Seismic vulnerability of existing R.C. buildings: A simplified numerical model to analyse the influence of the beam-column joints collapse

In order to evaluate seismic vulnerability of existing reinforced concrete buildings, a simplified approach is proposed to take into account the beam-column joints shear collapse. This collapse is described by a link element which is introduced between column and beam. To develop and verify this element, several comparisons have been performed with experimental results of laboratory test and numerical results obtained by a two-dimensional finite element model specifically carried out for this check.The link element uses a tri-linear moment-rotation law, compatible with standard Italian and European codes, whose features can be estimated by limited structural and geometrical information, which is a typical situation on older existing structures, and by standard code recommendations.In order to give a preliminary evaluation of the seismic capacity for existing R.C. frames, taking into account the beam-column joints behaviour, this link element has been introduced in a one-dimensional model of bearing structure of the Unit N.1 of the Santa Maria Annunziata Hospital in Florence (Italy) and pushover analyses have been carried out.