• International Journal of Highway Engineering
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• v.14 no.2
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• pp.29-36
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• 2012

In this study, frequently passing vehicles with two, three, four, and five axles were chosen through traffic volume analysis in Kyung-In Expressway in order to analyze how the road roughness and vehicle speed affect on the dynamic loads for roads in various vehicle classes. Dynamic loads according to chosen vehicles are estimated by TruckSim program. Dynamic load amplification factor is ratio between dynamic and static loads, and it is also determined for each vehicle classes. From the result of dynamic loads estimated by the dynamic load amplification factor, it is shown that for three-axles vehicle, when IRI is 3.5 and vehicle speed is 100km/hr, asphalt pavements receive additional 36% of static loads in maximum. The analysis of the amplification factor according to each vehicle classes also indicates that the amplification factor increases as the distance between the axles becomes smaller and each axle receives more loads.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.19-28
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• 2013

The longitudinal axial strain in the plastic hinge region of reinforced concrete (RC) columns influences on the structural behavior of RC structures subjected to reversed cyclic loading. This strain decreases the effective compressive strength of concrete and increases the lateral displacements between stories by causing the elongation of member length. This paper investigated the effects of the axial force on the elongation of a RC member by using a sectional analysis of RC members. The analytical and experimental results indicated that the axial force decreased the axial strain in the plastic hinge region of RC columns. In this study, a model was proposed to predict the axial strain of RC columns. The proposed model considering the effects of axial force ratio consisted of three path types ; Path 1-loading region, Path 2-unloading region, and Path 3-reversing cyclic loading region. The axal strains predicted by the proposed model were compared with the test results of RC columns with various axial force ratios, and agreed reasonably with the observed longitudinal strains.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.6
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• pp.98-104
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• 2015

Excessive thrust acting on the rotor of pump can cause the damage of pump or the decrease of pump lifetime. Therefore, for ensuring the safety of LOX pump of a liquid rocket engine, the thrust of pump rotor is estimated by similarity tests. Axial thrust is indirectly measured by an axial thrust measurement unit positioned outside pump. Radial thrust is calculated based on pressure distribution of volute scroll. As a result, axial and radial thrust are increased when the flowrate of pump decreases. However, both thrusts do not affect the stability of pump rotor since their values are not large.

• Computational Structural Engineering
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• v.8 no.4
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• pp.117-127
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• 1995

The objective of this research is to investigate the effectiveness of rotating orthotropic axes model in analyzing reinforced concrete planar members under cyclic as well as monotonic loading. The structural members to be addressed are moderately reinforced beams, columns, beam-column joints, and shear walls, whose failure occurs due to compressive crushing after extensive crack propagation, The rotating orthotropic axes model which is usually used for monotonic loading is developed for cyclic loading. With the existing cyclic material models of reinforcing steel and bond-slip, this material model is used for the finite element analysis. For monotonic loading, the analytical results of the rotating orthotropic axes model are compared with reinforced concrete beams which have brittle failure. For Shear wall members under cyclic loading, the analyses are compared with the experiments for the ultimate load capacity, nonlinear deformation, and pinching effect due to crack opening and closing.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1990.11a
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• pp.69-72
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• 1990

최근의 전자및 광학기기 분야에 있어서의 준부신 발전은 다면경 가공기나 초정밀 절삭, 연삭기와 같은 초정밀 가공기계의 개발과 실용화에 힘입은 바 크다. 이러한 초정밀 가공기의 성능을 좌우하는 핵심 요소로서 주축계를 들 수 있으며, 비교적 소형 경량의 공작물을 가공하는 기계의 주축용 베어링으로는 볼 베어링이나 오일 베어링을 대신하여 공기베어링이 점차 널리 사용되고 있다. 일반적으로 주축으로 사용되는 베어링은 원통형 레이디얼 베어링과 원판형 스러스트 베어링이 결합된 형식이 주류를 이루나 이러한 베어링은 스러스트 판과 축의 직가곧 가공오차가 존재하기 때문에 가공하기는 쉬우나 회전시에 의의 영향에 의해 회전 정밀도 유지가 어렵다는 단점을 지니고 있다. 이러한 단점을 보완하기 위하여 사용되는 베어링에는 원추형(conical) 베어링과 구면형(spherical) 베어링이 쓰이고 있다. 이러한 원추형 베어링과 구면형 베어링은 가공오차를 베어링과 축의 현압 연마로써 없애줄 수 있으며 베어링이 축방향 하중과 경방향 하중을 동시에 지지하여 줌으로써 기계 전체의 부피를 줄이고 회전 정밀도를 향상시켜 주는 것으로 알려져 있다. 그러나 구면의 베어링 간극을 정확히 가공하기 어려운 단점이 있어 축과 베어링을 현압연마하여 가공한 후에 두부품을 중심선상에서 분리시키므로써 요구되는 간극을 얻을 수 있는 원추형 베어링이 많이 쓰이고 있다. 본 연구에서는 직접 수치 해법을 이요하여 원추형 베어링의 유막내의 압력 분포를 계산하고 이 합력인 하중지지 용량이 축방향 하중과 경방향 하중을 지지하는 특성을 이론적으로 검토하여 외부 가압 원추형 베어링으 특성수를 파악하여 설계자료를 제시하고자 한다.

