方形箍筋约束混凝土轴压力学性能尺寸效应试验研究

Experimental Study on Size Effect of Compressive Response of Concrete Confined by Square Stirrups

基于11组方形箍筋约束混凝土棱柱体试件的轴心受压试验,通过对比各试件的破坏形态、应力-应变关系曲线、峰值强度、峰值应变以及峰值后变形能力等指标,研究了试件尺寸和箍筋形式对约束混凝土力学性能的影响规律以及尺寸效应随体积配箍率的变化规律.结果表明:在体积配箍率和箍筋形式均相同的情况下,随着试件几何尺寸的增大,峰值强度、峰值应变以及峰值后变形能力均呈下降趋势;体积配箍率越低,峰值强度的尺寸效应越显著,而峰值应变以及峰值后变形能力的尺寸效应越弱;对于体积配箍率相同的试件,当箍筋形式随试件尺寸的增大变得越来越复杂时,大尺寸试件的峰值强度增幅较小,其值仍低于箍筋形式最简单的小尺寸单箍试件.而峰值应变以及峰值后变形能力均有较大幅度提升,其值高于箍筋形式简单的小尺寸单箍试件.最后,将各试件的核心区混凝土峰值强度与2个典型模型的预测结果进行了对比,计算结果显示,传统模型不能很好地预测试件尺寸对峰值强度的影响.

In this research, the axial compressive experiments were conducted through 11 groups of prism specimens confined by square stirrups. The failure mode, stress-strain curve, peak strain and peak strength, and post-peak deformation capacity were evaluated; influences of the specimen size and the stirrups configuration on the mechanical properties of confined concrete were investigated. The change rule of the size effect along with the changes of the volumetric ratio of transverse reinforcement was discussed. Results show that for the specimens with the same volumetric ratio and the same configuration of stirrups, the peak strength, peak strain and post-peak deformation capacity decrease along with the specimen size increasing; for the specimens with the lower volumetric ratio of transverse reinforcement, the size effect on the peak strength is more obvious than that of the specimens mentioned above, while the peak strain and post-peak deformation capacity become comparatively weaker; for the specimens with the same volumetric ration of transverse reinforcement with various stirrups configuration, the increasing value of the peak strength for the larger size specimen become smaller, and it is smaller than that of the smaller specimen with the simplest stirrups configuration; while the peak strain and the post-peak deformation capacity increase greatly, which are larger than that of the smaller specimen with the simplestconfiguration. Comparing the peak strength for core concrete with the results calculated by using two typical models, it is showed that the results obtained from the typical models cannot predict the influence of the size on the peak strength perfectly.