箍筋约束混凝土圆柱轴压破坏尺寸效应行为

开展了12组不同尺寸几何相似的箍筋约束混凝土圆柱轴心受压破坏试验，试验的工况参数为:配箍率为1.26%和2.89%；圆柱尺寸（直径）相似比为1∶1.5∶2.25，圆柱最大直径为576 mm；圆柱长细比为3。根据试验结果探讨了箍筋约束作用混凝土圆柱破坏模式及轴压强度尺寸效应的影响规律。基于Ba?ant尺寸效应律思想，提出了能反映尺寸影响的箍筋约束混凝土圆柱轴压承载力计算理论，与试验结果的良好吻合证明了修正承载力计算理论的合理性。最后，建立了钢筋混凝土柱破坏行为及尺寸效应模拟的3D细观尺度数值分析方法，在模拟结果与试验结果吻合良好的基础上，扩展模拟了更大尺寸圆柱的破坏行为。

SIZE EFFECT ON THE FAILURE OF STIRRP-CONFINED REINFORCED CONCRETE COLUMNS UNDER AXIAL COMPRESSION

A total of 12 geometric similar stirrup-confined circular reinforced concrete (RC) columns subjected to axial compression were designed and tested. In the tests, two stirrup ratios of 1.26% and 2.89% were utilized. The structural similarity ratio of the columns was 1:1.5:2.25. The maximum cross-sectional diameter was 576 mm, and the slenderness ratio was 3. The confinement effect on the failure patterns and the axial compressive strength of the stirrup-confined columns was explored. Moreover, based on the basic theory of the Size Effect Law (SEL) proposed by Ba?ant, a modified formula for evaluating the bearing capacity of stirrup-confined RC columns was developed, which can reflect the effect of structural size. Good agreement between the theoretical results and the test results indicated the reasonability of the modified formula. Finally, a 3D meso-scale numerical method for the simulation of the failure behavior and size effect of RC members was established. The simulated results were consistent with the tested ones, and the meso-scale simulation method was then extended to model the failure of circular RC columns with larger structural dimensions.