Influence of beam-column joints behaviour on seismic response of R.C. existing buildings

For R.C. buildings it is usual to perform structural linear and non-linear analyses, in static and dynamic field, considering the beam-column joints as rigid and with infinite resistance and afterwards execute resistance verifications on them. It is well known that beam-column joints fragile behaviour plays a fundamental role in the response of structures and in the identification of their seismic capacity. In this paper a mono-dimensional numerical model, easily implementable in commercial software package, is developed. The model is capable to describe the non-linear structural behaviour of beam-column joints. The results of the numerical push over analyses carried out with this model are compared with those obtained with a second bi-dimensional numerical model available in scientific literature and conveniently calibrated. The proposed model is able to prevent the fragile collapse of the beam-column joints and the consequent ductility structural reduction. Implemented in the commercial software package, the model can be used in non-linear vulnerability analyses to assess the influence of joints behaviour on the response of overall R.C. buildings and to evaluate the effect of structural interventions with the goal to increase the carrying capacity and ductility of structures. With the aim to check the reliability of the proposed model, two joints of existing R.C. building Ospedale Santa Maria Annunziata a Bagno a Ripoli (Italy) are analized as case study