Towards an integrated vulnerability-based approach for evaluating, managing and mitigating earthquake risk in urban areas

Tese de doutoramento em Civil EngineeringSismos de grande intensidade, como aqueles que ocorreram na Turquía-Síria (2023) ou México (2017) deviam chamar a atenção para o projeto e implementação de ações proativas que conduzam à identificação de bens vulneráveis. A presente tese propõe um fluxo de trabalho relativamente simples para efetuar avaliações da vulnerabilidade sísmica à escala urbana mediante ferramentas digitais. Um modelo de vulnerabilidade baseado em parâmetros é adotado devido à afinidade que possui com o Catálogo Nacional de Monumentos Históricos mexicano. Uma primeira implementação do método (a grande escala) foi efetuada na cidade histórica de Atlixco (Puebla, México), demonstrando a sua aplicabilidade e algumas limitações, o que permitiu o desenvolvimento de uma estratégia para quantificar e considerar as incertezas epistémicas encontradas nos processos de aquisição de dados. Devido ao volume de dados tratado, foi preciso desenvolver meios robustos para obter, armazenar e gerir informações. O uso de Sistemas de Informação Geográfica, com programas à medida baseados em linguagem Python e a distribuição de ficheiros na ”nuvem”, facilitou a criação de bases de dados de escala urbana para facilitar a aquisição de dados em campo, os cálculos de vulnerabilidade e dano e, finalmente, a representação dos resultados. Este desenvolvimento foi a base para um segundo conjunto de trabalhos em municípios do estado de Morelos (México). A caracterização da vulnerabilidade sísmica de mais de 160 construções permitiu a avaliação da representatividade do método paramétrico pela comparação entre os níveis de dano teórico e os danos observados depois do terramoto de Puebla-Morelos (2017). Esta comparação foi a base para efetuar processos de calibração e ajuste assistidos por algoritmos de aprendizagem de máquina (Machine Learning), fornecendo bases para o desenvolvimento de modelos de vulnerabilidade à medida (mediante o uso de Inteligência Artificial), apoiados nas evidências de eventos sísmicos prévios.Strong seismic events like the ones of Türkiye-Syria (2023) or Mexico (2017) should guide our attention to the design and implementation of proactive actions aimed to identify vulnerable assets. This work is aimed to propose a suitable and easy-to-implement workflow for performing large-scale seismic vulnerability assessments in historic environments by means of digital tools. A vulnerability-oriented model based on parameters is adopted given its affinity with the Mexican Catalogue of Historical Monuments. A first large-scale implementation of this method in the historical city of Atlixco (Puebla, Mexico) demonstrated its suitability and some limitations, which lead to develop a strategy for quantifying and involving the epistemic uncertainties found during the data acquisition process. Given the volume of data that these analyses involve, it was necessary to develop robust data acquisition, storing and management strategies. The use of Geographical Information System environments together with customised Python-based programs and cloud-based distribution permitted to assemble urban databases for facilitating field data acquisition, performing vulnerability and damage calculations, and representing outcomes. This development was the base for performing a second large-scale assessment in selected municipalities of the state of Morelos (Mexico). The characterisation of the seismic vulnerability of more than 160 buildings permitted to assess the representativeness of the parametric vulnerability approach by comparing the theoretical damage estimations against the damages observed after the Puebla-Morelos 2017 Earthquakes. Such comparison is the base for performing a Machine Learning assisted process of calibration and adjustment, representing a feasible strategy for calibrating these vulnerability models by using Machine-Learning algorithms and the empirical evidence of damage in post-seismic scenarios.This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), reference UIDB/04029/2020. This research had financial support provided by the Portuguese Foundation of Science and Technology (FCT) through the Analysis and Mitigation of Risks in Infrastructures (InfraRisk) program under the PhD grant PD/BD/150385/2019

Towards a semi-quantitative approach for assessing evacuation scenarios in the context of Popocatépetl Volcano, México - The case of San Pedro Tlalmimilulpan

