• Wind and Structures
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• v.7 no.4
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• pp.251-264
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• 2004

The effects of a class of nonlinear Tuned Mass Dampers on the aeroelastic behavior of SDOF systems are investigated. Unlike classical linear TMDs, nonlinear constitutive laws of the internal damping acting between the primary oscillator and the TMD are considered, while the elastic properties are keept linear. The perturbative Multiple Scale Method is applied to derive a set of bifurcation equations in the amplitude and phase and a parametric analysis is performed to describe the postcritical scenario of the system. Both cubic- and van der Pol-type dampings are considered and the dependence of the limit-cycle amplitudes on the system parameters is studied. These new results, compared with the previously obtained bifurcation scenario of a SDOF aeroelastic oscillator equipped with a linear TMD, show a detrimental effect on the maximum limit-cycle amplitude reduction of the nonlinear TMD. However, the analyses evidence that in the parameter region away from the perfect tuning condition the nonlinear connection can be used to tune the system with an enhancement of the limit-cycle amplitude reduction.

• Earthquakes and Structures
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• v.10 no.1
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• pp.239-260
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• 2016

Tuned mass dampers (TMDs) have been frequently proposed to mitigate the detrimental effects of dynamic loadings in structural systems. The effectiveness of this protection strategy has been demonstrated for wind-induced vibrations and, to some extent, for seismic loadings. Within this framework, recent numerical studies have shown that beneficial effects can be achieved by placing a linear TMD on the roof of linear elastic structural systems subjected to pulse-like ground motions. Motivated by these positive outcomes, closed-form design formulations have been also proposed to optimize the device's parameters. For structural systems that undergo a near-fault pulse-like ground motion, however, it is unlikely that their dynamic response be linear elastic. Hence, it is very important to understand whether such strategy is effective for inelastic structural systems. In order to provide new useful insights about this issue, the paper presents statistical results obtained from a numerical study conducted for three shear-type hysteretic (softening-type) systems having 4, 8 and 16 stories equipped with a linear elastic TMD. The effectiveness of two design procedures is discussed by examining the performances of the protected systems subjected to 124 natural pulse-like earthquakes.

• Smart Structures and Systems
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• v.33 no.6
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• pp.431-447
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• 2024

The Hybrid Mass Damper (HMD) has proven effective in mitigating vibrations in high-rise structures subject to seismic and wind-induced excitations. One derivative configuration of the HMD mounts an Active Mass Damper (AMD) atop a Tuned Mass Damper (TMD). However, the control efficacy of such HMDs may be compromised when confronted with loads that exceed their design parameters. Additionally, the confined structural space within high-rise structures often limits the feasibility and economic viability of retrofitting HMD systems. This study introduces an Acceleration-based Fuzzy Power Approach Rate Sliding Mode Control (AFP-SMC) algorithm aimed at enhancing the control efficacy of HMDs while minimizing their stroke and force output requirements. Employing the Canton Tower as a research prototype, an analytical model incorporating HMDs was established, and a comparative analysis between the AFP-SMC and Linear Quadratic Gaussian (LQG) control algorithms was conducted for efficacy. The control performance of the AFP-SMC control algorithm under different control parameter variations was investigated. Furthermore, by experimentally assessing the AMD subsystem within the Canton Tower, friction and ripple force formulas were derived to bolster the analytical model, thereby validating the robustness of the AFP-SMC algorithm. The results show that the proposed AFP-SMC algorithm effectively reduces the vibration response of the structure and the stroke and control force output of HMDs, and exhibits superior overall control performance and robustness compared to the LQG algorithm.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.374-381
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• 2003

In this study, the reduction schemes of ICRS(In-Cabinet Response Spectra), the main part of seismic safety qualification of old nuclear power plant(USI A-46 problem), are studied. To obtain accurate dynamic characteristics of cabinet structure, the cabinet structure modeled by frame model and its eigen analysis is performed. The three types of seismic retrofitting scenarios, such as 1) the installation of bracing, 2) installation of damper, 3) installation of tuned mass damper(TMD), are established and evaluated for the decreasing of ICRS. In the cases of 1) ＆ 2), since, the retrofitted structures show larger ICRS than that of original structure, the careful considerations are need in the application of these methods. Though, the case of TMD show the best retrofitting result, the tuning between the real structure and analysis model is estimated the essential step of retrofitting.

• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.4
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• pp.157-164
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• 2022

The TMD has a simpler structure than other vibration control devices and shows excellent control performance for the standardized vibration occurring in the structure. However, when the vibration cycle of the structure coincides with the vibration cycle of the TMD due to the sudden external loads, the off-tuning occurs, which threatens the structure while increasing the vibration width of the TMD. Therefore, Electromagnetic Tuned Mass Damper (ETMD) was developed as a semi-active TMD that prevents off-tuning while exhibiting excellent control performance like TMD. To verify the control performance of the developed ETMD, the bending behavior control performance evaluation experiment using a simple beam bridge was performed. The experimental method compared the mutual control power by experimenting with the existing TMD method and the developed ETMD under nine excitation frequency conditions. As a result, it was confirmed that the control effect of ETMD was about 4.85% higher than that of TMD at 3.02Hz, which generates the maximum displacement in the simple beam bridge. Also, the off-tuning occurred in some excitation conditions when using TMD, although the off-tuning did not occur when using ETMD. Therefore, the excellent control performance of the ETMD developed in this study was verified.

