An important portion of the historical built environment, which is characterized by un-reinforced masonry, is particularly vulnerable to collapse in case of earthquakes, as demonstrated by recent events. Strategies to target the facades of the most vulnerable buildings need to be tailored for retrofitting and emergency planning. In this research, a novel expeditious vulnerability assessment method, particularly suitable for historical masonry aggregates, is proposed. The method allows assessing the vulnerability index based on information available from external surveys on the building, thus facilitating and speeding up the investigation. If other more precise information (e.g., curbs and tie rods effectiveness) is available, the vulnerability estimation can be improved. The method focuses on out-ofplane mechanisms of the facade, which cause debris to fall on adjacent streets, impeding emergency response. The expeditious method is tailored starting from analytical methods applied on a large sample of historical buildings hit by earthquakes, and validated by means of comparison with kinematic analysis and observed damage state on a relevant case study, Caldarola (Macerata, Central Italy, which was struck by the earthquake in 2016). Results show a good agreement between the proposed method, the kinematic analysis, and the observed damage state of the considered case study, with 75% and 87.5% correspondence, and the method is especially precise for evaluating highly damaged facades.

Urban Built Environments (UBE) are increasingly prone to SLow-Onset Disasters (SLODs) such as air pollution and heatwaves. The effectiveness of sustainable risk-mitigation solutions for the exposed individuals’ health should be defined by considering the effective scenarios in which emergency conditions can appear. Combining environmental (including climatic) conditions and exposed users’ presence and behaviors is a paramount task to support decision-makers in risk assessment. A clear definition of input scenarios and related critical conditions to be analyzed is needed, especially while applying simulation-based approaches. This work provides a methodology to fill this gap, based on hazard and exposure peaks identification. Quick and remote data-collection is adopted to speed up the process and promote the method application by low-trained specialists. Results firstly trace critical conditions by overlapping air pollution and heatwaves occurrence in the UBE. Exposure peaks (identified by remote analyses on the intended use of UBEs) are then merged to retrieve critical conditions due to the presence of the individuals over time and UBE spaces. The application to a significant case study (UBE in Milan, Italy) demonstrates the approach capabilities to identify key input scenarios for future human behavior simulation activities from a user-centered approach.

Citizens in dense built environments are susceptible to the simultaneous occurrence of Slow Onset Disaster (SLOD) events, being particularly prone to increasing temperatures and air pollution. Previous research works have assessed these events’ arousal separately and have identified when their intensity is critical. However, few have integrated their analysis, possibly limited by the quality and granularity of available data, the accessibility and distribution of sensors, and measurements not emulating the surroundings of a pedestrian. Thus, this work performed an outdoor meso-scale multi-hazard-based risk analysis to study the aggregated effects of the SLODs mentioned above. The study was carried out to narrow down the time-frames within 2019 in which these two events could have affected citizens’ health the most. A weighted fuzzy logic was applied to superimpose climatic (temperature, humidity, wind speed, and solar irradiance) and air quality (particulate matter, ozone, and ammonium) distress (true risk) on an hourly basis, allocated using set healthy and comfortable ranges for a specific dense urban climate context within Milan (Italy), processing data from Milano via Juvara station. The findings show that sensitive groups were at risk of high temperature and pollution separately during 26% and 29% of summer and mid-season hours, respectively; while multi-hazard risk would arise during 10.93% of summer and mid-season hours, concentrated mainly between 14:00 and 20:00.

Terrorist impacts have been increasing over time in many countries, being one of the most significant threats for the Built Environment (BE), intended as a network of open spaces (streets, squares) and facing buildings, and their users. Such risk is affected by a combination of strategic functions and crowd conditions. This work traces, for the first time, the state-of-the-art consolidated Risk Mitigation and Reduction Strategies (RMRSs). Solid RMRS regulatory frameworks from all over the world are collected. The results show how classification criteria distinguish them by attack targets and typologies, effectiveness over time/space, and physical implementation versus management-based deployment. Nevertheless, these criteria seem to be too fragmented, failing in pursuing RMRSs selection in a holistic outlook. Thus, a new classification adopting the BE composing elements (physical elements, layout, access/surveillance systems, safety/security management) as key-factors is provided. Features, dependencies and coordination among them are discussed in a sustainability-based perspective, by showing how the main challenges for RMRSs’ design concern applicability, redundancy, and users’ emergency support. Safety/security management strategies have the overall highest sustainability level and play a pivotal role with respect to the other BE composing elements, which should be planned in reference to them. In addition, a human-centred approach (individuals’ interactions with BEs and RMRSs) will also be needed. These results will support efforts to include simulation-oriented approaches into RMRSs selection, effectiveness and feasibility analyses.

