Earthquake early warning-enabled smart base isolation system
Introduction
Earthquakes are constant threats to human civilization. In the last few decades, with the deployment of seismometers in many parts of the world, we are now able to detect tremors around the globe, including those in remote areas and seafloors. Government agencies such as the United State Geological Survey (USGS) and Japan Meteorological Agency (JMA) publish real-time or near real-time earthquake information. However, prediction of earthquakes is still difficult, and large earthquakes in areas near populous urban areas continue to cause enormous damages and casualties. Recent earthquakes such as the 2008 Sichuan Earthquake, the 2011 Tohoku Earthquake and 2015 Nepal Earthquake caused a large number of lives and widespread destructions. Continual efforts have been made to mitigate seismic risks. Recently, the Earthquake Early Warning (EEW) System has been developed and deployed. The principle of EEW is based on the characteristics that the seismic P-Wave travels 1.73 to 1.85 times faster than the more destructive S-wave [1]. When P-wave is detected, the approximate location of the epicentre is estimated, and a warning signal is broadcasted to the affected areas prior to the arrival of the S-wave. The principle of EEW is presented in Fig. 1. Japan is the first nation in the world to offer nation-wide EEW to the public in 2007. Estimated seismic intensity [2] are broadcasted. Earthquake warning is broadcast through television, radio, mobile networks, the Internet and specific EEW-enabled devices. Similar warning systems are now available in Taiwan, parts of China and many other earthquake-prone regions of the world. In Japan, EEW provides earthquake warnings in the order of seconds, providing reaction time to mitigate larger earthquake disasters such as shutting down certain industrial operations, reducing train speed and evacuating personnel [3]. For areas close to the epicentre, there will be insufficient time to send out warning signal due to operational delays and this area is called the blind zone. The current blind zone of EEW is about 50–70 km2 [4].
The possibilities offered by EEW system may not be limited to the issue of warning signals. In highly urbanized areas, the time required to evacuate an entire building such as a high-rise structure is much longer than the time provided by the EEW. In contrast, the activation of certain mechanisms appears to be feasible to mitigate seismic risks in some industrial processes and to enhance the protection of critical systems. This paper presents an investigation into an EEW-enabled smart base isolation system. The proposed system consisted of a base isolation that can be disabled or enabled by locking or releasing movable components. Compared to traditional passive base isolation systems, the proposed system has the following key features:
- (1)
When the base isolation system is disabled by a locking mechanism, the main structure possesses high lateral-force resistance and prevents excessive wind-induced displacements;
- (2)
The base isolation system is designed with minimal friction and no supplemental stiffness or damping. It maximizes performance when the structure is subjected to horizontal ground motions; and
- (3)
After ground motion ceases, actuators re-centre the main structure to its initial position and re-engages the shear keys to lock the base isolation, and
- (4)
The system is fully-automated and repeatable.
In a previous study, the authors investigated into a one-dimensional base-isolation system using EEW [5]. The previous design used electromagnetic switches to facilitate rapid deployment of base isolation. This paper presents a design which is a successor to the previous design that it is a two-dimensional base isolation system and it uses linear actuators instead of electromagnetic switches. This paper first presents the current state-of-the practice of base isolation, particularly focuses in the use of cross-linear bearings (CLBs) in Japan. It is followed by a numerical study into the effect of using supplementary damping devices in conjunction with CLB systems. The paper then describes the conceptual design of the proposed EEW-enabled smart base isolation system. A laboratory-scale experimental verification using a shake table is presented.
Section snippets
General descriptions
In the last few decades, there has been a massive growth for development of earthquake-resistant structures and their associated technologies. Supplemental energy dissipating devices such as viscous fluid dampers, friction dampers, metallic yielding dampers; buckling-restrained-braces, etc. have been commercially available and widely applied worldwide. On the other hand, base-isolation is regarded as one of the most mature technologies. Isolation devices are typically positioned at the base of
General descriptions
The proposed EEW-enabled base isolation system is a combination of a passive isolation system, EEW connectivity, sensors, shear keys and actuators. Fig. 7 shows a schematic diagram of the proposed system. A structure is supported on low-friction cross-linear bearings which permits the main structure to decouple from horizontal ground shaking. However, the base isolation system is locked against movement by horizontal shear keys. The shear keys unlock the base isolation under three conditions:
Experimental setup and instrumentations
A lightweight 6-level test model made of acrylic plastic and aluminium strips is used in the experimental investigation. Columns are made of 4 mm thick clear acrylic plastic strips. Floor plates are made of 3 mm thick timber boards and they are connected to columns via aluminium brackets and steel bolts. Steel masses are positioned centrally on each floor and the total mass of the model frame is 7.5 kg (excluding base plate and base isolation rails). The first three natural frequencies when the
Conclusion
The deployment of Earthquake Early Warning (EEW) system in Japan and other earthquake-prone regions in the world open new opportunities of seismic-risk mitigation for structures. EEW systems are capable of detecting fast traveling earthquake P-waves and send warning signals to the public prior to the arrival of more destructive S-waves. This paper proposes a smart base-isolation system which is connected to the EEW system. The system consists of a microcontroller which is programmed to
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
References (22)
The operation and performance of earthquake early warnings by the Japan meteorological agency
Soil Dyn. Earthq. Eng.
(2011)- et al.
Application of an earthquake early warning system and a real-time strong motion monitoring system in emergency response in a high-rise building
Soil Dyn. Earthq. Eng.
(2011) - et al.
A smart mechatronic base isolation system using earthquake early warning
Soil Dyn. Earthq. Eng.
(2019) - et al.
Intelligent seismic isolation system using air bearings and earthquake early warning
Soil Dyn. Earthq. Eng.
(2011) - et al.
Wind effects on habitability of base-isolated buildings
J. Wind Eng. Ind. Aerodyn.
(2002) - et al.
Seismic isolation of nuclear power plants
Nucl. Eng. Technol.
(2014) - et al.
Magnitude estimation using the first three seconds P-wave amplitude in earthquake early warning
Geophys. Res. Lett.
(2006) - et al.
Earthquake Early Warning Systems
(2007) - et al.
A review of seismic isolation for buildings: historical development and research needs
Buildings
(2012) - et al.
NEES/E-Defense Base-isolation tests: Effectiveness of friction pendulum and Lead-rubber bearings systems
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