Numerical study on shear capacity of geometrically similar RC interior beam-column joints

Reinforced concrete (RC) beam-column joints often present brittle shear failure in the core area. The objective of the study is to study the effects of stirrup ratio and axial load ratio on the shear capacity of geometrically similar beam column joints having different structural sizes. In this work, a series of 3D mesoscale simulations on the shear failure of RC beam-column joints were conducted and validated, in which the concrete heterogeneity was considered explicitly. The simulation results indicate that stirrups can improve the shear strength of joints, enhance the ductility, improve deformation ability, while weaken the size effect on the nominal shear strength. Moreover, the increasing axial load ratio would lead to the increase of shear strength, as well as the increase of size effect. Based on the modeling results, a novel semiempirical and semitheoretical size effect law considering the quantitative effect of stirrups and axial load ratio was proposed. In addition, the proposed size effect law was verified against with some available test data.