• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.467-474
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• 2002

이 연구에서는 점탄성감쇠기가 설치된 구조시스템의 통합최적설계 방법을 제시하였다. 최적화를 위한 목적함수로는 구조시스템이 유발하는 사회적 비용을 의미하는 총 생애주기비용을 사용함으로써, 구조제어 시스템의 성능에 기반한 경제적 유익을 극대화하도록 하였다. 구조물의 층별 기둥 강성 및 점탄성감쇠기의 사용량 등을 설계변수로 하여 생애주기비용함수를 정의하였으며, 통합시스템을 동시에 최적화하기위한 방법으로 유전자 알고리즘을 적용하였다. 동일한 초기비용을 사용하며 통합최적설계를 수행하지 않은 설계를 통해 얻어진 지진응답과 비교한 결과, 제안하는 통합 설계방법은 보다 우수한 진동제어효과를 발휘하는 것으로 나타났다.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.5 s.39
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• pp.55-64
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• 2004

In this paper, the preliminary design procedure of magnetorheological (MR) dampers is developed for controlling the building response induced by seismic excitation. The dynamic characteristics and control effects of the modeling methods of MR dampers such as Bingham, biviscous, hysteretic biviscous, simple Bouc?Wen, Bouc?Wen with mass element, and phenomenological models are investigated. Of these models, hysteretic biviscous model which is simple and capable describing the hysteretic characteristics, is used for numerical studies. The capacity of MR damper is determined as a portion of not the building weight but the lateral restoring force. A method is proposed for optimal placement and number of MR dampers, and its effectiveness is verified by comparing it with the simplified sequential search algorithm. Numerical results indicate that the capacity, number and the placement can be reasonably determined using the proposed design procedure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.5
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• pp.438-445
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• 2007

A Helmholtz resonator as a stabilization device to control high-frequency combustion instabilities in liquid rocket engine is adopted and its damping capacity is verified by linear acoustic analysis and atmospheric acoustic tests. To compare the results of acoustic attenuation effect in accordance with uni-resonator's geometry, quantitative analyses were made in the cases of various orifice diameters and lengths. Next, in the experiments to compare the results of acoustic attenuation effect by a difference in the number of resonators, damping capacity of harmful resonant frequency was improved by the increase of the number of resonators. On the other hand, attenuation efficiency of the frequency tended rather to lower due to over damping from the point of view of absorption coefficient. As the result, tuning the suitable geometry for the resonator to the resonant frequency is required for the control using the resonator. Also, the design of resonator's geometry and the choice of its number are important to put up the optimal efficiency in consideration of restriction of its volume.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.1
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• pp.31-36
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• 2001

본 논문에서는 지점근처에 납-전단 댐퍼(LSD)가 설치된 케이블의 동적 거동에 대해 다루었다. 이러한 동적 거동에 대한 파악은 케이블의 진동 감소 목적으로 댐퍼를 설계하는 경우 중요한 절차중 하나이다. 납-전단 댐퍼와 같은 이력형 댐퍼의 실제 이력곡선에 기초하여 본 연구에서는 납-전단 댐퍼의 이력곡선을 완전 탄소성으로 가정하였다. 납-전단 댐퍼의 역학적 모델은 등가 켈빈 모델을 사용하였으며 케이블의 새그 효과를 고려하였다. 납- 전단 댐퍼의 용량이라고 할 수 있는 항복력을 설계변수로 선택하고 케이블에 최적의 감쇠효과를 부여하는 동적학적 관계에 대해 연구하였다. 또한 댐퍼가 케이블에 설치되는 지점과 케이블의 장력에 대한 댐퍼의 감쇠효과에 대해서도 연구하였다. 매개변수 해석결과 케이블의 기하학적 형상 및 댐퍼의 설치조건에 따라 납-전단 댐퍼가 케이블에 부가하는 감쇠의 크기가 변함을 알 수 있었으며, 이때 최대의 감쇠성능을 발휘하는 최적 항복력이 존재하는 것을 알았다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.10a
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• pp.19-22
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• 2004

