• Title/Summary/Keyword: 편심도

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Study of Apparent Mass and Apparent Eccentric Mass to Vertical Whole-body Vibration by Using Strain-gage Type Six-axis Force Plate (6축 힘측정판을 이용한 수직방향 전신진동에 대한 겉보기질량 및 겉보기편심질량에 대한 고찰)

  • Jeon, Gyeoung-Jin;Kim, Min-Seok;Ahn, Se-Jin;Jeong, Weui-Bong;Yoo, Wan-Suk
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.10
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    • pp.897-904
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    • 2011
  • When whole-body is exposed to vertical vibration, asymmetry shape of human body affects the response on the translational(fore-aft, lateral, vertical) and rotational(roll, pitch, yaw) motion. While the translational motion has been studied with various titles, it has been rare to study the rotational motion of human body exposed to vertical excitation because of lack of experimental equipment. This study was performed by using a 6-axis force plate installing strain gage type sensors for the rotational response. Sixteen male subjects were exposed to vertical vibration on rigid seat in order to investigate apparent mass of three translational motion and apparent eccentric mass of three rotational motion. Random signal was generated to make excitation vibration which was on an effective frequency range of 3~40 Hz, and magnitude of 0.224 m/s2 r.m.s. The frequency range and magnitude used was selected for the vibration of passenger vehicle on idling condition. As the result, cross-axis apparent masses of fore-and-aft and lateral direction were not significant showing 20 % and 3 % of vertical apparent mass relatively. And apparent eccentric mass of pitch motion was dominant when compared to that of roll and yaw motion, which is reasoned by asymmetry direction of human body sitting on a seat.

Seismic Isolation Effects Due to the Difference Between the Center of Mass of the Building and the Center of Stiffness of Isolation Layer (건물의 질량중심과 면진층의 강성중심 차이에 따른 면진효과)

  • Hur, Moo-Won;Chun, Young-Soo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.5
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    • pp.107-115
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    • 2014
  • In this study, we examined the seismic isolation effects due to the difference between the center of mass of the building and the center of stiffness of isolation layer. Because the base isolation technique is a technique that is highly dependent on the performance of seismic isolation devices installed on the seismic isolation layer, we have to examine the horizontal stiffness of seismic isolation devices after making them. If difference between the design stiffness and the actual stiffness of the seismic isolation device occurred, a big problem may be generated in the upper members on the seismic isolation layer. The analytical results show that the more eccentricity increases, the more maximum response acceleration, story shear and the member forces of the upper part of the structure increases, and the damage is expected to be in excess. Therefore, it is recommended that if possible, isolation devices have to be designed to coincide the center of mass of the building with the center of stiffness of isolation layer. If not after making isolation devices, they need to be relocated to prevent the eccentricity.

A Model for Simplified 3-dimensional Analysis of High-speed Train Vehicle (TGV)-Bridge Interactions (고속철도차량(TGV)-교량 상호작용의 단순화된 3차원 해석모델)

  • 최창근;송명관;양신추
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.13 no.2
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    • pp.165-178
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    • 2000
  • The simplified model for 3-dimensional analysis of vehicle-bridge interactions is presented in this study. By using the analysis model which includes the eccentricity of axle loads and the effect of the torsional forces acting on the bridge, the more accurate analysis results of the behavior of the bridge can be obtained. The equations of kinetic energy, potential energy and damping energy are expressed by degrees of freedom of the vehicle and the bridge. And then by applying Lagrange's equations of motion, the equations of motion of the vehicle and the bridge are obtained. By deriving the equations of forces acting on the bridge considering the vehicle-bridge vertical interactions and also by identifying the position of vehicle as time goes by, mass matrix, stiffness matrix, damping matrix and load vector of vehicle-bridge system are constructed in accordance with the position of vehicles. Then using Newmark's β-method(average acceleration), the equations of motion for the total vehicle bridge system are solved.

