• Title, Summary, Keyword: MR damper

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Investigation of Adaptability of Smart Top-Story Isolation System to Structures in Regions of Low-to-Moderate Seismicity (스마트 최상층 면진시스템의 중약진지역 적용성 평가)

  • Kim, Hyun-Su;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
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    • v.12 no.4
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    • pp.71-80
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    • 2012
  • Because a smart isolation system cannot be used as a base isolation system for tall buildings, top-story or mid-story isolation systems are required. In this study, adaptability of a smart top-story isolation system for reduction of seismic responses of tall buildings in regions of low-to-moderate seismicity has been investigated. To this end, 20-story example building structure was selected and an MR damper and low damping elastomeric bearings were used to compose a smart base isolation system. Artificial earthquakes generated based on design spectrum of low-to-moderate seismicity regions are used for structural analyses. Based on numerical simulation results, it has been shown that a smart top-story isolation system can effectively reduce both structural responses and isolation story drifts of the building structure in low-to-moderate seismicity regions in comparison with a passive top-story isolation system.

Analysis on the Effects of the Lower Extremities Muscle Activation during Muscular Strength Training on an Unstable Platform with Magneto-Rheological Dampers (MR 댐퍼를 적용한 불안정판에서 하지 근력 훈련이 근 활성도에 미치는 영향 분석)

  • Choi, Y.J.;Piao, Y.J.;Kwon, T.K.;Kim, D.W.;Kim, J.J.;Kim, N.G.
    • Journal of Biomedical Engineering Research
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    • v.28 no.5
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    • pp.636-646
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    • 2007
  • Adequate postural control depends on the spatial and temporal integration of vestibular, visual, and somatosensory information. Especially, the musculoskeletal function is essential to maintain the postural control. The experimental studies was performed on the muscular activities in the lower extremities during maintaining and moving exercises on an unstable platform with Magneto Rheological(MR) dampers. The unstable platform of the developed system was controlled by electric currents to the MR dampers. A subject executed the maintaining and moving exercises which are presented through the display monitor. The electromyographies of the eight muscles in lower extremities were recorded and analyzed in the time and the frequency domain: the muscles of interest were rectus femoris(RF), biceps femoris(BF), tensor fasciae latae(TFL), vastus lateralis(VL), vastus medialis(VM), gastrocnemius(Ga), tibialis anterior(TA), Soleus(So). The experimental results showed that the muscular activities differed in the four moving exercises and the nine maintaining exercises. For the anterior-posterior pattern, the TA showed highest activities; for the left-right pattern, the TFL; for the 45, $-45^{\circ}$ pattern, the TFL and TA. Also, the rate of the increase in the muscular activities were affected by the condition of the unstable platform with MR dampers for the maintaining and moving exercises. The experimental results suggest that the choice of different maintaining and moving exercises could selectively train different muscles in various intensity. Futhermore, the findings suggested that the training using this system can improve the ability of postural control.

Integrated cable vibration control system using Arduino

  • Jeong, Seunghoo;Lee, Junhwa;Cho, Soojin;Sim, Sung-Han
    • Smart Structures and Systems
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    • v.23 no.6
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    • pp.695-702
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    • 2019
  • The number of cable-stayed bridges has been increasing worldwide, causing issues in maintaining the structural safety and integrity of bridges. The stay cable, one of the most critical members in cable-stayed bridges, is vulnerable to wind-induced vibrations owing to its inherent low damping capacity. Thus, vibration mitigation of stay cables has been an important issue both in academia and practice. While a semi-active control scheme shows effective vibration reduction compared to a passive control scheme, real-world applications are quite limited because it requires complicated equipment, including for data acquisition, and power supply. This study aims to develop an Arduino-based integrated cable vibration control system implementing a semi-active control algorithm. The integrated control system is built on the low-cost, low-power Arduino platform, embedding a semi-active control algorithm. A MEMS accelerometer is installed in the platform to conduct a state feedback for the semi-active control. The Linear Quadratic Gaussian control is applied to estimate a cable state and obtain a control gain, and the clipped optimal algorithm is implemented to control the damping device. This study selects the magnetorheological damper as a semi-active damping device, controlled by the proposed control system. The developed integrated system is applied to a laboratory size cable with a series of experimental studies for identifying the effect of the system on cable vibration reduction. The semi-active control embedded in the integrated system is compared with free and passive mode cases and is shown to reduce the vibration of stay-cables effectively.

