Seismic Performance of Reinforced Concrete Columns Confined in Square Steel Tube with Thin Steel Wall

在试验研究阶段，共有23根受约束于方钢管内的钢筋混凝土柱（管柱）受到循环剪力的双重曲率变形。试验参数为柱长径比（2.0 ~ 4.0）、宽壁厚比（B/t=28 ~ 117）、轴向载荷大小。在研究的基础上，得出以下结论。长径比为2.0和4.0的管柱破坏模式分别为剪切破坏和受弯破坏。值得注意的是，即使在剪断短柱中，随着位比的降低和轴向荷载水平的降低，其侧向变形能力也大大增强。基于Sakino和San提出的约束混凝土应力-应变模型，采用等效应力块的简化方法可以较好地计算柱的抗弯强度。它们应该通过考虑末端桩的额外约束效应的因素来增强。AIJ-A方法是一种基于塑性理论的分析方法，虽然低估了大侧配钢比试件的承载力，但可以较好地评价以剪切为主的短柱试件的侧向承载能力。另一方面，也可以使用Arakawa的经验剪切公式。

In the experimental phase of research, total of twenty-three reinforced concrete columns confined in square steel tube (tubed columns) were subjected to cyclic shearing force and deformed in a double curvature pattern. The experimental parameters were aspect ratio of column (2.0-4.0), width to wall-thickness ratio (B/t=28- 117), and magnitude of axial load. The following conclusions are reached on bases of the research.1. The failure modes of tubed columns with aspect ratio of 2.0 and 4.0 are shear failure and flexural failure, respectively. It is noteworthy that lateral deformation capacity is greatly enhanced with the decrease in Bit ratio and with the decrease of axial load level even in the short columns failed in shear.2. The flexural strengths of columns can be satisfactorily evaluated using the simplified method that utilizes the equivalent stress block based on the stress-strain model for confined concrete proposed by Sakino and San. They should be enhanced using a factor that takes the effect of extra confinement from end stubs into consideration.3. The lateral load capacities, as dominated by shear, for short column specimens can be fairly evaluated using AIJ-A method, which is analytical method based on plastic theory, although it underestimates the capacity of specimens with large lateral steel ratios. On the other hand, the Arakawa's empirical shear formula also can be used.