• Title/Summary/Keyword: Equivalent Dynamic Stiffness

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Equivalent Static Analysis of Progressive Collapse Using Equivalent Load for Stiffness (강성등가하중을 이용한 등가정적 연쇄붕괴 해석)

  • Hwang, Young-Chul;Kim, Gye-Joong;Kim, Chee-Kyeong
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.375-380
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    • 2007
  • The goal of this paper is to develop a rational static method which consider efficiently the dynamic effect of the gravity load following sudden removal of element. For this goal this paper introduce the equivalent load for element stiffness which is a preceding research result and will develop equivalent static analysis which will be able to predict the maximum behavior considering dynamic effect. Some examples are provided to verify it. Equivalent static analysis is compared with the analysis method which is recommended by the GSA2003 guidelines and the time-history analysis which is the most accurate for dynamic behavior.

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Equivalent Stiffness Analysis of Rubber Bushing Considering Large Deformation and Size Effect (부싱의 대변형거동과 크기를 고려한 등가 강성 해석)

  • Lee, Hyun Seong;Sung, Myung Kyun;Kim, Heung Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.4
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    • pp.271-277
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    • 2017
  • In this paper, the amplitude and frequency dependent dynamic characteristics of the equivalent stiffness of a rubber bushing are investigated. A new mathematical model is proposed to explain the large deformation and size effect of a rubber bushing. The proposed model consists of elastic, viscous, and frictional stress components and the equivalent strain. The proposed model is verified using experimental results. The comparison shows that the proposed model can accurately predict the equivalent stiffness values of a rubber bushing under various magnitudes and frequencies. The developed model could be used to predict the dynamic equivalent stiffness of a rubber bushing in automotive engineering.

A Study on the Dynamic Analysis Modeling of Industrial Robot's Wrist Power Transmission (산업용 로봇 손목 동력 전달계의 동특성 해석 모델 연구)

  • 김우형;정두한;최영삼;정진태;임흥순
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.243-246
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    • 2004
  • The dynamic characteristic of a wrist power transmission examine closely with mass property, to present the model which induce the vibration is ultimately the purpose. A robot wrist power transmission for analysis model got the mass property through the approach to be the experimental. A bearing equivalent stiffness which supports the axis and a gear contact equivalent stiffness are determined by the simplicity analysis model compared the result of the experiment. We calculate the vibration tendency of the robot wrist power transmission by an analysis tool which is called the RecurDyn. We compared it with a signal analysis experiment's which a robot operation happens which is based on the ambient noise.

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Dynamic analysis of spindle system with magnetic coupling(1) (마그네틱 커플링을 장착한 축계의 동적해석(I))

  • Kim, S.K.;Lee, S.J.;Lee, J.M.
    • Journal of the Korean Society for Precision Engineering
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    • v.11 no.4
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    • pp.99-105
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    • 1994
  • In this study, the transverse and the torsional vibration analyses of a precision dynamic drive system with the magnetic coupling are accomplished. The force of the magnetic coupling is regarded as an equivalent transverse stiffness, which has a nonlinearity as a function of the gap and the eccentricity between a driver and a follower. Such an equivalent stiffness is calculated by and determined by the physical law and the calculated equivalent stiffness is modelled as the truss element. The form of the torque function transmitted through the magnetic coupling is a sinusoidal and such an equivalent angular stiffness, which represents the torque between a driver and a follower, is modelled as a nonlinear spring. The main spindle connected to a follower is assumed to a rigid body. And then finally we have the nonlinear partial differential equation with respect to the angular displacements. Through the procedure mentioned above, we accomplish the results of the torsional vibration analysis in a spindle system with the magnetic coupling.

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A Study on the Equivalent Dynamic Stiffness of Bearing-pedestal (베어링 대의 등가 동강성에 관한 고찰)

  • Kim, Hee-Soo;Bae, Yong-Chae;Lee, Hyun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.5 s.110
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    • pp.452-456
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    • 2006
  • The critical speeds and mode shapes are most important to determine the behaviors of rotor in designing rotating machinery. As the capacity and span of turbine-generator increases, the turbine-generator system is composed of many components such as bearings, pedestal, turbine and hood and so on. Also, it is getting flexible and has many critical speeds. Especially, as the characteristics of bearing-pedestal are very complicated, they affect the entire vibration characteristics of turbine-generator system. In this paper, it is observed how to determine the equivalent dynamic stiffness of bearing-pedestal by analytical and experimental method.

A Study on the Equivalent Dynamic Stiffness of Bearing-Pedestal (베어링-페데스탈의 등가 강성에 관한 고찰)

  • Kim, Hee-Soo;Bae, Yong-Chae;Lee, Hyun;Lee, Dae-Seong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.263-266
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    • 2005
  • The critical speeds and mode shapes are most important to determine the behaviors of rotor in designing rotating machinery. As the capacity and the span of turbine-generator increases, the turbine-generator system has many components such as bearings, pedestal, turbine and baseplates etc. and it is getting flexible and has many critical speeds. Especially, the characteristics of bearing-pedestal are very complicated and then they affect the entire vibration characteristics of turbine-generator system. In this paper, it is observed how to determine the equivalent dynamic stiffness of bearing-pedestal by analytic and experimental method.

