不同应变率作用下钢筋混凝土梁柱节点抗震性能研究

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。

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

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.