低配箍率既有框架柱抗震变形能力研究

Research on seismic deformation capacity of existing concrete frame columns with low volumetric ratio of transverse reinforcement

基于15个不同配箍率RC框架柱拟静力试验研究,发现对配箍率低于现行设计规范要求的框架柱,当设计轴压比不小于0.6时,其极限位移角并不能达到1/50;采用试验所得数据对已有框架柱极限位移角计算公式进行复核,结果表明该公式不能很好地适用于既有建筑中常见的配箍率不满足现行设计规范要求的框架柱;对比分析了常用的几种约束混凝土本构关系,认为Saatcioglu-Razvi模型最为合理。基于Open Sees建立有限元模型,其中对于约束混凝土本构关系采用Saatcioglu-Razvi模型模拟,计算结果与试验结果吻合良好;通过150个纤维有限元模型计算,研究了箍筋配置对低配箍率框架柱变形能力的影响,结果表明在保持配箍特征值不变前提下,增大箍筋间距（箍筋强度随之增大）会使框架柱极限位移角减小;修改并提出了适用于低配箍率既有框架柱的极限位移角计算公式。

15 specimens were tested showing that the ultimate drift ratios of RC columns with transverse reinforcement ratios lower than the current codified requirements are less than 1/50 when the axial compression ratio is not less than 0.6. The current formulas calculating the ultimate drift ratio of RC columns were checked on the basis of the experimental data. It is shown that these formulas are not fully applicable to the RC columns with low transverse reinforcement ratio. Based on comparisons among several models, the Saatcioglu-Razvi＇ s stress-stain relationship is considered to be the best for confined concrete. OpenSees models based on the Saatcioglu-Razvi＇ s stress-stain relationship were established. And the numerical results agree well with the test results. 150 FE models were analyzed and the influences of transverse reinforcement on the seismic performance of the concrete frame columns were studied. It is shown that with the same volumetric ratio, the ultimate drift ratio decreases when the transverse reinforcement space increases. Furthermore, a modified formula for calculating the ultimate drift ratios of RC columns with low volumetric ratio of transverse reinforcement has been proposed.