Volcanic exposure implies multiple hazards for human settlements. The identification of the potential hazards that volcanic activity can entail is a challenge requiring assessing the specific situations that a determined place would face. Popocatépetl, a volcano in the centre of México, represents a significant hazard source, and it is located within a densely populated region with more than 20 million people. Despite the existence of a colour-based volcano alert level system for the current activity of the volcano, it is relevant to assess which local scenarios are more likely depending on numerous variables, namely, related to the distance from the volcano. A semi-quantitative analysis was carried out based on existing hazard maps and considering the probability of occurrence of volcanic explosivity, taking the settlement of San Pedro Tlalmimilulpan as a case study. This analysis led to a hierarchised rank of hazards, providing a basis for analysing multiple scenarios through failure mode and event analysis, failure tree analysis and event tree analysis. This process facilitates the contextualisation of the multiple challenges and potential chains of events that emergency actions, namely, emergency evacuations, would face. The analysis of the critical paths can help to identify critical aspects that could hinder the post-event response.This research was funded by the Portuguese Foundation for Science and Technology (FCT) through the grant number PD/BD/150385/2019

Characterisation of the historic urban landscape through the Aristotelian four causes: towards comprehensive GIS databases

The Historic Urban Landscape provides a basis to comprehensively study the city, considering the numerous agents and stakeholders involved in the urban phenomenon. However, the characterisation of the city is challenging, due to the numerous ways of reading and using the city. Although several theoretical approaches address the process of documenting the city, there is still a gap related to the design of a generalised, holistic, and comprehensive framework. This article aims to contribute to this purpose by discussing the concept of the Historic Urban Landscape (HUL) and its implications for the characterisation of the urban phenomena. The Aristotelian theory of the causes is proposed here as a suitable approach for the description, characterisation, and analysis of virtually any entity by first discussing its theoretical basis and then testing it in a real building located in the historical city, Guimarães, Portugal. A set of tools related to Geographic Information System databases are comprehensively explored during the implementation process of the approach, allowing to identify and discuss a set of limitations, challenges, and opportunities.This research was funded by the European Union through the European Social Found and the Portuguese Foundation for Science and Technology (FCT) through the grant number PD/BD/150385/2019

Assessing and Managing Risk in Historic Urban Areas: Current Trends and Future Research Directions

Historic urban centres are, almost by definition, risk-prone areas. The buildings in the historical sites are often highly vulnerable to natural and human-made hazards, not only due to their construction and material characteristics but also because they are usually very degraded due to ineffective maintenance and conservation policies. Moreover, the recent world tourism boom has led to a significant increase in the number of people who live, work and visit these areas, which, together with land use and climate change-related impacts, make historic centres particularly exposed areas. This paper addresses the issue of assessing and managing risk in historic urban centres departing from the complexity of defining the historic city and the concept of risk, providing a comprehensive discussion on current trends and future research directions in this field. After analysing the most suitable methodologies to assess the vulnerability of these areas to different hazards, the focus is on data collection and organisation-related issues and how the different vulnerability assessment outputs can be used to manage and mitigate risk. Vulnerability and loss scenarios, evacuation and emergency planning, and retrofit and cost-benefit analyses are some of the aspects addressed herein. This discussion includes some considerations on the accuracy of these approaches and aspects related to their calibration and validation, covering from empirical calibration models to advanced artificial Intelligence-based techniques

Evaluación de la vulnerabilidad sísmica de edificios históricos de mampostería usando modelos semánticos apoyados en evidencias empíricas: Aprendizajes en México

La evaluación de la vulnerabilidad sísmica asociada a las construcciones históricas representa diversos retos metodológicos y de escala. La no linealidad en el comportamiento estructural en edificios de mampostería no reforzada, la variedad de soluciones constructivas y las incertidumbres inherentes al período de vida de estos edificios dificultan enormemente la aplicación de métodos de análisis generalizadores y representativos. Sin embargo, existen métodos paramétricos que ofrecen la posibilidad de evaluar (de manera semicuantitativa) el nivel de seguridad de un edificio ante ciertas demandas sísmicas. Tales métodos han sido diseñados y calibrados sobre la evidencia empírica (daños y colapsos) recogida tras sismos de gran magnitud, destacando una serie de parámetros que influyen significativamente el comportamiento sísmico de edificios históricos. Los modelos semánticos apoyados en estos parámetros son lo suficientemente fáciles de construir como para considerar su aplicación a escala urbana, a través del uso de herramientas como las bases de datos geográficas, métodos de visualización remota e, incluso, catálogos existentes. Este trabajo presenta una serie de experiencias realizadas en ciudades históricas mexicanas para discutir la conveniencia, limitaciones y oportunidades que estas estrategias pueden significar para una gestión y mitigación más eficaz del riesgo sísmico