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An Experimental Study on Allowable Compressive Stress at Prestress Transfer in Pre-Tensioned Concrete Members (프리텐션된 콘크리트 부재의 프리스트레스 도입시 허용압축응력에 관한 실험적 연구)

  • Lee, Jeong Yeon;Lee, Deuck Hang;Kim, Kang Su;Park, Min Kook;Yoon, Sang Chun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.4
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    • pp.9-17
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    • 2012
  • In the previous research, allowable compressive stress was analyzed based on strength theory, in which primary effect factors on the allowable compressive stress, such as eccentricity ratio, section type, section size, prestress and self-weight moment, were considered. As its results, allowable compressive stress equations were proposed. As a series of the previous research, this paper presents an experimental study on the prestress at transfer of pre-tensioned members with different eccentricity ratios. The results shows that ACI318-08 and EC2-02 are unconservative for the members under low eccentricity ratios, and they are conservative for the members under high eccentricity ratios. Compared to the code provisions, the results indicates that the proposed equation reasonably well evaluates the allowable compressive stresses for those with different eccentricity ratios.

Thermal Performance of the Bubble Jet Loop Heat Pipe Using Eccentric Heater in Evaporating Section (증발부에 편심 가열부를 사용한 버블젯 루프 히트파이프의 열성능)

  • Kim, Jong-Soo;Kim, Sung-Bok
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.12
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    • pp.652-658
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    • 2015
  • The Bubble Jet Loop Heat Pipe (BJLHP) is designed to operate in the horizontal orientation. The motion of the bubble generated by boiling working fluid on a heater surface in the evaporating section of the BJLHP helps the working fluid transfer heat to the condensing portion. In this study, we changed the position of the heater in the evaporating section from concentric to eccentric. The concentric heater is located at the center of the tube in the evaporating part, and the eccentric heater is located at the bottom of the inner surface of the same tube. We used R-134a as the working fluid, and the charging ratio was 50%vol. We measured the temperatures of the evaporating and condensing sections by changing the input electric power from 50 W to 200 W, measuring every 50 W. The results of the experiment show that the effective thermal conductivity of BJLHP using an eccentric heater is four times higher than the BJLHP obtained using a concentric heater. Additionally, we conducted a visualization experiment on the evaporating portion of BJLHP to determine why the effective thermal conductivity was higher. The working fluid was water, and we took pictures of the flow visualization for BJLHP. Nucleate boiling with the eccentric heater was more intense and generated more bubbles. Therefore, the eccentric heater was more saturated by the liquefied working fluid.

A Geometrically Nonlinear Analysis for the Eccentric Degenerated Beam Element Considering Large Displacements and Large Rotations (대변위 밀 대회전을 고려한 편심된 격하 보요소의 기하학적 비선형해석)

  • Jae-Wook Lee;Young-Tae Yang
    • Journal of the Society of Naval Architects of Korea
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    • v.29 no.4
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    • pp.227-233
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    • 1992
  • To study the large displacement and large rotation problems, geometrically nonlinear formulation of eccentric degenerated beam element has been developed, where the restrictions of infinitesimal rotation increments are removed and the incremental equations are derived using the Taylor series expansion of the displacement function at time t+dt. The geometrically nonlinear analyses are carried out for the cases of cantilever, square frame, shallow arch and 45-degree bend beam and all of them are compared with each of the other results published. The element developed in the present research can be efficiently utilized for analysis of the nonlinear behaviours of structures when displacements and rotations are large.

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Improvement of Interoperability of IFC for Geometry and Location of Structural Members (구조부재의 형상과 위치에 대한 IFC 상호운용성 개선)

  • Jung, Jong-Hyun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.2
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    • pp.1170-1175
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    • 2014
  • The purpose of this study is to improve the interoperability of IFC for the basic data such as the size of member section, length, thickness, reference location, and eccentricity of the structural members. For this, the method to represent the basic data of structural member is proposed. In the proposed method, the most important criteria is the way that engineers recognize and treat the basic data of structural members. Then, in this study, an IFC file is generated based on the proposed method for a simple RC building composed of members and it is examined that the correct basic data can be derived from the IFC file in the way that engineers do in practice. From the results of the examination, the proposed method is expected to improve the interoperability of IFC for the basic data.