Planning for preparedness, in terms of multi-hazard disasters, involves testing the relevant abilities to mitigate damage and build resilience, through the assessment of deterministic disaster scenarios. Among risk-prone assets, open spaces (OSs) play a significant role in the characterization of the built environment (BE) and represent the relevant urban portion on which to develop multi-risk scenarios. The aim of this paper is to elaborate ideal scenarios—namely, Built Environment Typologies (BETs)—for simulation-based risk assessment actions, considering the safety and resilience of BEs in emergency conditions. The investigation is conducted through the GIS data collection of the common characteristics of OSs (i.e., squares), identified through five parameters considered significant in the scientific literature. These data were processed through a non-hierarchical cluster analysis. The results of the cluster analysis identified five groups of OSs, characterized by specificmorphological, functional, and physical characteristics. Combining the outcomes of the cluster analysis with a critical analysis, nine final BETs were identified. The resulting BETs were linked to characteristic risk combinations, according to the analysed parameters. Thus, the multi-risk scenarios identified through the statistical analysis lay the basis for future risk assessments of BEs, based on the peculiar characteristics of Italian towns.

Earthquakes affect the safety of the users hosted in both indoor and outdoor urban built environments, especially in Historic Built Environments (HBEs). Many full HBE-scale risk-assessment methods are defined, while methodologies oriented to local analysis of meso-scale elements, such as Open Spaces (OSs), are still limited. Nevertheless, OSs play a crucial role in the first emergency phases, like in the evacuation process, since they host emergency paths and gathering areas. The seismic risk of an OS mainly depends on the combination of the damage suffered from facing buildings and the exposure, which mainly refers to the quantification of human lives. Damage levels result from the combination of vulnerability and hazard-related issues, while exposure is essentially affected by the number of OS users, whose spatial distribution is strongly time-dependent. Methods to quickly combine these issues are needed, especially in view of the deeper insights for the implementation of risk-reduction strategies (i.e. according to simulation-based approaches). This work offers a novel methodology to quickly perform Seismic Risk Assessment and Management of an OS by correlating damage levels to exposure-related issues. The method is composed of two specific matrices, which are developed according to quick literature-based approaches prone to rapid meso-scale applications in HBEs, also by non-expert technicians. The “damage matrix” links the site hazard to the building vulnerability. The assessed damage levels are combined with the users’ exposure into the “consequences matrix”, to estimate the risk in emergency conditions for the OS users, thus supporting decision-makers in promoting robustness/preparedness strategies.

Open spaces (OSs), such as streets, squares, and green areas, in existing built environments (BEs) are key places in disaster risk management. The seismic risk in the OSs is strictly related to BE characteristics. Scientific literature mainly focuses on extrinsic factors affecting risk, which are related to BE elements on the OSs frontier (e.g., buildings) that could cause indirect effects on the OSs. Conversely, just a few risk assessment studies consider intrinsic factors, which are related to OS elements that could suffer direct effects. Moreover, synoptic studies on such factors are still missing. Through literature-based research, the paper identifies specific factors influencing seismic risk in the OSs, focusing notably on intrinsic vulnerability. The literature review methodology includes both a systematic review from Scopus databases and a traditional bibliographic search using snowball analysis. According to the final selected papers, risk factors are classified into five categories of OS characteristics: morpho-typology; physical; construction; use and users; and context. Statistical analysis of the categories’ recurrence in the final papers firstly allows current literature gaps to be defined. The results also provide a preliminary OSs risk index weighting each category in terms of such recurrences, thus representing a first useful step to support non-expert stakeholders in a preliminary assessment of priorities to define the seismic risk of OSs. 

