• 한국구조물진단유지관리공학회 논문집
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• 제19권5호
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• pp.38-44
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• 2015

본 논문에서는 효과적인 제진설계를 구현하기 위한 설계기술 개발의 일환으로 최근 제안된 Exo-type 감쇠시스템을 활용하여 15층과 20층의 연구 대상 건물을 대상으로 감쇠시스템의 최적 강성비와 적용된 감쇠장치의 최적 항복비에 따른 철근콘크리트 라멘조 건물의 제진 효과를 검토해 보았다. 해석결과, Exo-type 감쇠시스템을 3개층 적용 시에는 대상 건물 15층과 20층 모두 밑면전단력과 최상층 최대응답변위 감소라는 관점에서 유효한 제진효과를 얻기 위해서는 Exo-type 감쇠시스템과 대상 건물의 강성비는 7.0 이상 확보를 하여야 하며, 감쇠시스템에 적용된 감쇠장치의 항복비는 대상 건물의 층전단력의 약 8.0% 이상 확보할 필요가 있는 것으로 나타났다. 또한, Exo-type 감쇠시스템을 5개 층 적용 시에는 대상 건물 15층과 20층 모두 Exo-type 감쇠시스템과 대상 건물의 강성비는 2.5 이상 확보 하여야 하며, 감쇠시스템에 적용된 감쇠장치의 대상 건물의 층전단력의 약 3.5%이상 확보할 필요가 있는 것으로 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.60-65
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• 2003

In this study, for estimating responses of a controlled structure and determining the maximum control force of velocity-dependent damping devices, three estimation models such as Fourier envelope convex model, probability model, and Newmark design spectrum are used. For this purpose, a procedure proposed by Gupta (1990) for estimating spectral velocity using pseudo-spectral velocity which is given by the estimation models is used and modified to consider the effects of increased damping ratio by the damping device. Time history results indicate that Newmark design spectrum gives the best estimation of maximum control force for over all period structures.

• Structural Engineering and Mechanics
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• 제74권1호
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• pp.19-32
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• 2020

Metallic energy-dissipation dampers are widely used in structures. They are comprised of an added damping and stiffness (ADAS) device with many parallel, diamond-shaped hole plates, the neck width of which is an important parameter. However, no studies have analyzed the neck width's influence on the ADAS device's performance. This study aims to better understand that influence by conducting a pseudo-static test on ADAS, with three different neck widths, and performing finite element analysis (FEA) models. Based on the FEA results and mechanical theory, a design neck width range was proposed. The results showed that when the neck width was within the specified range, the diamond-shaped hole plate achieved an ideal yield state with minimal stress concentration, where the ADAS had an optimal energy dissipation performance and the brittle shear fracture on the neck was avoided. The theoretical values of the ADAS yield loads were in good agreement with the test values. While the theoretical value of the elastic stiffness was lower than the test value, the discrepancy could be reduced with the proposed modified coefficient.

• 한국항공우주학회지
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• 제35권5호
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• pp.438-445
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• 2007

액체로켓엔진에서 발생하는 고주파 연소 불안정 제어를 위한 수동 안정화 제어 기구로 음향공을 적용하여, 선형 음향 해석 및 상온 음향 실험을 통해 감쇠 효과의 적합성을 검증하였다. 단일 음향공의 기하학적 형상에 따른 음향 감쇠 효과를 비교하기 위하여 오리피스 직경, 길이를 변화시킨 몇 가지 음향공 모델에 대해 유해 공진주파수 감쇠 효과를 정량적으로 비교, 분석하였다. 다음으로 음향공의 개수에 따른 음향 감쇠 효과를 비교하였다. 주파수 응답함수를 통한 유해주파수 감쇠 성능은 개수 증가에 따라서 우수해졌지만 흡음계수를 통한 최적의 효율 관점에서 볼 때 오히려 과도한 댐핑으로 인한 해당 주파수의 감쇠 효율이 낮아지는 경향이 발생한다. 결론적으로 음향공을 이용한 제어를 위해서는 유해주파수를 감쇠시킬 수 있는 기하학적 형상을 통한 정확한 동조가 필요하다. 또한, 부피의 제약을 고려한 최적의 효율을 발휘할 수 있는 음향공의 형상 설계와 개수의 선택이 절대적으로 필요함을 입증한다.

• Smart Structures and Systems
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• 제21권3호
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• pp.359-371
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• 2018

Strong seismic events commonly cause large drift and deformation, and functionality failures in the superstructures. One way to prevent functionality failures is to design structures which are ductile and flexible through yielding when subjected to strong ground excitations. By developing forces that assist motion as "negative stiffness forces", yielding can be achieved. In this paper, we adopt the weakening and damping method to achieve a new approach to reduce all of the structural responses by further adjusting damping phase. A semi-active control system is adopted to perform the experiments. In this adaptation, negative stiffness forces through certain devices are used in weakening phase to reduce structural strength. Magneto-rheological (MR) dampers are then added to preserve stability of the structure. To adjust the voltage in MR dampers, an inverse model is employed in the control system to command MR dampers and generate the desired control forces, where a velocity control algorithm produces initial required control force. An extensive numerical study is conducted to evaluate proposed methodology by using the smart base-isolated benchmark building. Totally, nine control systems are examined to study proposed strategy. Based on the numerical results of seven earthquakes, the use of proposed strategy not only reduces base displacements, base accelerations and base shear but also leads to reduction of accelerations and inter story drifts of the superstructure. Numerical results shows that the usage of inverse model produces the desired regulated damping, thus improving the stability of the structure.

