EngineeringYear Book 2019The Keio University Library Old Building, completed in 1912, is a designated important cultural property. It was heavily damaged by the 1923 Great Kanto Earthquake and by the bombing of Tokyo during the Second World War. Each time it was repaired. But despite the restoration work, the brick and granite building was still vulnerable to earthquakes. This project was a retrot for the designated sections of the building that would improve their resistance against earthquakes while preserving their historic design. Because the library’s Stack Room No. 2 is adjacent to the designated Main Building and Stack Room No. 1, it was included in a retrofit plan for all three spaces. Seismic isolation was provided by spherical sliding bearings, which can absorb the tremors and wave energy of an earthquake even when the load is highly unbalanced. By reinforcing the brick foundations of the building with lateral bracing beams and supporting the foundations from below with spherical sliding bearings, the seismic performance of the building was improved without damaging its brick structure.慶應義塾図書館旧館は、明治45年に竣工した組積煉瓦造建物です。関東大震災・戦災などによって大きな被害を受け、その都度改修が行なわれてきましたが、耐震性に問題がありました。そのため、重要文化財の指定範囲の空間については意匠性を維持しながら、耐震性向上のため免震レトロフィットにて改修を計画をしました。計画にあたり、第2書庫が重要文化財である旧館・第1書庫に近接して建てられているため、旧館・第1書庫・第2書庫合わせた免震計画としています。免震装置には、荷重が偏在していても地震の揺れ、エネルギーを大きくゆっくり吸収する球面すべり支承を採用し、煉瓦基礎を包むように梁で補強し、基礎下に球面すべり支承を配置することで、煉瓦躯体を傷めることなく耐震性向上を図ることができました。建物南側外観免震装置荷重移行階段室から大会議室・正面玄関側内観組積煉瓦造の免震レトロフィット慶應義塾図書館旧館（重要文化財）Seismic Isolation Retrofit System – Keio University Old LibraryEngineering015
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