The historical built environment (HBE) in urban areas is prone to disasters, which threaten both people and the historical built heritage itself. In such a scenario, risks depend on the combination between different possible (multi-) hazards (including climate change-related ones), the vulnerability and exposure of HBE users, and the physical (morphology-, typology- and construction-related) features of the HBE. In this context, squares are relevant components of the HBE from a meso‑scale perspective, which is based on the layout and morphology of open spaces, buildings blocks and their users. Squares host cultural heritage and attract users, both tourists and citizens. Moreover, squares are nodal points for the emergency path network and are crucial and significantly affected during the immediate aftermath of the disaster occurrence (e.g. by debris on the ground in the case of seismic hazard during the evacuation phase). Current approaches for risk assessment and mitigation entail the consideration of each specific square, but this approach is time-consuming, scattered between the different hazards and complex to apply to a multi-risk perspective. Therefore, this work provides a methodology to identify and classify the most relevant physical features of squares in the HBE, which are able to improve or worsen the performance of the HBEs to multi-risks from multi-hazard scenarios. The research is rooted in the existing literature and strengthened by experts’ judgement analyses. The proposed methodology synthesizes the considered relevant features of the squares in the HBE into quantitative parameters, which allow to verify the vulnerability to multi-risk of the squares. Such parameters are further organized into classes for the typological assessment of the multi-risk. To test and detail the parameters, the method is tested on a relevant case study, which is the Italian context. Indeed, such a case study is relevant not only for being subject to multi-risks (e.g., seismic, terrorist, heatwave and air pollution), but also because the vast majority of the urban areas are composed by HBEs and hosts cultural heritage sites. Moreover, in this context, squares have not only an environmental, but also a social and economic importance in the HBE and are thus particularly relevant. Then, in the relevant case study of Italy, further detailing and calibration of the defined classes of the relevant parameters, as well as their ranges, are tested on 133 squares, which cover the entire Italian territory. Results demonstrate that the identified classes and ranges of the parameters are suitable for describing historical squares by arranging them into typologies for multi-risks assessment. Although the parameters are here presented for the Italian context, they are of general value and could be tested in other contexts, by calibrating the ranges as illustrated for the specific considered sample. Thus, the outcomes of this work allow moving towards the classification of squares into built environment typologies according to the meso‑scale perspective, provide the bases for and promoting the application of expeditious approaches to multi-risk assessment in the HBE.

Pedestrians are increasingly exposed to slow-onset disasters (SLODs), such as air pollution and increasing temperatures in urban built environments (BEs). Pedestrians also face risks that arise from the combination of the BE features, the effects of SLODs on the microclimate, their own characteristics (e.g., health and ability), and the way they move and behave in indoor and outdoor BE areas. Thus, the effectiveness of sustainable risk-mitigation solutions for the health of the exposed pedestrians should be defined by considering the overlapping of such factors in critical operational scenarios in which such emergency conditions can appear. This work provides an innovative method to define a BE-oriented pedestrian risk index through a dynamic meso-scale approach that considers the daily variation of risk conditions. The method is ensured by a quick-to-apply approach, which also takes advantage of open-source repositories and tools to collect and manage input data, without the need for time-consuming in situ surveys. The resulting risk conditions are represented through meso-scale maps, which highlight the risk differences between BEs by focusing on their open spaces as fundamental parts of the urban road network. The method is applied to a significant case study (in Milan, Italy). The results demonstrate the ability of the approach to identify key input scenarios for risk assessment and mapping. The proposed methodology can: (1) provide insights for simulation activities in critical BE conditions, thanks to the identification of critical daily conditions for each of the factors and for single and multiple risks and (2) support the development of design and regeneration strategies in SLOD-prone urban BEs, as well as the identification of priority areas in the urban BE.

Among other risks, contemporary cities are exposed to terrorism. In addition to being sensitive targets, recent events in Europe have underlined the relevance of public open spaces (squares, streets, etc.) as particularly defenseless parts of Urban Built Environments (UBEs). Despite the fact that previous theoretical studies about radicalism have highlighted the “regional” dimension of the threat, the assessment of terroristic risk is still related to American guidelines. This creates new research scenarios for European UBEs and associated Outdoor Areas (UBEOAs). Thus, this paper provides two correlated main goals. The first is the phenomenological analysis of terrorist threats in European UBEs, starting from the events catalogued in the Global Terrorism Database. Specifically, the matrix of risk is assessed by combining (i) the main urban Environmental Classes (ECs) and their sub-classes, referred to as Outdoor Areas (OutECs), and (ii) the Attack Types (ATs) in order to determine the most efficient and recurrent combination of attack methods and targets (AT-EC and AT-OutEC). Then, the paper identifies the parameters influencing the terroristic risk of the most recurrent and efficient attacks identified in European UBEOAs, starting from (i) the analysis of inherent features of the European phenomenon, (ii) previous experiences in the literature and (iii) the permitted strategies and guidelines in European States. The main results are related to the relevance of Armed Assault and Bombing/Explosion Ats and Open Areas with the presence of public and strategic/symbolic buildings (ECs), while an interesting point of discussion is represented by physical obstacles.

