Influences of beam and column bar bond on failure mechanism in reinforced concrete interior beam-column joints

Reinforced concrete (R/C) interior beam-column joint specimens were tested under column axial loading and reversed cyclic lateral loading to study the joint failure mechanism and the relation between story shear and joint shear. The bond transfer from the beam and column longitudinal bars to surrounding concrete in a joint was important in enhancing the story shear. It was judged that the joint core concrete failed by diagonal compression since the compressive principal strain within a joint panel increased with the story drift and exceeded the strain at the concrete compressive strength in cylinder tests. The joint shear force, which was computed by the manner that residual tensile force of beam bars caused by lateral expansion in a joint concrete was eliminated, decreased with the decrease in the story shear or was kept almost constant.