外张拉式自复位方钢管混凝土柱脚抗震性能试验研究

外张拉式自复位方钢管混凝土柱脚是一种便于钢绞线张拉和耗能部件更换的自复位柱脚节点。根据钢绞线与防屈曲钢板(BRS板)布置方式的不同,将自复位柱脚分为Ⅰ型、Ⅱ型和Ⅲ型,以适应平面和空间复位模式。通过3个3/4比例的Ⅰ型自复位柱脚的低周往复荷载试验,研究初始预应力、轴压比对柱脚承载能力、自复位性能和抗震性能等的影响。结果表明:在竖向荷载和水平往复荷载的共同作用下,外张拉式自复位方钢管混凝土柱脚的滞回曲线为典型的"双旗帜"形,该柱脚具有良好的自复位能力和耗能能力;加载至4%侧移角时,柱和钢绞线仍保持弹性,仅BRS板进入塑性状态,因此通过更换BRS板可以实现震后的快速修复;增大轴压比和钢绞线初始预应力,可有效提高柱脚的承载力,增大自复位能力,变形能力和耗能能力减小。所提出的自复位柱脚弯矩计算式,计算结果与试验结果吻合较好。

Experimental study on seismic behavior of self-centering concrete-filled square steel tubular column base with external prestressing

It is convenient for self-centering (SC) concrete-filled square steel tubular (CFST) column base with external prestressing to exert post-tensioned（PT）force and replace the buckling restrained steel plates (BRS plates). In this paper, Type Ⅰ, Type Ⅱ and Type Ⅲ of SC-CFST column bases that can be applied to in-plane and three-dimensional self-centering frames were proposed, based on different arrangement of PT strands and BRS plates. The low cyclic loading tests on 3/4 scaled Type Ⅰ SC-CFST column base were also conducted, and the load carrying capacity, self-centering capacity and seismic performance were studied with different initial PT forces and axial compression ratios. The findings show that the hysteretic curves of SC-CFST column base are typical double-flag shape with great self-centering capability and energy dissipation capacity. Besides, the CFST column and steel strands remain elastic even at 4% story drift angle except for the BRS plates, so that the column base could be repaired rapidly by using new BRS plates after design earthquake. Increasing the axial compression ratio and initial PT force can increase the bearing capacity and self-centering capacity, while decrease deformation capacity and energy dissipation capacity of column base. Moreover, formulas of moments of SC-CFST column base are proposed, and the calculated result agrees well with the test moment of SC-CFST column base.