钢筋混凝土抗震框架节点受力机理及轴压比影响的试验研究

通过19个剪压比水平和轴压比水平不同的接近足尺的钢筋混凝土框架中间层中间节点梁柱组合体的低周反复加载试验,对节点的传力机理以及轴压比对节点抗震性能的影响规律进行了分析研究,取得了以下结果:(1)随着轴压比的增加,梁筋在节点内的粘结滑移量明显减小。节点的作用剪力较大时,梁筋的粘结退化加剧;(2)通过对节点内不同受力阶段箍筋应变的量测,明确了平行受力方向箍肢除承受桁架机构的拉力外,还与垂直受力方向的箍肢一起对节点核心区双向交替斜向受压混凝土发挥重要约束作用;(3)节点作用剪力在中等以上作用水平时,轴压比的增大对节点抗震抗剪的延性起不利作用。

Experimental investigation of shear mechanism and effect of axial-compression ratio on joints in earthquake-resistant reinforced concrete frames

Reversed cyclic tests of 19 nearly full-scale interior beamcolumn joints of reinforced concrete frames,with different shear compression ratios and axial compression ratios,were carried out to investigate the shear transfer mechanism in the joint and the effect of the axial compression ratio to the seismic behavior of the joint.The conclusions are drawn as follows:(1) Bond slip of the beam rebars from the joint is significantly decreased as the axial compression ratio increases.At higher level of shear in the joint,the bond deterioration of beam rebars has increased;(2) Measurements on the stirrup strains in the joint show that the stirrup lag parallel in the direction of acting force not only sustains the tension in the truss mechanism,but also confines the reversed cyclic diagonal compressive concrete strut in the joint core;(3)It is confirmed that when the acting shear in the joint is moderate or greater,increase of the axial compression ratio is significantly unfavorable to the ductility in seismic shear.