Nonlinear optimal control for reducing vibrations in civil structures using smart devices

  • Contreras-Lopez, Joaquin;Ornelas-Tellez, Fernando;Espinosa-Juarez, Elisa
    • Smart Structures and Systems
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    • v.23 no.3
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    • pp.307-318
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    • 2019
  • The frequently excessive vibrations presented in civil structures during seismic events or service conditions may result in users' discomfort, or worst, in structures failure, producing economic and even human casualties. This work contributes in proposing the synthesis of a nonlinear optimal control strategy for semiactive structural control, with the main characteristic that the synthesis considers both the structure model and the semiactive actuator nonlinear dynamics, which produces a nonlinear system that requires a nonlinear controller design. The aim is to reduce the unwanted vibrations in the response of civil structures, by means of intelligent fluid semiactive actuator such as the Magnetorheological Damper (MRD), which is a device with a low level of power consumption. The civil structures for which the proposed control methodology can be applied are those admitting a state-dependent coefficient factorized representation model, such as buildings, bridges, among others. A scaled model of a three storey building is analyzed as a case study, whose dynamical response involves displacement, velocity and acceleration of each one of the storeys, subjected to the North-South component of the September 19th., 2017, Puebla-Morelos (7.1M), Mexico earthquake. The investigation rests on comparing the structural response over time for two different conditions: with no control device installed and with one MRD installed between the first floor and the ground, where a nonlinear optimal signal for the MRD input voltage is determined. Simulation results are presented to show the effectiveness of the proposed controller for reducing the building's dynamical response.

Vibration Control of Adjacent Buildings using a Smart Sky-bridge (스마트 스카이브릿지를 이용한 인접건물의 진동제어)

  • Kang, Joo-Won;Chae, Seoung-Hun;Kim, Hyun-Su
    • Journal of Korean Association for Spatial Structures
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    • v.10 no.4
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    • pp.93-102
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    • 2010
  • In this study, a smart sky-bridge composed of MR damper and FPS has been proposed and vibration control performance of a smart sky-bridge for the connected buildings was investigated. To this end, 10-story and 20-story building structures connected by a smart sky-bridge were selected as example structures and El Centro and Kobe earthquakes, which have near and far fault ground motion characteristics respectively, were used for time history analyses. In order to effectively control the smart sky-bridge, fuzzy logic controller was developed and multi-objective genetic algorithm was used to optimize fuzzy logic controllers. Based on optimization results, it has been seen that there is a trade-off between seismic responses of 10-story and 20-story buildings and a suite of Pareto optimal solutions of fuzzy logic controllers for seismic response control can be obtained by multi-objective genetic algorithm. It is shown from numerical study that seismic responses of adjacent buildings can be efficiently controlled by using a smart sky-bridge.

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Microvibration Control of High Technology Facilities Subjected to Train-induced Excitation using Smart Base Isolation (열차진동하중을 받는 첨단시설물의 스마트 면진시스템을 이용한 미진동제어)

  • Kim, Hyun-Su;Kang, Joo-Won;Kim, Young-Sik
    • Journal of Korean Association for Spatial Structures
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    • v.12 no.2
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    • pp.99-108
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    • 2012
  • Microvibration problem of high-technology facilities, such as semi-conductor plants and TFT-LCD plants, has been considered as important factors that affects the performance of products and thus it is regarded as important in facilities with high precision equipments. In this paper, various base isolation control systems are used to investigate their microvibration control performance. To this end, train-induced ground acceleration is used for time history analysis and three-story example building structure is employed. Microvibration control performance of passive and smart base isolation systems have been investigated in this study. Based on numerical simulation results, it has been verified that smart base isolation system can control microvibration of a high-technology facility subjected to train-induced excitation.

Study of Integrated Optimal Design of Smart Top-Story Isolation and Building Structures in Regions of Low-to-Moderate Seismicity (중약진지역 구조물과 스마트 최상층 면진시스템의 통합최적설계에 대한 연구)

  • Kim, Hyun-Su;Kang, Joo-Won
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.5
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    • pp.13-20
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    • 2013
  • In order to reduce seismic responses of a structure, additional dampers and vibration control devices are generally considered. Usually, control performance of additional devices are investigated for optimal design without variation of characteristics of a structure. In this study, multi-objective integrated optimization of structure-smart control device is conducted and possibility of reduction of structural resources of a building structure with smart top-story isolation system has been investigated. To this end, 20-story example building structure was selected and an MR damper and low damping elastomeric bearings were used to compose a smart base isolation system. Artificial earthquakes generated based on design spectrum of low-to-moderate seismicity regions are used for structural analyses. Based on numerical simulation results, it has been shown that a smart top-story isolation system can effectively reduce both structural responses and isolation story drifts of the building structure in low-to-moderate seismicity regions. The integrated optimal design method proposed in this study can provide various optimal designs that presents good control performance by appropriately reducing the amount of structural material and damping device.

