Reliability of census data for typological identification of existing residential buildings: the case study of Bologna

In the framework of seismic risk assessment at the regional scale, the evaluation of the vulnerability of existing buildings is crucial and is generally based on the identification of structural typologies or archetypes. With reference to residential buildings, it is important to collect reliable data for a correct determination of masonry and reinforced concrete (RC) building types. In Italy, ISTAT (National Institute of Statistics) provides a wide range of datasets that are generally used as the major data source for seismic risk studies. These data, generally available as aggregate data at the census zone level, provide information about the characteristics of the buildings - such as construction age, materials, and occupancy – and allow the study of the vulnerability of these zones. The objective of this study is to evaluate their reliability through a comparison with building-by-building data. First, an on-site building- by-building investigation was conducted in a district of the city of Bologna. In this study, observed building characteristics were compared with the corresponding ISTAT data to identify divergence and assess data accuracy on the census zones. Based on these data, masonry and RC building typologies were identified and compared between the data sources. This comparison allowed to highlight, on the one hand, the importance of the survey activity, but, on the other hand, the potential use of the census data. In addition, with the objective of implementing the CARTIS methodology in the city of Bologna, both the data and the typological identification were adopted. The CARTIS form enables vulnerability analysis by contributing to the inventory of typological- structural distributions. For the CARTIS assessment, the study of the historical evolution of the city was fundamental for the creation of Sectors, along with the building features such as construction material, age, and building characteristics. The research contributes to assessing the reliability of the ISTAT data for further vulnerability assessments of residential building assets.