• Title, Summary, Keyword: non-proportional damping

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FFT-based Spectral Analysis Method for Linear Discrete Structural Dynamics Models with Non-Proportional Damping (비 비례적 감쇠를 갖는 선형 이산 구조동력학 모델에 대한 FFT-활용 스펙트럴해석법)

  • Lee U-sik;Cho Joo-yong
    • Journal of the Korean Society for Railway
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    • v.9 no.1
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    • pp.63-68
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    • 2006
  • This paper proposes a fast Fourier transform(FFT)-based spectral analysis method(SAM) for the dynamic responses of the linear discrete dynamic models with non-proportional damping. The SAM was developed by using discrete Fourier transform(DFT)-theory. To verify the proposed SAM, a three-DOF system with non-proportional viscous damping is considered as an illustrative example. The present SAM is evaluated by comparing the dynamic responses obtained by SAM with those obtained by Runge-Kutta method.

A displacement-based seismic design procedure for buildings with fluid viscous dampers

  • Banuelos-Garcia, Francisco H.;Ayala, Gustavo;Lopez, Saul
    • Earthquakes and Structures
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    • v.18 no.5
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    • pp.609-623
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    • 2020
  • This paper presents a displacement-based seismic design procedure for new structures with fluid viscous dampers and/or for existing structures, where these devices are required as a retrofit measure and damage control. To consider the non-proportional damping produced by these devices in a conventional modal spectral analysis, the effect of the fluid viscous dampers is approximated as the sum of a proportional damping matrix and a complementary matrix which is representative of non-proportional damping matrix. To illustrate the application of this procedure and evaluate the performance of structures designed with the procedure proposed, five regular plane frames: 8, 12, 17, 20 and 25-storey, and an 8-storey building are designed. The seismic demands used for design and validation were the records obtained at the SCT site during the 1985 Michoacan earthquake, and that of the 2017 Morelos - Puebla earthquake obtained at the Culhuacan site, both stations located on soft soil sites. To validate the procedure proposed, the performances and damage distributions used as design targets were compared with the corresponding results from the nonlinear step-by-step analyses of the designed structures subjected to the same seismic demands.

Analysis of Eigenderivative for the Non-Proportional Damped Structure Using the Iterative Method of the Sensitivity Coefficient (감도계수 반복법을 이용한 비비례감쇠계의 고유치 및 고유벡터 변화량 해석)

  • Lee Jung-Youn
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.7
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    • pp.750-756
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    • 2006
  • This study predicts the modified eigenvectors and eigenvalues of the non-proportional damped structure due to the change in the mass, damping and stiffness of structure by iterative method of the sensitivity coefficient using the original dynamic characteristic. The method is applied to the non-proportional damped 3 degree of freedom system by modifying the mass, damping and stiffness. The predicted dynamic characteristics are showed a good agreement with these from the structural reanalysis using the modified mass, damping and stiffness.

Experimental Modal Analysis using Proportional Viscous.Hysteretic Damping System on the Rolling Stock (비례점성.히스테리시스 감쇠계에 의한 철도차량의 실험모드해석)

  • 최문길;김창남;김의간
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.86-91
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    • 1996
  • In this study, the modal analysis is adopted for the investigation of vibratory characteristics of a rolling stock. A governing equation for this system is deverived on a condition that the rolling stock is in proportional viscous damping and proportional hysteretic damping. By applying this method a computational modal analysis software is developed. The validity and reliability of this method is verified by comparing the results for the above case and with those of a system having proportional viscous damping and a system having general viscous damping. A system that has non-linearity, an error from the calculation may occur in the analysis. In this case, we applied the piecewise linear method to estimate the modal parameters.

