あと施工開口に鋼管補強を施した既設耐震壁の性能評価
原子力発電所施設の改修工事では，設備の増設や更新に伴い，既設の耐震壁に設備配管用の開口が新たに設けられることが多い。新設開口の設置に伴い，開口周囲には補強筋が配置されるが，定着長さまで考慮するとはつり範囲は広範囲となる。そこで，はつり範囲を狭くする補強法として鋼管を用いる方法を考案した。その効果を確認するため，耐震壁実験と非線形FEM解析による検討を行った。検討の結果，開口間隔を開口径の約4倍とした小開口試験体の耐力は補強の有無に係わらず無開口とほぼ同程度となった。また，大開口試験体では本補強法を施すことで無補強に比べ耐力が1割程度上昇した。また，本補強法を適用した耐震壁の耐力は既往の評価式を用いて評価できることを確認した。
キーワード：既設耐震壁，あと施工開口，開口補強，鋼管補強，耐震壁実験，FEM解析
＊１ 技術センター 都市基盤技術研究部 構造研究室
＊２ 原子力本部 原子力設計部
＊３ 原子力本部 原子力構造技術部
Performance Evaluation on Existing RC Shear Wall with New Openings Reinforced with Steel Tube
In the renovation of nuclear power plant buildings, there are many situations in which new openings for piping equipment must be created in existing shear walls for the expansion or renewal of facilities. To create new opening, concrete would need to be scraped off considerably for additional rebar placement around the openings so that the anchorage length requirements can be met. Therefore, we considered the use of steel tubes as a reinforcement method to reduce the amount of scraping. To verify the effectiveness of this method, shear wall tests and a non-linear FEM analysis were conducted. The results indicated that the maximum strength of a small-opening specimen with an opening spacing approximately four times larger than the opening diameter was almost the same as that of a specimen with no opening, regardless of whether the specimen was reinforced or not. In the case of a large-opening specimen, the maximum strength increased by about 10% compared with a non-reinforced specimen by providing steel tube reinforcement. It was also confirmed that the maximum strength of shear walls with steel tube reinforcement can be evaluated by using the existing evaluation formula.
Keywords: existing shear wall, new opening, opening reinforcement, steel tube reinforcement, shear wall test, FEM analysis
*1 Structure Research Section, Urban Engineering Research Department, Taisei Advanced Center of Technology
*2 Design Department, Nuclear Facilities Division
*3 Structural Engineering Department, Nuclear Facilities Division