# Measuring the Seismic Resilience of Housing Systems in Italy
###### Abstract
Based on the reference literature [28; 29; 30; 31; 33], ULCs can be identified and described as follows:  
* The Operational Limit Condition (OLC) is reached when the housing system's functionality is greater than 99.5%. In such a condition, the housing system is fully functional or has a slight local loss that is not significant at the urban level. * The Damage Limit Condition (DLC) is characterized by a functionality greater than 90% but less than or equal to 99.5%, for which the housing system suffers a provisional and localized limitation and the overall urban functionality (considering all urban sub-systems) undergoes a temporary or partial reduction. * Life Safety Limit Condition (LSLC) is experienced when the housing system functionality is greater than 70% but less than or equal to 90%. This condition corresponds a partial functionality limitation, while the overall urban functionality exhibits a significant or prolonged loss without invalidating its general performance. * The Collapse Limit Condition (CLC) is attained if the housing system functionality is greater than 50% but less than or equal to 70%. This implies that the housing system and many other urban sub-systems are damaged in the medium or long term, while the residual urban functionality is retained by some sub-systems. * The Emergency Limit Condition (ELC) is attained when the housing system functionality is less than or equal to 50%. For this last condition, urban resilience could be more challenging because the housing system is totally compromised and its recovery is not obvious. Only emergency areas and strategic buildings and infrastructures could continue to function in the urban settlement. The peculiarity of the Italian condition, particularly in southern regions, has always highlighted the key role of residential building stock in the general assessment of community resilience [24; 34]. Because of this, studies on the large-scale seismic behavior of Italian residential buildings have increased in recent years (e.g., [28; 35; 36; 37; 38; 39]). By following an empirical, analytical or hybrid approach [35], these studies develop fragility curves in terms of vulnerability and height classes that allow users to estimate the expected damage of masonry and RC buildings in seismic risk analysis performed with poor census data. For urban applications, an innovative procedure has also been recently proposed to derive fragility curves of road networks from the seismic damage of nearby residential buildings [40]. The key role of residential buildings is now unanimously recognized, and studies on community resilience are strongly tied to them and their quantitative assessments. For this reason, this article focuses on residential building stock. The realization that residential building stock is only a component (that is very relevant) of the general measurement of community resilience is embodied in the proposed procedure and its operational choices. The latter depend strongly on the large spatial scale considered. However, the assessment at that territorial scale (and its corresponding approximations) is fundamental to the overall governance of supra-regional territories. In the present work, a new framework is proposed to quantify the community's resilience to seismic hazards in large-scale applications. It is based on previous studies in which restoration data are derived from the 2012 Northern Italy Earthquake. Policymakers can leverage this study's findings to make decisions about future mitigation strategies and training programs in disaster preparedness. The first part of the article briefly describes the proposed framework. It is then applied to all municipalities in five regions of southern Italy. Finally, the main results in terms of average functionality levels over time and concerning ULCs are discussed, highlighting advantages, limitations, and future research directions in the conclusions.