Simplified seismic vulnerability analysis of historic residential buildings with fragility curves

In the disciplines dealing with the preservation of the built heritage, the assessment of the seismic vulnerability plays a decisive role. A high number of numerical models have been developed to simulate the behaviour of different building typologies subjected to seismic action, but requiring a in-depth knowledge of the object of study they are not suitable for urban scale analysis. The widespread historical built heritage in Italy, as in many other countries, requires the definition of rapid and reliable assessment procedures that allows a large-scale evaluation of the vulnerability of historical buildings before a seismic event. This analysis should be based on existing databases, such as the Reluis-Cartis database, without necessarily proceeding at this stage with detailed investigations of each individual building. Based on state-of-the-art procedures, a methodology is proposed for the fast construction of the fragility curves starting from information available on the Reluis-Cartis database. The curves define the relationship between the probability of reaching a safety factor or a vulnerability index in function of the seismic acceleration PGA. The methodology allows to understand the probability of loss of the structural safety in function of a given PGA. The developed methodology is applied here in two cases: (a) a small historic building hit by several earthquakes in order to calibrate the methodology and (b) to a set of historic building of the same typology in a historic center never hit by earthquakes in order to assess the level of the probability of loss of the structural safety given the code defined PGA, as well as to draw conclusions on prioritizing intervention strategies at the urban scale.