• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.159-163
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• 2005

A dynamic vibration absorber using the Zener's model has been taken into account with respect to frequency response characteristics. The concept of the tuned mass damper with a single degree of freedom has been well applied for many industrial fields, because many researchers have extensively studied various basic characteristics, performance and optimization methods for long time. The Zener's model has an additional spring, which is connected between a damper and a mass, while the tuned mass damper with a single degree of freedom consists of a mass, a spring and a damper connected in parallel. In previous works, the basic performance and characteristics of the Zoner's model as a dynamic vibration absorber have not been investigated. In this study, the frequency response characteristics according to the parameter change of the Zener's model have been described. In order to find the optimum value of several parameters, we use iterative scheme with three dimensional frequency response diagram by MATLAB programming. Present results shows the Zener's model can give more good damping performance than the simple tuned mass damper, and the numerical of optimization method should be developed for the efficient vibration absorbtion.

• Earthquakes and Structures
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• v.24 no.1
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• pp.21-36
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• 2023

Structural vibrations generated by earthquakes and wind loads can be controlled by varying the structural parameters such as mass, stiffness, damping ratio, and geometry and providing a certain amount of passive or active reaction forces. A Double-Tuned Mass Dampers (DTMDs) system, which is simple and more effective than the conventional single tuned mass damper (TMD) system for vibration mitigation is presented. Two TMDs tuned to the first two natural frequencies were used to control vibrations. Experimental investigations were carried out on a three degrees-of-freedom frame model to investigate the effectiveness of DTMDs systems in controlling displacements, accelerations, and base shear. Numerical models were developed and validated against the experimental results. The validation showed a good match between the experimental and numerical results. The validated model was employed to investigate the behavior of a five degrees-of-freedom shear building structure, wherein mass dampers with different mass ratios were considered. The effectiveness of the DTMDs system was investigated for harmonic, seismic, and white noise base excitations. The proposed system was capable of significantly reducing the story displacements, accelerations, and base shears at the first and second natural frequencies, as compared to conventional single TMD.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.351-358
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• 2020

This paper presents a tuned mass damper (TMD) utilizing a parametric design technique to reduce the dynamic responses to seismic loads of retractable large spatial structures. An artificial intelligence algorithm was developed to automatically search for the installation position of the damping device. This enables confirming the dynamic response of the structure in real time while finding the optimum position for the damping device. Further, the optimum mass of the damping device is determined from among several alternatives, and a design that can be effectively applied to both open and closed conditions of the roof is obtained.

• Journal of Aerospace System Engineering
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• v.4 no.4
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• pp.28-36
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• 2010

Current tanks have been developed to increase mobility and firepower, and its maximum range and destructive power are improved. This great change causes remained vibration of a gun barrel after firing. For this reason, people are trying to control vibration of gun barrel effectively. This thesis presents a modeling method and analysis results for gun barrel by using a thermal shroud as an absorber mass. DTS(Dynamically Tuned Shroud) is a vibration damping system using a thermal shroud as an added mass for decreasing remained vibration. The model has an advantage that the gun barrel's vibration can be decreased by dissipating a kinetic energy of thermal shroud without install an additional dynamic absorber to tip of the gun barrel. For analyzing the damping performance of the DTS, We derived an equation of motion of the barrel after setting a mathematical modeling, and found out the frequency analysis and tendency according to stiffness ratio between barrel and shroud.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.9
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• pp.706-715
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• 2014

Recently, the medical community has been enthusiastically welcoming robots that are able to provide high-quality medical services across the board, including assisting the surgeons during surgeries. In response, many higher education institutions and research facilities started to conduct various experiments and studies about these robots. During such research, it was discovered that the arm of one particular robot type that is being developed to assist surgeries are prone to vibrate even from the weakest impact, in addition to other residual vibration problems. We attempted to reduce such dynamic response by using a MF-TMD that is produced by adding magnetic fluid to ECD. We verified the MF-TMD's performance by testing it within various frequency bands and attenuations. We then designed a cantilever that was structurally similar to the robot's arm. We attached the MF-TMD to this cantilever and conducted a pilot experiment, which validated our hypothesis that MF-TMD will reduce the robot arm's vibrations through its optimal damping ratio. Henceforth, we attached the MF-TMD to the robot arm in question and conducted a performance experiment in which we tuned the MF-TMD's frequency and damping factor to its optimal level and measured the vibrations of the arm. The experiment demonstrated that the vibrations that occurred whenever the arms rotated were significantly reduced.

