• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.6
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• pp.589-596
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• 2008

This study introduces the design of a bi-directional damper using a tuned mass damper(TMD) and a tuned liquid column damper(TLCD) and presents experimental verifications to confirm its control performance. The damper used in this study behaves as a TMD in a specific translational direction and acts as a TLCD in the other orthogonal direction. First, shaking table test is performed to investigate the coupled effect of control forces produced by TMD and TLCD. Then, the parameters that affect to dynamic characteristics of the proposed damper are quantitatively evaluated based on the experimental results. Testing results shows that the damper used in this study produces control forces coupled by TLCD and TMD, as it is excited by waves with an incident angle. Also, it is observed that the damper can be used to reduce bi-directional responses of building structures.

• Earthquakes and Structures
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• v.14 no.5
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• pp.459-465
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• 2018

Reducing response of buildings during earthquakes by mass dampers, has been examined in many articles and books. Nowadays, many researchers are trying to realistically examine this type of dampers by new methods of performance. In this paper, for the better study of tuned mass damper (TMD), two schematic models are presented for a passive TMD with softening stiffness (softening TMD) and a passive TMD with hardening stiffness (hardening TMD). Then by modeling and analysis of the damper on a single degree of freedom (SDOF) structure and an 11-story steel building, the dampers performance was evaluated. State space was used for damper and structure modeling and to solve nonlinear equations, the Newton-Raphson method was used. The results show that when the structure is subjected to the Chi-Chi earthquake, response of the sixth floor in the system without TMD reduces 54.0% in comparison to the structure with softening TMD. This percentage of reduction for hardening TMD is 55.0%. Also for the Tabas earthquake, reduction in the RMS acceleration of the sixth floor in the system with hardening TMD is 96.2% more than the structure without TMD. This percentage of reduction for hardening TMD is 96.3%.

• Structural Engineering and Mechanics
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• v.86 no.4
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• pp.573-587
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• 2023

A conventional tuned mass damper (TMD) provides a passive control option to suppress the structures' wind- or earthquake-induced vibrations. However, excessive displacements of the TMD raise concerns in the practical implementation. Therefore, this study proposes a novel TMD designed for and deployed on a high-rise sightseeing tower. The device consists of an integrated two-way slide rail mount and an eddy current damper (ECD) with a stroke control mechanism. This stroke control mechanism allows the damping coefficient to automatically increase when the stroke reaches a predetermined value, preventing excessive damper displacements during large earthquakes. The corresponding two-stage damping parameters are designed with a variable-thickness copper plate to enable the TMD stroke within a specified range. Thus, this study discusses the detailed design schemes of the device components in TMD. The designed two-stage damping parameters are also numerically verified, and the structural responses with/without the TMD are compared. As seen in the results, the proposed TMD yields effective control authority to limit the acceleration response within a comfort level. In addition, this TMD resolves the spatial availability for the damper movement in high-rise buildings by the controllable damping mechanism.

• Wind and Structures
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• v.30 no.6
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• pp.663-678
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• 2020

Robust semi-active vibration control of wind turbines using tuned mass dampers (TMDs) is a promising technique. This study investigates a 1.5 megawatt wind turbine controlled by eight different types of tuned mass damper systems of equal mass: a passive TMD, a semi-active varying-spring TMD, a semi-active varying-damper TMD, a semi-active varying-damper-and-spring TMD, as well as these four damper systems paired with an additional smaller passive TMD near the mid-point of the tower. The mechanism and controllers for each of these TMD systems are explained, such as employing magnetorheological dampers for the varying-damper TMD cases. The turbine is modelled as a lumped-mass 3D finite element model. The uncontrolled and controlled turbines are subjected to loading and operational cases including service wind loads on operational turbines, seismic loading with service wind on operational turbines, and high-intensity storm wind loads on parked turbines. The displacement and acceleration responses of the tower at the first and second mode shape maxima were used as the performance indicators. Ultimately, it was found that while all the semi-active TMD systems outperformed the passive systems, it was the semi-active varying-damper-and-spring system that was found to be the most effective overall - capable of controlling vibrations about as effectively with only half the mass as a passive TMD. It was also shown that by reducing the mass of the TMD and adding a second smaller TMD below, the vibrations near the mid-point could be greatly reduced at the cost of slightly increased vibrations at the tower top.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.51-62
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• 2006

