• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.126-128
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• 2009

• Structural Engineering and Mechanics
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• v.36 no.5
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• pp.561-573
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• 2010

The potential of the liquid column vibration absorber (LCVA) as a seismic vibration control device for structures has been explored in this paper. In this work, the structure has been modeled as a linear, viscously damped single-degree-of-freedom (SDOF) system. The governing differential equations of motion for the damper liquid and for the coupled structure-LCVA system have been derived from dynamic equilibrium. The nonlinear orifice damping in the LCVA has been linearized by a stochastic equivalent linearization technique. A transfer function formulation for the structure-LCVA system has been presented. The design parameters of the LCVA have been identified and by applying the transfer function formulation the optimum combination of these parameters has been determined to obtain the most efficient control performance of the LCVA in terms of the reduction in the root-mean-square (r.m.s.) displacement response of the structure. The study has been carried out for an example structure subjected to base input characterized by a white noise power spectral density function (PSDF). The sensitivity of the performance of the LCVA to the coefficient of head loss and to the tuning ratio have also been examined and compared with that of the liquid column damper (LCD). Finally, a simulation study has been carried out with a recorded accelerogram, to demonstrate the effectiveness of the LCVA.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.121-125
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• 2007

LCVA has an advantage that its natural frequency can be easily controlled by changing the area ratio of the vertical column and horizontal part. The previous studies investigated the dynamic characteristics of the LCVA under harmonic load. This study experimentally obtained the first and second mode natural frequencies of the LCVA from shaking table tests using white noise and compared the values with the ones by previous study. Test results show that the measured first mode natural frequency of the LCVA is larger than the calculated one when the area ratio is larger than 1. The second mode frequency increases with the increasing area ratio, which is due to the sloshing motion effect resulting from the large area of the vertical column.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.177-183
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• 1996

By utilizing the concept of normal modes, nonlinear dynamics is studied on pendulum dynamic absorber. When the spring mode loses the stability in undamped free system, a dynamic two-well potential is formed in Poincare map. A procedure is formulated to compute the forced responses associated with bifurcating mode and predict double saddle-loop phenomenon. It is found that quasiperiodic motion and stable periodic motion coexist in some parameter ranges, and only periodic motions or rotation of pendulum with chaotic fluctuation are observed in other ranges.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.3
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• pp.473-478
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• 1987

In this paper the optimum values of natural frequency ratio and damping ratio for damped systems were studied by numerical analysis. The relation between the amplitude ratio and frequency ratio obtained for the non-linear dynamic vibration absorber was found and it was compared with that of linear system. The results shows that the optimum frequency ratio decreases and the optimum damping ratio increases when the mass ratio of the damped system increases. The resonance frequency ratio and amplitude ratio decrease as mass ratio increases for the non-linear spring system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.145-149
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• 2000

In this paper, Firstly, it is shown that the bending mode vibration of check valve is comparatively large because resonance. Secondly in order to decrese the bending mode vibration of check valve, some practical dynamic vibration absorber have been developed and its effectiveness is investigated as installing it at the check valve of piping system practically.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.308-312
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• 2001

This research is concerned with development of the passive-active vibration absorber using piezoelectric actuators. This active-passive isolation system consists of 4-pairs of PZT actuators bonded on accordion type of mounting bracket and a spring-damper located in center. Hence, the active system is connected in parallel to the passive system. In this paper, we discuss the dynamic characteristics of the addressed system. Based on the series of experiment, it is found that the proposed system can cope with the external disturbances. The controller design is currently under investigation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.4
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• pp.13-21
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• 2001

Electrorheological(ER) fluid is a kind of smart material with variable shear stress and dynamic viscosity under various electric field intensity. Electric field can control the damping characteristics of ER damper. The objective of this study is the analysis of the performance of ER damper and its application to shock absorber. Idealized nonlinear Bingham plastic shear flow model is used to predict the velocity profile between electrodes. Cylindrical dashpot ER damper with moving electrode is constructed and tested under various electric fields. The analytic and experimental results for damping force are compared and discussed. Drop test system using ER damper is prepared to identify transient vibration characteristics. The rebound is eased as the applied electric field increases. When semi-active control algorithm is applied, rebound phenomenon disappears and vibration energy level decays faster than the case of zero electric field.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.27-34
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• 2015

Dynamic vibration absorbers are widely used in machinery, buildings, and structures, including bridges. Two cases of their usage are considered in this paper. One is a simply supported beam subjected to either a moving force or a sequence of moving forces, which simulates a train-bridge interaction problem. The other is a case where a primary system is mounted on a base that is not grounded and is excited by an external force. The conditions that the dynamic vibration absorbers must meet in these cases are found and compared to those for usual cases where bases of primary systems are grounded.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.371-377
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• 2009

In this paper, the dynamic characteristic of vibrating system which has translational and rotational degrees of freedom is studied. The moment of inertia of the system is modeled here as the inerter and the equivalent model to the system is proposed using dynamic stiffness method. It is shown that the size of inerter plays a major role to determine the dynamic characteristic of the system. This two degree of freedom system(DOF) is applied as a dynamic vibration absorber(DVA) to the elimination of single peak of main body. The solution for the undamped DVA is presented in analytical form while the damped DVA is designed using fixed point theory. The numerical examples are presented for verifying the methods.