Earthquake-resistant systems in traditional masonry construction: two examples from Mediterranean vernacular architecture

The issue of the construction details for seismic protection is discussed in relation to solutions used within traditional vernacular Mediterranean construction prior to the development of scientific seismic design. The topic relates, in particular, to two housing examples, one in Italy and one in Greece: an Apennine village in L’Aquila province, and on the Ionian island of Lefkada, where critical environmental conditions include also soil related problems. In this context, the paper aims to develop a detailed qualitative description of the different seismic protection solutions characterizing these building typologies. Both examples are based on masonry structural systems, but the final results are completely different. The Italian typology, analyzed in detail in the case of Castelvecchio Calvisio village, corresponds to houses arranged along rows parallel to the contour lines; the historical centre is formed by interconnected building units resulting into compact structural aggregates, further connected by covered walkways and flying buttresses. The Greek typology corresponds to independent adjacent units, normally with one single storey and a maximum of three, with stone masonry walls at the ground floor and a frame structure at the upper levels, based on the mixed use of timber and brick elements. The analysis of the building framework and of the seismic protection elements is based on the results of a detailed survey work carried out on site, supplemented by the study of local economical and historical conditions, by the examination of historical earthquakes and of the subsequent reconstruction and strengthening interventions. As a general conclusion, analyses have shown that the traditional building techniques in both the cases of Castelvecchio Calvisio and Lefkada allow for resistance levels of the masonry structures basically in line with the design requirements in force today.