2011年東北地方太平洋沖地震における東京湾沿岸の免震構造物の挙動
2011年3月11日に発生した東北地方太平洋沖地震の際に、免震建物で得られた観測記録を分析した。免震建物のタイプは、柱頭免震、塔頂免震、パーシャルフロート免震、基礎免震の4種類である。前3棟は当社技術研究所に、後1棟は震源により近い東北大学にある。何れの建物でも、建物内で観測された加速度は、地表あるいは隣接する耐震建物で同時に観測された加速度に比べて1/2から1/3に低減されていることが確認された。また、研究所内に建つ3棟については、首都圏における巨大地震を想定したシミュレーション解析を実施して、免震効果を検討した。
Dynamic Behavior of Seismic Isolated Buildings on Tokyo Bay Area in the 2011 Tohoku-Pacific Earthquake
The 2011 Tohoku-Pacific Earthquake that occurred on March 11, 2011 caused devastating damage to the northeast Pacific coast region. Three different types of seismic isolated buildings stand in the grounds of Shimizu Corporation's Institute of Technology in Tokyo. In addition, Shimizu Corporation and Tohoku University jointly built a test building for seismic isolation within the Sendai campus in Miyagi prefecture, which was near the epicenter of the 2011 Tohoku-Pacific Earthquake. The effects of applied seismic isolation methods were verified through the observed earthquake responses of the four seismic isolated buildings subjected to this earthquake. In each of the three seismic isolated buildings in the institute, the observed accelerations on the floors were reduced to about half compared to those on the ground. In the test seismic isolated building in Tohoku University, the observed accelerations on the roof were reduced to about one third compared to those in an adjacent conventional seismically designed building.