EACS 2016 paper - Dynamic Behaviour of a Seven-Storey Seismically Isolated Building during the 2011 Tohoku Earthquake

2017-03-28T15:18:25Z (GMT) by Toshihide Kashima
EACS 2016 Paper No. 127

The Building Research Institute (BRI) operates a strong motion network that covers buildings in major cities across Japan. In 2010, as one of stations in the BRI strong motion network, the seven-story Tsukuba Town Hall building, which is a precast prestressed concrete frame structure, was equipped with a seismic isolation system consisting of; 11 natural rubber bearings, 45 lead-plugged rubber bearings and 9 steel-damper-combined rubber bearings. The building suffered extremely strong shaking with the Tohoku Earthquake of 11 March 2011. The accelerometer installed on the ground near the building, 334 kilometres far away from the epicentre, red out the peak ground acceleration higher than 1G. Even in this situation, the seismic isolation system successfully reduced the seismic acceleration exceeding 3 m/s2 on the foundation to less than one third. The analysis of the strong motion data obtained during the 2011 Tohoku Earthquake verified the excellent performance of the seismic isolation system. The maximum deformation of the isolation devices reached nearly 70 mm. Based on the analysis of the strong motion data on 84 earthquakes that occurred during the period from 2010 to 2016, dynamic characteristics of the seismic isolation system and the superstructure were discussed. The stiffness of the seismic isolation system showed a clear decline in the large displacement range. The damping effect of the seismic isolation system remained satisfactorily stable. We concluded that the seismic isolation system installed in the Tsukuba Town Hall building worked properly and effectively as expected in the structural design.