Validation of a Simplified Model for External Beam–Column Joints in RC Frames

The beam-column joints are crucial elements where the stresses arriving from the horizontal and vertical structural elements at the boundaries come with very high gradients. These elements are therefore directly involved in the seismic forces transfer. It is well known from recent history that past earthquakes have highlighted a poor performance of the beam-column joints, mainly because, until a few years ago, the joints were not designed, but simply assumed as rigid elements, showing serious limits to seismic actions. The model is based on post-cracking equilibria and it allows to trace the performance of the nodes highlighting the activation thresholds of different failure modes. The model has been validated through a database of 270 experimental tests on beam-column joints, showing, on average, better performance than currently available formulations.