Reliability Analysis of Single and Continuous Span Composite Plate and Box Girder Designed by LRFD Method under Flexure (LRFD법으로 설계된 단경간 및 연속경간 강합성 플레이트 거더 및 박스 거더의 휨에 대한 신뢰도해석)

  • Shin, Dong Ku;Roh, Joon Sik;Cho, Eun Young
    • Journal of Korean Society of Steel Construction
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    • v.20 no.1
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    • pp.183-193
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    • 2008
  • The reliability analysis of simply-supported and continuous composite plate girder and box girder bridges under flexure was performed to provide a basic data for the development of LRFD c ode. The bridges were designed based on LRFD specification with newly proposed design live load which was developed by analyzing traffic statistics from highways and local roads. A performance function for flexural failure was expressed as a function of the flexural resistance of composite section and the design moments due to permanent load and live load. For the flexural resistance, the statistical parameters obtained by analyzing over 16,000 domestic structural steel samples were used. Several different values of bias factors for the live load moment from 1.0 to 1.2 were used. Due to the lack of available domestic measured data on the moment by permanent loads, the same statistical properties used in the calibration of ASHTO-LRFD were ap plied. The reliability indices for the composite girder bridges with various span lengths, different live load factors, and bias fact or for the live load were obtained by applying the Rackwitz-Fiessler technique.

Evaluation of Internal Bracing Member Forces due to Distortional Behaviors of Tub Section Steel Box Girders (U형 강박스 거더의 뒤틀림 거동에 의한 내부 수직브레이싱 부재력 평가)

  • Kim, Kyung-Sik
    • Journal of Korean Society of Steel Construction
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    • v.23 no.2
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    • pp.249-259
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    • 2011
  • In this study, the distortional behaviors of tub-section steel girders subjected to torsional loading were analyzed, and predictor equations were developed for estimating the member forces induced in the internal bracing system installed in the steel tub girders. Torsional loadings originated either by eccentric vertical loading or girder curvature were decomposed into the pure torsional force component that does not affect the distortional box deformation, and into the distortional force component that directly induces box distortion. The axial member forces induced in the internal cross frames were formulated as a function of the magnitude of torsional loading through the analytical investigation of the interactions between the distortional force component and internal cross frames. To verify the proposed equations, three-dimensional finite element analysis (3D FEA) was conducted for the straight simple-span girder and the three-span continuous girder samples. Very good agreement was found between the member forces from the FEA and the proposed equations.

Proportional Resonant Feedforward Contrl Algorithm for Speed Ripple Reduction of 3-phase SPMSM (3상 영구자석 동기전동기의 속도 맥동 저감을 위한 비례공진 전향보상 제어 알고리즘)

  • Lee, Seon-Yeong;Hwang, Seon-Hwan;Kim, Gyung-Yub;Park, Jong-Won
    • Journal of IKEEE
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    • v.24 no.4
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    • pp.1104-1108
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    • 2020
  • This paper propose a variable proportional resonant feedforward algorithm for reducing the speed ripple of a three-phase permanent magnet synchronous motor. In general, the torque ripples can be generated by electrical pulsation due to current measurement errors and dead time and mechanical pulsation because of rotor eccentricity and eccentric load. These torque pulsations can cause speed pulsations of the motor and degrade the operating performance of the motor drive system. Therefore, in this paper, the factors of the speed ripple is analyzed and an algorithm to reduce the speed ripple is proposed. The proposed algorithm applied a variable proportional resonant controller in order to reduce the specific operating frequency included in the speed pulsation, and utilized a feedforward compensation controller structure to perform the compensation operation. The proposed algorithm is verified through various experiments.