• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.9
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• pp.862-873
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• 2007

Energy dissipation devices can be considered as an alternative for the seismic performance enhancement of existing structures based on the strengthened seismic design code. In this study, seismic response mitigation effects of friction dampers are investigated through the shaking table test of a full scale 3 story building structure. Frist, the bilinear force-displacement relationship of a structure-brace-friction damper system and the effect of brace-friction damper on the increase of frequency and damping ratio are identified. Second, frequency, displacement, and torque dependent characteristics of the friction damper are investigated by using harmonic load excitation tests. Finally, the shaking table tests are performed for a full scale 3 story steel frame. System identification results using random signal excitation indicated that brace-friction damper increased structural damping ratio and frequency, and El Centro earthquake test showed that brace-friction damper reduced the peak displacement and acceleration significantly. In particular, it was observed that the damping effect due to friction damper becomed obvious when the structure was excited by more intensive load causing frequent slippage of the friction dampers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.414-419
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• 2020

An artificial intelligence-based cable tension estimation model was developed to expand the utilization of data obtained from cable accelerometers of cable-stayed bridges. The model was based on an algorithm for selecting the natural frequency in the tension estimation process based on the vibration method and an applied artificial neural network (ANN). The training data of the ANN was composed after converting the cable acceleration data into the frequency, and machine learning was carried out using the characteristics with a pattern on the natural frequency. When developing the training data, the frequencies with various amplitudes can be used to represent the frequencies of multiple shapes to improve the selection performance for natural frequencies. The performance of the model was estimated by comparing it with the control criteria of the tension estimated by an expert. As a result of the verification using 139 frequencies obtained from the cable accelerometer as the input, the natural frequency was determined to be similar to the real criteria and the estimated tension of the cable by the natural frequency was 96.4% of the criteria.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.323-330
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• 2012

This study deals with the experiments of liquid dampers with multi cells whose vertical tubes are divided into several square columns for easily changing natural frequencies. Shaking table test is performed to verify control effectiveness of the dampers which are installed on a building structure. To design liquid dampers, a 64-story building structure is reduced to a SDOF structure with 1/20 of similitude laws based on acceleration. The structure model is made up to adjust its mass and stiffness easily, with separate mass and drive parts. Mass parts indicate real structure's weights and drive parts indicate real structure's stiffness with springs and LM guides. Manufactured liquid damper has 18 cells and its natural frequency ranges are 0.65Hz to 0.81Hz. Shaking table test is carried out with one way excitation to compare with only accelerations of a large-scale structure and a structure installed with liquid dampers. Control performance of the liquid damper is expressed by the transfer function from shaking table accelerations to the large-scale structure ones. Testing results show that the liquid damper reduced a large-scale structure's response by tuned natural frequencies.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.127-132
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• 2001

자기유변유체감쇠기를 이용한 반능동 제어 시스템은 최근에 개발되어 승용차의 승차감 향상을 위한 진동제어에 사용되고 있다. 본 연구에서는 바람, 지진, 파랑 등에 대한 대형구조물의 진동제어를 위한 MR 감쇠기의 적용성을 분석하기 위하여, 미국 토목학회에서 제안한 76층 건물의 풍하중에 대한 진동제어에 관한 Benchmark Problem에 대하여 수치모의 해석을 수행하였다. 연구결과로부터, 풍하중에 대한 고층 건물의 진동제어를 위하여 MR 감쇠기를 이용한 반능동 제어의 성능은 능동형 동조질량 감쇠기의 성능과 유사함을 확인할 수 있었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.9-15
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• 2003

This paper presents a design procedure for viscoelastic dampers to be installed in a full-scale steel structure and observes their vibration control effect, based on the excitation method and the dynamic characteristics of the structure investigated in the companion paper, Additional damping ratios required to reduce the maximum displacement to a given level were obtained by convex model. The size of dampers was determined by observing the change in modal damping ratio due to the change in damper stiffness using the modal strain energy method, The effect of the supporting braces was also considered in the determination of the modal properties. Two viscoelastic dampers were installed at the first and second inter-stories, respectively and their response reduction is verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.10a
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• pp.185-190
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• 1993

