Unified Simplified Capacity Model for Beam-Column Joints into RC Moment Resisting Frame

Abstract

Seismic vulnerability of reinforced concrete (RC) buildings is strongly influenced by beam-column joints. Horizontal and vertical structural members converge in beam-column joints, as extremely delimited areas where the internal forces in concrete core and reinforcing bars have elevated stress gradients. In order to fully understand the seismic behavior of RC buildings and the related failures of T- and X-shaped beam-column joints (external corner and internal-positioned), an analytical model of RC joint behavior is proposed in a unified and simplified way. The equilibrium equations of cracked joint portions allow the assessment of internal stresses’ evolution at increasing values of column shear forces. In this way, the strength hierarchy is evaluated in terms of capacity for the different potential failure modes. This can drive, as a useful tool for designers, the design of new efficient structures or the assessment of existing ones to occur, with subsequent interventions to move an initial undesired failure mode to a more suitable one. Nearly 500 experimental results of tests available in the literature are compared with the analytical predictions of the proposed model.