• Earthquakes and Structures
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• 제14권6호
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• pp.567-576
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• 2018

This manuscript introduces a new damping device which is composed of a water tank and a pendulum. The new damping device can be tuned to multiple frequencies. In addition, it has a higher energy dissipation capacity when compared with the conventional Tuned Liquid Dampers (TLDs). In order to evaluate the efficiency of this new damping device a series of free vibration and forced vibration tests were conducted on a scaled down single-story one-bay steel frame. Two different configurations were studied for the mass of the pendulum that included a completely and a partially submerged mass. It was observed that the completely submerged configuration led to 44% higher damping ratio when compared with the conventional TLD. In addition, the completely submerged configuration reduced the peak displacement response of the structure 1.6 times more than the conventional TLD. The peak acceleration response of the structure equipped with the new damping device was reduced twice more than the conventional TLD. It was also found that, when the excitation frequency is lower than the resonance frequency, the conventional TLD performs better than the partially submerged configuration of the new damping device.

• 한국정밀공학회지
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• 제26권6호
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• pp.81-89
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• 2009

Dancer systems are typical equipment for attenuation of tension disturbances. Lately, demands for high speed roll-to-roll machines are rising but it is prior to attenuate the tension variation on the web entering into the printing zone to achieve the speed increment. Maintaining a constant tension before the first printing cylinder is the key of high speed, high quality printing. Dancer has been researched in two ways, whether it is controlled or not. The first one is active dancer and the other one is passive dancer. In the active dancer, a position of idle roll of dancer is measured and the roll is moved by external hydraulic cylinder to control tension disturbances. While the passive one composed with spring, damper and idle roll has no external actuator to position the idle roll. The tension disturbance causes movement of dancer roll and the displacement of the roll regulates the tension variation. On the other hand a composite type of dancer is applied for roll-to-roll printing machines. It has same apparatus as passive dancer. The displacement of roll is measured and front(or rear) driven roller is controlled to position the roll. In this paper, it is presented an analysis of pendulum dancer including position feedback PI control and logic for PI gain tuning in roll-to-roll machines. Pole-zero map and root locus with varying system parameters gives a design method for control of the dancer.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.209-216
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• 2005

The controller that can control the smart base isolation system consisting of M damper and friction pendulum systems(FPS) is developed in this study. A fuzzy logic controller (FLC) is used to modulate the M damper force because the FLC has an inherent robustness and ability to handle non-linearities and uncertainties. A genetic algorithm (GA) is used for optimization of the FLC. When earthquake excitations are applied to the structures equipped with smart base isolation system, the relative displacement at the isolation level as well as the acceleration of the structure should be regulated under appropriate level. Thus, NSGA-II(Non-dominated Sorting Genetic Algorithm) is employed in this study as a multi-objective genetic algorithm to meet more than two control objectives, simultaneously. NSGA-II is used to determine appropriate fuzzy control rules as well to adjust parameters of the membership functions. Effectiveness of the proposed method for optimal design of the FLC is judged based on computed responses to several historical earthquakes. It has been shown that the proposed method can efficiently find Pareto optimal sets that can reduce both structural acceleration and base drift from numerical studies.

• Structural Engineering and Mechanics
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• 제66권6호
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• pp.749-759
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• 2018

Aiming at widely used high-pier bridges in Sichuan-Tibet Railway, this paper presents an investigation to design and evaluate the seismic vibration reduction effects of several measures, including viscous damper (VD), friction pendulum bearing (FPB), and tuned mass damper (TMD). Primarily, according to the detailed introduction of the concerned bridge structure, dynamic models of high-pier bridges with different seismic vibration reduction (SVR) measures are established. Further, the designs for these SVR measures are performed, and the optimal parameters of these measures are investigated. On this basis, the vibration reduction effects of these measures are analyzed and assessed subject to actual earthquake excitations in Wenchuan Earthquake (M=8.0), and the most appropriate SVR measure for high-pier bridges in Sichuan-Tibet Railway is determined at the end of the work. Results show that the height of pier does not obviously affect the performances of the concerned SVR measures. Comprehensively considering the vibration absorption performance, installation and maintenance of all the employed measures in this paper, TMD is the best one to absorb vibrations induced by earthquakes.

• 한국소음진동공학회논문집
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• 제16권4호
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• pp.420-427
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• 2006

In this study, wind loads transmitted to a transmission tower from transmission lines are mitigated using rotational viscoelastic dampers. First, the wind load characteristics in a transmission tower is investigated considering the effect of the transmission lines through stochastic analysis. The assemblage of the transmission line and insulator are modeled as a double pendulum system connected to the SDOF model of the tower. From the result of the stochastic analysis, the background component of the overturing moment caused by the wind loads acting on the transmission lines are found to have considerable portion in the total overturning moment. Based on this observation result, a strategy Installing rotational viscoelastic damper (VED) between tower arm and transmission line is proposed for the mitigation of the transmission line reactions, which play a role as dynamic loads on a transmission tower. For the purpose of verification, time history analysis is conducted for different wind velocities and VED parameters. The analysis result shows that the rotational VED is effective for the mitigation of the background component rather than the resonance component of the transmission line reactions and achieves the reduction ratio of 50% even for higher wind speed.