Implementing open-source information systems for assessing and managing the seismic vulnerability of historical constructions

Reducing the uncertainty about the structural vulnerability of historical constructions comprises the selection of reasonably generalised approaches in a context of a significant typological variability; the difficulty of performing large-scale assessments with reasonable reliability; and the lack of dedicated infrastructures for efficiently storing, sharing, managing, and updating data – an issue that is even more relevant for small (and often isolated) settlements. This work presents a proposal to set up a geographic database for surveying, calculating and storing the seismic vulnerability index of masonry constructions using an adapted version of the GNDT-II approach. Some critical steps for setting up Geographical Information System (GIS) databases for storing and managing the fields of a parameter-based vulnerability assessment are presented. Then, some alternatives for distributing the database are introduced, including cloud-based distribution and Transactional Web Feature Service (WFS-T) protocols, even using virtual servers. Additionally, an alternative front-end for accessing data and calculating the vulnerability index of constructions and levels of damage is presented. The main objective is to offer a replicable and feasible workflow to be performed even with reduced infrastructure and computational resources but can be easily connected and associated to a progressively enlarged system based on free and open-source software

On the use of web mapping platforms to support the seismic vulnerability assessment of old urban areas

European countries are affected by various levels of seismic hazard, including many areas with medium to high seismicity. Heavy damage over large areas has been observed in past earthquakes in these countries, particularly in masonry buildings located in historical centers, confirming the need for enhancing the current knowledge on the seismic vulnerability of these constructions, so more informed technical and political decisions towards the mitigation of the risk can be taken. However, the characterization of building stocks for engineering purposes is still an open issue due to the enormous amount of resources that such a project would require. Nevertheless, the availability of virtual images and maps represents an outstanding opportunity for having remote approaches to urban environments. The role of on-site inspections can be complemented or even substituted by means of these remote approaches, provided it is complemented with suitable approaches. The use of these resources is not new, but the critical assessment of their capabilities and limitations deserves a critical discussion. The present paper aims at assessing the opportunities offered by web-based mapping platforms in the context of seismic vulnerability assessment of masonry buildings in old urban areas. After evaluating the advantages and shortcomings of some of the most popular web-based mapping services, an explanatory application to a set of 39 buildings located in the historic center of the city of Leiria (Portugal) is presented and critically discussed, contrasting the results obtained by using on-site and remote inspections. Two different seismic vulnerability assessment approaches are applied and analyzed herein, confirming that web-based mapping platforms can represent an efficient and cost-effective complement to traditional field surveys when the large-scale seismic vulnerability of old urban areas is of interest

On the use of web mapping platforms to support the seismic vulnerability assessment of old urban areas

European countries are affected by various levels of seismic hazard, including many areas with medium to high seismicity. Heavy damage over large areas has been observed in past earthquakes in these countries, particularly in masonry buildings located in historical centers, confirming the need for enhancing the current knowledge on the seismic vulnerability of these constructions, so more informed technical and political decisions towards the mitigation of the risk can be taken. However, the characterization of building stocks for engineering purposes is still an open issue due to the enormous amount of resources that such a project would require. Nevertheless, the availability of virtual images and maps represents an outstanding opportunity for having remote approaches to urban environments. The role of on-site inspections can be complemented or even substituted by means of these remote approaches, provided it is complemented with suitable approaches. The use of these resources is not new, but the critical assessment of their capabilities and limitations deserves a critical discussion. The present paper aims at assessing the opportunities offered by web-based mapping platforms in the context of seismic vulnerability assessment of masonry buildings in old urban areas. After evaluating the advantages and shortcomings of some of the most popular web-based mapping services, an explanatory application to a set of 39 buildings located in the historic center of the city of Leiria (Portugal) is presented and critically discussed, contrasting the results obtained by using on-site and remote inspections. Two different seismic vulnerability assessment approaches are applied and analyzed herein, confirming that web-based mapping platforms can represent an efficient and cost-effective complement to traditional field surveys when the large-scale seismic vulnerability of old urban areas is of interest

