Seismic vulnerability analysis for masonry hospital structures: expeditious and detailed methods

Italy is a territory characterized by a high seismic risk. The assessment of the structural vulnerability for existing buildings is a key aspect for the seismic risk reduction, in particular for strategic and relevant buildings because of their importance for the civil protection. In case of a large sample of buildings, a first screening in terms of vulnerability must be performed with an expeditious empirical approach, in order to highlight the most vulnerable objects and, as a consequence, to decide which buildings are to examine at first with detailed analyses. In this work, the statistical results of an empirical approach (Vulnerability Index Method) are illustrated for the considered sample of buildings, composed both from reinforced concrete and masonry structures. Then, focusing on the masonry structures, a comparison among the results of the Vulnerability Index Method and the detailed analytical analyses (pushover analyses) on a subset of structures is proposed, showing that there is a relation among them, which can be used in order to obtain more information about the behaviour of the structures: indeed, the empirical approach gives as result of the investigation only a Vulnerability Index in the range 0%-100%, where low values correspond to low vulnerable structures, while the detailed analyses, studying the behaviour of the building through structural models, can give some indicators of the seismic risk for the considered structure. The comparison among the two typologies of approach allows the construction of a new expeditious vulnerability assessment method, based on the Vulnerability Index Method form. This new method, simply using the same information of the Vulnerability Index Method, leads to a first estimation of the global capacity of the structure, expressed in terms of PGAC (peak ground acceleration of capacity). It is also possible to obtain the related index of risk considering the seismic hazard of the construction site. All these information can help the Administrations in the management of their existing buildings, giving some suggestions in order to decide how to use the resources for further specific detailed analyses, which still remain necessary for the correct evaluation of the security of a structure.