新旧混凝土结合面抗剪性能的尺寸效应

为研究新旧混凝土结合面抗剪性能的尺寸效应，以结合面不同处理方式（凿毛和凿毛+植筋）和结合面尺寸（高度分别为100、200、330、440 mm，宽度均为200 mm）为试验参数，对2组共16个Z字形新旧混凝土结合试件进行了抗剪试验。结果表明：凿毛试件和植筋试件结合面的抗剪性能均表现出明显的尺寸效应；凿毛试件的临界极限强度和弹性抗剪刚度分别为结合面高度100 mm试件的51%和32%；植筋试件的临界开裂强度、极限强度和弹性抗剪刚度分别为结合面高度100 mm试件的65%、76%和41%。结合面高度大于1 000 mm后，描述凿毛和植筋2类试件结合面抗剪性能特征参数的尺寸效应均趋于稳定；基于试验和分析结果，建立了凿毛和植筋处理时结合面的黏结-滑移本构模型，提出了表征结合面抗剪性能各特征参数尺寸效应律的计算式，可供工程结构设计和分析时参考。

Size Effect of the Shear Performance on the Bonding Interface Between New and Old Concrete

To investigate the size effect of the shear performance on the bonding interface between new and old concrete, a shear test was conducted on 16 Z-shaped specimens in two groups with different interface treatments (i.e., chiseling and post-installed rebar) and interface sizes; the bonding interface of the specimen samples has the same width of 200 mm and different heights of 100 mm, 200 mm, 330 mm, and 440 mm, respectively. The experimental results demonstrate that the shear performance of the bonding interface for chiseling and post-installed rebar specimens varied with the interface size. Compared to the corresponding results of the specimen with a bonding interface height of 100mm, the critical ultimate strength and elastic shear stiffness of the chiseling specimen decreased by 49% and 68%, respectively; the critical cracking strength, critical ultimate strength, and elastic shear stiffness of the post-installed rebar specimen decreased by 35%, 24%, and 59%, respectively. When the height of the bonding interface was larger than 1 000 mm, the effect of interface size on the characteristic parameters used for describing the shear performance of the bonding interface tended to be stable for both the chiseling and post-installed rebar specimens. Based on the experimental and analytical results, bond-slip constitutive models applicable to the bonding interface of chiseling and post-installed rebar specimens were proposed, and the equations for characterizing the size effect law of the characteristic parameters of the shear performance for the bonding interface were developed. The proposed models and equations can be used for the design and analysis of engineering structures.