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Dynamic properties of a building with viscous dampers in non-proportional arrangement

  • Suarez, Luis E.;Gaviria, Carlos A.
    • Structural Engineering and Mechanics
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    • v.55 no.6
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    • pp.1241-1260
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    • 2015
  • Any rational approach to define the configuration and size of viscous fluid dampers in a structure should be based on the dynamic properties of the system with the dampers. In this paper we propose an alternative representation of the complex eigenvalues of multi degree of freedom systems with dampers to calculate new equivalent natural frequencies. Analytical expressions for the dynamic properties of a two-story building model with a linear viscous damper in the first floor (i.e. with a non-proportional damping matrix) are derived. The formulas permit to obtain the equivalent damping ratios and equivalent natural frequencies for all the modes as a function of the mass, stiffness and damping coefficient for underdamped and overdamped systems. It is shown that the commonly used formula to define the equivalent natural frequency is not applicable for this type of system and for others where the damping matrix is not proportional to the mass matrix, stiffness matrix or both. Moreover, the new expressions for the equivalent natural frequencies expose a novel phenomenon; the use of viscous fluid dampers can modify the vibration frequencies of the structure. The significance of the new equivalent natural frequencies is expounded by means of a simulated free vibration test. The proposed approach may offer a new perspective to study the effect of viscous dampers on the dynamic properties of a structure.

Soft story retrofit of low-rise braced buildings by equivalent moment-resisting frames

  • Ebadi, Parviz;Maghsoudi, Ahmad;Mohamady, Hessam
    • Structural Engineering and Mechanics
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    • v.68 no.5
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    • pp.621-632
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    • 2018
  • Soft-story buildings have bottom stories much less rigid than the top stories and are susceptible to earthquake damage. Therefore, the seismic design specifications need strict design considerations in such cases. In this paper, a four-story building was investigated as a case study and the effects of X-braces elimination in its lower stories studied. In addition, the possibility of replacement of the X-braces in soft-stories with equivalent moment resisting frame inspected in two different phases. In first phase, the stiffness of X-braces and equivalent moment-resisting frames evaluated using classic equations. In final phase, diagonals removed from the lowest story to develop a soft-story and replaced with moment resisting frames. Then, the seismic stiffness variation of moment-resisting frame evaluated using nonlinear static and dynamic analyses. The results show that substitution of braced frames with an equivalent moment-resisting frame of the same stiffness increases story drift and reduces energy absorption capacity. However, it is enough to consider the needs of building codes, even using equivalent moment resisting frame instead of X-Braces, to avoid soft-story stiffness irregularity in seismic design of buildings. Besides, soft-story development in the second story may be more critical under strong ground excitations, because of interaction of adjacent stories.

A Study on the Equivalent Model of the Support Structure for Rotordynamic Analysis (회전축계의 진동해석을 위한 지지구조물의 등가모델에 관한 연구)

  • 최복록;박진무
    • Journal of KSNVE
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    • v.10 no.1
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    • pp.153-159
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    • 2000
  • This paper presents a new method for including the dynamic stiffness of the stationary parts in rotordynamic analysis. As a consequence of the support dynamics, critical speeds are varied and/or additional critical speeds are introduced. Therefore, dynamic effects of the support are often significant in high speed turbomachinery, but most of analysis has considered the support as a rigid body or a simple structure. The proposed method is based on the coupled characteristics of the driving point and transfer frequency response functions of the support system to model the equivalent spring-mass series in finite element analysis. To demonstrate the applicability of the simulation procedures provided, it is applied to the rotor model of the double suction centrifugal pump. Results of the suggested equivalent-support rotor model including coupled effects agree well with the entire pump model.

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Dynamic Response Analysis of 2.5MW Wind Turbine Gearbox with Flexible Pins (유연핀을 적용한 2.5MW급 풍력발전기용 기어박스의 동응답 해석)

  • Cho, Jin-Rae;Jeong, Ki-Yong
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.1
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    • pp.37-44
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    • 2016
  • This study is concerned with the numerical investigation of dynamic characteristics of 2.5MW-class wind turbine gearbox in which the misalignment improvement of plenary gear shafts by the flexible pins and the dynamic impact response are analyzed by the finite element method. The tooth contact between gears is modelled using the line element having the equivalent tooth stiffness and the contact ratio to accurately and effectively reflect the load transmission in the internal complex gear system. The equivalent tooth stiffness is calculated by utilizing the tooth deformation analysis and the impulse torque is applied to the input shaft for the dynamics response characteristic analysis. Through the numerical experiments, the equivalent tooth stiffness model was validated and the misalignment improvement of planetary gear shafts was confirmed from the comparison with the cases of fixed shafts at one and both ends.