• Title/Summary/Keyword: 점탄성감쇠기

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Design of Viscoelastic Dampers Using Effective Damping Ratio (유효감쇠비를 이용한 점탄성 감쇠기의 설계)

  • 최현훈;김진구
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2001.04a
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    • pp.371-378
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    • 2001
  • To enhance seismic performance of a structure ATC-40 and FEMA-273 propose technical strategies such as increasing strength, altering stiffness, and reducing demand by employing base isolation and energy dissipation devices. Specifically the energy dissipation devices directly increase the ability of the structure to dampen earthquake response. However nonlinear dynamic time history analysis of a structure with energy dissipation devices is complicated and time consuming. In this study a simple and straightforward procedure is developed using effective damping ratio to obtain the required amount of viscoelastic dampers in order to meet given performance objectives. Parametric study has been performed for the period of the structure, yield strength, and the stiffness after the first yield. According to the analysis results, earthquake demand and required damping ratio were reduced by installing viscoelastic dampers. The results also show that with the addition of the supplemental damping evaluted by the proposed method the performance of the model structures are well restrained within the target point.

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A Study on the improvement of damping and optimal design of beam flexure for the passive vibration isolator (수동형 음강성 저주파 제진기의 감쇠 성능 향상과 빔 유연체의 최적 설계에 관한 연구)

  • Lee, Gil-Yong;Chang, Hee-Doh;Park, Young-Ho;Park, In-Hwang;Han, Dong-Chul
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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    • pp.189-195
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    • 2008
  • The vibration isolator system(VIS) which has very low natural frequency could be designed by applying an axial compressive force to the beam-column flexure(BCF). In this paper a new shape of the BCF is suggested. It has stepwise axially varying properties by viscoelastic damping layer. So it has internal structural damping by damping layer during deformation. First the analytic solution is obtained for the BCF. And its critical load, buckling mode, stiffness and stress distributions are investigated. Also the dynamic properties of the VIS consist of the damping layered BCF are studied. Finally the optimal design procedure of damping layered BCF for the VIS is suggested. The improved performance of suggested VIS is verified by some experiments.

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Cost-Effectiveness Evaluation of the Structure with Viscoelastic Dampers (점탄성감쇠기를 설치한 구조물의 비용효율성 평가)

  • 고현무;함대기;조상열
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2001.04a
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    • pp.387-393
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    • 2001
  • Installing vibration control devices in the structure rises as a solution instead of increasing structural strength considering construction cost. Especially, viscoelastic dampers show excellent vibration control performance at low cost and are easy to install in existing structures compared with other control devices. Therefore, cost-effectiveness of structure with viscoelastic dampers needs to be evaluated. Previous cost-effectiveness evaluation method for the seismically isolated structure(Koh et al., 1999;2000)is applied on the building structure with viscoelastic dampers, which combines optimal design and cost-effectiveness evaluation for seismically isolated structures based on minimum life-cycle cost concept. Input ground motion is modeled in the form of spectral density function to take into account acceleration and site coefficients. Damping of the viscoelastic damper is considered by modal strain energy method. Stiffness of shear building and shear area of viscoelastic damper are adopted as design variables for optimization. For the estimation of failure probability, transfer function of the structure with viscoelastic damper for spectral analysis is derived from the equation of motion. Results reveal that cost-effectiveness of the structure with viscoelastic dampers is relatively high in how seismic region and stiff soil condition.

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Validation of Structural Safety on Multi-layered Blade-type Vibration Isolator for Cryocooler under Launch Vibration Environment (적층형 블레이드가 적용된 냉각기용 진동절연기의 발사환경에서의 구조건전성 검증)

  • Jeon, Young-Hyeon;Ko, Dai-Ho;Jo, Mun-Shin;Oh, Hyun-Ung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.7
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    • pp.575-582
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    • 2018
  • The spaceborne cooler is applied to cool down of the focal plane of the infrared detector of the observation satellite. However, this cooler induces unnecessary micro-jitter which can degrade the image quality of the high-resolution observation satellite. In this study, we proposed a multi-layered blade type vibration isolator to attenuate micro-vibration generated from a spaceborne cooler, while assuring structural safety of the cooler under severe launch loads without an additional launch-lock device. The blade of the isolator is formed with multi-layers in order to obtain durability against fatigue failure and an adhesive is applied between each layers for granting high damping capability under launch vibration environment. In this study, the basic characteristics of the isolator were measured using the free-vibration test. The effectiveness of the isolator design was demonstrated by launch vibration test at qualification level.

