• Title/Summary/Keyword: dynamic eccentricity

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Wind-induced lateral-torsional coupled responses of tall buildings

  • Wu, J.R.;Li, Q.S.;Tuan, Alex Y.
    • Wind and Structures
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    • v.11 no.2
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    • pp.153-178
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    • 2008
  • Based on the empirical formulas for power spectra of generalized modal forces and local fluctuating wind forces in across-wind and torsional directions, the wind-induced lateral-torsional coupled response analysis of a representative rectangular tall building was conducted by setting various parameters such as eccentricities in centers of mass and/or rigidity and considering different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional coupled responses of the tall building were studied comprehensively by structural dynamic analysis. Extensive computational results indicated that the torsional responses at the geometric center of the building may be significantly affected by the eccentricities in the centers of mass and/or rigidity. Covariance responses were found to be in the same order of magnitude as the along-wind or across-wind responses in many eccentricity cases, suggesting that the lateral-torsional coupled effects on the overall wind-induced responses can not be neglected for such situations. The calculated results also demonstrated that the torsional motion contributed significantly to the total responses of rectangular tall buildings with mass and/or rigidity eccentricities. It was shown through this study that the framework presented in this paper provides a useful tool to evaluate the wind-induced lateral-torsional coupled responses of rectangular buildings, which will enable structural engineers in the preliminary design stages to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test.

Dynamic Response Analysis of Twisted High-Rise Structures according to the Core Location Change (코어 위치 변화에 따른 비틀림 초고층 구조물의 동적응답분석)

  • Chae, Young-Won;Kim, Hyun-Su;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
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    • v.22 no.1
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    • pp.17-24
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    • 2022
  • Currently, the construction trend of high-rise structures is changing from a cube-shaped box to a free-form. In the case of free-form structures, it is difficult to predict the behavior of the structure because it induces torsional deformation due to inclined columns and the eccentricity of the structure by the horizontal load. For this reason, it is essential to review the stability by considering the design variables at the design stage. In this paper, the position of the weak vertical member was analyzed by analyzing the behavior of the structure according to the change in the core position of the twisted high-rise structures. In the case of the shear wall, the shear force was found to be high in the order of proximity to the center of gravity of each floor of the structure. In the case of the column, the component force was generated by the axial force of the outermost beam, so the bending moment was concentrated on the inner column with no inclination.

A Parametric Study on the Characteristics of the Oil-Lubricated Wave Journal Bearing (오일윤활 웨이브 저어널 베어링의 특성해석)

  • 서현승;임윤철
    • Tribology and Lubricants
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    • v.14 no.4
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    • pp.100-107
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    • 1998
  • A new bearing concept, the wave journal bearing, has been developed to improve the static and dynamic performance of a hydrodynamic journal bearing. This concept features a wave in bearing surface. Not only straight but also twisted wave journal bearing are investigated numerically. The performances of straight and twisted bearings are compared to a plain journal bearing over a wide range of eccentricity. The bearing load and stability characteristics are dependent on the geometric parameters such as the number of waves, the amplitude and the start point of the wave relative to the applied load direction. The wave journal bearing, especially for the twisted one, offers better stability than the plain journal bearing under all eccentricity and load orientation.

An Analysis of Wave Journal Bearing (웨이브 저어널 베어링의 특성해석)

  • 서현승;임윤철
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1998.04a
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    • pp.190-197
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    • 1998
  • A new bearing concept, the wave journal bearing, has been developed to improve the steady and dynamic performance of a hydrodynamic journal bearing. This concept features a wave in inner bearing surface. Not only straight but also twisted wave journal bearing are investigated numerically. The performances of straight and twisted bearings are compared to a plain journal bearing over a relatively wide range of eccentricity. The bearing load and stability characteristics are dependent on the geometric parameters such as the number of waves, the amplitude and the starting point of the wave relative to the applied load. The wave journal bearing, especially for the twisted one, offers better stability than the plain journal bearing under all eccentricity and all wave to load orientation.

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Design Eccentricity in Equivalent Seismic Load Using Modal Analysis (모드 해석을 이용한 등가 지진하중에서의 설계 편심)

  • 조소훈;이명규
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2001.09a
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    • pp.268-275
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    • 2001
  • Modal analysis does well predict the elastic dynamic response of the torsionally unbalanced structure. But modal analysis overestimates the rotation of the structure in inelastic range, so one side members require ductility too much and the others require ductility too small in comparison with torsionally balanced structure. In this paper, in order to reduce difference of ductility demand between both side members of the torsionally unbalanced structure, design eccentricity of seismic load is evaluated and the method determining the strength center of structure is proposed using modal analysis. For several cases, the ductility demand of stucture is compared to investigate the propriety of the proposed approach.

