Study on Super-Long-Period Active Isolation System Considering Relatively Long Period Seismic Wave

2004 ◽  
Vol 2004.5 (0) ◽  
pp. 269-270
Author(s):  
Tomo Sasaki ◽  
Satoshi Fujita ◽  
Minagawa Keisuke ◽  
Takafumi Fujita ◽  
osamu Takahashi
Keyword(s):  
Seismic Wave ◽  
Isolation System ◽  
Long Period ◽  
Active Isolation

Research and Development of Intelligent Seismic Isolation System Using Air Bearing

2008 ◽  
Author(s):  
Satoshi Fujita ◽  
Keisuke Minagawa ◽  
Mitsuru Miyazaki ◽  
Go Tanaka ◽  
Osamu Takahashi
Keyword(s):  
Friction Coefficient ◽  
Seismic Wave ◽  
Seismic Isolation ◽  
Seismic Waves ◽  
Air Bearing ◽  
Natural Period ◽  
Isolation System ◽  
Long Period ◽  
Isolation Device ◽  
Isolation Performance

This study aims at research and development of the intelligent seismic isolation system using air bearings as isolation device and Earthquake Early Warning (EEW) as trigger of isolation system. In October 2007, EEW was started providing to resident of Japan. The EEW system expects earthquake intensity and arrival time at particular place by analysis of seismic wave that was observed near the earthquake center. Therefore social and technical application of the system is strongly expected for suppression of disaster scale. On the other hand, long period seismic waves having predominant period of from a few seconds to a few ten seconds have recently been observed in various earthquakes. Also resonances of high-rise buildings and sloshing of petroleum tanks in consequence of long period seismic waves have been reported. In metropolises of Japan such as Tokyo, Osaka and Nagoya, it is expected that long period seismic waves are excited in large earthquakes because these are located on sedimentary layers. Therefore the isolation system having very long natural period or no natural period is required. In this study, we propose an isolation system having no natural period by using air bearing as isolation device. Air bearing is a bearing that can reduce contact friction between floor and the bearing by thin air film produced by compressed air. In general, the air bearing is used as heavy machinery moving equipment. The approximate friction coefficient is 0.0005 to 0.001, so that the system using air bearing almost isolates seismic wave. In addition, the EEW is applied as trigger of isolation. The EEW is applied for turning gas and electrical heater off, too. P-wave sensor is also equipped and it can operate as trigger in case of near-field earthquake or when EEW system could not work properly. Furthermore, steel plate equipped at the bottom of the air bearing can operate as friction bearing when air bearing does not work. In this paper, we describe results of earthquake response analysis of the intelligent isolation system using air bearing. From results of the analysis, it was confirmed that response acceleration depends on friction coefficient only, and the system has good isolation performance not only against typical seismic wave, such as El Centro wave, but also against long period seismic wave. However residual displacement remains after seismic input stopped. Additionally, experimental test was executed so as to investigate basic performance of isolation. As a result, it was confirmed that the isolation system has good isolation performance.

Fundamental Study on the Super-Long-Period Active Isolation System

2005 ◽  
Vol 128 (4) ◽  
pp. 502-507
Author(s):  
Keisuke Minagawa ◽  
Satoshi Fujita
Keyword(s):  
Control System ◽  
Seismic Isolation ◽  
Seismic Waves ◽  
Control Force ◽  
Natural Period ◽  
Isolation System ◽  
Hydraulic Actuators ◽  
Long Period ◽  
Active Isolation ◽  
Rubber Bearings

Background: Since the Hanshin-Awaji Earthquake Disaster, the number of isolated structures has been greatly increased. The natural period of the isolation system is designed around 3s, because the predominate period of observed seismic waves is usually 0.1 to 1s. However, relatively long period seismic waves have been observed in various earthquakes, and the resonances of long-period structures, such as high-rise buildings, during earthquakes have been reported at the same time. Therefore the natural period needs to be extended. When extending the natural period of the isolated structure using rubber bearings, its stiffness needs to be reduced. It is more difficult to extend the natural period of the isolation system than the conventional system because of a buckling problem. Therefore we propose a super-long-period active seismic isolation system as a new method for extending the natural period of the isolated structure. This system consists of rubber bearings and hydraulic actuators. Method of approach: In this study, we designed a control system by using the model matching method. This is one of the classical control system design methods. Additionally we applied a genetic algorithm (GA) to select parameters of a transfer function. Results: The system designed by applying the GA could reduce response acceleration sufficiently compared with the input acceleration. Further waveforms of the response acceleration retain almost straight forwardly, so this indicates good performance of isolation. Therefore, application of super-long-period active isolation is an effective technique to improve the performance of isolation. However, the control forces are big, and the system needs 95.5×106N for the El Centro NS wave as control force. This force is equivalent to 21 actuators that are used in a large shake table, so there are few possibilities to realize active isolation. Conclusion: The required control force of hydraulic actuators is big, although the super-long-period active isolation system possesses good performance of isolation compared with the conventional isolation system. Therefore it is difficult to apply this isolation system to the real structure. However, the problem regarding requirements of the actuator should be solved because of the realization of an active seismic isolation system. Therefore, we will examine for the parameters of the system and semi-active isolation system.