• 한국항공우주학회지
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• 제34권6호
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• pp.59-66
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• 2006

액체 로켓엔진에서의 고주파 연소불안정 제어를 위한 수동 안정화 제어 기구로 음향공을 적용하여 감쇠 효과의 적합성을 검증하였다. 우선, 기본형 모델링 연소실에서 발생한 유해 공진주파수는 음향공의 동조를 통하여 효과적으로 감쇠될 수 있음을 확인 하였다. 또한, 음향공의 기하학적 형상에 따른 음향 감쇠 효과를 비교하기 위하여, 주요 설계 변수를 변화시킨 몇 가지 음향공 모델에 대해 유해 공진주파수 감쇠 효과를 정량적으로 비교, 분석하였다. 선형음향해석과 실험적 방법 모두 만족할만한 일치성을 나타내었으며, 오리피스 입구 면적이 가장 크거나 오리피스 길이가 가장 짧은 경우에서 감쇠 효과가 가장 크게 나타났다. 결론적으로 음향공을 이용한 최적의 음향공 제어를 위해서는 음향공 부피를 고려한 최적의 음향공 설계가 절대적으로 필요함을 입증한다.

• 대한조선학회논문집
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• 제40권1호
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• pp.1-7
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• 2003

The effect of the passive anti-rolling tanks(ART) decreases when the roll period of the vessel does not match the designed oscillating period of the fluid in the tank. In order to improve the effect of the passive ART, the damping plates are installed in the lower duct of the ART to adjust the oscillating period of the fluid. The effects of the damping plates on the oscillating period of the fluid and the changes of the stabilizing moments are examined through the series of bench tests. Acryl model tank larger than 1m breadth is made to minimize the viscous effect of the tank and the stabilizing moments of the tank are measured for various roll angles. Using the obtained tank damping coefficient, RAO(Response Amplitude Operator) value in the resonance range is computed and the stabilizing effect of a ART has been estimated.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1995년도 추계학술발표회논문집(2)
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• pp.1021-1026
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• 1995

The seismic responses of a base isolated Pressurized Water Reactor (PWR) are investigated using a mathematical model which expresses the superstructure as lumped mass-spring model and the seismic isolator as an equivalent spring-damper. Time history analyses are performed for the 1940 E1 Centre earthquakes in both horizontal and vertical directions. In the analysis, structural damping of 5% is used for the superstructure. The isolator damping ratios of 12% for horizontal and 5% for vertical directions are used. The acceleration responses in base isolated PWR superstructure with high damping rubber bearings are much smaller than those in fixed base structure in horizontal direction. However, the vertical acceleration responses at the superstructure in the base isolation system are amplified to some extent. It is suggested that the vertical seismic responses at the superstructure should be reduced by introducing a soft vertical isolation device.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.453-460
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• 2006

Stay cables, such as used in cable-stayed bridges, are prone to vibration due to their low inherent damping characteristics. Recently some studies have shown that active and semiactive control system using MR damper can potentially achieve both higher performance levels than passive control system and adaptability with few of the detractions. However, a control system including a power supply, controller, and sensors is required to maximize the performance of the MR damper and this complicated control system is not effective to most of large civil structures. This paper proposes a smart complex damping system which consists of toggle system and MR dampers by introducing electromagnetic induction(EMI) system as an external power source to MR damper. The performance of the proposed damping device has been compared with that of the passive-type control systems employing a MR damper, a linear viscous damper, and EMI system.

• Structural Engineering and Mechanics
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• 제55권6호
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• pp.1261-1278
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• 2015

Due to their low intrinsic damping, stay cables in cable-stayed bridges have often exhibited unanticipated and excessive vibrations which result in increasing maintenance frequency and disruption to normal operations of the entire bridges. Mitigation of undesired cable vibration can be achieved by attaching an external damping device near the anchorage. High Damping Rubber (HDR) dampers have many advantages such as compact size, better aesthetics, easy maintenance, temperature stability, and cost benefits; therefore, they have been widely used to increase cable damping. Although a single damper has been shown to reduce cable vibrations, it is not the most effective method due to geometric constraints. This paper proposes the use of two HDR dampers to improve effectiveness and robustness in suppressing cable vibration. Oscillation parameters of the cable-dampers system were investigated in detail by modeling the stay cable as a taut string and each HDR damper as complex-valued impedance and by using an analytical formulation of the complex eigenvalue problem. The problem of two HDR dampers arbitrarily located along a cable is solved and the solution is discussed. Asymptotic formulas to calculate the damping ratios of the cable with two HDR dampers installed near the anchorage(s) are proposed and compared with the exact solutions. Further, a design example is presented in order to justify the methodology. The results of this study show that when the two HDR dampers are installed close to each other on the same end of the cable, some interaction between the dampers leads to reduced damping ratio. When the dampers are on the opposite ends of the cable, they are effective in increasing damping ratio and can provide better vibration reduction to multiple modes.