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Effects and dynamic characteristics of the core‐suspended isolation system assessed by long‐term structural health monitoring
Author(s) -
Nakamura Yutaka,
Okada Keiichi
Publication year - 2021
Publication title -
earthquake engineering and structural dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.218
H-Index - 127
eISSN - 1096-9845
pISSN - 0098-8847
DOI - 10.1002/eqe.3437
Subject(s) - seismic isolation , microtremor , seismology , structural engineering , truss , acceleration , peak ground acceleration , base isolation , earthquake engineering , geology , structural health monitoring , damping ratio , isolation (microbiology) , engineering , ground motion , vibration , physics , microbiology and biotechnology , biology , telecommunications , classical mechanics , frame (networking) , quantum mechanics
The seismic isolation mechanism of the core‐suspended isolation (CSI) system comprises a double layer of inclined rubber bearings installed on top of a reinforced core structure. A multilevel structure is then suspended from a hat truss or umbrella girder constructed on the seismic isolation mechanism. The first building to use the CSI system was the Safety and Security Center in Tokyo, Japan, whose structural health monitoring system has detected and recorded 231 earthquake motions since 2006, including the 2011 Tohoku Pacific Earthquake (2011‐TPE). The present study estimates the dynamic characteristics of this CSI‐equipped building in earthquakes, and the effects of the CSI system are revealed via the observed earthquake records. The temporal changes of the fundamental period and damping factor are estimated from the 2011‐TPE; the fundamental period increases with the deformation of the isolation level, whereas the fundamental damping factor is only related weakly to that deformation. The 231 observed earthquake records reveal that the CSI system performs seismic isolation by reducing the response acceleration of the suspended structure by roughly a half for peak ground accelerations exceeding 30 cm/s 2 . Daily microtremor observations are used to diagnose earthquake damage; the fundamental frequencies in each direction remain almost constant and were not changed by the 2011‐TPE.