• Title/Summary/Keyword: Base Excitation

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A Study on Base Isolation Performance of MR Dampers Using Clipped-Optimal Control (Clipped-Optimal Control을 사용한 MR 감쇠기의 면진성능에 관한 연구)

  • 고봉준;이종세
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2003.04a
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    • pp.529-536
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    • 2003
  • As large structures such as high-rise buildings and cable-stayed bridges become lighter and more flexible, the necessity of structural control for reducing excessive displacement and acceleration due to seismic excitation is increased. As a method to minimize seismic damages, various base isolation systems are adopted or considered for adoption. In this study, the seismic performance of MR dampers are studied and compared with that of the NZ system as a base isolation system. As the control algorithm of the MR damper, the clipped-optimal control(applied LQR method) is employed. A five-story building is modeled and the seismic performance of the two systems subjected to three different earthquakes is compared. The results show that the MR damper system can provide superior protection than the NZ system for a wide range of ground motions.

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A Study on the Manufacturing and Dynamic Charateristics of Vibration Absorber Using Piezoceramics and Isolation Pad (압전세라믹과 방진고무를 이용한 진동흡수장치의 제작과 동적특성 연구)

  • Heo, Seok;Kwak, Moon-k
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.477-482
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    • 2002
  • This research is concerned with the study of an active vibration absorber using piezoelectric actuators and Isolation pad. The active isolation system consists of 4-pairs of PZT actuators bonded on the surface of an aluminum plate and a passive damping material. The active system is connected to the passive system in series. The Signals of the accelerometers are fed into the PZT actuator through the controller. We proposed a new control technique which can deal with the shock as well as the base excitation in this study. The Positive Acceleration Feedback(PAE) tuned to the natural frequency of the vibration isolation system is used to suppress the vibrations caused by the shock using the top accelerometer signal. The Negative Acceleration Feedback (NAF) based on the base acceleration signal is used to counteract the base motion. Experimental results show that the proposed active vibration isolation system can suppress vibrations.

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Application of Smart Isolation Platform for Microvibration Control of High-Tech Industry Facilities (첨단기술산업 시설물의 미진동제어를 위한 스마트 면진플랫폼의 적용)

  • Kim, Hyun-Su;Kang, Joo-Won;Kim, Young-Sik
    • Journal of Korean Association for Spatial Structures
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    • v.14 no.2
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    • pp.87-94
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    • 2014
  • In this study, a smart isolation platform has been developed for control of microvibration of high-technology facilities, such as semi-conductor plants and TFT-LCD plants. Previously, microvibration control performance of a smart base isolation system has been investigated. This study compared microvibration control performance of a smart isolation platform with that of conventional base isolation and fixed base. For this purpose, train-induced ground acceleration is used for time history analysis. An MR damper was used to compose a smart isolation platform. A fuzzy logic controller was used as a control algorithm and it was optimized by a multi-objective genetic algorithm. Numerical analysis shows that a smart isolation platform can effectively control microvibration of a high-technology facility subjected to train-induced excitation compared with other models.

Seisminc Response of Base Isolated Structures with MR Dampers (MR 감쇠기를 적용한 기초격리구조물의 지진응답)

  • 고봉준;황인호;이종세
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2003.09a
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    • pp.505-512
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    • 2003
  • As large structures such as highrise buildings and cable-stayed bridges become lighter and more flexible, the necessity of structural control for reducing excessive displacement and acceleration due to seismic excitation is increased. As a means to minimize seismic damages, various base isolation systems are adopted or considered for adoption. In this study, the seismic performance of M dampers are studied and compared with that of the NZ system as a base isolation system As the control algorithm of the MR damper, the clipped-optimal control(applied LQR method) is employed. A five-story building is modeled and the seismic performance of the two systems subjected to three different earthquakes is compared. The results show that the M damper system can provide superior protection than the NZ system for a wide range of ground motions.

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Rocking response of self-centring wall with viscous dampers under pulse-type excitations

  • Zhang, Lingxin;Huang, Xiaogang;Zhou, Zhen
    • Earthquakes and Structures
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    • v.19 no.3
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    • pp.215-226
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    • 2020
  • A self-centering wall (SCW) is a lateral resistant rocking system that incorporates posttensioned (PT) tendons to provide a self-centering capacity along with dampers to dissipate energy. This paper investigates the rocking responses of a SCW with base viscous dampers under a sinusoidal-type pulse considering yielding and fracture behaviour of the PT tendon. The differences in the overturning acceleration caused by different initial forces in the PT tendon are computed by the theoretical method. The exact analytical solution to the linear approximate equation of motion is also provided for slender SCWs. Finally, the effects of the ductile behaviour of PT tendons on the rocking response of a SCW are analysed. The results demonstrate that SCWs exhibit two overturning modes under pulse excitation. The overturning region with Mode 1 in the PT force cases separates the safe region of the wall into two parts: region S1 with an elastic tendon and region S2 with a fractured tendon. The minimum overturning acceleration of a SCW with an elastic-brittle tendon becomes insensitive to excitation frequency as the PT force increases. After the plastic behaviour of the PT tendon is considered, the minimum overturning acceleration of a SCW is increased significantly in the whole range of the studied wg/p.