• Computational Structural Engineering
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• v.11 no.4
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• pp.197-207
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• 1998

전단변형 효과를 무시하는 경우에 비대칭 선형 변단면을 갖는 박벽 공간 보의 안정성 해석을 위한 일반이론을 유도한다. 비대칭 선형 변단면의 임의점을 통과하는 부재축과 단면의 주축의 방향과 무관하고 부재축과 직각을 이루는 두 개의 좌표축을 도입하여 직각좌표계를 정의한다. 정의된 좌표축을 기준으로 유한한 회전각의 2차항을 고려하는 변위장을 도입하여 연속체에 대한 가상일의 원리로부터 탄성변형에너지, 그리고 초기응력에 의한 포텐셜에너지를 유도한다. 이를 이용하여 비대칭 선형 변단면을 갖는 박벽 공간 보의 안정성해석을 위한 평형방정식을 제시한다. 3차 Hermitian 다항식을 변위파라미터의 형상함수로 사용하여 박벽 공간 보의 탄성강도 및 기하강도행렬을 상정할 뿐만 아니라, 단면의 좌표축에 상관없이 임의의 위치에 작용하는 하중에 대한 하중보정강도행렬(load-correction stiffness matrix)을 제시한다. 본 이론 및 방법의 타당성을 검증하기 위하여 수치해석을 수행하고 문헌의 결과 및 쉘요소를 사용한 해석결과와 비교하여 본 이론의 정당성을 입증한다.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.117-127
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• 2007

In this study, we evaluate the strength of steel box beam-to-column connections subjected to axial loads in steel frame piers. The T-connection strength was reduced due to the column axial force in the two-story pier structure. To examine this phenomenon, non-linear FEM analysis was carried out and the analytical procedure was verified by comparing it with experimental results. To clarify the effect of the axial force and major design parameters in connection with strength, influence of panel zone width-thickness ratio, sectional area, and axial force was investigated using FEM analysis. Also, the theoretical strength equations were suggested by stress distribution of panel zone. The strength of the T-connection was compared with one of the one-story pier structure connections. As a result, the strength evaluation equations are proposed in consideration of the panel zone width-thickness ratio and sectional area ratio for the T-connections.

• Journal of the wind engineering institute of Korea
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• v.22 no.4
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• pp.163-169
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• 2018

In this study, wind loads exerted on the offshore wind turbine rotor in parked condition were predicted with variations of wind speeds, yaw angles, azimuth angle, pitch angles, and power of the atmospheric boundary layer profile. The calculated wind loads using blade element theorem were compared with those of estimated aerodynamic loads for the simplified blade shape. Wind loads for an NREL's 5 MW scaled offshore wind turbine rotor were also compared with those of NREL's FAST results for more verification. All of the 6-component wind loads including forces and moments along the three axis were represented on a non-rotating coordinate system fixed at the apex of rotor hub. The calculated wind loads are applicable for the dynamic analysis of the wind turbine system, or obtaining the over-turning moment at the foundation of support structure for wind turbine system.

• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.251-260
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• 2001

It is required to evaluate the axial strain of reinforced concrete beams in order to predict the ductility of reinforced concrete beams subjected to reversed cyclic loading. A model was proposed to determine the axial strains In reinforced concrete beams by analysing the behavior of reinforced concrete sections and comparing with published test results. The proposed axial strain model inclusively reflected four kinds of paths : Path 1-steel bar in an elastic stage or a unloading region; Path 2-after flexural yielding; Path 3-a slip region; and Path 4-a reversing loading region. The equations to predict the axial strains of each path were proposed. The proposed equations took into account the effects of the loading program. Comparison of axial strains between experimental results and the results from proposed equations showed to be in a good agreement with experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.391-398
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• 2016

This study focused on the aerodynamic loads of the horizontal axis wind turbine blade due to the normal turbulence inflow condition. Normal turbulence model (NTM) includes the variations of wind speed and direction, and it is characterized by turbulence intensity and standard deviation of flow fluctuation. IEC61400-1 recommends the fatigue analysis for the NTM and the normal wind profile (NWP) conditions. The aerodynamic loads are obtained at the blade hub and the low speed drive shaft for MW class horizontal axis wind turbine which is designed by using aerodynamically optimized procedure. The 6-components of aerodynamic loads are investigated between numerical results and load components analysis. From the calculated results the maximum amplitudes of oscillated thrust and torque for LSS with turbulent inflow condition are about 5~8 times larger than those with no turbulent inflow condition. It turns out that the aerodynamic load analysis with normal turbulence model is essential for structural design of the wind turbine blade.