钢筋混凝土框架结构梁柱中节点动态力学性能试验研究

摘要

Due to the rate sensitivity of materials,reinforced concrete members are sensitive to the strain rate,with varying mechanical properties at different strain rates.The majority of previous studies have focused more on the rate effect of concrete and reinforcement,but less on beam-column joints under high strain rate.The dynamic mechanical properties of 15 interior beam-column joint combination specimens subjected to various axial compression ratios were studied in the paper.The failure pattern of interior beam-column joint was predicted by binomial logistic regression model.The test results show that with the increasing of strain rate,the number of cracks in the joint declines continuously with a tendency to single main crack damage.The shear deformation in the core area of the joint and the angle between diagonal crack and vertical axial force decrease continuously as the axial compression ratio increases.Serious damage part of the joint transfers with the increasing of axial compression ratio or strain rate.The increasing of strain rate has adverse effect on the bond strength of reinforcement,and increases the bond slip of reinforcement.It can be found by the comparison of different specifications that the joint shear strength factor specified by ASCE SEI 41-06 is higher while that specified by ACI 352R-02 is more reasonable.However,both ASCE SEI 41-06 and ACI 352R-02 do not consider the effect of axial compression ratio on the joint shear carrying capacity.In contrast with the aforementioned building codes,GB50010-2010 considers the axial compression ratio effect with more reasonable calculation results.The study shows that if the values relating dynamic strength of concrete and reinforcement are directly substituted into the quasi-static design formulas to calculate the shear carrying capacity of the beam-column joint,it is unsafe due to the overestimate of the shear carrying capacity of the joint. An empirical equation to predict the dynamic increase factor of horizontal shear carrying capacity of beam-column joints under different axial compression ratios and strain rates was also proposed through multi-variate linear regression analysis.%受材料率敏感性的影响，钢筋混凝土构件具有率敏感效应，其受力性能在不同应变率水平下均有所不同。以往的研究多数集中于混凝土和钢筋材料率效应的研究，有关梁柱节点试件快速加载下的研究相对较少。研究了15个梁柱中节点在不同轴压比下的动态力学性能。运用二项式逻辑回归模型，预测了梁柱节点组合体的破坏形式，发现：随着应变率的提高，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；轴压比增大后，节点核心区的剪切变形以及斜裂缝与竖向轴力的夹角减小，应变率或轴压比增大后，节点组合体严重损伤部分发生转移；应变率的提高，对钢筋黏结强度起不利影响，钢筋滑移量随应变率的提高而增大。对比不同规范对节点抗剪承载力的计算公式发现，ASCE SEI 41－06规定的节点剪切强度因子偏高，ACI 352R －02规定的节点剪切强度因子较为合理，但 ASCE SEI 41－06和 ACI 352R－02都没有考虑轴压比对节点抗剪承载力的影响，相比之下 GB50010－2010考虑了轴压比的影响，计算结果更合理。在拟静态设计公式中采用材料动态强度的方法计算其承载力，往往会过高估计梁柱节点的抗剪承载力，是偏于不安全的。通过多元线性回归分析，得到了不同应变率及轴压比下节点水平抗剪承载力增大系数的经验方程。