• Journal of the Korean Society of Safety
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• v.8 no.1
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• pp.80-87
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• 1993

This paper summarizes an experimental and analytical study on the application of viscoelastic dampers as energy dissipation devices in structural applications. Shaking table tests are carried out on the viscoelastically damped structure and the obtained structural responses are compared to those of the inelastic analysis results for the same test structure with no dampers added. It can be concluded the viscoelastic dampers are effective in reducing excessive vibrations of structures under strong earthquake ground motions. It is also observed that the increase in structure's stiffness by the addition of dampers can not contribute to improving the seismic response of a structure. In general. the reduction of the seismic response by adding the dampers to the structure is mostly resulted from the increased damping effect. It is found that the modal strain energy method can be used to reliably predict the equivalent structural damping. and the seismic response of a viscoelastically damped structure can be accurately estimated by conventional modal analysis techniques.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.241-248
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• 1987

The theoretical backgrounds of the several methods were surveyed and reviewed to fin out the adequate one to determine equivalent modal damping values in solving the dynamic problem of soil-structure interaction by mode superposition method. Furthermore the rigorous damping matrix of equation of motion was obtained through component mode synthesis technique and used in direct integration of the equation. The analytical results by direct integration method were compared with those of mode superposition approach using the various sets of equivalent modal damping values calculated by the methods to be reviewed. Two types of superstructures and four kinds of subsurface conditions were considered and combined to make soil-structure coupled models. It was realized that dissipating energy method gives the equivalent modal damping values which lead the most similar results to direct integration ones. In case of fixed base, the responses of all methods except stiffness weighted approach are almost equal to those of direct integration method.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.47-54
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• 2001

Unbond brace hysteretic dampers are generally used to prevent or decrease structural damage in building structures subjected to strong earthquake by its energy dissipating hysteretic behavior. In the study, a straightforward design procedure for unbond brace hysteretic dampers was developed. The required amount of equivalent damping to satisfy given performance acceptance criteria was obtained conveniently based on the capacity spectrum method without carrying out time-consuming nonlinear dynamic time history analysis. Then the size of the unbond braces is determined from the required equivalent damping. Parametric study has been performed for the design variables such as natural period, yield strength, the stiffness after the first yield stress of the unbond brace. The procedure was applied to 5-story and 10-story steel frames for verification of the proposed method. According to the earthquake time history analysis results, the maximum displacement of the model structure with unbond braces supplied in accordance with the proposed method corresponds well with the given target displacement.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.17-27
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• 2005

This paper presents an integrated optimum design and a cost effectiveness evaluation method of a viscoelastically damped structural system. The criterion selected for the optimization is the minimization of the life?cycle cost which is a function of structural sizing variables and the amount of the viscoelastic damper. A genetic algorithm is used as a numerical searching technique in order to simultaneously find the optimum parameters of the integrated system. Optimal distributions of design variables according to various seismic characteristics are investigated by applying the proposed design method to a numerical example of a 10?story building structure. The cost effectiveness of viscoelastically damped structural system is also evaluated by comparing the life-cycle cost of the structure without viscoelastic dampers. The results show that the viscoelastic damper is effective in a region of low to moderate seismicity.

• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.139-149
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• 1998

동적하중하에서 강섬유보강 콘크리트(SFRC)는 유연도 및 균열억제에서 우수한 재료로서 최근에 각종 구조물에 널리 사용되었으며, 특히 내진설계를 위한 강섬유보강 콘크리트 의 재료적 감쇠에 관한 규명이 절실히 요구되고 있다. 본 연구는 강섬유보강 콘크리트(SFRC)보의 재료적 감쇠효과증진을 실험적 및 수치해석적 방법으로 규명하는 데에 목적이 있으며, 일반적으로 강섬유 보강콘크리트(SFRC)보의 감쇠거동은 인장철근비, 강섬유의 혼입량과 형태, 콘크리트의 강도 그리고 응력의 크기에 좌우된다. 강섬유보강 콘크리트보의 감쇠비는 보의 균열상태 변화에따른 동적실험결과로부터 얻을 수 있으며, 일반적으로 강섬유보강 콘크리트는 증가된 에너지감쇠능력으로 인장철근이 소성전 상태에서 철근 콘크리트보의 경우보다 향상된 감쇠거동을 갖고 있는 것으로 판명되었다. 이들 결과의수치해석적인 입증을 위하여 curvature(곡률)와 감쇠값사이의 관계를 기초로 유한요소프로그램 (TICAL)을 개발하였으며, 결론적으로 0.44%인장철근비을 갖고 있는 강섬유보강 콘크리트의 감쇠비는 하중상태에 따라 철근 콘크리트보의 경우보다 약 5%에서 35%정도 향상된 감쇠비를 갖고 있는 것으로 조사되었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.6
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• pp.1-14
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• 2007

