Numerical investigation of seismic vulnerability of existing RC structures: a case study

Recently the issue of a new Italian seismic code has resulted in an extensive program for seismic assessment of strategic and relevant buildings, particularly the school buildings.Aremarkable case is represented by the school building of Londa, a small town near to Florence, built in 1974. For this building a complete information about material properties and structural characteristics is available since the Seismic Department of the Region of Tuscany has started a large program for assessment of seismic vulnerability of existing RC public buildings, based on destructive and non destructive tests. The structural organism of this building, which is rather irregular, presents many seismic vulnerability sources, originated by design and construction errors, together with the problem of a low concrete strength. In this paper, the seismic response of such structure is analyzed by means of nonlinear dynamic analysis, considering actual material properties and structural characteristics. The input ground motions are an ensemble of accelerograms representative of the seismic action required by the new Italian seismic code. It is found that the structure can resist extremely low intensity earthquakes, with a PGA well below the design one in the seismic zone 2, which Londa belongs to.