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Vibration Analysis and Its Application of a Linear Motion Guide Supported by Rolling Ball Bearings (볼 베어링을 이용하는 직선 운동 가이드의 진동 해석 및 응용)

  • Choi Jae Seok;Yi Yong-sub;Kim Yoon Young;Lee Dong Jin;Lee Sung Jin;Yoo Jeonghoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.7 s.238
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    • pp.955-963
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    • 2005
  • This research investigates dynamic characteristics of a linear motion (LM) guide through a experimental result and theoretical analysis. The stiffness in the LM guide is determined by the preloading due to the minus clearance between the ball bearing and the contact surface and it can be derived by Hertzian contact theory and the nonlinear motion of equation. The vibration analysis is performed using Lagrange equations and its result agrees with the experiment result. Using the sensitivity analysis on design parameters such as the contact angles of ball bearings and the eccentricity of mass center, the variation of the natural frequencies can be predicted.

Dynamic Behavior Analysis for HDD Spindle Motors with Rotor Eccentricity (HDD 스핀들 구동용 BLDC 전동기의 편심을 고려한 동적 거동 해석)

  • 김태종;김경태;황상문
    • Journal of KSNVE
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    • v.10 no.6
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    • pp.977-984
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    • 2000
  • Vibration of disk drive spindle is one of the major limiting factors in achieving higher track densities in hard disk drives. Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the motor air-gap. In this paper, radial magnetic forces for symmetric and asymmetric BLDC motor are calculated with respect to the various rotor eccentricity using analytic method. Based on the results of the radial magnetic forces, transient whirl responses of the spindle motor are analyzed using finite element and transfer matrices. Results show that an asymmetric motor has a worse effects on unbalanced magnetic forces and vibration when mechanical and magnetic coupling exists.

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An Experimental Study on Dynamic Stiffness Measurement of Air Journal Bearing (공기 정압 저어널 베어링에서 동강성 측정에 관한 실험적 연구)

  • 이종렬;이준석;이득우;김태형;박보선
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2001.04a
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    • pp.429-434
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    • 2001
  • This paper has been presented the dynamic effect by the journal speed, eccentricity and source positions in order to overcome the defects of air bearing such as low stiffness and damping coefficient. Choosing two row sources position of air bearing is different from previous investigations in the side of pressure distribution of air film by the wedge effects. An experimental study was performed to compare theoretical analysis. The dynamic stiffness was measured in actual cutting. It helps predicting of air spindle s characteristic in machining of die more precisely. The results of investigated characteristics was applied to air spindle for high speed milling.

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Development of train/bridge interaction Analysis program Consideration braking (열차 제동하중을 고려한 차량/교량 상호 작용 해석기법 개발)

  • Yun hee sub;Kim Man-Cheol;Han sang chel
    • Proceedings of the KSR Conference
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    • 2005.11a
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    • pp.1177-1183
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    • 2005
  • This paper presents the effects of dynamic response of the railway bridge through the suspension system when the train is moving with uniform speed and non-uniform speed Railway bridges are subjected to dynamic loads generated by the interaction between moving vehicles and the bridge structures. these dynamic loads result in response fluctuation in bridge members. To investigate the real dynamic behavior of the bridge, a number of analytical and experimental investigation should be carried out. This paper, a train/bridge interaction analysis program considerate braking action. New scheme consideration of braking action on the bridge using speed-dependent braking function is presented. This program also used torsional degree of freedom and constraint equation based on geometrical relationship in order to take into consideration three-dimensional eccentricity effect due to the operation on double track through quasi three-dimensional analysis.

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Development of a Static and Dynamic Characteristics Analysis System for Machine -Tool Spindle Systems with 3 Lobe Sliding Bearings (3원호 미끄럼 베어링을 적용한 공작기계 주축계의 정적 및 동적 특성 해석시스템 개발)

  • 조재완
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.9 no.4
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    • pp.99-107
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    • 2000
  • In this study, a static and dynamic characteristics analysis system for machine tool spindle systems with 3 lobe sliding bearing is developed based on Timoshenko theory, finite element method and windows programming techniques. And the characteristics value of 3 lobe sliding bearing such as eccentricity ratio, attitude angle, friction coefficient , stiffness coefficients, damping coefficients and so on, are determined by using the thermal equilibrium conditions of spindle systems. Since the developed system has various analysis modules related to static deformation analysis, modal analysis, frequency responses analysis and so on, it can be utilized to perform systematically the design an devaluation process of spindle systems with 3 lobe sliding bearing under windows GUI environment.

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