• Wind and Structures
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• 제30권6호
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• pp.663-678
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• 2020

Robust semi-active vibration control of wind turbines using tuned mass dampers (TMDs) is a promising technique. This study investigates a 1.5 megawatt wind turbine controlled by eight different types of tuned mass damper systems of equal mass: a passive TMD, a semi-active varying-spring TMD, a semi-active varying-damper TMD, a semi-active varying-damper-and-spring TMD, as well as these four damper systems paired with an additional smaller passive TMD near the mid-point of the tower. The mechanism and controllers for each of these TMD systems are explained, such as employing magnetorheological dampers for the varying-damper TMD cases. The turbine is modelled as a lumped-mass 3D finite element model. The uncontrolled and controlled turbines are subjected to loading and operational cases including service wind loads on operational turbines, seismic loading with service wind on operational turbines, and high-intensity storm wind loads on parked turbines. The displacement and acceleration responses of the tower at the first and second mode shape maxima were used as the performance indicators. Ultimately, it was found that while all the semi-active TMD systems outperformed the passive systems, it was the semi-active varying-damper-and-spring system that was found to be the most effective overall - capable of controlling vibrations about as effectively with only half the mass as a passive TMD. It was also shown that by reducing the mass of the TMD and adding a second smaller TMD below, the vibrations near the mid-point could be greatly reduced at the cost of slightly increased vibrations at the tower top.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.597-602
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• 2006

Many researches have been studied several vibration control device such as TMD and TLD to reduce the influence of wind or seismic waves for high-rise buildings. TLD provides some advantages such as easy installation and low maintenance cost. However, because of the difficulties in evaluating the characteristics of TLD, the dynamic characteristics of TLD must be investigated by experiment or analysis. In this study, the dynamic response analysis of structure with TLD was carried out to verify the vibration control ability of the proposed TLD for high-rise building with about 60 stories. A real seismic wave was used, and the parameter of interest was chosen by the height of water level in the same shape of water tank. From the numerical results, the responses of structure with water tank were confirmed to be safer than those of structure without water tank.

• Wind and Structures
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• 제21권6호
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• pp.609-623
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• 2015

Seismic reliability analysis of a jacket-type support structure for an offshore wind turbine was performed. When defining the limit state function by using the dynamic response of the support structure, a number of dynamic calculations must be performed in a First-Order Reliability Method (FORM). That means analysis costs become too high. In this paper, a new reliability analysis approach using a static response is used. The dynamic effect of the response is considered by introducing a new parameter called the Peak Response Factor (PRF). The probability distribution of PRF can be estimated by using the peak value in the dynamic response. The probability distribution of the PRF was obtained by analyzing dynamic responses during a set of ground motions. A numerical example is presented to compare the proposed approach with the conventional static response-based approach.

• 한국강구조학회 논문집
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• 제18권2호
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• pp.173-180
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• 2006

구조물의 지진응답은 기초지반조건의 영향을 받는다. 이 연구에서는 고정지반과 연약지반을 고려한 3, 5, 7층 철골 건축구조물의 밑면전단력을 산정하기 위해 선형 시간이력지진해석과 비선형 Pushover 정적지진해석을 수행하였다. 등가정적강성식으로 구한 기초지반강성은 SAP2000의 Link 요소 중 Damper 요소를 사용하여 입력하였다. 범용구조해석 프로그램 SAP2000에 의한 시간이력으로 구한 철골건축구조물의 밑면전단력을 국내내진설계기준, UBC-97 설계응답스펙트럼, Pushover 정적 비선형해석으로 구한 밑면전단력과 비교하였다. 중력하중과 풍하중으로 설계된 철골 건축구조물은 0.11g의 중진에 대해 탄성응답을 보였고, 탄성 연약지반에서 구조물-지반의 상호작용과 지반 증폭에 의해 구조물의 변위와 밑면전단력이 증가되었다. 따라서, 중약진 지역에서의 건축구조물은 연약지반의 특성을 고려하여 탄성지진해석을 수행하는 것이 더 합리적이다.

• 한국지진공학회논문집
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• 제20권2호
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• pp.125-134
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• 2016

In order to improve seismic safety of nuclear power plant (NPP) structures in high seismicity area, seismic isolation system can be adapted. In this study, friction pendulum system (FPS) is used as the seismic isolation system. According to Coulomb's friction theory, friction coefficient is constant regardless of bearing pressure and sliding velocity. However, friction coefficient under actual situation can be changed according to bearing pressure, sliding velocity and temperature. Seismic responses of friction pendulum system with constant friction and various velocity-dependent friction are compared. The velocity-dependent friction coefficients of FPS are varied between low-and fast-velocity friction coefficients according to sliding velocity. From the results of seismic analysis of FPS with various cases of friction coefficient, it can be observed that the yield force of FPS becomes larger as the fast-velocity friction coefficient becomes larger. Also, the displacement response of FPS becomes smaller as the fast-velocity coefficient becomes larger.