The historical built environment (HBE) is constantly prone to many risks causing sudden (e.g., earthquakes and terrorist attacks) or slow (e.g., climate change-related and environmental pollution) onset of emergency conditions. Morphological, physical, and constructive characteristics are critically linked to system vulnerability and users’ exposure. In particular, open spaces (OSs) in the HBE represent typical attractors for the community in urban areas for leisure and touristic purposes and critical scenarios in case of a disaster. In fact, besides daily and hourly temporalities in everyday use, OSs also play a pivotal role in the immediate disaster response phases, considering sudden-onset events. Understanding which scenarios characterize OSs is critical to evaluate them from a multi-risk perspective and to propose effective mitigation strategies in multiple critical situations. To this end, this work offers a survey form template of the OS within the HBE according to a holistic but quick-to-apply approach. Placed in the context of the Project of Relevant National Interest (PRIN) BE S2ECURe, the survey form assesses the relationships between frontier elements and those contained in the OSs, focusing on literature-based identification of vulnerability, exposure, and hazard factors affecting risk. These factors are organized into five sections as the basis for classification criteria of OSs: (1) morpho-typological, (2) geometrical-spatial, (3) constructive, (4) use, and (5) context. The application to eight case studies contributes to the validation of the survey, showing its ability to trace both the level of complexity and the main characteristics of the analyzed scenario. Furthermore, the survey form can be properly and quickly applied by non-specialized technicians, such as local authorities, thus representing the first step to support planners in data collection and risk assessment of historical OSs.

​Public Open Spaces (POSs) such as streets and squares, in our cities are characterized by spatio-temporal variations of users' vulnerability and exposure in view of the hosted social, governmental, religious, and commercial functions. Single or multi-risks conditions in POSs can hence vary over time. This work proposes a methodology to perform local-scale analyses on use patterns in real-world POSs, pursuing a quick-to-apply approach based on remote analysis tools and easy-to-apply surveys, to be also used by non-expert technicians. Main literature-based factors concerning users' vulnerability/exposure and methods for their collection are identified. Rules to define typological (that is recurring) scenarios are provided through specific key performance indicators relating to overall POS use and daily/hourly temporalities. The methodology capabilities are preliminary assessed through a sample of 56 squares in historic Italian cities, considering working days and holidays. Results trace the overall typological characterization of the squares sample adopting a “robust-to-outliers” approach, and provide bases for expeditious assessment of users' vulnerability and exposure scenarios. The typological scenarios can be then used to support rapid risk assessment actions in POSs by safety designers and local authority technicians, and employed as input in simulation-based analyses to include the users' features in the related evaluations.

The relationships between the Built Environment (BE) and SUdden-Onset Disasters (SUOD) are increasingly the focus of hazard mitigation investigation. Specifically, in the Historic Built Environment (HBE), defined as the network of buildings, infrastructure, and open spaces of the compact historic city, recent and past events have shown the need for an elevation of the resilience of the resident community. Previous studies by the author’s research team have objectified the characterisation of HBEs prone to SUODs. What emerged was the primary importance of open spaces in the Built Environment as elements to be characterised with respect to possible emergency phases and BE user behaviour. Specifically, the Historic Built Environment Typologies (H-BETs) can help to evaluate user behaviour during and after the event. Focusing on the role of the classification of the open spaces, the paper presents the H-BETs and their potential role in the multi-risk assessment of the compact historic town. The specific risk conditions of the urban areas (e.g., crowding, the complexity of the overall form of BEs, characteristics of built elements, uses of BEs), and the physical characteristics of historic urban BE (e.g., the height of the built fronts, number, and type of accesses, the slope of the ground) are considered together in order to propose a classification of different type of open spaces, starting from morphological classes towards the definition of a complete typological categorisation, representative of the urban system’s variables that interact with the identified SUOD hazards.

A behavioural-based approach can be used to assess how users’ reactions to surrounding environmental conditions can alter the urban Built Environment (BE) risk to Slow Onset Disasters (SLODs). Public Open Spaces (POSs) in the BE are relevant scenarios, due to micro-climate-related stress, users’ vulnerabilities (e.g., age, health frailty) and exposure time. Simulation methods can support behavioural-based risk-assessment, but results are generally site-specific. Performing analysis on BE Typologies (BETs) can improve robustness, since BETs represent archetypes from real-world scenarios. This work adopts a behavioural-based approach to evaluate time-dependant users’ risks of POSs in different BETs due to SLODs-related stress (i.e., heat, air pollution). UTCI and AQI values are mapped within each BET. Users’ distributions are then calculated depending on thermal acceptability correlations. Key Performance Indicators are developed associating users’ distribution to SLODs effects on health (i.e., sweat rate, water loss; health affection rate probability). The approach is applied to Italian BETs, under one relevant climate, rating their heat and air pollution risks. Results suggest critical conditions for toddlers. In detail, about 2-hour high heat exposure could result in dehydration, while 1-hour exposure to low NO2 concentration could result in +1% mortality probability. This approach could potentially support decision-makers on BE risk-assessment.