To dale, lots of types of tuned mass dampers are developed and investigated to reduce dynamic responses of a structure due to various causes. In this study, control performance of semi-active tuned mass damper(STMD), that can change the damping of tuned mass damper in real time based on structural responses, was investigated with respect to various types of excitation employing numerical simulation. Skyhook control algorithm was used to appropriately modulate the damping ratio of semi-active damper that composes STMD. The control effectiveness of a STMD under harmonic and random excitation were evaluated using a single-degree-of-freedom (SDOF) structure in comparison with a conventional passive tuned mass damper (TMD). The robustness of a STMD and a passive TMD were compared along with the variation of the mass of a SDOF structure. The control performance of STMD using magnetorheological (MR) damper was also investigated in this study. Based on the numerical studios, it was shown that the control effectiveness of the STMD was significantly superior to that of a passive TMD with respect to harmonic and random excitation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.582-587
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• 2007

In this study, based on the results from the sinusoidal base excitation analyses of a single degree of freedom system with a tuned mass damper (TMD), it is verified that optimal friction force can improve the performance of a TMD like a linear viscous damper which has been usually used in general TMD. The magnitude of the optimal friction increases with increasing mass ratio of the TMD and decreases with increasing structural damping. Particularly, it is observed that the optimized friction force gives better control performance than the optimized viscous damping of the TMD. However, because the performance of the TMD considerably deteriorates when the friction force increases over the optimal value, it is required to keep the friction force from exceeding the optimal value.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.6 s.123
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• pp.553-559
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• 2007

In this study, based on the results from the sinusoidal base excitation analyses of a single degree of freedom system with a tuned mass damper (TMD), it is verified that optimal friction force can improve the performance of a TMD like a linear viscous damper which has been usually used in general TMD. The magnitude of the optimal friction increases with increasing mass ratio of the TMD and decreases with increasing structural damping. Particularly, it is observed that the optimized friction force gives better control performance than the optimized viscous damping of the TMD. However, because the performance of the TMD considerably deteriorates when the friction force increases over the optimal value, it is required to keep the friction force from exceeding the optimal value.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.53-61
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• 2007

A conventional passive TMD is only effective when it is tuned properly. In many practical applications, inevitable off-tuning of a TMD occurs because the mass in a building floor could change by moving furnishings, people gathering, etc. When TMDs are offtuned, TMDs their effectiveness is sharply reduced. Moreover, the off-tuned TMs can excessively amplify the vibration levels of the primary structures. This paper discusses the application of a new class of MR damper, for the reduction of floor vibrations duo to machine and human movements. The STMD introduced uses a MR damper called to semi-active damper to achieve reduction in the floor vibration. Here, the STMD and the groundhook algorithm are applied to a single degree of freedom system representative or building floors. The performance or the STMD is compared to that or the equivalent passive TMD. In addition, the effects of off-tuning due to variations in the mass of the floor system. Comparison of the results demonstrates the efficiency and robustness of STMD with respect to equivalent TMD.

• Journal of Korean Association for Spatial Structures
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• v.21 no.2
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• pp.41-48
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• 2021

A smart tuned mass damper (TMD) is widely studied for seismic response reduction of various structures. Control algorithm is the most important factor for control performance of a smart TMD. This study used a Deep Deterministic Policy Gradient (DDPG) among reinforcement learning techniques to develop a control algorithm for a smart TMD. A magnetorheological (MR) damper was used to make the smart TMD. A single mass model with the smart TMD was employed to make a reinforcement learning environment. Time history analysis simulations of the example structure subject to artificial seismic load were performed in the reinforcement learning process. Critic of policy network and actor of value network for DDPG agent were constructed. The action of DDPG agent was selected as the command voltage sent to the MR damper. Reward for the DDPG action was calculated by using displacement and velocity responses of the main mass. Groundhook control algorithm was used as a comparative control algorithm. After 10,000 episode training of the DDPG agent model with proper hyper-parameters, the semi-active control algorithm for control of seismic responses of the example structure with the smart TMD was developed. The simulation results presented that the developed DDPG model can provide effective control algorithms for smart TMD for reduction of seismic responses.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1091-1097
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• 2011

In the present study, TMD(tuned mass damper) with eddy current damping is proposed to suppress the vibration of a cantilever beam effectively. The advantages of TMD are that it is simple and its performance are excellent at any particular frequency. However, TMD may have the low performance at other frequency. To solve this problem and improve its performance, this study applies the eddy current damping to TMD. This TMD with ECD is named as MTMD(magnetically tuned mass damper). MTMD is designed for the vibration suppression of a cantilever beam. The mathematical modeling, simulation, and experiments of the cantilever beam with MTMD are performed. From analytic and experimental results, it can be concluded that the vibration suppression performance of MTMD are excellent.