• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.52-59
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• 2015

In this paper, the vibration control effect of the isotropic damping devices (so-called Kagome dampers) was investigated by applying the Kagome dampers to a 20-story frame structure apartment. A new Kagome Damper System (KGDS) composed of the dampers and supporting column was proposed and numerical analyses were performed to investigate the effects of stiffness ratio between controlled structure and supporting column, the damper size and the number of the dampers. The numerical analysis results of a structure with KGDS up to the third story showed that the stiffness ratio should be higher than 6.4 and the damper size be at least $700{\times}700mm$ to effectively reduce the base shear and the maximum drift of the uppermost story. When the KGDS was installed up to the fifth story, the stiffness ratio should be higher than 7.0 and damper size needs to be at least $500{\times}500mm$ for obtaining the target performance.

• Smart Structures and Systems
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• v.19 no.6
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• pp.665-678
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• 2017

In this paper the tuned mass-damper-inerter (TMDI) is considered for passive vibration control and energy harvesting in harmonically excited structures. The TMDI couples the classical tuned mass-damper (TMD) with a grounded inerter: a two-terminal linear device resisting the relative acceleration of its terminals by a constant of proportionality termed inertance. In this manner, the TMD is endowed with additional inertia, beyond the one offered by the attached mass, without any substantial increase to the overall weight. Closed-form analytical expressions for optimal TMDI parameters, stiffness and damping, given attached mass and inertance are derived by application of Den Hartog's tuning approach to suppress the response amplitude of force and base-acceleration excited single-degree-of-freedom structures. It is analytically shown that the TMDI is more effective from a same mass/weight TMD to suppress vibrations close to the natural frequency of the uncontrolled structure, while it is more robust to detuning effects. Moreover, it is shown that the mass amplification effect of the inerter achieves significant weight reduction for a target/predefined level of vibration suppression in a performance-based oriented design approach compared to the classical TMD. Lastly, the potential of using the TMDI for energy harvesting is explored by substituting the dissipative damper with an electromagnetic motor and assuming that the inertance can vary through the use of a flywheel-based inerter device. It is analytically shown that by reducing the inertance, treated as a mass/inertia-related design parameter not considered in conventional TMD-based energy harvesters, the available power for electric generation increases for fixed attached mass/weight, electromechanical damping, and stiffness properties.

• Journal of Korean Association for Spatial Structures
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• v.6 no.1 s.19
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• pp.101-109
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• 2006

An initial member sections of steel structures is selected by experience of expert building structural designers. And appropriate member section is designed by repeat calculation through structural analysis. Therefore an initial assumption of member section is necessary for saving the time for structural design and is important to acquire safety of building structures. Also brace damper are generally used to prevent or decrease stuctural damage by its hysteretic behavior in building structures subjected to strong earthquake. Based on plastic design, the initial section of members for architectural steel structures with hysteretic damper braces is presented and seismic effect of structural behavior by the ratio of damper stiffness to structural story stiffness is estimated in this paper.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.81-87
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• 2017

This paper describes the dynamic behavior and enhancement of Korean high-speed trains. The tail vibration reduction method of the yaw damper installation method change, which was derived from previous research, was applied to the running test of high-speed train. In addition, the vibration reduction method for the entire vehicle was derived by a numerical method and its effect was confirmed by a running test. The improved design was applied to the double-deck high-speed train coaches and the commissioning proceeded without problems in dynamic behavior. Sensitivity analysis of the suspension parameters affecting the critical speed of Korean next-generation high-speed trains was performed and four design variables that greatly affected the critical speed were derived. These were in the order of the primary elastic joint x-directional stiffness, the secondary yaw damper series stiffness, the secondary lateral damper damping coefficient, and the carbody damper damping coefficient. By optimizing the design variables, the suspension parameter that improves the critical speed by 23.3% can be used in the commercial designs of Korean next-generation high-speed trains.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.54-61
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• 2013

Stay cable has a strong axial rigidity due to large initial tension and, on the other hand, it has a weak laterally flexural rigidity. Wind loads or traffic loads cause the cables to vibrate significantly and affect the mechanical properties and the performance of cables of cable-stayed bridge (CSB). Therefore, the development of vibration reduction design is an urgent task to control the vibration vulnerable long-span bridges. As Friction damper (FD) shows to reduce the amplitude and duration time of vibration of cable of CSB from measured date in field test, friction damper can be considered that it is effective device significantly to reduce the amplitude and duration time in vibration of cable of CSB under traffic load, wind load and so on. Vibration characteristics of cable can change according to manufacturing method and type of established form. Nevertheless, analysis method in this study can present the design of friction damper for vibration reduction of cable of cable-stayed bridge from now on.

