高強度鉄筋コンクリート用棒鋼の耐火性能

　高強度鉄筋コンクリート用棒鋼の火災時および火災後の機械的性質を得るために，高温および加熱冷却後の引張試験を実施した．
　常温から1000℃までの熱間引張試験を実施した結果，USD685の高温時の機械的性質を把握し，高温時の応力―ひずみ関係はRamberg-Osgood型の非線形特性で良好にモデル化できることがわかった．
　さらに，高強度鉄筋コンクリート用棒鋼（SD490およびUSD685）の火災後の引張試験を実施した．棒鋼への加熱条件は，ISO-834で示されている30〜180分の標準加熱曲線に対し，ＲＣ柱の熱伝導解析を実施して算定した．ＲＣ柱に配された棒鋼の火災後の機械的性質は，火災を受ける前のそれと実質的に変化がなかった．

Fire Resistance of High-strength Reinforced Concrete Bars

Tensile tests of rebars for high-strength concrete buildings were carried out to obtain their mechanical properties during/after fire.
As for high-temperature tests, the test samples of USD685 rebars were subjected to temperatures of 20 to 1000 ℃. The stress-strain relationships can be well represented with Ramberg-Osgood type nonlinear curves.
Post-fire tests were performed on SD490 and USD685 samples. Heating conditions were based on cross-sectional finite difference analyses of a typical RC column, to be exposed to 30- to 180-minute long ISO834 fires. Post-fire mechanical characteristics of the rebars located in the column were virtually identical to those obtained prior to heating.