Development of Structural Health Monitoring System Combined With Earthquake Early Warning System for Real-Time Earthquake Information Navigation

Abstract eng:
The authors have developed an integrated regional Earthquake Early Warning (EEW) system having on-line Structural Health Monitoring (SHM) function, in- and surrounding Miyagi prefectural area, Japan. The system makes it possible to provide more accurate, reliable and immediate earthquake information by combining the national (JMA/NIED) EEW system, based on advanced real-time communication technology. The EEW/SHM system comprises high sensitive sensors (lager than 120dB), data logger with variable sampling rate/variable packet length, which is installed in each public building and software for SHM and EEW. All observation data are transferred to the data server at IRIDeS, Tohoku University via the Internet. The system development started from 2008 and got some important data during the 2008 Iwate-Miyagi Nairiku earthquake and also the 2011 Great East Japan Earthquake (hereafter, the 2011 Tohoku earthquake). After the huge earthquake, the system was extended to 15 buildings with different azimuth angle for a city with a population exceeding one million people, Sendai and inland industrial area. The system installed buildings consist of different structural types, different foundation types, and different geological conditions in- and surrounding Miyagi prefectural areas. The continuous SHM observation data are utilized for structural health monitoring and building motion prediction as real-time earthquake information. By combining a structural analysis model, damage degree evaluation can be performed. Real-time observation data is also used for estimating damage of some important parts of structural elements such as bottom of corner columns, and head of piles in case of pile foundation building. Due to comparison of analytical and observation information, accuracy enhancement in modelling of a building structure will be performed, which gives to academic contribution. The real-time earthquake observation data due to the EEW/SHM network makes it possible to enhance the real-time ground motion prediction of a site. Structural response prediction before severe shaking is also possible based on investigation of transfer functions between a target site and front sites together with ground motion amplification considering non-linearity of surface soil layers. Not only peak ground motion (PGA, PGV) but also spectral ground motion prediction has been investigated so far by the authors. By combining the verified structural modelling through the SHM, the real-time spectral prediction can contribute accurate structural response, which is important for non-structural elements and valuable and important equipment. The real-time ground motion and structural response prediction can be used to issue accurate navigation information for earthquake damage reduction, which leads to social contribution. In future, real-time waveform prediction will become possible using front-site waveform information to connect to active- and semi-active structural control. This paper describes current status of system development and extension including basic conception. Then described are temperature dependency of dynamic characteristics based on the long-term continuous observation data and the amplitude dependent dynamic characteristics based on earthquake observation data including the 2011 Tohoku earthquake. Finally the author insists on the necessity of ‘Navigation’ based on the EEW/SHM system, which is based on the combination of the observation data and structural analysis for the next generation earthquake disaster prevention system.

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