• Structural Engineering and Mechanics
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• v.78 no.1
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• pp.87-102
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• 2021

Long span cross-rope suspension structure is an innovative structural system evolved from typical Cross-Rope Suspension (CRS) guyed tower, a type of supporting system with short span suspension cable supporting overhead power transmission lines. In mountainous areas, the span length of suspension cable was designed to be extended to hundreds or over one thousand meters, which is applicable for crossing deep valleys. Vortex Induced Vibration (VIV) of overhead power transmission lines was considered to be one of the major factors of its fatigue and service life. In this paper, VIV and its controlling by Stockbridge damper for long span CRS was discussed. Firstly, energy balance method and finite element method for assessing VIV of CRS were presented. An approach of establishing FE model of long span CRS structure with dampers was introduced. The effect of Stockbridge damper for overall vibration of CRS was compared in both theoretical and numerical approaches. Results indicated that vibration characteristics of conductor in long span CRS compared with traditional tower-line system. Secondly, analysis on long span CRS including Stockbridge damper showed additional dampers installed were essential for controlling maximum dynamic bending stresses of conductors at both ends. Moreover, factors, including configuration and mass of Stockbridge damper, span length of suspension cable and conductor and number of spans of conductor, were assessed for further discussion on VIV controlling of long span CRS.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.141-148
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• 2021

In this study, the technology to prevent lateral deformation of steel dampers was reviewed and applied to the clamp type dampers. As for the experimental method, the rocking behavior was applied as in the previous study. The evaluation variables are the existing research results (SV-260) without lateral deformation prevention details and the test results (V-1, V-1R) with lateral deformation prevention details. Where, V-1 is the lateral deformation prevention detail at the lower part of the damper, and V-1R is the lateral deformation prevention detail at the lower part and upper part of the damper. As a result of evaluating the moment, drift ratio, and energy dissipation capacity relative to SV-260 at the time of maximum load, the maximum moments of V-1 and V-1R were increased by 1.22 times and 1.36 times compared to SV-260, and the maximum drift ratio increased by 2.41 times and 2.92 times. In addition, the energy dissipation capacity also increased by 1.39 times and 1.52 times, respectively. Therefore, the application of lateral deformation prevention details to the steel damper was evaluated as appropriate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.649-654
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• 2019

Stable haptic interaction with virtual environments is essential not only for the safety of the user but also for improving the immersion of the user. If the coefficient of a virtual spring is increased, the system becomes unstable. Therefore, the coefficient of the virtual spring is limited. The haptic system with the high-frequency zero-order-hold (HF-ZOH) is proposed to enhance the stability margin of a virtual spring. In this paper, the relationship among the sampling period of HF-ZOH, the coefficient of the physical damper, and the maximum stable margin of the virtual spring is analyzed. The lager the coefficient of the physical damper is, the shorter the sampling period of the HF-ZOH is, the larger the stable region of the virtual spring becomes. If the ratio N is larger than 40, the stable region of the proposed method is about three times to eight times that of the previous method, according to the coefficient of the physical damper. Hence the method enables to improve the user's realism in virtual environments.

• Structural Engineering and Mechanics
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• v.76 no.6
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• pp.709-724
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• 2020

The typical inerter system, the tuned viscous mass damper (TVMD), has been proven to be efficient. It is characterized by an energy-dissipation-enhancement effect, whereby the dashpot deformation of TVMD can be amplified for enhanced energy dissipation efficiency. However, existing studies related to TVMD have mainly been performed on elastic structures, so the working mechanism remains unclear for nonlinear structures. To deal with this, an energy-spectrum analysis framework is developed systematically for classic bilinear hysteretic structures with TVMD. Considering the soil effect, typical bedrock records are propagated through the soil deposit, for which the designed input energy spectra are proposed by considering the TVMD parameters and structural nonlinear properties. Furthermore, the energy-dissipation-enhancement effect of TVMD is quantitatively evaluated for bilinear hysteretic structures. The results show that the established designed input energy spectra can be employed to evaluate the total energy-dissipation burden for a nonlinear TVMD structure. Particularly, the stiffness of TVMD is the dominant factor in adjusting the total input energy. Compared with the case of elastic structures, the energy-dissipation-enhancement effect of TVMD for nonlinear structures is weakened so that the expected energy-dissipation effect of TVMD is replaced by the accumulated energy dissipation of the primary structure.

• Coupled systems mechanics
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• v.12 no.3
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• pp.277-295
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• 2023

Unsymmetrical high-rise buildings (HRBs) subjected to earthquake represent a difficult challenge to structural engineering, especially taking into consideration the effect of soil-structure interaction (SSI). L-shape in plan HRBs suffer from big straining actions when are subjected to an earthquake (in x- or y-direction, or both x- and y- directions). Additionally, the disastrous effect of seismic pounding may appear between two adjacent unsymmetrical HRBs. For two unsymmetrical L-shape in plan HRBs subjected to earthquake in three different direction cases (x, y, or both), including the SSI effect, different methods are investigated to mitigate the seismic pounding and thus protect these types of structures under the earthquake effect. The most effective technique to mitigate the seismic pounding and help in seismically protecting these adjacent HRBs is found herein to be the use of a combination of pounding tuned mass dampers (PTMDs) all over the height (at the connection points) together with tuned mass dampers (TMDs) on the top of both buildings.