• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.154-157
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• 2010

본 논문에서는 비선형 동적해석법을 이용하여 감쇠기의 적용이 철골조 건물의 연쇄붕괴 방지에 미치는 영향을 평가하였다. 단자유도 구조물에서 감쇠비의 변화에 따라 폭발하중이 구조물의 응답에 미치는 영향을 분석하였고, 15층 3경간 철골조 건물에서는 일정한 감쇠비 하에서 경간을 6m, 9m, 12m로 달리 하면서 감쇠기 설치 효과를 비교하였다. 단자유도 시스템의 경우 감쇠비가 증가 할수록 폭발하중에 의한 진동이 빠르게 감소하고 변위의 감소폭도 커지는 경향을 보였다. 15층 철골조 건물에서도 역시 감쇠기를 설치할 경우 수직 처짐 및 초기 진동을 제어하는 효과가 있었다. 구조물의 경간이 증가하여 수직 변위가 증가 할수록, 감쇠기에 의해 소산된 에너지도 증가하기 때문에 수직 처짐 제어효과가 큰 것으로 나타났다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.199-208
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• 2010

A friction damper installed at a building shows nonlinear behavior since its stick and slip states are occurred repeatedly depending on the amplitude of external loadings to dissipate input energy. Friction damping is existed for the building with a friction damper. In additionally viscous one is inherently included. Therefore, the building installed in such combined damping is quite involved to find the analytical solution. In this study, first, displacement and acceleration characteristics are identified based on the exact solution for a single-degree-freedom building with a friction damper having both friction and viscous damping. Second, in free vibration, the equivalent viscous damping ratio is obtained by the energy dissipation. Third, numerical analysis is carried out to find response configuration with various friction force ratios. Fourth, corresponding equivalent viscous damping ratio is derived with the finding that the response reaches into steady-state for both friction and viscous damped structure. It is deduced using balance of input external energy and output dissipation energy for steady-state response. Finally, the equivalent viscous damping ratios of free or harmonic vibration are verified through nonlinear analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.5
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• pp.15-23
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• 2010

To reduce the vibration levels, additional dissipation elements such as dry friction dampers are sometimes integrated into bladed disk assembly. In this study, forced response analysis systems for a tuned bladed disk with friction dampers were developed and verified. For the efficient nonlinear vibration analysis, multi-harmonic balanced method and cyclic boundary condition were used. Also, mode shapes obtained using fictitious mass method were used to describe the motion of the structures with the concentrated structural nonlinearity, friction damper. The relative convergence of fictitious mass and traditional unconstrained modes were compared.

• The Journal of Engineering Geology
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• v.6 no.2
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• pp.95-102
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• 1996

A study on the attenuation of ground vibration was carried out on the soil layer using seismic exploration method. A 12-channel engineering seismograph was used to acquire real digital amplitude data in field work. Frequency analysis of seismic data shows maximum spectrum amplitude around 40Hz. Relative amplitude decreases exponentially as the distance increases and the attenuation factors are n = 0.25 and a = 0.13-0.20. Internal attenuation indexes(a) are 0.13 and 0.20 in the wet soil zone and the vegatated soil zone, respectively. It means that ground vibration attenuates faster in vegatated soil zone than in wet soil zone. Average internal attenuation coefficient(h) was determined to be 0.094 from seismic velocity and frequency analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.97-100
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• 2004

물질의 진동감쇠 특성을 평가하는 대표적인 시험법은 ISO 6721, ASTM E 756 등에서 찾아 볼 수 있다. 이들 규격에서는 비접촉 가진방법으로 전자석 시스템을 사용한다. 하지만 이와 같은 방법은 강판 단독으로의 시험은 간편하나 비자성체 물질이나 도료를 도포 할 경우, 별도의 금속판이 필요하다. 또한 그에 따른 금속판의 감쇠특성을 별도로 평가해야 되며, 접착제에 대한 영향도 고려해야 된다. 이에 대한 보완으로 음압가진 방법을 이용한 비접촉 가진을 강철과 플라스틱에 적용하였다. 실험결과, 강철과 플라스틱의 공진주파수에 따른 손실계수와 탄성계수는 전자석을 이용한 실험결과와 일치하였다.

• Journal of KSNVE
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• v.10 no.1
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• pp.64-73
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• 2000

We present finite element equations in the Laplace-domain for linear viscoelastic and viscoelstically damped structures governed by a constitutive equation involving factional order derivative opeartors. These equations yield a nonstandard eigenproblem consisted of frequency dependent stiffness matrix. To solve this nonstandard eigenproblem we suggest an eigenvalue iteration procedure in the Laplace-domain. Improved Zenor and GHM material function type constitutive equations in the Laplace-domain are also available for this procedure. From above equations, complex eigenvalues and complex eigenvectors are obtained. Using obtained eigenvalues and eigenvectors, time domain analysis is performed by means of mode superposition. Finally, finite element solutions of viscoelastic and viscoeleastically damped sandwich beam are presented as an example.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.33-39
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• 1996

A theoretical study of the forced vibration response of a cantilevered beam with non-linear dry friction damping is analyzed by various slip displacements and force levels for the position coordinates of spring-mass-damper and external exciting force. A component mode analysis is carried out based on the constraint conditions and Lagrange multipliers to treat physical systems with non-linear damping. The analysis has shown that the basic phenomena observed for a simply supported beam with a dry friction damper attached are also observed for cantilevered beam.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.107-115
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• 2007

In this paper, the damping ratios of two methods, namely the half-power bandwidth method and random decrement method from the vibration measurement were examined. Ambient vibration tests were conducted on two steel-framed and one composite tall building ranging from 27 to 36 stories. The performance of the half-power bandwidth method was investigated using four sample sizes, such as 1024, 2048, 4096 and 8192. Damping by the half-power bandwidth method is slightly more overestimated than the random decrement method due to insufficient record length. Damping evaluation by the half-power bandwidth method was found to be enhanced when using the narrower bandwidth with long recorded data.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.6
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• pp.589-596
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• 2008

This study introduces the design of a bi-directional damper using a tuned mass damper(TMD) and a tuned liquid column damper(TLCD) and presents experimental verifications to confirm its control performance. The damper used in this study behaves as a TMD in a specific translational direction and acts as a TLCD in the other orthogonal direction. First, shaking table test is performed to investigate the coupled effect of control forces produced by TMD and TLCD. Then, the parameters that affect to dynamic characteristics of the proposed damper are quantitatively evaluated based on the experimental results. Testing results shows that the damper used in this study produces control forces coupled by TLCD and TMD, as it is excited by waves with an incident angle. Also, it is observed that the damper can be used to reduce bi-directional responses of building structures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.125-129
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• 2009

본 연구에서는 동강성법을 이용하여 2자유도 진동시스템을 모델링하였다. 등가 모델을 구성한 후 Inertance의 크기에 따라 변화되는 시스템의 특성을 규명하였다. 2자유도 진동 시스템을 단일 모우드 소거에 적용할 경우 해석적인 설계 방법론을 1) 감쇠가 없는 경우 2) 1개의 감쇠기를 갖는 경우로 나누어 제시하였다.