• 한국공간구조학회논문집
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• 제6권2호
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• pp.61-68
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• 2006

본 논문에서는 패시브 진돈제어시스템을 설치한 실대물 K형 철골브레이스 골조의 실험결과를 다루었다. 패시브 진동제어시스템은 점탄성물질을 이용하여 새롭게 개발된 댐퍼를 사용하였다. 이 실험모델의 진동제어 효율성을 확인하고 철골조 브레이싱의 진동반응특성을 조사하기 위하여 일련의 실험을 행하였다. 자유진동실험결과 댐퍼를 설치시 설치하지 않은 경우와 비교하여 3배정도의 진동제어능력을 나타냈다. 점탄성물질 난류댐퍼의 효율성은 진동실험에 의하여 확인되었다.

• Computers and Concrete
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• 제7권4호
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• pp.317-329
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• 2010

The paper describes localization of deformation in a bar under tensile loading. The material of the bar is considered as non-linear viscous elastic and the bar consists of two symmetric halves. It is assumed that the model represents behavior of the quasi-brittle viscous material under uniaxial tension with different loading rates. Besides that, the bar could represent uniaxial stress-strain law on a single plane of a microplane material model. Non-linear material property is taken from the microplane material model and it is coupled with the viscous damper producing non-linear Maxwell material model. Mathematically, the problem is described with a system of two partial differential equations with a non-linear algebraic constraint. In order to obtain solution, the system of differential algebraic equations is transformed into a system of three partial differential equations. System is subjected to loadings of different rate and it is shown that localization occurs only for high loading rates. Mathematically, in such a case two solutions are possible: one without the localization (unstable) and one with the localization (stable one). Furthermore, mass is added to the bar and in that case the problem is described with a system of four differential equations. It is demonstrated that for high enough loading rates, it is the added mass that dominates the response, in contrast to the viscous and elastic material parameters that dominated in the case without mass. This is demonstrated by several numerical examples.

• Structural Engineering and Mechanics
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• 제53권1호
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• pp.57-71
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• 2015

This study investigates the feasibility of retrofitting an existing building by connecting the existing building to a new building using connecting dampers. The new building is base-isolated and viscoelastic dampers are assigned as connecting dampers. Scaled models are tested under three different earthquake records using a shaking table. The existing building and the new building are 9 and 8 stories respectively. The existing building model shows more than 3% increase in damping ratio. The maximum dynamic responses and the root mean square responses of the existing building model to earthquakes are substantially reduced by at least 20% and 59% respectively. Further, numerical models are developed by conducting time-history analysis to predict the performance of the proposed seismic mitigation system. The predictions agree well with the test results. Numerical simulations are carried out to optimize the properties of connecting dampers and base isolators. It is demonstrated that more than 50% of the peak responses can be reduced by properly adjusting the properties of connecting dampers and base isolators.

• Steel and Composite Structures
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• 제23권6호
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• pp.691-714
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• 2017

Rotating fluid induced vibration and instability of embedded piezoelectric nano-composite separators subjected to magnetic and electric fields is the main contribution of present work. The separator is modeled with cylindrical shell element and the structural damping effects are considered by Kelvin-Voigt model. Single-walled carbon nanotubes (SWCNTs) are used as reinforcement and effective material properties are obtained by mixture rule. The perturbation velocity potential in conjunction with the linearized Bernoulli formula is used for describing the rotating fluid motion. The orthotropic surrounding elastic medium is considered by spring, damper and shear constants. The governing equations are derived on the bases of classical shell theory (CST), first order shear deformation theory (FSDT) and sinusoidal shear deformation theory (SSDT). The nonlinear frequency and critical angular fluid velocity are calculated by differential quadrature method (DQM). The detailed parametric study is conducted, focusing on the combined effects of the external voltage, magnetic field, visco-Pasternak foundation, structural damping and volume percent of SWCNTs on the stability of structure. The numerical results are validated with other published works as well as comparing results obtained by three theories. Numerical results indicate that with increasing volume fraction of SWCNTs, the frequency and critical angular fluid velocity are increased.

• 한국지진공학회논문집
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• 제5권3호
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• pp.45-55
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• 2001

본 연구는 점탄성 감쇠기의 최적설계에 관한 연구로서 기존에 독립적으로 설계되던 점탄성 감쇠기와 설치용 가새 강성의 동시 최적설계 방법을 제시하였다. 이를 위해 직렬 연결된 점탄성 감쇠기와 가새를 상태방정식으로 모델링하였으며 최대응답계수를 이용해서 각층 최대 층간변위를 구속조건으로 하여 최적화 문제를 구성하였다. 구속조건에 대한 기울기 정보를 계산하는 과정에서 구조물의 동적거동에 관한 구속조건을 포함시켜서 문제를 재구성함으로써 변수를 줄일 수 있었다. 설계예제를 통해 현실적으로 충분한 가새 강성이 제공될 수 없는 경우에는 층간변위 구속조건을 만족시키기 위해서 가새 강성을 고려한 감쇠기 설계가 필요함을 확인할 수 있었다. 또한 가새 강성을 최적화 변수에 포함시킴으로써 불필요한 가새 강성을 줄일 수 있었으며 이를 보상하기 위한 감쇠기 물량의 상대적인 증가는 크지 않다는 것을 확인할 수 있었다.