Abstract The inelastic buckling of longitudinal steel bar is one of the major damage states of reinforced concrete (RC) column under seismic loading, which may result in a reduction of section moment capacity and ductility. However, the relationship between bar buckling and deterioration in seismic behaviors of RC column has normally been proposed based on the theoretical analysis, direct experimental verification is scarce, and the differences between the buckling behavior of individual steel bar and that of longitudinal bar in RC column remain unclear. In this paper, a series of experiments on cantilever RC columns and individual bars were conducted to study the buckling behavior by means of the measured lateral buckling displacements of the bars. A new method was proposed to measure two components of the lateral buckling displacements of longitudinal bars and individual bars in orthogonal directions, the reliability and accuracy of the proposed method have been identified by the comparison of measured buckling displacement of corner bars in two identical RC specimens. Based on the measured lateral buckling displacements of reinforcing bar in RC columns and corresponding individual bar, the onset of buckling and the buckling direction of the two kinds of steel bars were analyzed. It is found that buckled main bars in RC columns behave differently with individual steel bars due to the constraint effect of cover concrete. The equivalent average stress of main bar was determined by creating a mapping between the buckling displacement of bar in RC section and the average stress of individual bar. On the basis of the buckling displacements and the equivalent average stress, the effects of bar buckling on the post-peak bearing capacity and the displacement ductility of RC column were investigated. The results show that the degradation of the post-peak lateral force of RC column is generally weaker than the strength deterioration of buckled steel bar due to the load redistribution between longitudinal reinforcement and surrounding core concrete.

中文翻译：

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钢筋屈曲对钢筋混凝土柱抗震性能影响的试验研究

摘要 纵向钢筋非弹性屈曲是钢筋混凝土柱在地震荷载作用下的主要破坏状态之一，可能导致截面弯矩承载力和延性降低。然而，钢筋屈曲与钢筋混凝土柱抗震性能劣化之间的关系通常是基于理论分析提出的，缺乏直接的实验验证，并且钢筋的屈曲性能与钢筋混凝土柱中纵筋的屈曲性能存在差异仍然不清楚。在本文中，对悬臂 RC 柱和单个钢筋进行了一系列实验，通过测量钢筋的横向屈曲位移来研究屈曲行为。提出了一种测量纵向钢筋和单根钢筋在正交方向上的横向屈曲位移的两个分量的新方法，通过对两个相同钢筋混凝土试件实测角钢筋屈曲位移的比较，验证了该方法的可靠性和准确性。 . 根据实测钢筋混凝土柱和相应单根钢筋的横向屈曲位移，分析了两种钢筋的屈曲开始和屈曲方向。发现由于保护层混凝土的约束作用，RC柱中的屈曲主钢筋与单个钢筋的行为不同。主钢筋的等效平均应力通过创建钢筋混凝土截面中钢筋的屈曲位移与单个钢筋的平均应力之间的映射来确定。在屈曲位移和等效平均应力的基础上，研究了钢筋屈曲对钢筋混凝土柱峰后承载力和位移延性的影响。结果表明，由于纵向钢筋与周围核心混凝土之间的荷载重新分配，RC柱峰值后侧向力的退化一般弱于屈曲钢筋的强度退化。