231 Study On Super-long-period Active Isolation System

2003 ◽  
Vol 2003 (0) ◽  
pp. _231-1_-_231-6_
Author(s):  
Keisuke Minagawa ◽  
Hironori Hamazaki ◽  
Satoshi Fujita ◽  
Takafumi Fujita ◽  
Osamu Takahashi
Keyword(s):  
Isolation System ◽  
Long Period ◽  
Active Isolation

Isolation Performance of Intelligent Seismic Isolation System Using Air Bearing

2009 ◽  
Author(s):  
Satoshi Fujita ◽  
Keisuke Minagawa ◽  
Mitsuru Miyazaki ◽  
Go Tanaka ◽  
Toshio Omi ◽  
...  
Keyword(s):  
Seismic Isolation ◽  
Seismic Waves ◽  
Three Dimensional ◽  
Vertical Motion ◽  
Air Bearings ◽  
Natural Period ◽  
Isolation System ◽  
Vertical Excitation ◽  
Long Period ◽  
Isolation Performance

This paper describes three-dimensional isolation performance of seismic isolation system using air bearings. Long period seismic waves having predominant period of from a few seconds to a few ten seconds have recently been observed in various earthquakes. Also resonances of high-rise buildings and sloshing of petroleum tanks in consequence of long period seismic waves have been reported. Therefore the isolation systems having very long natural period or no natural period are required. In a previous paper [1], we proposed an isolation system having no natural period by using air bearings. Additionally we have already reported an introduction of the system, and have investigated horizontal motion during earthquake in the previous paper. It was confirmed by horizontal vibration experiment and simulation in the previous paper that the proposed system had good performance of isolation. However vertical motion should be investigated, because vertical motion varies horizontal frictional force. Therefore this paper describes investigation regarding vertical motion of the proposed system by experiment. At first, a vertical excitation test of the system is carried out so as to investigate vertical dynamic property. Then a three-dimensional vibration test using seismic waves is carried out so as to investigate performance of isolation against three-dimensional seismic waves.

Seismic wave energy inferred from long-period body wave inversion

1988 ◽  
Vol 78 (5) ◽  
pp. 1707-1724
Author(s):  
Masayuki Kikuchi ◽  
Yoshio Fukao
Keyword(s):  
Seismic Wave ◽  
Wave Energy ◽  
Body Wave ◽  
Empirical Relation ◽  
P Waves ◽  
Average Value ◽  
Long Period ◽  
Wave Inversion ◽  
Moment Ratio ◽  
Order Of Magnitude

Abstract The seismic wave energy is evaluated for 35 large earthquakes by inverting far-field long-period P waves into the multiple-shock sequence. The results show that the seismic wave energy thus obtained is systematically less than that inferred from the Gutenberg-Richter's formula with the seismic magnitude. The difference amounts to one order of magnitude. The results also show that the energy-moment ratio is well confined to a narrow range: 10−6 < ES/Mo < 10−5 with the average of ∼5 × 10−6. This average value is exactly one order of magnitude as small as the energy-moment ratio inferred from the Gutenberg-Richter's formula using the moment magnitude. Comparing the energy-moment ratio with Δσo/2μ, where Δσo and μ are the stress drop and the rigidity, we obtain an empirical relation: ES/Mo ∼ 0.1 × Δσ0/2μ. Such a relation can be interpreted in terms of a subsonic rupture where the energy loss due to cohesion is not negligible to the seismic wave energy.

scholarly journals Study of Active Isolation System with Feedforward Control.

