Seismic prevention and mitigation in historical centres: the impact of r.c. structures

After recent seismic events, the topic of seismic prevention and mitigation in historical centres is become very important, in particular for a seismic prone areas, like Italy, Greece, Portugal, in which a lot of historical towns, for high quantity of old buildings and for their urban structure, suffered a lot of damages. In the past, for this reason, the Authors described and discussed a strategy for seismic prevention and mitigation of historical centres, analyzing them in terms of structural safety. This approach was based on two relevant steps: the first is to study the Urban Risk, the second is to program the Post-Earthquake Activity. The first activity is the analysis of a complex system aiming to individuate the nodal fragility, the second tends to evaluate the buildings safety and the occupancy conditions for these buildings. In this paper a particular aspect of this topic will be discussed, i.e. how different typologies of buildings, that coexist in historical towns, could influence the reconstruction strategy. In fact, when one thinks to an old building isn't only a masonry historical building, an old building could be a more recent r.c. building designed without any seismic provisions or, as unfortunately usual, realized with poor quality material. Considering that in recent seismic events often this class of buildings caused a lot of damages and deaths, an efficient procedure to approach the impact of r.c. structures on seismic prevention and mitigation in historical centres has to be considered a fundamental goal to reach.