• Earthquakes and Structures
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• v.4 no.1
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• pp.63-84
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• 2013

A semi-active mass damping (SMD) system with magnetorheological (MR) dampers focusing on low- and mid-rise buildings is proposed in this paper. The main purpose of this study is to integrate the reliable characteristics of the traditional tuned mass damper (TMD) and the superior performance of the active mass damper (AMD) to the new system. In addition, the commonly seen solution of deploying dense seismic dampers throughout the structure nowadays to protect the main structure is also expected to switch to the developed SMD system on the roof with a similar reduction performance. In order to demonstrate this concept, a full-size three-story steel building representing a typical mid-rise building was used as the benchmark structure to verify its performance in real life. A numerical model with the interpolation technique integrated was first established to accurately predict the behavior of the MR dampers. The success of the method was proven through a performance test of the designated MR damper used in this research. With the support of the MR damper model, a specific control algorithm using a continuous-optimal control concept was then developed to protect the main structure while the response of the semi-active mass damper is discarded. The theoretical analysis and the experimental verification from a shaking table test both demonstrated the superior mitigation ability of the method. The proposed SMD system has been demonstrated to be readily implemented in practice.

• International Journal of High-Rise Buildings
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• v.8 no.2
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• pp.117-123
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• 2019

Tall buildings are prone to wind-induced vibrations due to their slenderness whereby peak structural accelerations may be higher than the recommended maximum value. The common countermeasure is the installation of a tuned mass damper (TMD) near the highest occupied floor. Due to the extremely large modal mass of tall buildings and because of the narrow to broad band type of wind excitation the TMD mass may become inacceptable large - in extreme cases up to 2000 metric tons. It is therefore a need to develop more efficient TMD concepts which provide the same damping to the building but with reduced mass. The adaptive TMD concept described in this paper represents a solution to this problem. Frequency and damping of the adaptive TMD are controlled in real-time by semi-active oil dampers according to the actual structural acceleration. The resulting enhanced TMD efficiency allows reducing its mass by up to 20% compared to the classical passive TMD. The adaptive TMD system is fully fail-safe thanks to a smart valve system of the semi-active oil dampers. In contrast to active TMD solutions the adaptive TMD is unconditionally stable and its power consumption on the order of 1 kW is negligible small as controllable oil dampers are semi-active devices. The adaptive TMD with reduced mass, stable behavior and lowest power consumption is therefore a preferable and cost saving damping tool for tall buildings.

• Smart Structures and Systems
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• v.26 no.1
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• pp.49-61
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• 2020

This paper proposes a novel high performance vibration control device, multiple tuned mass dampers-inerters (MTMDI), to suppress the oscillatory motions of structures. The MTMDI, similar to the MTMD, involves multiple tuned mass damper-inerter (TMDI) units. In order to reveal the basic performance of the MTMDI, it is installed on a single degree-of-freedom (SDOF) structure excited by the ground acceleration, and the dynamic magnification factors (DMF) of the structure-MTMDI system are formulated. The optimization criterion is determined as the minimization of maximum values of the relative displacement's DMF for the controlled structure. Based on the particle swarm optimization (PSO) algorithm to tune the optimum parameters of the MTMDI, its performance has been investigated and evaluated in terms of control effectiveness, strokes, stiffness and damping coefficient, inerter element force, and robustness in frequency domain. Meanwhile, further comparison between the MTMDI with MTMD has been conducted. Numerical results clearly demonstrate the MTMDI outperforms the MTMD in control effectiveness and strokes of mass blocks. Additionally, in the aspects of frequency perturbations on both earthquake excitations and structures, the robustness of the MTMDI is also better than the MTMD.

• International Journal of High-Rise Buildings
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• v.10 no.2
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• pp.85-92
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• 2021

Dynamic vibration absorbers (DVAs) in the form of tuned sloshing dampers (TSDs) and tuned mass dampers (TMDs) are commonly used to reduce the wind-induced motion of high-rise buildings. Full-scale performance of structure-DVA systems must be evaluated during the DVA commissioning process using structural monitoring data. While the random decrement technique (RDT) is sometimes employed to evaluate the DVA performance, it is shown to have no theoretical justification for application to structure-DVA systems, and to produce erroneous results. Subsequently, several practical methods with a sound theoretical basis are presented and illustrated using simulated and real-world data. By monitoring the responses of the structure and DVA simultaneously, it is possible to directly measure the effective damping of the system or perform system identification from which the DVA performance can be evaluated.

• Wind and Structures
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• v.5 no.5
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• pp.407-422
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• 2002

Passive control of the flutter condition of suspension bridges using a combined vertical and torsional tuned mass damper (TMD) system is presented. The proposed TMD system has two degrees of freedom, which are tuned close to the frequencies corresponding to vertical and torsional symmetric modes of the bridge which get coupled during flutter. The bridge-TMD system is analyzed for finding critical wind speed for flutter using a finite element approach. Thomas Suspension Bridge is analyzed as an illustrative example. The effectiveness of the TMD system in increasing the critical flutter speed of the bridge is investigated through a parametric study. The results of the parametric study led to the optimization of some important parameters such as mass ratio, TMD damping ratio, tuning frequency, and number of TMD systems which provide maximum critical flutter wind speed of the suspension bridge.