1992 ◽  
Vol 58 (552) ◽  
pp. 2381-2387 ◽  
Author(s):  
Masashi YASUDA ◽  
Takahide OSAKA ◽  
Masao IKEDA
Keyword(s):  
Feedforward Control ◽  
Isolation System ◽  
Active Isolation

Dynamic Analysis of an Active Flexible Isolation System

2003 ◽  
Author(s):  
Kongjie Song ◽  
Lingling Sun ◽  
Yuguo Sun ◽  
Bing Zhang
Keyword(s):  
Active Control ◽  
Power Flow ◽  
Low Frequency ◽  
Coupled System ◽  
Isolation System ◽  
Active Isolation ◽  
Dynamic Modification ◽  
Mobility Method ◽  
Feed Forward Controller ◽  
Flexible Foundation

This paper is dedicated to the structure dynamic modification in an active isolation system supported by a flexible foundation, in order to improve the effectiveness of the active control strategy. The coupled vibration between machine-sprung and flexible foundation substructure is examined, using the subsystem mobility method. The vibration transmission in this coupled system is presented in terms of power flow. The interaction between structure controlled and the adaptive feed-forward controller is investigated theoretically. The numerical results show that: the location of the active mounts and the first mode frequency of the flexible foundation have evident influence on the effect of active control, especially at low-frequency band.

Fundamental Study on the Super-Long-Period Active Isolation System

2004 ◽  
Author(s):  
Keisuke Minagawa ◽  
Satoshi Fujita
Keyword(s):  
Control System ◽  
Seismic Isolation ◽  
Seismic Waves ◽  
Model Matching ◽  
Fundamental Study ◽  
Natural Period ◽  
Isolation System ◽  
Long Period ◽  
Rubber Bearings ◽  
Classical Control

Since the Hanshin-Awaji Earthquake Disaster, the number of isolated structures has been greatly increased. The natural period of the isolation system is designed around 3 seconds, because predominate period of observed seismic waves is usually 0.1 to 1 second. However, relatively long period seismic waves have been observed in various earthquakes, and the resonance of long-period structures, such as high-rise buildings, during earthquakes have been reported at the same time. Therefore the natural period needs to be extended. When extending the natural period of the isolated structure using rubber bearings, its stiffness needs to be reduced. It is more difficult to extend the natural period of the isolation system than the conventional system because of its buckling problem. Therefore we propose a super-long-period active seismic isolation system as a new method for extending the natural period of the isolated structure. This system consists of rubber bearings and actuators. In this study, we designed a control system by using the model-matching-method. This is one of the classical control system design methods. We investigated the isolation performance by numerical analysis. In addition, we selected the optimal variables of transfer function using genetic algorithm.

Effects of Damper Force Ranges and Ground Motion Pulse Periods on the Performance of Semi-Active Isolation Systems

2003 ◽  
Author(s):  
Henri Gavin ◽  
Julie Thurston ◽  
Chicahiro Minowa ◽  
Hideo Fujitani
Keyword(s):  
Ground Motion ◽  
Large Scale ◽  
Base Isolation ◽  
Near Field ◽  
Shaking Table ◽  
Isolation System ◽  
Active Isolation ◽  
Isolation Systems ◽  
Fail Safe ◽  
Strong Ground

A large-scale base-isolated steel structural frame was tested at the shaking table laboratory of the National Research Institute for Earth Sciences and Disaster Prevention. These collaborative experiments featured auto-adaptive media and devices to enhance the performance of passive base isolation systems. The planning of these experiments involved determining appropriate device control methods, the development of a controllable damping device with fail-safe characteristics, and the evaluation of the performance of the controlled isolation system subjected to strong ground motion with pronounced near-field effects. The results of the planning study and their large-scale experimental confirmation provide guidelines for the development and implementation of auto-adaptive damping devices for full scale structures.

scholarly journals An Artificial Seismic Wave Suitable for Suspended Converter Valve in the UHVDC Transmission Project

2019 ◽  
Vol 118 ◽  
pp. 02039
Author(s):  
Jin Xiao ◽  
Mingduo Huang ◽  
Qiguo Sun
Keyword(s):  
Finite Element ◽  
Seismic Wave ◽  
Seismic Design ◽  
Response Spectrum ◽  
Time History ◽  
Element Model ◽  
Series Method ◽  
Long Period ◽  
Standard Response ◽  
The Finite Element Model

The finite element model of suspended converter valve in an UHVDC transmission project with characteristics of flexible is constructed, and its vibration characteristics are simulated and analyzed firstly. The results show that this kind of suspended converter valve has obvious long-period character. Secondly, the long period phase of standard response spectrum in Code for Seismic Design of Buildings (GB50011-2010) is modified, and then the artificial seismic wave is synthesized employing the triangular series method. The result shows that this artificial seismic wave has long-period character. Finally, the time-history seismic dynamic simulation of the converter valve is done, and the seismic responses of the converter valve excited by three kinds of seismic wave with different period characters are compared and analyzed. The results show that the swing and stress of the suspended converter valve are larger under the long-period seismic wave synthesized in this paper. The quasi-resonance damage caused by long-period seismic wave should be concerned specially in the actual UHVDC transmission project.

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