Multilevel approach to the analysis of the historical buildings: application to four centers in seismic area finalised to the evaluation of the repair and strengthening techniques

An investigation procedure proposed by the authors is here applied on a building patrimony in seismic area previously considered as minor, but meaningful testimonies of cultural heritage, aimed to a critical review of the effectiveness of the applied repair techniques. 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 was applied to four historic centres situated in Umbria (Italy) and the survey of the buildings allowed to define an abacus of the typical collapse mechanisms, useful to define the seismic vulnerability also for other similar centres and to critically evaluate the past and future repair techniques.