• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.459-464
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• 2007

Seismic control performance of MR dampers, which have severe nonlinearity, differs with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally, response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.879-885
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• 2006

Seismic control performance of MR dampers, which have severe nonlinearity, differs with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally, response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

• 한국소음진동공학회논문집
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• 제18권1호
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• pp.87-93
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• 2008

Seismic control performance of MR dampers, which have severe nonlinearity, varies with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally. response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.427-430
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• 2002

The present parer outlines the system identification and vibration control performance of air traffic control tower of Yangyang international airport with tuned mass damper(TMD). From the free vibration test, natural frequency, damping ratio and mode shape of tower are obtained and these values are compared with the values from numerical analysis. In the vibration control test to evaluate the vibration control performance, equivalent damping ratio increased by tuned mass damper are obtained in case the TMD is operated as passive mode. Damping ratio of tower evaluated from free vibration test is about $1.0{\%}$. It is very low value than damping ratio recommended in general code. Damping ratio of passive mode is about $5{\%}$. These equivalent damping ratio increased by TMD is enough to enhance the serviceability of tower structure under wind load.

• Steel and Composite Structures
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• 제14권4호
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• pp.349-365
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• 2013

Structures consisting of concrete and steel parts, which are irregular in damping ratios are investigated. This investigation is a code-based seismic design of such structures. Several practical difficulties encountered, due to inherent differences in the nature of dynamic response of each part, and the different damping ratios of the two parts. These structures are irregular in damping ratios and have complex modes of vibration so that their analysis cannot be handled with the readily available commercial software. Therefore, this work aims to provide simple yet sufficiently accurate constant values of equivalent damping ratios applied to the whole structure for handling the damping irregularity of such structures. The results show that the equivalent damping ratio changes with the height of the building and the kind of the structural system, but it is constant for all accelerations values. Thus, available software SAP2000 applied for seismic analysis, design and the provisions of existing seismic codes. Finally, evaluation of different kinds of structural system used in this research to find the most energy dissipating one found by finding the best value of quality coefficient.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.503-510
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• 2006

Seismic control performance of MR dampers, which have severe nonlinearity, differs with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with an MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with an MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed.

• 한국지진공학회논문집
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• 제12권1호
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• pp.43-55
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• 2008

비틂시험에서 전단탄성계수와 감쇠비에 상응하는 변형률 산정의 복잡성은 여러 방법에 의하여 해결되어 왔다. 특히, 수정 등가반경법은 공진주/비틂전단 시험의 모든 변형률 영역에서 변형률에 따른 등가반경비 곡선을 보다 효과적으로 나타내는데 적합하다. 감쇠비 산정시 수정 등가반경법을 쌍곡선 모델, 수정 쌍곡선 모델, 램버그오스굿 모델등에 적용시켜 보았다. 연구결과는 감쇠비 산정시 재래식 등가반경법에 의한 하나의 등가반경 수치를 사용하는 것은 적절치 않다는 것을 보여주었다. 이력감쇠뿐 아니라 미소변형률 영역에서의 흙의 감쇠 현상을 고려하기 위하여 새로운 모델이 개발되었고, 이러한 두 가지 복합감쇠에 상응하는 변형률 산정시 부가적 조정이 필요한지 검토해 보았다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.459-466
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• 2002

The purpose of this study is to propose a new method for evaluating equivalent damping ratios of a structure with supplemental damping devices to assess their control effect quantitatively. A MDOF system is transformed to an equivalent SDOF system based on the assumption that the first mode dominates structural response. Approximate closed-form formulas for the evaluation of the first damping ratio are presented for various damping devices. Through numerical analysis of a ten-story building equipped with damping devices, the effectiveness of equivalent SDOF model and closed form formulas are verified.

• Smart Structures and Systems
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• 제30권6호
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• pp.627-637
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• 2022

Recent years, direct displacement-based design (DDBD) procedure is proposed for the design of un-bonded posttensioned (UPT) concrete wall systems. In the DDBD procedure, the determination of the equivalent viscous damping (EVD) ratio is critical since it would influence the strength demand of the UPT wall systems. Nevertheless, the influence of EVD ratio determination of the UPT wall systems were not thoroughly evaluated. This study was aimed to investigate the influence of different EVD ratio determinations on the DDBD procedure of UPT wall systems. Case study structures with four, twelve and twenty storeys have been designed with DDBD procedure considering different EVD ratio determinations. Nonlinear time history analysis was performed to validate the design results of those UPT wall systems. And the simulation results showed that the global responses of the case study structures were influenced by the EVD ratio determination.

• Steel and Composite Structures
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• 제13권6호
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• pp.501-519
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• 2012

As an alternative to current conventional force-based assessment methods, the energy-based seismic performance of a code-designed 20-storey high-rise steel building is evaluated in this paper. Using 3D nonlinear dynamic time-history method with consideration of additional material damping effect, the influences of different restoring force models and P-${\Delta}/{\delta}$ effects on energy components are investigated. By combining equivalent viscous damping and hysteretic damping ratios of the structure subjected to strong ground motions, a new damping model, which is amplitude-dependent, is discussed in detail. According to the analytical results, all energy components are affected to various extents by P-${\Delta}/{\delta}$ effects and a difference of less than 10% is observed; the energy values of the structure without consideration of P-${\Delta}/{\delta}$ effects are larger, while the restoring force models have a minor effect on seismic input energy with a difference of less than 5%, but they have a certain effect on both viscous damping energy and hysteretic energy with a difference of about 5~15%. The paper shows that the use of the hysteretic energy at its ultimate state as a seismic design parameter has more advantages than seismic input energy since it presents a more stable value. The total damping ratio of a structure consists of viscous damping ratio and hysteretic damping ratio and it is found that the equivalent viscous damping ratio is a constant for the structure, while the equivalent hysteretic damping ratio approximately increases linearly with structural response in elasto-plastic stage.