钢筋混凝土框架变梁中节点抗震性能试验研究

Experimental research on seismic behavior of irregular interior joints in RC frame structure

完成了10个1/3缩尺钢筋混凝土框架变梁中节点试件的低周反复荷载试验,分析了变梁中节点的破坏形态、刚度退化和滞回耗能等力学性能,研究了梁柱尺寸变化、轴压比、配箍率等参数对该类节点抗震性能的影响。研究结果表明:变梁中节点初裂出现在小梁与上柱组成的小核心区,最终破坏区域主要发生在大梁与下柱组成的大核心区;变梁中节点通裂荷载与极限荷载比较接近,变梁中节点大、小梁端滞回曲线差别显著,大梁滞回曲线呈反S形,小梁滞回曲线呈较为饱满的弓形,小梁截面尺寸变化对试件的抗震性能影响显著;变梁中节点的强度衰减、刚度退化明显,耗能能力较差,按常规节点设计构造的变梁中节点不能满足刚性节点的要求。

According to the experimental investigation on ten 1/3-scale RC frame specimens with irregular interior joints under low cyclic reversed loading,the failure process and failure patterns were obtained.The failure characteristics,mechanical behaviors of the irregular interior joints such as the load displacement hysteretic loops,rigidity deterioration and energy dissipation were analyzed.The experimental study was conducted focusing on the effect of joint core dimensions,hoop percentage and axial compression ratio on seismic behavior of irregular interior joints.Test results indicate that the first crack appeares in the minor core（determined by the low beam and the top column）,and the final failure appears in the large core（determined by the high beam and the bottom column）.The critical crack load is quite same value as the ultimate load of the irregular interior joints.The load displacement hysteretic loops of low beam and high beam are quite different each other,the hysteretic loops of all the high beams show a reversed S-shape exhibited sever pinching with little energy dissipation.On the contrary,those of the low beams show a hooked end shape with improved energy dissipation.The seismic behavior of the beam-column joint subassemblage is significantly influenced by the dimensions of low beams,and this poor behavior of the beam-column joint subassemblage is due to formation of the diagonal tension cracks within the joint core region,inadequate confinement to the concrete and the significant bond deterioration along the beam bars through the joints.The reinforcing details of the test specimen,which are designed under the guideline of current codes,can not preserve the structural integrity and satisfy the strong joint demand.