Parametric and machine learning-based analysis of the seismic vulnerability of adobe historical buildings damaged after the September 2017 Mexico earthquakes

In September 2017, two strong earthquakes hit the central region of Mexico, producing substantial damage to the historical buildings. A retroactive analysis for assessing the pre-event seismic vulnerability of these constructions allowed for testing the suitability of an existing parameter-based approach based on material and geometrical features. More than 160 adobe buildings in four municipalities of the State of Morelos were surveyed and included in a vulnerability-oriented GIS database. Data were collected on-site and managed by resorting to open-source GIS software combined with a Python-based database management tool and a cloud-based platform for onsite data collection using mobile devices. The parameter-based approach was used for assessing the analytical seismic vulnerability of the buildings and implementing a secondary, more conservative assessment that considers uncertainties associated with the data acquisition process. The capabilities of the database were further used to train a Machine Learning algorithm aimed at overcoming some representativeness limitations of the parameter-based analytical method. This third approach was found to be suitable for assessing the vulnerability of the building typologies addressed in this investigation. Although the implementation discussed in this paper is limited to a specific vernacular typology, it can be used to conduct customized local calibrations

The rupestrian church of San Pietro da Morrone (Matera, Italy): insights and photogrammetric-based characterisation

Rupestrian cultural assets are remarkable examples of human occupation of the territory. As for any other cultural asset, the characterisation of rupestrian buildings is critical for their conservation and protection. However, there are a number of difficulties and challenges that are inherent in the physical singularities of these architectonic constructions, namely related to their geometrical irregularities. It is therefore important to use an appropriate approach to describe the geometry of these assets by overcoming some limitations that conventional measurement and surveying approaches have. The production of digital three-dimensional models is consequently a very useful and promising approach in this context. For most cultural assets and in particular geometrically complex objects, the approach is useful in reconstructing geometrical inner or exterior surfaces by means of photographic information. Photogrammetry is a technique used to acquire valuable and accurate three-dimensional information, which generates reliable models that also include integrated works, such as paintings or sculptures. The present work explores the suitability of this approach in the context of a remarkable case of rupestrian architecture, that of the church of San Pietro da Morrone. The building, located in the historical city of Matera (Italy), witnessed a series of transformations and varied uses, before it was abandoned in the middle of the 20th century. The experimental survey of this building provides a first insight into its geometry and a point of reference for discussing the implementation of a photogrammetric approach, its advantages, limitations and possibilities.I beni culturali rupestri sono esempi notevoli di occupazione umana del territorio. Come per ogni altro bene culturale, la caratterizzazione degli edifici rupestri è fondamentale per la loro conservazione e tutela. Tuttavia vi sono una serie di difficoltà e sfide che sono inerenti alle singolarità fisiche di queste costruzioni architettoniche, in particolare legate alle loro irregolarità geometriche. È quindi importante utilizzare un approccio specifico per descrivere la geometria di questi beni superando alcune limitazioni che hanno gli approcci convenzionali di misurazione e rilevamento. La produzione di modelli tridimensionali digitali è quindi un metodo molto utile e promettente in questo contesto. Per la maggior parte dei beni culturali e in particolare per gli oggetti geometricamente complessi, l’approccio è utile per ricostruire superfici geometriche interne o esterne per mezzo di informazioni fotografiche. La fotogrammetria è una tecnica utilizzata per acquisire informazioni tridimensionali preziose e accurate, che genera modelli affidabili che includono anche opere integrate, come dipinti o sculture. Il presente lavoro esplora l’adeguatezza di questo approccio nel contesto di un caso notevole di architettura rupestre, quello della chiesa di San Pietro da Morrone. L’edificio, situato nella storica città di Matera (Italia), ha subito una serie di trasformazioni e vari usi, prima di essere abbandonato a metà del XX secolo. Il rilievo sperimentale di questo edificio fornisce una prima visione della sua geometria e un punto di riferimento per discutere l’implementazione di un approccio fotogrammetrico, i suoi vantaggi, limiti e possibilità