付着良好な梁降伏型RC内部接合部の必要せん断補強筋量

抄録

The current New Zealand code for concrete structures requires that the horizontal shear reinforcement within a beam column joint must carry the total joint shear force unless the axial force of the column is large enough or the plastic hinge regions of the beams are relocated away from the column faces. This requirement has raised international arguments. Experiments in New Zealand yielded a conclusion that the requirement was not conservative. Experiments in Japan yielded another conclusion that one half the shear reinforcement required by the New Zealand code was enough to keep the joint elastic after reversed cyclic loadings of large deflection angle. Assuming a simple stress distribution along the periphery of the joint as shown in Fig.2 and considering shear resistant mechanisms shown in Figs.4, 6 and 8, this paper derived a design equation, Eq. (16). Normally, the derived equation requires smaller amount of horizontal shear reinforcement than the current New Zealand code, especially for the following cases : a) the joint shear stress is small, b) the axial force is small, c) the amount of the top beam reinforcement is larger than the bottom, and d) the amount of the vertical shear reinforcement is large. The derived equation agreed with both the experimental results in New Zealand and those in Japan, which seemed contradictory each other.