Optimal design method of nonlinear damping system for seismic response control of adjacent structures is studied in this paper. The objective functions of the optimal design are defined by structural response and total amount of the dampers. In order to obtain a solution minimizing two mutually conflicting objective functions simultaneously, multi-objective optimization technique based on genetic algorithm is adopted. In addition, stochastic linearization method is embedded into the multi-objective framework to efficiently estimate the seismic responses of the adjacent structures interconnected by nonlinear hysteretic dampers without performing nonlinear time-history analyses. As a numerical example to demonstrate the effectiveness of the proposed technique, 20-story and 10-story buildings are considered and MR dampers of which hysteretic behaviors vary with the magnitude of the input voltage are considered as nonlinear hysteretic damper interconnecting two adjacent buildings. The proposed approach can provide the optimal number and capacities of the MR dampers, which turned out to be more economical than the uniform distribution system while maintaining similar control performance. The proposed damper system is verified to show more stable performance in terms of the pounding probability between two adjacent buildings. The applicability of the proposed method to the design problem for optimally placing semi-active control system is examined as well.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.203-213
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• 2004

This study investigates the seismic responses of two structures connected by a sky-bridge equipped with viscoelastic dampers (VED) at the bridge-building connections. The applicability of the method is verified first by observing RMS (root-mean-squared) responses of two-degrees-of-freedom systems subjected to white noise ground excitation. Then model structures with various number of stories are analyzed using earthquake ground motions to observe the effect of the varying size of VED on the reduction of dynamic responses. According to the analysis results, there exists a proper size of VED which minimizes the structural responses. It is also observed that the effectiveness of VED increases as the difference of natural frequencies between the two connected structures increases.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.403-410
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• 2001

고층 빌딩의 풍하중에 의한 진동을 제어하기 위하여 MR 유체감쇠기를 이용한 반능동 제어 시스템의 설계에 대하여 연구하였다. 제안된 설계기법의 효율성을 검증하기 위하여 3차 ASCE benchma가 구조물을 대상으로 수치 모의 해석을 수행하였다. 유전자 알고리즘을 사용하여 MR 감쇠기의 76층 빌딩내에서의 최적위치와 용량을 결정하였으며, clipped optimal control 제어기법을 사용하여 가속도 되먹임 구조를 갖는 MR 감쇠기의 제어 알고리즘을 구성하였다. 수치 모의 해석 결과로부터 MR 감쇠기는 ATMD와 유사한 제어 성능을 가지고 있으며 매우 작은 규모의 파워 시스템만으로 운영이 가능한 효율적이고 안정적인 시스템임을 확인할 수 있었다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.72-77
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• 2001

고층 빌딩의 풍하중에 의한 진동을 제어하기 위하여 MR 유체감쇠기를 이용한 반능동 제어 시스템의 설계에 대하여 연구하였다. 제안된 설계기법의 효율성을 검증하기 위하여 ASCE benchmark 구조물을 대상으로 수치 모의 해석을 수행하였다. 유전자 알고리즘을 사용하여 MR 감쇠기의 76층 빌딩 내에서의 최적위치와 용량을 결정하였으며, clipped optimal control 제어기법을 사용하여 가속도 되먹임 구조를 갖는 MR 감쇠기의 제어 알고리즘을 구성하였다, 수치 모의 해석 결과로부터 MR 감쇠기는 ATMD와 유상한 제어 성능을 가지고 있으며 매우 작은 규모의 파워 시스템만으로 운영이 가능한 효율적이고 안정적인 제어 시스템임을 확인할 수 있었다.