方钢管混凝土柱延性的实验研究

针对结构抗震设计对延性的要求,对不同轴压比、长细比和混凝土标号的7根方钢管混凝土柱试件进行了低周反复加载实验,得到了框架柱的荷载位移曲线、骨架曲线以及各阶段的荷载位移值,据此分析了各种因素对方钢管混凝土柱延性的影响.实验结果表明:剪力滞引发了方钢管混凝土柱的塑性铰,塑性铰的扩展是柱端承载力下降的根本原因,增大轴压比将引起塑性铰更早出现,进而降低框架柱的延性和水平抗剪能力；增大长细比可以延缓塑性铰出现,提高柱的延性和耗能能力,但是水平抗剪能力下降；提高混凝土强度等级可以降低大轴压比、大长细比带来的不利因素.实验结果与有限元计算数据吻合良好.

An Experimental Study of Ductility for Concrete-filled Square Steel Tubular Column

In view of the requirement of structure seismic design for ductility, a group of low cyclic loading test was carried out for seven concrete-filled square steel tubular column specimens with different axial load ratios, slenderness ratios and concrete grades. Then, the load-displacement curve, the skeleton curve of these frame columns and the load-displacement value of each stage were obtained. Based on these data, an analysis on various factors that affect the ductility of concrete-filled square steel tubular columns was conducted. Results show that the decline of bearing capacity in the end-column is mainly due to the germination and expansion of the plastic hinge of pillar. Furthermore, the increase of axial compression ratio will lead to earlier emergence of plastic hinges, which and then reduces the ductility and horizontal anti-shearing capacity of the frame column. In addition, the increase of slenderness ratio can delay the plastic hinge emergence that improves the ductility and energy dissipation capacity of columns, but on the other hand decreases the horizontal anti-shearing capacity. As a result, adopting higher grade concrete can effectively reduce the negative effects due to the larger axial compression ratio and slenderness ratio. Experimental results are in good agreement with the data from finite element calculations.