Squares in the urban historical built environment are public open spaces prone to the risk of terrorist acts, essentially because they are ideal soft targets and attract significant user densities. Risk assessment methods should consider how users behave in them, both before and during an accident (i.e., the evacuation process). In addition to squares’ morphology and layout, and considering that urban areas are more and more prone to the effects of increasing temperatures, outdoor climate conditions can alter the initial scenario. In fact, such conditions can lead users to gather in specific outdoor areas, where they can look for shadows and shelter. This work hence proposes a simulation-based approach to assess how differences in users’ behaviours in response to increasing temperatures and squares’ morphology can alter the risk of terrorist acts in an emergency evacuation. An agent-based model is developed to simulate the interactions between users, hazards and the historical built environment. The work considers four typological squares prone to terrorist acts since they host a special building attracting users in front of it. These squares are derived from the analysis of Italian historical contexts within the BE S2ECURe project. Users are generated in the public open space (thus, before the terrorist act) depending on the intended uses of the square and on the outdoor temperature, which is affected by the square’s morphology. Three different users’ behaviours are modelled to consider (or not) the effects of the outdoor temperature on users’ thermal acceptability levels in an increasing temperature situation. Then, two evacuation scenarios are simulated: (a) a general evacuation process, without attackers, as the baseline for the risk assessment; and (b) an armed assault with cold weapons, to define one of the most probable attack situations in open spaces. Evacuation performance indicators are developed to assess users’ risk. Preliminary verifications demonstrate the capabilities of the approach. The results show that higher differences in evacuation indicators are noticed in large and asymmetric squares, since their conditions highly affect the variability of users’ behaviours in response to increasing temperatures. At the same time, stronger safety behaviours in response to increasing temperatures could reduce emergency issues because they allow users to be more dispersed and initially placed farther from the attack area. Decision-makers could take advantage of the proposed approach and simulation tool, moving towards an effectiveness analysis of solutions to increase the thermal comfort of users in respect of the risk levels during an evacuation. Finally, applications to real-world scenarios are thus encouraged to compare such idealized results with effective conditions.

A key role in making cities resilient has been acknowledged in raising risk preparedness and awareness of urban communities, by appropriate education and communication strategies, which should rely on innovative and pervasive tools. In this regard, an outstanding paradigm shift is driven by the advancement of Virtual Reality, which can take advantage of Serious Games, for helping individuals develop responsive behaviours in case of both slow and sudden disasters and, thus, boosting effective human-urban-building interaction within a wider process of safety and sustainability. To this end, the paper proposes a VR-SG training prototype for multi-hazard scenarios in urban open spaces. The prototype integrates results from phenomenological and behavioural analyses and is applied to representative typologies of the built environment. The prototype is demonstrated for heat wave protection and earthquake response through the design and implementation of its functional features – virtual environment, interaction mode, learning outcomes and storyline – and its informative contents, including simulation-based data on surface temperatures, extent of falling debris and crowd motion. The final goal is to validate a reliable and flexible tool in view of wide replication in urban contexts for both instructing on critical situations and communicating mitigation strategies.

The assessment of risk in the Built Environment (BE) involves understanding the inseparable relationship between the physical space and its users. In emergency management, particularly during Sudden-Onset Disasters (SUODs), effective evacuation is crucial for individuals’ resilience in BE. Key Performance Indicators (KPIs) offer a quantitative approach to risk assessment, facilitating a systematic evaluation of various risks within BE. The research focuses on seismic events and terrorist acts as relevant SUODs and proposes KPIs derived from literature-based indicators to assess the impact of construction and morphological features of Built Environment Typologies (BETs) and user-related factors on urban open space risk (behaviors, exposure, vulnerability). These KPIs are then applied to established BETs, that are archetypes from real-world configurations of urban open spaces, and tested through seismic and terrorist risk scenarios along with emergency simulations. Results indicate significant variations among BETs, emphasizing the importance of factors, such as geometry (static KPIs) and evacuation behaviour (dynamic KPIs) in determining risk levels. Evacuation route length and complexity emerge as critical in larger BETs, while insufficient safe areas pose challenges in smaller ones. This KPI-based approach is recognized as a crucial step toward establishing a comprehensive metric for risk assessment in BE open spaces, with potential real-world applications to quantify the efficacy of risk mitigation measures. The results demonstrate the KPIs' potential in quantifying disaster risks and user behaviours, representing a crucial step towards an overarching metric for BE-risk assessment during SUODs in open spaces.