• Smart Structures and Systems
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• v.13 no.2
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• pp.319-341
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• 2014

A family of smart tuned mass dampers (STMDs) with variable frequency and damping properties is analyzed under harmonic excitations and ground motions. Two types of STMDs are studied: one is realized by a semi-active independently variable stiffness (SAIVS) device and the other is realized by a pendulum with an adjustable length. Based on the feedback signal, the angle of the SAIVS device or the length of the pendulum is adjusted by using a servomotor such that the frequency of the STMD matches the dominant excitation frequency in real-time. Closed-form solutions are derived for the two types of STMDs under harmonic excitations and ground motions. Results indicate that a small damping ratio (zero damping is the best theoretically) and an appropriate mass ratio can produce significant reduction when compared to the case with no tuned mass damper. Experiments are conducted to verify the theoretical result of the smart pendulum TMD (SPTMD). Frequency tuning of the SPTMD is implemented through tracking and analyzing the signal of the excitation using a short time Fourier transformation (STFT) based control algorithm. It is found that the theoretical model can predict the structural responses well. Both the SAIVS STMD and the SPTMD can significantly attenuate the structural responses and outperform the conventional passive TMDs.

• Smart Structures and Systems
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• v.20 no.4
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• pp.461-472
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• 2017

Explicit design formulae of liquid column vibration absorber (LCVA) for suppressing harmonic vibration of structures with small inherent structural damping are developed in this study. The developed design formulae are also applicable to the design of a tuned mass damper (TMD) and a tuned liquid column damper (TLCD) for damped structures under harmonic force excitation. The optimum parameters of LCVA for suppressing harmonic vibration of undamped structures are first derived. Numerical searching of the optimum parameters of tuned vibration absorber system for suppressing harmonic vibration of damped structure is conducted. Explicit formulae for these optimum parameters are then obtained by a series of curve fitting techniques. The analytical result shows that the control performance of TLCD for reducing harmonic vibration of undamped structure is always better than that of non-uniform LCVA for same mass and length ratios. As for the effects of structural damping on the optimum parameters, it is found that the optimum tuning ratio decreases and the optimum damping ratio increases as the structural damping is increased. Furthermore, the optimum head loss coefficient is inversely proportional to the amplitude of excitation force and increases as the structural damping is increased. Numerical verification of the developed explicit design expressions is also conducted and the developed expressions are demonstrated to be reasonably accurate for design purposes.

• Structural Engineering and Mechanics
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• v.87 no.4
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• pp.305-315
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• 2023

The idea of the combination of the fractional-order operators with the brain emotional learning-based intelligent controller (BELBIC) is developed for implementation in seismic-excited structures equipped with active mass damper (AMD). For this purpose, a new design framework of the mentioned combination namely fractional-order BEBIC (FOBELBIC) is proposed based on a modified-teaching-learning-based optimization (MTLBO) algorithm. The seismic performance of the proposed controller is then evaluated for a 15-story building equipped with AMD subjected to two far-field and two near-field earthquakes. An optimal BELBIC based on the MTLBO algorithm is also introduced for comparison purposes. In comparison with the structure equipped with a passive tuned mass damper (TMD), an average reduction of 44.7% and 42.8% are obtained in terms of the maximum absolute and RMS top floor displacement for FOBELBIC, while these reductions are obtained as 30.4% and 30.1% for the optimal BELBIC, respectively. Similarly, the optimal FOBELBIC results in an average reduction of 42.6% and 39.4% in terms of the maximum absolute and RMS top floor acceleration, while these reductions are given as 37.9% and 30.5%, for the optimal BELBIC, respectively. Consequently, the superiority of the FOBELBIC over the BELBIC is concluded in the reduction of maximum and RMS seismic responses.

• Structural Engineering and Mechanics
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• v.66 no.6
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• pp.749-759
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• 2018

Aiming at widely used high-pier bridges in Sichuan-Tibet Railway, this paper presents an investigation to design and evaluate the seismic vibration reduction effects of several measures, including viscous damper (VD), friction pendulum bearing (FPB), and tuned mass damper (TMD). Primarily, according to the detailed introduction of the concerned bridge structure, dynamic models of high-pier bridges with different seismic vibration reduction (SVR) measures are established. Further, the designs for these SVR measures are performed, and the optimal parameters of these measures are investigated. On this basis, the vibration reduction effects of these measures are analyzed and assessed subject to actual earthquake excitations in Wenchuan Earthquake (M=8.0), and the most appropriate SVR measure for high-pier bridges in Sichuan-Tibet Railway is determined at the end of the work. Results show that the height of pier does not obviously affect the performances of the concerned SVR measures. Comprehensively considering the vibration absorption performance, installation and maintenance of all the employed measures in this paper, TMD is the best one to absorb vibrations induced by earthquakes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1093-1101
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• 2005

Hybrid mass damper systems have recently been introduced as a dynamic vibration absorber to exploit the benefits of both the conventional tuned mass damper system and the active control system. A hybrid system is programmed to function as either a conventional TMD or as an active system according to the wind conditions and the resultant building and damper mass vibration characteristics. This paper deals with the design of the robust controller for the control of the flexible box structure. The control algorithm was devised based on $H_2$(LQG) robust control logic with acceleration feedback and to improve the capability of the controller Kalman Filter was accepted for the system. To test the ability of the robust controller using the linear motor damper system, performance tests and simulations were carried out on the full-scale steel frame structure. Through the performance tests, it was confirmed that acceleration levels are reduced down.