Performance Evaluation of Viscoelastic Dampers installed in the Steel Frame Structures Using the shaking table set (진동대 실험을 통한 강골조 구조물에 설치된 점탄성 감쇠기의 성능평가)

  • Kim, Jin-Gu;Seo, Hyun-Su;Kwon, Min-Ho;Lim, Jeong-Hee;Kim, Jin-Sup
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.7 no.1
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    • pp.32-38
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    • 2016
  • It has been many efforts for reinforcement of existing structure since the number of earthquake has been increased world widely. Especially the occurrence of earthquake surrounding area of Korean peninsular is dramatically increased. Since the buildings in Korea have not been designed to carry the lateral and shear force caused by earthquake, the building will experience massive damages even under moderate earthquake. For this reason, the viscoelastic damper is proposed in this paper to enhance the earthquake resistance of a steel frame buildings. The viscoelastic dampers have been able to increase the overall damping of the structure significantly, hence improving the overall performance of dynamically sensitive structures. In this paper, Viscoelastic dampers designed are consists of FRP panel and viscoelastic material. In this paper, evaluate the performance of the viscoelastic damper through the experiment.

Hybrid Vibration Control of Smart Laminated Composite Beams using Piezoelectric and Viscoelastic Material (압전재료와 점탄성 재료를 이용한 지능 복합적층보의 하이 브리드 진동제어)

  • Kang, Young-Kyu
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.10
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    • pp.148-153
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    • 2001
  • Active control of flexural vibrations of smart laminated composite beams has been carried out using piezoceramic sensor/actuator and viscoelastic material. The beams with passive constrained layer damping hale been analyzed by formulating the equations of motion through the use of extended Hamilton's principle. The dynamic characteristics such as damping ratio and modal damping of the beam are calculated for various fiber orientations by means of iterative complex eigensolution method. This paper addresses a design strategy of laminated composite under flexural vibrations to design structure with maximum possible damping capacity.

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Aeromechanical stability analysis and control of helicopter rotor blades (헬리콥터 회전날개깃의 안정성 해석과 제어)

  • Kim, J.S.;Chattopadhyay, Aditi
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.9 no.1
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    • pp.59-69
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    • 2001
  • The rotor blade is modeled using a composite box beam with arbitrary wall. The active constrained damping layers are bonded to the upper and lower surfaces of the box beam to provide active and passive damping. A finite element model, based on a hybrid displacement theory, is used in the structural analysis. The theory is capable of accurately capturing the transverse shear effects in the composite primary structure, the viscoelastic and the piezoelectric layers within the ACLs. A reduced order model is derived based on the Hankel singular value. A linear quadratic Gaussian (LQG) controller is designed based on the reduced order model and the available measurement output. However, the LQG control system fails to stabilize the perturbed system although it shows good control performance at the nominal operating condition. To improve the robust stability of LQG controller, the loop transfer recovery (LTR) method is applied. Numerical results show that the proposed controller significantly improves rotor aeromechanical stability and suppresses rotor response over large variations in rotating speed by increasing lead-lag modal damping in the coupled rotor-body system.

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Inelastic Analysis of Steel Frame Structures with Viscoelastic Damper (점탄성 감쇠기가 설치된 철골조 건물의 비탄성 해석)

  • 김진구
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2000.04a
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    • pp.186-193
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    • 2000
  • In this study the effect and applicability of viscoelastic dampers on the seismic reinforcement of steel framed structures are investigated in the context of the performance based design approach. The effect of the damper on dissipating the input seismic energy was investigated with a single degree of freedom system. For analysis models a five-story steel frame subjected to gravity load and a ten-story structure subjected to gravity and wind load were designed. the code-specified design spectrums were constructed for each soil type and performance objective and artificial ground excitation records to be used in the nonlinear time history analysis were generated based on the design spectrums. Interstory drift was adopted as the primary performance criterion. According to the analysis results both model structures turned out to satisfy the life safety performance level for most of the soil conditions except for the soft soil. It was also found that the seismic performance could be greatly enhanced by installing viscoelastic dampers on appropriate locations.

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A comparative study on the methods for analyses of viscoelastically damped structures (점탄성 감쇠기가 설치된 구조물의해석방법에 관한 연구)

  • 김진구
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1999.04a
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    • pp.135-142
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    • 1999
  • Although the vibration control effects of viscoelastic dampers in building structures have been well proved by numerous theoretical and practical examples it is difficult to find an outstanding method for analysis of viscoelastically damped structures satisfying both exactness and efficiency. Thus in this study four analysis methods for viscoelastically damped structures that are currently used or can be applied for the those system are speculated and compared to provide bass for developing a better method for analysis of viscoelastically damped structures. The seismic response time history inter-story drfts and analysis time recorded by computer simulation of four different methods are compared. Among these methods complex modal superposition approach turns out to be ecomomic and accurate procedure.

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Shaking Table Test of a Structure with Added Viscoelastic Dampers (점탄성 감쇠기가 설치된 구조물의 진동대 실험)

  • Kim., Jin-Koo;Kwon., Young-Jip
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.4
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    • pp.197-203
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    • 2001
  • This study presents the results of shaking table test of scaled model structures with added viscoelastic dampers, which are considered to be one of the most efficient means of upgrading existing structures against seismic loads. The experimental results were compared with those from analysis based on the linear modeling of viscoelastic dampers. The parameters obtained from free vibration test were utilized in the analysis. According to the results the added viscoelastic dampers turned out to be effective in reducing the responses of the model structures. It was also found that the analysis with linear modeling of viscoelastic dampers could simulate the test results accurately.

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