Seismic behavior comparison of reinforced concrete interior beam-column joints based on different loading methods

Abstract

Due to the difference in loading point, experimental researches on seismic behavior of beam-column joint can be generally divided into two types, namely loading at beam ends (BL method) and loading at column top end (CL method). This paper presents an experimental investigation aimed at comparing the cyclic behavior of interior beam-column joints with different loading methods. Four groups of full-scale interior beam-column subassemblages were tested under reversed cyclic loading. Two identical specimens were tested under two different loading methods in each group. On the basis of the experimental results, the paper discusses the distinctions of cyclic behaviors under different loading methods in terms of crack pattern, joint shear strength, joint shear transfer mechanism, joint shear deformation, longitudinal bar-slip, energy dissipation, and stiffness degradation. In addition, a numerical simulation of these four groups of specimens is shown and discussed. The experimental results and numerical analyses confirm that the loading method can have certain influence on the cyclic behavior of the beam-column joints. The joint shear strength, joint shear deformation and longitudinal beam bar slip of beam-ends loading specimens (BL specimens) are considerably larger than that of column-end loading specimens (CL specimens), although the loading protocol used for CL method is more severe than BL method in terms of number of loading cycles. In consequence, the influence of loading method should be considered when the seismic behavior of the beam-column joint is evaluated according to a great number of existing beam-column joint tests.