 축하중비와 주철근비를 고려하였으며 낮은 축하중비에서 주철근 좌굴 방지를 위한 최소 규정을 도입하였다. 제안된 식은 일반적인 도로교상의 축하중비를 고려하면 기존 내진규정에 비해 매우 완화된 심부구속철근비를 갖게 된다. 따라서 문제로 나타나고 있는 시공성과 경제성이 상당히 향상될 수 있으리라 판단된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.800-806
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• 2011

Thermal expansion which occurs at the high speed rail joint is proportional to the free length from the point of fixity. This thermal expansion behaves similar to free expansion because the girder longitudinal stiffness is much larger than longitudinal resistance of rail pads. But the longitudinal displacement in the long rail is nominal because the longitudinal support condition of the girder is normally MFM(movable-fix-movable) system. Due to these girder expansion characteristics, there is longitudinal relative displacement at the rail pad and rail fastener spring which connects rail and girder. If the relative displacement between rail and girder is beyond the elastic limit for the rail pad, rail fastener system shall be applied using sliding fastener to prevent rail pad damage and fastener separation resulting from slip. On the other hand, train vertical vibration and tilting can occur due to the lack of fastener vertical force if the sliding fastener is applied at the girder joint. In the high speed rail bridge, vibration can occur due to the spring stiffness of the elastomeric bearing, also both vertical downward and upward displacement can occur. The elastomeric bearing vertical movement can cause rail displacement and finally the stability of the ballast is reduced because the gravel movement is induced.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.816-825
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• 2002

During the manufacture of a ship, longitudinal deformation is produced by fillet welding on the BuiltUp beam used to improve the longitudinal strength of a ship. This deformation needs a correcting process separate from a manufacture process and decreases productivity and quality. This deformation is caused by welding moment, which is the value multiplied the shrinking force due to welding by the distance from the neutral axis on a cross section of Built-Up beam. This deformation can be offset by generating a moment which is the same magnitude with and is located in an opposite direction to the welding moment on web plate by induction heating. Accordingly, this study clarifies the creation mechanism of the longitudinal deformation on Built-Up beam with FEM analysis and presents the preventative method of this deformation by induction heating basing the mechanism and verifies its validity through analysis and experiments. The induction heating used here is performed by deciding its location and quantity with experiments and simple equations and by applying them to areal structure.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권1호
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• pp.9-15
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• 2013

This paper presents a uniform analytical model by energy method and Fourier series expansion to analyze detent force in uneven magnetic field for permanent magnet linear synchronous motor (PMLSM). The model reveals that detent force in long-primary type is mainly influenced by non-ideal distribution of permanent magnet magnetic motive force, while nounified air-gap permeance makes a great impact on detent force of short-primary type. Hence, magnetic field similarity of motor design techniques referring rotary counterpart are adopted. For long-primary type novel method of splitting edge magnets is proposed to reduce end effects force, and optimal widths of edge tooth in short-primary type also verify the effectiveness of magnetic field similarity. The experimental results validate finite element analysis results.

• 콘크리트학회논문집
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• 제18권6호
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• pp.749-757
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• 2006

최근 세계 도처에서 발생한 지진은 수많은 사상자를 발생시키었음은 물론 사회기간시설물에도 많은 피해를 주고 있다. 본 연구에서는 사각형 철근콘크리트 교각의 합리적인 심부구속철근비 산정식을 도출하기 위하여 내진성능에 영향을 미치는 주요 인자에 대하여 분석하였다. 본 연구에서 국내외 54개의 실험 결과를 분석한 결과 축하중비와 주철근비가 변위연성도에 큰 영향을 주는 주요 변수임을 확인하였으나, 이 변수들은 현 도로교설계기준의 심부구속철근비 산정식에는 고려가 되어있지 않고 있다. 따라서 이 실험 결과들을 이용하여 사각형 철근콘크리트 교각의 합리적인 심부구속철근비 산정식을 제안하였다. 본 연구에서 제안된 심부구속철근비 산정식은 기존 규정에 축하중비와 주철근비를 고려하였으며, 또한 낮은 축하중비에서 주철근 좌굴 방지를 위한 최소 규정을 도입하였다. 제안된 식은 일반적인 도로교상의 축하중비를 고려하면 기존 규정에 비해 매우 완화된 심부구속철근비를 갖게 된다. 따라서 문제로 나타나고 있는 시공성과 경제성이 상당히 향상될 수 있으리라 판단된다.