Vulnerability analysis of the historical buildings in seismic area by a multilevel approach

An investigation procedure is proposed by the authors to study the vulnerability of the diffuse historic building patrimony in seismic area previously considered as minor, but meaningful testimonies of cultural heritage. The research suggests a "minimal" investigation program, which can support the designers in their projects. The knowledge of existing buildings is approached by considering different analysis levels: history, materials, structural morphology of the wall section, observed damage mechanisms, effectiveness of retrofitting techniques. The methodology, calibrated on four historic centres situated in Umbria (Italy), allowed to define an abacus of the typical collapse mechanisms. This procedure is useful to define the seismic vulnerability also for other similar centres and to critically evaluate the past and future repair techniques.