Chaotic Behavior on Rocking Vibration of Rigid Body Block Structure under Two-dimensional Sinusoidal Excitation (In the Case of No Sliding)

  • Jeong, Man-Yong;Lee, Hyun-;Kim, Ji-Hoon;Kim, Jeong-Ho;Yang, In-Young
    • Journal of Mechanical Science and Technology
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    • v.17 no.9
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    • pp.1249-1260
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    • 2003
  • This present work focuses on the influence of nonlinearities associated with impact on the rocking behavior of a rigid body block subjected to a two-dimensional excitation in the horizontal and vertical directions. The nonlinearities in rocking system are found to be strongly dependent on the impact between the block and the base that abruptly reduces the kinetic energy. In this study, the rocking systems of the two types are considered : The first is an undamped rocking system model that disregards the energy dissipation during the impact and the second is a damped rocking system, which incorporates energy dissipation during the impact. The response analysis is carried out by a numerical method using a non-dimensional rocking equation in which the variations in the excitation levels are considered. Chaos responses are observed over a wide range of parameter values, and particularly in the case of large vertical displacements, the chaotic characteristics are observed in the time histories, Poincare sections, the power spectral density and the largest Lyapunov exponents of the rocking responses. Complex behavior characteristics of rocking responses are illustrated by the Poincare sections.

Dynamic analysis and performance optimization of permendur cantilevered energy harvester

  • Ghodsi, Mojtaba;Ziaiefar, Hamidreza;Mohammadzaheri, Morteza;Omar, Farag K.;Bahadur, Issam
    • Smart Structures and Systems
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    • v.23 no.5
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    • pp.421-428
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    • 2019
  • The development of the low power application such as wireless sensors and health monitoring systems, attract a great attention to low power vibration energy harvesters. The recent vibration energy harvesters use smart materials in their structures to convert ambient mechanical energy into electricity. The frequent model of this harvesters is cantilevered beam. In the literature, the base excitation cantilevered harvesters are mainly investigated, and the related models are presented. This paper investigates a tip excitation cantilevered beam energy harvester with permendur. In the first section, the mechanical model of the harvester and magneto-mechanical model of the permendur are presented. Later, to find the maximum output of the harvester, based on the response surface method (RSM), some experiments are done, and the results are analyzed. Finally, to verify the results of RSM, a harvester with optimum design variables is made, and its output power is compared. The last comparison verifies the estimation of the RSM method which was about $381{\mu}W/cm^3$.

Design of a decoupled PID controller via MOCS for seismic control of smart structures

  • Etedali, Sadegh;Tavakoli, Saeed;Sohrabi, Mohammad Reza
    • Earthquakes and Structures
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    • v.10 no.5
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    • pp.1067-1087
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    • 2016
  • In this paper, a decoupled proportional-integral-derivative (PID) control approach for seismic control of smart structures is presented. First, the state space equation of a structure is transformed into modal coordinates and parameters of the modal PID control are separately designed in a reduced modal space. Then, the feedback gain matrix of the controller is obtained based on the contribution of modal responses to the structural responses. The performance of the controller is investigated to adjust control force of piezoelectric friction dampers (PFDs) in a benchmark base isolated building. In order to tune the modal feedback gain of the controller, a suitable trade-off among the conflicting objectives, i.e., the reduction of maximum modal base displacement and the maximum modal floor acceleration of the smart base isolated structure, as well as the maximum modal control force, is created using a multi-objective cuckoo search (MOCS) algorithm. In terms of reduction of maximum base displacement and story acceleration, numerical simulations show that the proposed method performs better than other reported controllers in the literature. Moreover, simulation results show that the PFDs are able to efficiently dissipate the input excitation energy and reduce the damage energy of the structure. Overall, the proposed control strategy provides a simple strategy to tune the control forces and reduces the number of sensors of the control system to the number of controlled stories.

Seismic base isolation of precast wall system using high damping rubber bearing

  • Tiong, Patrick L.Y.;Adnan, Azlan;Rahman, Ahmad B.A.;Mirasa, Abdul K.
    • Earthquakes and Structures
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    • v.7 no.6
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    • pp.1141-1169
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    • 2014
  • This study is aimed to investigate the seismic performance of low-rise precast wall system with base isolation. Three types of High Damping Rubber Bearing (HDRB) were designed to provide effective isolation period of 2.5 s for three different kinds of structure in terms of vertical loading. The real size HDRB was manufactured and tested to obtain the characteristic stiffness as well as damping ratio. In the vertical stiffness test, it was revealed that the HDRB was not an ideal selection to be used in isolating lightweight structure. Time history analysis using 33 real earthquake records classified with respective peak ground acceleration-to-velocity (a/v) ratio was performed for the remaining two types of HDRB with relatively higher vertical loading. HDRB was observed to show significant reduction in terms of base shear and floor acceleration demand in ground excitations having a/v ratio above $0.5g/ms^{-1}$, very much lower than the current classification of $0.8g/ms^{-1}$. In addition, this study also revealed that increasing the damping ratio of base isolation system did not guarantee better seismic performance particularly in isolation of lightweight structure or when the ground excitation was having lower a/v ratio.

Experimental and numerical investigation of wire rope devices in base isolation systems

  • Calabrese, Andrea;Spizzuoco, Mariacristina;Losanno, Daniele;Barjani, Arman
    • Earthquakes and Structures
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    • v.18 no.3
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    • pp.275-284
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    • 2020
  • The scope of this study is the comparison between experimental results of tests performed on a base isolated building using helical wire rope isolators (WRs), and results of Nonlinear Response History Analyses (NRHAs) performed using SAP 2000, a commercial software for structural analysis. In the first stage of this research, WRs have been tested under shear deformation beyond their linear range of deformation, and analytical models have been derived to describe the nonlinear response of the bearings under different directions of loading. On the following stage, shaking table tests have been carried out on a 1/3 scale steel model isolated at the base by means of curved surface sliders (CSS) and WRs. The response of the structure under ground motion excitation has been compared to that obtained using numerical analyses in SAP 2000. The feasibility of modelling the nonlinear behavior of the tested isolation layer using multilinear link elements embedded in SAP 2000 is discussed in this paper, together with the advantages of using WRs as supplemental devices for CSSs base isolated structures.