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Spectral Analysis Method for the Multi-DOFs Dynamic Systems with Non-Proportional Damping (비비례 진동감쇠를 갖는 선형 동역학계의 스펙트럴 해석법)

  • Cho, Joo-Yong;Kim, Sung-Hwan;Lee, U-Sik
    • Proceedings of the KSR Conference
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    • pp.411-416
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    • 2004
  • This paper introduces a fast Fourier transform (FFT)-based spectral analysis method for the transient responses as well as the steady-state responses of linear dynamic systems with non-proportional damping. The force vibration of a non-proportionally damped three-DOF system is considered as the illustrative numerical example. The proposed spectral analysis method is evaluated by comparing with the numerical solution obtained by the Runge-Kutta method

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Comparison of Damping Matrix Estimation Methods for Model Updating (모형개선을 위한 감쇠행렬 추정법의 비교)

  • Lee, Gun-Myung;Ju, Young-Ho;Park, Mun-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.20 no.10
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    • pp.923-930
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    • 2010
  • Finite element models of dynamic systems can be updated in two stages. In the first stage, mass and stiffness matrices are updated neglecting damping, and in the second stage, damping matrices are estimated with the mass and stiffness matrices fixed. Three methods to estimate damping matrices for this purpose are proposed in this paper. The methods include one for proportional damping systems and two for non-proportional damping systems. Method 1 utilizes orthogonality of normal modes and estimates damping matrices using the modal parameters extracted from the measured responses. Method 2 estimates damping matrices from impedance matrices which are the inverse of FRF matrices. Method 3 estimates damping using the equation which relates a damping matrix to the difference between the analytical and measured FRFs. The characteristics of the three methods are investigated by applying them to simulated discrete system data and experimental cantilever beam data.

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.

Estimation of Damping Matrices for Dynamic Systems (동적 시스템의 감쇠행렬 추정)

  • Lee, Gun-Myung;Kim, Kyung-Ju;Ju, Young-Ho
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.10
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    • pp.1021-1027
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    • 2009
  • Finite element models of dynamic systems can be updated in two stages. In the first stage, mass and stiffness matrices are updated neglecting damping. In the second stage, a damping matrix is estimated with the mass and stiffness matrices fixed. Methods to estimate a damping matrix for this purpose are proposed in this paper. For a system with proportional damping, a damping matrix is estimated using the modal parameters extracted from the measured responses and the modal matrix calculated from the mass and stiffness matrices from the first stage. For a system with non-proportional damping, a damping matrix is estimated from the impedance matrix which is the inverse of the FRF matrix. Only one low or one column of the FRF matrix is measured, and the remaining FRFs are synthesized to obtain a full FRF matrix. This procedure to obtain a full FRF matrix saves time and effort to measure FRFs.

Efficient Dynamic Response Analysis Using Substructuring Reduction Method for Discrete Linear System with Proportional and Nonproportional Damping

  • Choi, Dong-Soo;Cho, Maeng-Hyo;Kim, Hyun-Gi
    • International Journal of Aeronautical and Space Sciences
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    • v.9 no.1
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    • pp.85-99
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    • 2008
  • The dynamic response analysis for large structures using finite element method requires a large amount of computational resources. This paper presents an efficient vibration analysis procedure by combining node-based substructuring reduction method with a response analysis scheme for structures with undamped, proportional or nonproportional damping. The iterative form of substructuring reduction scheme is derived to reduce the full eigenproblem and to calculate the dynamic responses. In calculating the time response, direct integration scheme is used because it can be applied directly to the reduced model. Especially for the non proportional damping matrix, the transformation matrices defined in the displacement space are used to reduce the system. The efficiency and the effectiveness of the present method are demonstrated through the numerical examples.

Effects of damping on the linear stability of a free-free beam subjected to follower and transversal forces

  • Kavianipour, O.;Sadati, S.H.
    • Structural Engineering and Mechanics
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    • v.33 no.6
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    • pp.709-724
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    • 2009
  • In this paper a free-free uniform beam with damping effects subjected to follower and transversal forces at its end is considered as a model for a space structure. The effect of damping on the stability of the system is first investigated and the effects of the follower and transversal forces on the vibration of the beam are shown next. Proportional damping model is used in this work, hence, the effects of both internal (material) and external (viscous fluid) damping on the system are noted. In order to derive the frequency of the system, the Ritz method has been used. The mode shapes of the system must therefore be extracted. The Newmark method is utilized in the study of the system vibration. The results show that an increase in the follower and transversal forces leads to an increase of the vibrational motion of the beam which is not desirable.