An Experimental Study of Ductility for Concrete-filled Square Steel Tubular Column
方钢管混凝土柱延性的实验研究

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.