Miglioramento sismico mediante sistemi dissipativi: il caso studio della scuola di Bisignano

In the present paper, the seismic vulnerability of the “Collina Castello” school in Bisignano (CS) is studied. The structure is presently monitored by the Department of Civil Protection and an extensive experimental investigation (both on mechanical properties of the materials and the global dynamic behaviour) was recently carried out. The structure is characterized by one-directional reinforced concrete frames and infills with symmetrical distribution, but with different characteristics in the two directions. The study investigates firstly the infills effect on the seismic capacity of the R.C. structure. In fact, it is well known that the presence of infills may significantly modify the seismic response of R.C. buildings. Modelling the infills as equivalent truss systems, an identification process is performed in order to identify the equivalent stiffness of the masonry panels starting from dynamic experimental tests. Then, some non-linear dynamic analyses are performed in order to verify the effectiveness of two different dissipation systems (viscous dampers or dissipative bracing systems) in reducing the seismic vulnerability of the structure, also considering the infill damage caused by the seismic action. A concentrated plasticity FE model is used, where the law governing the plastic hinge behaviour depends on both geometrical and mechanical properties of the cross section. The results indicate a significant improvement of the structural response when dissipative brace systems are adopted, and some design criteria are discussed, where the requirement of reducing both floor displacement drifts and axial forces acting on the brace systems must be met.