不同应变率作用下钢筋混凝土梁柱节点抗震性能研究

STUDY ON THE SEISMIC PERFORMANCE OF REINFORCED CONCRETE BEAM-COULUMN JOINTS UNDER DIFFERENT STRAIN RATES

动荷载作用下,由于应变率效应的影响,钢筋混凝土梁柱节点呈现出与拟静力加载时不同的性质。以往的研究,多数集中于梁柱节点模型以及轴压比、混凝土强度、纵筋率等各种影响因素的研究,对于应变率对节点力学性能影响的研究相对较少。对3个梁柱节点组合体试件,采用位移控制方式加载,考虑应变率效应,梁端加载速度分别为0.4,4,40 mm/s。对比不同加载速率的影响,对节点破坏形态、承载能力、刚度退化和耗能能力进行详细论述。研究结果表明:随应变率的提高,节点组合体的破坏形态没有本质变化,但节点组合体内的裂缝数量不断减少,更倾向于单一主裂缝破坏;应变率越高,组合体的屈服点承载力和极限承载力越高,并且屈服点承载力提高的程度较极限承载力明显;在一定范围内,组合体的承载力、刚度和耗能能力均随着应变率的提高而增强,当超过一定范围之后,承载力和刚度急剧下降,耗能能力减弱,应变率的提高反而有不利影响。因此,在实际设计中,考虑应变率的影响,对梁柱节点有着重要的意义。

In the circumstances of dynamic loading , the reinforced concrete beam-column joint exhibits different properties with those presented in the case of quasi-static loads, due to the effect of strain rate .The majority of previous studies were focused more on the beam-column joint model as well as axial load ratio , concrete strength , longitudinal reinforced ratio etc , but less on the strain rate effect on the beam-column joint performance .Considering the strain rate effect , three beam-column joint specimens with displacement control loading were studied , respectively at the beam-end loading speed of 0.4 mm/s, 4 mm/s and 40 mm/s.Comparing the impact of different loading rates , the failure mode, carrying capacity, stiffness degradation and energy dissipation of the joint are discussed in detail . The results show that with the increasing of the strain rate , the failure mode of the beam-column joint does not changed essentially , but the number of crack within the joint continues to decline with the tendency to a single main crack damage .The higher the strain rate , the higher the yield carrying capacity and ultimate carrying capacity of the joint, and the degree of yield carrying capacity improvement is more obvious than that of ultimate carrying capacity . Within a certain range , the carrying capacity , stiffness and energy dissipation capacity of the joint are enhanced with the increase of strain rate .Beyond a certain range , the carrying capacity and stiffness decline sharply , and energy dissipation capacity is reduced as well , then the increase of strain rate will have adverse affect .Therefore, in the practical design , it is significant to consider the effect of strain rate on the beam-column joint .