Design and calibration of a semi-active control logic to mitigate structural vibrations in wind turbines

  • Caterino, Nicola;Georgakis, Christos T.;Spizzuoco, Mariacristina;Occhiuzzi, Antonio
    • Smart Structures and Systems
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    • v.18 no.1
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    • pp.75-92
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    • 2016
  • The design of a semi-active (SA) control system addressed to mitigate wind induced structural demand to high wind turbine towers is discussed herein. Actually, the remarkable growth in height of wind turbines in the last decades, for a higher production of electricity, makes this issue pressing than ever. The main objective is limiting bending moment demand by relaxing the base restraint, without increasing the top displacement, so reducing the incidence of harmful "p-delta" effects. A variable restraint at the base, able to modify in real time its mechanical properties according to the instantaneous response of the tower, is proposed. It is made of a smooth hinge with additional elastic stiffness and variable damping respectively given by springs and SA magnetorheological (MR) dampers installed in parallel. The idea has been physically realized at the Denmark Technical University where a 1/20 scale model of a real, one hundred meters tall wind turbine has been assumed as case study for shaking table tests. A special control algorithm has been purposely designed to drive MR dampers. Starting from the results of preliminary laboratory tests, a finite element model of such structure has been calibrated so as to develop several numerical simulations addressed to calibrate the controller, i.e., to achieve as much as possible different, even conflicting, structural goals. The results are definitely encouraging, since the best configuration of the controller leaded to about 80% of reduction of base stress, as well as to about 30% of reduction of top displacement in respect to the fixed base case.

Control Performance Evaluation of Smart Mid-story Isolation System with RNN Model (RNN 모델을 이용한 스마트 중간층 면진시스템의 제어성능 평가)

  • Kim, Hyun-Su
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.1
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    • pp.774-779
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    • 2020
  • The seismic response reduction capacity of a smart mid-story isolation system was investigated using the RNN model in this study. For this purpose, an RNN model was developed to make a dynamic response prediction of building structures subjected to seismic loads. An existing tall building with a mid-story isolation system was selected as an example structure for realistic research. A smart mid-story isolation system was comprised of an MR damper instead of existing lead dampers. The RNN model predicted the seismic responses accurately compared to those of the FEM model. The simulation time of the RNN model can be reduced significantly compared to the FEM model. After the numerical simulations, the smart mid-story isolation system could effectively reduce the seismic responses of the existing building compared to the conventional mid-story isolation system.

LRB-based hybrid base isolation systems for cable-stayed bridges (사장교를 위한 LRB-기반 복합 기초격리 시스템)

  • Jung, Hyung-Jo;Park, Kyu-Sik;Spencer, Billie-F.Jr.;Lee, In-Won
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.3
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    • pp.63-76
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    • 2004
  • This paper presents LRB-based hybrid base isolation systems employing additional active/semiactive control devices for mitigating earthquake-induced vibration of a cable-stayed 29 bridge. Hybrid base isolation systems could improve the control performance compared with the passive type-base isolation system such as LRB-installed bridge system due to multiple control devices are operating. In this paper, the additional response reduction by the two typical additional control devices, such as active type hydraulic actuators controlled by LQG algorithm and semiactive-type magnetorheological dampers controlled by clipped-optimal algorithm, have been evaluated bypreliminarily investigating the slightly modified version of the ASCE phase I benchmark cable-stayed bridge problem (i.e., the installation of LRBs to the nominal cable-stayed bridge model of the problem). It shows from the numerical simulation results that all the LRB based hybrid seismic isolation systems considered are quite effective to mitigate the structural responses. In addition, the numerical results demonstrate that the LRB based hybrid seismic isolation systems employing MR dampers have the robustness to some degree of the stiffness uncertainty of in the structure, whereas the hybrid system employing hydraulic actuators does not. Therefore, the feasibility of the hybrid base isolation systems employing semiactive additional control devices could be more appropriate in realfor full-scale civil infrastructure applications is clearly verified due to their efficacy and robustness.