In the future engine with high performance, the gas-liquid scheme injectors will be adopted and the role of the injector as an acoustic resonator is investigated as an advanced study The injector can play a significant role in acoustic damping and the optimum length of the injector to maximize the damping capacity is calculated as a function of baffle length.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.3
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• pp.34-40
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• 2008

Acoustic design parameters of a half-wave resonator are studied experimentally for acoustic stability in a model chamber. According to the standard acoustic-test procedures, acoustic-pressure signals are measured. Quantitative acoustic properties of damping factor and sound absorption coefficient are evaluated and thereby, the acoustic-damping capacity of the resonator is examined. The diameter and the number of a half-wave resonator, its distribution, and the diameter of an enclosure are selected as the design parameters for optimal tuning of the resonator. Aroustic-damping capacity of the resonator increases with its diameter. When the open-area ratio of the resonator exceeds the optimum value, over-damping appears, leading to the decrease in the peak absorption coefficient and the broadening of absorption bandwidth. As the resonator diameter increases, optimum open-area ratio decreases.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.351-358
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• 2020

This paper presents a tuned mass damper (TMD) utilizing a parametric design technique to reduce the dynamic responses to seismic loads of retractable large spatial structures. An artificial intelligence algorithm was developed to automatically search for the installation position of the damping device. This enables confirming the dynamic response of the structure in real time while finding the optimum position for the damping device. Further, the optimum mass of the damping device is determined from among several alternatives, and a design that can be effectively applied to both open and closed conditions of the roof is obtained.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.467-475
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• 2009

Existing studies have suggested Universal Curve only for supplemental damping by damper. Therefore net damping has been determined by means of arithmetic summation between intrinsic, aero-damping of cable and supplemental damping of damper. However linear combination approach by means of the arithmetic summation is not enough theoretical background. So validity of this approach should be verified in order to design adequate cable-damper system by engineers. This study establishes governing differential equation which can consider intrinsic, aero-damping and supplemental damping as well. And also analysis method is solved by combination of muller method and successive iteration method. Consequently, this study succeeds in verification for validity of linear combination approach. As a result of this study, linear combination approach is limitedly effective in case of low stiffness and optimum damping coefficient of damper, short distance from support to damper, lower vibration mode, low aero-damping, and normal windy environment. Whereas this study will be effective in case of opposite conditions, and existing studies or linear combination approach occur to further error. Meaning of this study presents exact solution for net damping of cable-damper system, and verifies linear combination approach by means of the analysis method. In the future, if monitoring of optimum damping coefficient of a damper against aero-damping is feasible on time, algorithm of this study will be available for control of cable and semi-active damper system such as magneto-rheological damper.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.1 s.41
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• pp.1-7
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• 2005

The optimal seismic retrofitting of NPP(Nuclear Power Plant) cabinet structures that contain seismic category 1 relays was studied in this paper. During earthquake event, the failure modes of relays are not appeared in form of structural failure, but are appeared in form of contact chatter of relay. Therefore, the retrofitting of cabinet has to be aimed at the reducing of the structural response, such as acceleration. In this study, the optimal characteristic values of dampers were searched by ${\mu}$-GA (micro-Genetic Algorithm) scheme for several installation patterns. To keep accuracy and efficiency of analysis, the structural models of cabinet were considered as a frame structure. The responses of structure were obtained inform of acceleration response spectra derived from the results of nonlinear time history analysis including damping nonlinearity. The objective function of the optimum procedure was constructed based on the maximum ratio of maximum spectral value and target GERS (General Equipment Ruggedness Spectra). The results show the good improvements of fitness for adequate retrofitting pattern. Especially, the improvements of fitness were remarkable when the values of damping exponents are low.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.3
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• pp.1-8
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• 2010

Acoustic tuning of quarter-wave resonator is investigated numerically to suppress combustion instability in liquid rocket engines. A model combustion chamber is adopted. First, basic acoustic characteristics are examined and acoustic damping is pursued by quarter-wave resonators. Next, for frequency tuning of the resonators, thermodynamic properties inside the acoustic resonators are estimated based on the numerical data. Maximum damping capacity is obtained when the resonators are designed to have the optimum length calculated with the properties. But, damping capacity induced by the resonators with the same length is comparable with it.