A new discrete macro-node element for the seismic behaviour modelling of reinforced concrete frames

Recent earthquakes have demonstrated that the seismic behaviour of existing reinforced concrete buildings, not designed to resist to earthquake loadings, is strongly affected by the local collapses of the beam-to-column joints that can be subjected to shear collapse of the central region or bond-slip of the longitudinal steel bars. In this paper a new macro-node element able to account for the nonlinear behaviour of the beam-to-column joints is presented. The model can be represented by a simple mechanical scheme constituted by an articulated quadrilateral whose rigid edges connect beams and columns through nonlinear discrete interfaces and whose internal deformability is related to a single degree of freedom only. The model is able to account for the shear failure of the joint region as well as the flexural and shear plastic deformations at the contact edges of the connected elements allowing the nonlinear modeling of a frame structure through an assemblage of non-linear macro-nodes connected by means of elastic frame elements.