鋼繊維補強コンクリートを適用した短スパン梁の開発
近年頻発する大地震を鑑みて，レジリエントな構造体を有する建築物が求められている。一方，建築計画では自由性に富んだ空間とするため，耐震要素を建物外周部やコア部に集約させる計画が増えている。高い耐震性と自由な建築計画を同時に実現する架構計画として，水平剛性の高い鉛直部材とそれをつなぐ短スパン梁によって耐震要素を構成する構造計画が考えられるが，短スパン梁を鉄筋コンクリート造で構築した場合，過大なひび割れが起こり，建物全体に多大な影響を与える恐れがある。本論文では，短スパン梁に鋼繊維補強コンクリートを適用することで，地震時に損傷の少ない高性能部材を開発した。開発にあたり，主筋の配筋方法，せん断スパン比，鋼繊維混入量をパラメータとした曲げせん断実験を行った。実験結果より，鋼繊維は短スパン梁部材の損傷抑止，靭性能向上に寄与し，その復元力特性は既往の評価手法を準用することで評価可能であることが分かった。
キーワード：鋼繊維補強コンクリート，短スパン梁，X 形配筋，ひび割れ幅，復元力特性
＊１ 技術センター 都市基盤技術研究部 構造研究室
＊２ 設計本部 構造設計第三部
Development of Short-Span Beams Using Steel Fiber-Reinforced Concrete
Due to the large earthquakes in recent years, there is a demand for buildings with a resilient structure. On the other hand, to increase the degree of freedom in architectural planning, seismic elements are being increasingly concentrated on the outer circumference or on the core of buildings. A structural plan in which the seismic elements are composed of vertical members with high horizontal rigidity and short-span beams connecting them can be considered as a structure that realizes both high seismic resistance and a high degree of freedom of building planning. However, reinforced concrete short-span beams can have a significant impact on the building due to excessive cracking. In this research, a high-performance member with reduced damage during an earthquake was developed by applying steel fiber-reinforced concrete to short-span beams. In the research, bending shear experiments were performed in which the experimental parameters were the main bar direction, shear span-to-depth ratio, and steel fiber content. From the experimental results, it was found that steel fiber contributes to damage reduction and improvement of ductility performance of short-span beams, and the hysteresis characteristics can be evaluated by applying the existing design methods.
Keywords: steel fiber-reinforced concrete, short-span beam, diagonally reinforcing bar, crack width, hysteresis characteristic
*1 Structure Research Section, Urban Engineering Research Department, Taisei Advanced Center of Technology
*2 Structural Engineering Department III, Design Division