• 한국공간구조학회논문집
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• 제8권4호
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• pp.91-100
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• 2008

본 연구에서는 sky-bridge로 연결된 고층건물의 진동제어성능을 검토하여 보았다. Sky-bridge를 이용한 진동제어의 원리는 서로 다른 동적특성을 가진 구조물이 sky-bridge를 통하여 제어력을 발휘함으로써 전체 시스템의 응답을 줄이는 것이다. 본 연구에서는 실제 건설 중인 sky-bridge로 연결된 고층건물(49층 및 42층)을 대상으로 구조물의 변위, 가속도 및 베어링반력, sky-bridge의 응력 등을 해석적인 방법으로 검토하였다. 이를 위하여 역사지진, 인공지진 및 풍동실험을 통해서 얻은 풍하중 시간이력을 사용하였다. 해석결과 sky-bridge를 사용하여 고층건물의 풍응답 및 지진응답을 효과적으로 줄일 수 있는 것을 확인하였다.

• 한국공간구조학회논문집
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• 제8권5호
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• pp.75-82
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• 2008

본 연구에서는 최상층면진시스템을 적용한 고층건물의 진동제어 가능성을 검토하여 보았다. 이를 위하여 20층 및 50층 건물을 예제구조물로 선택하였고 El Centro 남북방향 성분을 지진하중으로 사용하여 수치해석을 수행하였다. 그리고 인공풍하중을 사용하여 풍하중에 대한 예제구조물의 사용성을 검토하였다. 면진되는 상부층의 수를 변화시켜가면서 구조물의 응답을 평가함으로써 최적의 면진질량에 대해서 검토하였다. 또한 상부층면진시스템의 고유진동주기 변화에 따른 진동제어성능의 변화를 고정기초구조물과 비교하여 검토하였다. 해석결과 최상층면진시스템은 동조질량감쇠기로서 활용될 수 있으며 풍하중 및 지진하중에 대한 고층건물의 동적응답을 효과적으로 저감시킬 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.450-453
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• 2006

Coupling adjacent building with supplemental damping devices is a developing method of reduced structural response due to wind and seismic excitations. The philosophy is to allow structures, vibrating at different frequencies, to exert control forces upon one another to reduce the overall responses of the system. This paper studies the effect of installing vibration control devices of two high rise building structures(49 stories and 42 stories) connected by sky-bridge. According to the analysis results the use of sky-bridge can be effective in increasing damping ratio of the system.

• 한국지진공학회논문집
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• 제19권4호
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• pp.145-159
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• 2015

A seismic response analysis method for three-dimensional floating offshore structures due to seaquakes is developed. The hydrodynamic pressure exerted on the structure is calculated taking into account the compressibility of the sea water, the fluid-structure interaction, the energy absorption by the seabed, and the energy radiation into infinity. To validate developed method, the hydrodynamic pressure induced by the vibration of a floating massless rigid circular disk is calculated and compared with an exact analytical solution. The developed method is applied to seismic analysis of a support structure for a floating offshore wind turbine subjected to the hydrodynamic pressures induced from a seaquake. Analysis results show that earthquake response of a floating offshore structure can be greatly influenced by the compressibility of fluid, the depth (natural frequencies) of the fluid domain, and the energy absorption capacity of the seabed.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.3100-3111
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• 2021

Numerical modeling for the safety-related equipment used in a nuclear power plant (i.e., cabinet facilities) plays an essential role in seismic risk assessment. A full finite element model is often time-consuming for nonlinear time history analysis due to its computational modeling complexity. Thus, this study aims to generate a simplified model that can capture the nonlinear behavior of the electrical cabinet. Accordingly, the distributed plasticity approach was utilized to examine the stiffness-degradation effect caused by the local buckling of the structure. The inherent dynamic characteristics of the numerical model were validated against the experimental test. The outcomes indicate that the proposed model can adequately represent the significant behavior of the structure, and it is preferred in practice to perform the nonlinear analysis of the cabinet. Further investigations were carried out to evaluate the seismic behavior of the cabinet under the influence of the constitutive law of material models. Three available models in OpenSees (i.e., linear, bilinear, and Giuffre-Menegotto-Pinto (GMP) model) were considered to provide an enhanced understating of the seismic responses of the cabinet. It was found that the material nonlinearity, which is the function of its smoothness, is the most effective parameter for the structural analysis of the cabinet. Also, it showed that implementing nonlinear models reduces the seismic response of the cabinet considerably in comparison with the linear model.