快速加载下轴压比对RC梁柱节点抗震性能的影响

目前,梁柱节点抗震性能的研究多数为拟静力试验研究,有关梁柱节点动力试验研究相对较少。基于此,对四个梁柱节点组合体试件进行快速加载试验,以研究快速加载时轴压比对梁柱节点抗震性能的影响。此外,基于软化拉-压杆模型、库伦破坏准则、莫尔圆理论、节点组合体受力模型,推导了剪压复合受力状态下混凝土抗剪强度计算模型。研究表明:软化拉-压杆模型可用于预测节点组合体的抗剪承载力及破坏形态,混凝土抗剪强度计算模型,可用于预测考虑材料应变率效应后,轴压比对节点组合体抗剪承载力的影响规律;不同轴压比水平下,节点组合体裂缝类型和破坏形态相同,但随着轴压比的逐渐增大,节点核心区内裂缝数量不断减少,节点核心区的剪切变形及斜裂缝与竖向轴力的夹角不断减小,节点组合体严重损伤部分发生转移;相同位移水平下,正向加载的环线刚度始终大于反向加载的环线刚度;节点组合体抗剪承载力随轴压比的增大而增大,但效果不明显;轴压比增大对节点组合体耗能起有利作用。

Effects of axial compression ratio on aseismic performance of RC beam-column joint under rapid loading

At present, most beam-column joint’s aseismic performance studies are quasi-static test ones, dynamic test studies are less. Here, rapid loading tests were conducted for 4 beam-column joint combination specimens to study the effects of axial compression ratio on aseismic performance of beam-column joint under rapid loading. In addition, based on the softened strut-and-tie model, Coulomb failure criterion, Mohr’s circle theory and the mechanical model of joint combination, the calculation model of concrete shear strength was derived under the shear-compression composite stress state. The study showed that the softened strut-and-tie model can be used to predict the anti-shear load-bearing ability and failure modes of joint combination;the calculation model of concrete shear strength can be used to predict effect laws of axial compression ratio on anti-shear load-bearing ability of joint combination considering material strain rate effect;joint combinations have same failure modes and crack types under different axial compression ratios, however, with increase in axial compression ratio, number of cracks, shear deformation and angle between oblique crack and vertical axial force in joint core zone gradually decrease, transfers of joint combination’s serious damage parts happen;forward loading’s loop line stiffness is always larger than reverse loading’s one under the same displacement level;with increase in axial compression ratio, anti-shear load-bearing ability of joint combination increases, but the effect is not obvious;increase in axial compression ratio is beneficial to energy dissipation of joint combination.