Modelling of exterior RC beam-column joints for the seismic assessment of RC-frames

Past and recent seismic events underlined unexpected damage mechanisms of RC-frames consisting of widespread damages and collapses of beam-column joints. These outcomes, mainly concerned RC-frames designed before the introduction of modern seismic codes, clearly emphasize the paramount role of the beam-column joints in the context of the seismic safety assessment of RC-frames. In this paper, the Authors present a study devoted to numerically analyze the seismic response of RC-frames obtained by introducing in the finite element model of the frame with only beams and columns an additional component interposed between beam and column members able to reproduce the monotonic and cyclic nonlinear behavior of the beam-column joint element. In particular, the additional component consists of springs arranged according to the scissors model and characterized by constitutive laws calibrated by the Authors in a previous study with reference to different beam-column joint configurations. The numerical simulations carried out with reference to a literature case study highlight the importance of considering the contribution of the beam-column joints in the seismic analysis of RC frames.