• 조명전기설비학회논문지
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• 제28권3호
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• pp.63-71
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• 2014

A single-inverted-pendulum model is presented to simulate and predict the passive response of human balance control. This simplified biomechanical model was comprised of a torsional spring and damper, and a lump mass. An estimation of frequency response function was conducted to parameterize the complexity. The frequency domain identification method is used to identify the parameters of the model. The equivalent viscoelastic parameters of standing body were obtained and there was good conformity between the simulation and experimental result.

• Structural Engineering and Mechanics
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• 제30권1호
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• pp.1-20
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• 2008

The dynamic characteristics of the passive, semi-active, and active tuned-liquidcolumn dampers (or TLCDs) are studied in this paper. The design of the latter two are based on the first one. A water-head difference (or simply named as water head in this paper) of a passive TLCD is pre-set to form the so-called semi-active one in this paper. The pre-set of water head is released at a proper time instant during an earthquake excitation in order to enhance the vibration reduction of a structure. Two propellers are installed along a shaft inside and at the center of a passive TLCD to form an active one. These two propellers are driven by a servo-motor controlled by a computer to provide the control force. The seismic responses of a five-story shear building with a passive, semiactive, and active TLCDs are computed for demonstration and discussion. The responses of this building with a tuned mass damper (or TMD) are also included for comparison. The small-scale shaking-table experiments of a pendulum-like system with a passive or active TLCD to harmonic and seismic excitations are conducted for verification.

• 국제초고층학회논문집
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• 제3권1호
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• pp.35-48
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• 2014

In designing a 300 meter high skyscraper expected to be the tallest building in Japan, an earthquake-ridden country, we launched on the full-scale performance based design to ensure redundancy and establish new specifications using below new techniques. The following new techniques are applied because the existing techniques/materials are not enough to meet the established design criteria for the large-scale, irregularly-shaped building, and earth-conscious material saving and construction streamlining for reconstructing a station building are also required: ${\bullet}$ High strength materials: Concrete filled steel tube ("CFT") columns made of high-strength concrete and steels; ${\bullet}$ New joint system: Combination of outer diaphragm and aluminium spray jointing; ${\bullet}$ Various dampers including corrugated steel-plate walls, rotational friction dampers, oil dampers, and inverted-pendulum adaptive tuned mass damper (ATMD): Installed as appropriate; and ${\bullet}$ Foundation system: Piled raft foundation, soil cement earth-retaining wall construction, and beer bottle shaped high-strength CFT piles.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.733-740
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• 2016

To achieve bipedal walking in real human environments, a bipedal robot should be capable of modifiable walking both on uneven terrain with different heights and on flat terrain. In this paper, a novel walking pattern generator based on a 3-D linear inverted pendulum model (LIPM) is proposed to achieve this objective. By adopting a zero moment point (ZMP) variation scheme in real time, it is possible to change the center-of-mass (COM) position and the velocity of the 3-D LIPM throughout the single support phase. Consequently, the proposed method offers the ability to generate a modifiable pattern for walking on uneven terrain without the necessity for any extra footsteps to adjust the COM motion. In addition, a control strategy for bipedal walking on uneven terrain with unknown height is developed. The torques and ground reaction force are measured through force-sensing resisters (FSRs) on each foot and the foot of the robot is modeled as three virtual spring-damper models for the disturbance compensation. The methods for generating the foot and vertical COM of 3-D LIPM trajectories are proposed to achieve modifiable bipedal walking on uneven terrain without any information regarding the height of the terrain. The effectiveness of the proposed method is confirmed through dynamic simulations.

• Wind and Structures
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• 제17권3호
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• pp.263-274
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• 2013

A numerical technique for fluid-structure interaction, which is based on the finite element method (FEM) and computational fluid dynamics (CFD), was developed for application to an industrial chimney equipped with a pendulum tuned mass damper (TMD). In order to solve the structural problem, a one-dimensional beam model (Navier-Bernoulli) was considered and, for the dynamical problem, the standard second-order Newmark method was used. Navier-Stokes equations for incompressible flow are solved in several horizontal planes to determine the pressure in the boundary of the corresponding cross-section of the chimney. Forces per unit length were obtained by integrating the pressure and are introduced in the structure using standard FEM interpolation techniques. For the fluid problem, a fractional step scheme based on a second order pressure splitting has been used. In each fluid plane, the displacements have been taken into account considering an Arbitrary Lagrangian Eulerian approach. The stabilization of convection and diffusion terms is achieved by means of quasi-static orthogonal subscales. For each period of time, the fluid problem was solved and the geometry of the mesh of each fluid plane is updated according to the structure displacements. Using this technique, along-wind and across-wind effects have been properly explained. The method was applied to an industrial chimney in three scenarios (with or without TMD and for different damping values) and for two wind speeds, showing different responses.