Seismic vulnerability of existing buildings:observational and mechanical approaches for application in urban areas

Past and recent earthquakes have shown the high seismic vulnerability of old and historic down-town: the 2009 L’Aquila earthquake is one of the last dramatic examples, in which several historical centres (such as – besides L’Aquila - Onna, Castelnuovo, Villa Sant’Angelo,etc.) were severely struck, with heavy damages extended to the whole built-up areas and collapses of large portions (sometimes even of the totality) of many urban blocks. It follows the relevance of providing reliable vulnerability and risk analyses from the economic, cultural and life safety point of view. In this chapter, after some explanations on the damage levels and buildings type classification, some models to be used for vulnerability analyses are presented considering both the macroseismic and mechanical approaches and both unreinforced masonry (URM) and reinforced concrete (RC) buildings. In particular, in case of the macroseismic approach, the model proposed in Lagomarsino and Giovinazzi (2006) is discussed. In case of the mechanical one, the DBV-concrete and DBV- masonry (Displacement Based Vulnerability) methods proposed in Lagomarsino et al. 2010 have been adopted as reference; the DBV- masonry method starts from the model originally proposed in Cattari et al. (2005), whereas the DBV- concrete one from the DBELA method proposed in Crowley et al. (2004). In both cases, starting from the original formulations, some significant modifications have been introduced by the Authors.