최근 서울에서는 날로 심각해지는 교통난 해소대책으로 현재 운행중인 1-4 호선 외에 5-8호선의 공사가 한창 진행중이다. 이러한 지하철 통과 인접지역 에서는 지하철 운행 진동으로 인하여 상부나 인접 건물에 진동 영향이 우려 되는 경우가 많으며 이에 대한 대책으로 지하철 궤도부를 방진하거나 상부 의 건물을 지하철 구조체로부터 진동 절연하는 방법이 검토되고 있다. 이러 한 대책 수립시에는 대책후의 진동예측이 필요하며 지하철의 진동특성 입력 데이타 확보가 필수적이다. 본 연구에서는 이러한 필요성에 따라 서울의 2호 선 강남역과 교대역, 3호선 교대역 궤도부 주변 바닥과 벽체, 플랫폼, 표파는 층의 바닥에서 지하철 통과시의 전후, 좌우, 상하방향의 진동을 측정 분석하 여 추후 지하철 진동저감대책 수립에 기초자료로 제시하고자 한다.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.3
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• pp.173-184
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• 2005

A capillary action-induced tension develops in the tear layer between the contact lens and cornea, which leads to the restoring force due to difference in the layer thickness between either upper and lower or left and right side of the lens when it is displaced off the equilibrium position as a result of blinking. Suppose the lens was displaced a certain distance from the equilibrium position, lens starts to oscillate toward the equilibrium position with the decreasing amplitude due to the restoring force as well as the velocity dependent viscous damping force in the tear layer. A mathematical model which consists of the differential equations and their numerical solution was proposed to analyze the damped oscillations of lenses. The model predicts the time dependence of lenses after the blink varying the various parameters such as Be, diameters, masses and positions displaced from equilibrium. As the Be and mass of lens increases the rate of amplitude reduction decreases, which requires a more time for the lens to return to the equilibrium position. It seems that varying the lens' displacement and diameters affect the lens' motion very little.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.6 s.40
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• pp.55-66
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• 2004

Recently, many high-rise apartment buildings using the box system, composed of only reinforced concrete walls and slabs, have been constructed. In residential buildings such as apartments, vibrations occur from various sources and these vibrations transfer to neighboring residential units through walls and slabs. It is necessary to use a refined finite element model for an accurate vibration analysis of shear wall building structures. But it would take significant amount of computational time and memory if the entire building structure were subdivided into a finer mesh. Therefore, an efficient analytical method, which has only translational DOFs perpendicular to walls or slabs by the matrix condensation technique, is proposed in this study to obtain accurate results in significantly reduced computational time. If all of the DOFs except those perpendicular to walls or slabs in the shear wall structure eliminated using the matrix condensation technique at a time, the computational time for the matrix condensation would be significant. Thus, the modeling technique using super elements and substructuring technique is proposed to reduce the computational time for the matrix condensation. Dynamic analysis of 3-story and 5-story shear wall example structures were performed to verify the efficiency and accuracy of the proposed method. It was confirmed that the proposed method can provide the results with outstanding accuracy requiring significantly reduced computational time and memory.

• Computational Structural Engineering
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• v.3 no.4
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• pp.123-132
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• 1990

In current practice of earthquake resistant design the equivalent lateral force procedure is widely used because of its simplicity and convenience. But the equivalent lateral force procedure is derived based on the assumptions that the dynamic behavior of the structure is governed primarily by the fundamental vibration mode and the effect of higher modes is included in an approximate manner. Therefore the prediction of dynamic responses of structures using the equivalent lateral force procedure is not reliable when the effect of higher vibration modes on the dynamic behavior is significant. In this study, design seismic load which can reflect the effect of higher vibration modes is proposed from the point of view of proper assessment of story shears which have the major influence on the design moment of beams and columns. To evaluate the effect of higher modes, differences between the story force based on the equivalent lateral force procedure specified in current earthquake resistance building code and the one based on modal analysis using design spectrum analysis are examined. From these results an improved design seismic load for the equivalent lateral force procedure which can reflect the effect of higher vibration modes are proposed.

• Journal of Korean Society of Steel Construction
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• v.24 no.1
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• pp.91-99
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• 2012

In recently, the vibration control of adjacent buildings have been studied and magneto-rheological(MR) fluid dampers have been applied to seismic response control. MR dampers can be controlled with small power supplies and the dynamic range of this damping force is quite large. This MR damper is one of semi-active dampers as a new class of smart dampers. In this study, vibration control effect according to the installation location of the MR damper connected adjacent buildings has been investigated. Adjacent building structures with different natural frequencies were used as example structures. Groundhook control model is applied to determinate control force of MR damper. In this numerical analysis, it has been shown that displacement responses can be effectively controlled as adjacent buildings are connected at roof floors by MR damper. And acceleration responses can be effectively reduced when two buildings are connected at the mid-stories of adjacent buildings by MR damper. Therefore, the installation floor of the MR damper should be selected with seismic response control target.