GNGTS 2019 - Atti del 38° Convegno Nazionale

GNGTS 2019 S essione 2.2 345 systems. The purpose of this text is to provide a (not exhaustive) review of the literature to clarify the theoretical references that put the basis for the further steps summarized in the last paragraph. Framing urban resilience. From the 70’, but mostly in these last twenty years, a constellation of resilience definitions emerged in different disciplines, out of the psychological field – such as ecology, social science, economics, engineering fields – in reference to different objects: ecosystems, societies, complex system, urban environment. Because of the multidisciplinary nature of the concept, an exciting but also fragmented body of literature focused on resilience has been produced (Cutter et al. , 2008). Used for the first time in the field of ecology to define a measure of the persistence of systems and their ability to absorb change and disturbance and still maintain the same relationships between population or state variables (Holling, 1973), the concept of resilience has been defined also as the intrinsic capacity of a system stroked by a shock to adapt and survive by changing its nonessential attributes and rebuilding itself (Manyena 2006); or the ability of a system to return to its optimal condition in a short period of time (Haimes, 2009), that could include, as argued by Cutter et al. (2008), not only a system’s capacity to return to the state that existed before the disturbance, but also to advance the state through learning and adaptation (Folke, 2006). In the constellation of existing resilience definitions is however possible to assert that the main difference emerges between the engineering approach and the ecological one (Cimellaro, 2016; Cutter, 2008). The first perspective considers resilience as the ability of a system to recover towards a previous or an improved stable state (Bruneau et al. , 2003); while from the second perspective resilience is viewed as a given ecosystem’s capacity to reorganize and manage changes in order to maintain the same structure and functions (Holling, 2001). About this second perspective, an ambitious theoretical construct is the one framed by Holling, (2001), Gunderson and Holling, (2001) about the adaptive cycle: a hierarchical cross-scale structure where natural and human systems are linked in a continuous adaptive cycle of growth, conservation, release and renewal. In their view resilience potentially depends on these four different phases. For the current research, what is interesting about the concept of the adaptive cycle, is the relation between space and time scale, considering that in all systems adaptation and transformations occur as multi-scalar (spatial and temporal) process (Chelleri, 2012) in which every system plays into the others dynamic interaction as in a nested adaptive cycle (Holling, 2001). However, in the hazards arena most of the resilience models involved engineered systems (Cutter et al. , 2008) that consider the properties of resilient infrastructures – robustness, redundancy, resourcefulness, rapidity – as fundamental on order to reduce failure (Bruneau et al. , 2003). But, as claimed by Cutter et al. (2008), these frameworks often fail in capturing pre-event conditions that occur at the local level or to account for the vulnerability or resilience of the environment. Since a unique and shared definition of resilience is not still coined, mainly in the particular context of the city (Chelleri et al. , 2015), this research views the two different approaches (engineering and ecological) as separated but often linked theoretical perspectives, starting from the assumption that resilience has two different qualities: inherent (positive behaviour during non-crisis period) and adaptive (flexibility in response during seismic events) (Cutter, 2008). From an operational point of view some relevant works have tried to provide applied models to measure resilience in urban systems. At this research stage, authors were very focused on analysing and identifying common resilience dimensions refereed to urban contexts and organize a benchmark to categorized resilience indicators related to the resilience dimensions. In detail, five works have been selected as main references, as shown in the table (Tab.1). Next steps. This short contribute provided an overview of the on-going research project, presenting the main research question, showing the general setting of the research with a focus on the theoretical framework based on the literature review on resilience. The authors agree with the view of resilience as a dynamic process dependent on 1) pre-event conditions, 2) the damage provoked by the main-shock, 3) time(s), the temporal scale from the emergency