Experimental and numerical investigation of the effects of wind exposure on historical towns

摘要

The Italian territory has a particularly rich cultural landscape, being composed of about 20.000 historic towns and villages, identified as "minor" only because of their relatively small dimension in comparison with the large cities. Many of these urban centers, especially in the southern Lazio, have not undergone the dynamic housing transformation, typical of other old towns, such as abandonment, replacement of the inhabitants with the inclusion of new social classes, or reuse of all or part for tourist-commercial purpose. It would seem that they have retained a "modus vivendi" antinomical of the non-places of contemporary cities, preserving a high social quality of aggregative life within urban arrangements characterized by a strong aesthetic identity. However, most of them are suffering significant degradation due to intrinsic reasons, such as the characteristics of the materials and the quality of construction, or external anthropogenic or environmental factors, such as, respectively, the lack of maintenance, humidity, solar irradiation and wind exposure. Often, the impact of these factors is compounded by the geographical position where these urban centers are located. In fact, many settlements arose and flourished in the Middle Ages, as result of the aggregation of minor architecture grown spontaneously. While, on one hand their original urban composition and the strong empathetic relationship with the natural environment represent an indubitable aesthetic value, they also are among the factors of major vulnerability. Frequently, the degradation of buildings facades has to be sought in the planimetric morphology of roads, forming street canyons where powerful wind channels are conveyed. Alveolization of natural stones or detachment of plaster are triggered by the erosive capacity of the wind enhanced by the development of mold and plants induced by the detainment of water and the low solar irradiation. The analysis of the environmental context is a fundamental step for the preservation of the historic buildings and for the whole project of restoration. In the present research this study is performed on a village (Borgo San Rocco) located in the southern Lazio. In particular, in the present paper the authors present the results of a wider research activity aimed at