Teses de Doutoramento
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Assessment and improvement of energy use in wastewater systems
This research aims at developing a comprehensive approach for assessing the energy use and efficiency in wastewater systems, considering the water-energy-greenhouse gas (W-E-G) emissions nexus supported by methods and tools, such as a tailored energy balance and a performance assessment system (PAS). This approach is aligned with continuous improvement principles and allows carrying out the diagnosis of energy efficiency in wastewater systems supporting the building of a portfolio of energy use improvement measures responding to strategic objectives and attending to the systems
Ano: 2022
Autor(es): Jorge, C.
Keywords: Wastewater systems; Water-energy-greenhouse gas emissions nexus; Performance assessment; Energy efficiency; Energy balance
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Avaliação da eficiência energética nos serviços urbanos de águas. Guia para diagnóstico, priorização de alternativas, monitorização e revisão do plano de ação
A presente tese tem como objetivo melhorar a gestão dos sistemas de distribuição de água através da utilização de métodos probabilísticos e estatísticos para analisar os dados de contadores inteligentes. Assim, é proposta uma metodologia para avaliação da incerteza em medições de caudal dinâmicas, baseada apenas nas próprias medições, no método de bootstrap por blocos e no ajustamento de um modelo adequado aos dados em estudo. De seguida, é desenvolvida uma metodologia de amostragem probabilística estratificada dos clientes para identificação de uma amostra representativa onde deverão ser instalados contadores inteligentes, sendo os estratos definidos pelos grupos obtidos numa análise de clusters baseada em dados de faturação. É ainda apresentada uma metodologia para a decomposição¸ de séries temporais de caudal em consumo autorizado, consumo não autorizado, roturas e perdas, utilizando técnicas de suavização de séries temporais e análise do espetro singular (singular sprectum analysis). Por último, são testados alguns métodos robustos e de analise funcional para deteção de valores anómalos em series temporais de caudal.
Ano: 2022
Autor(es): Almeida e Silva, M.
Keywords: Sistemas de distribuição de água; Séries temporais de caudal; Incerteza; Decomposição de séries temporais; Amostragem estratificada
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Physical and Numerical Modelling of Wave Propagation Over Vegetation
Os efeitos das alterações climáticas aumentaram a necessidade de investigar a capacidade da vegetação em atenuar a força das ondas, nas zonas costeiras. Apoiando-se em modelação física, analítica e numérica da propagação de ondas sobre vegetação, este estudo teve como objetivos: i) analisar a diferença na dissipação de ondas sobre campos de vegetação rígida e flexível, ii) caracterizar o movimento de vegetação flexível, iii) estimar o coeficiente de arrasto de vegetação rígida e vegetação flexível, e iv) analisar a influência da flexibilidade (movimentoda vegetação) e da força de inércia no coeficiente de arrasto.
Ano: 2022
Autor(es): Reis, R.
Editor: IST
Keywords: Propagação/Dissipação de ondas; Análise de imagem; Movimento da vegetação; Coeficiente de arrasto; Vegetação flexível
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Understanding Flow Dynamics in Drinking Water Storage Tanks
Drinking water storage tanks are essential components of water supply systems to store water, to level off pressure in networks and to meet emergency storage. They are also frequent sources of deterioration of drinking water quality and safety owing to inadequate tank design and operation. Mostly, existing tanks design, dimensions and operation do not account for water mixing and renewal.
Ano: 2022
Autor(es): Pinheiro, A.
Keywords: Chlorine decay.; Particle image velocimetry; Residence time distribution; Drinking water safety; Water storage tanks
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Assessing the contribution of Nature-Based Solutions to urban resilience. A comprehensive assessment framework with focus on stormwater management and control.
Nature-Based Solutions (NBS) are crucial to achieving the goals of the United Nations Agenda 2030 for sustainable development and other global agendas, such as the Paris Agreement on Climate Change. In the last decade, the NBS umbrella concept has become more relevant intending to contribute to urban resilience and to address the climate change challenges. NBS are living solutions inspired by nature that use or mimic natural processes intending to face several societal challenges, from the perspective of resource-efficient use and the promotion of economic and environmental benefits. Currently, cities are encouraged to understand and measure the NBS contribution to identify adequate strategies for enhancing resilience and prioritize investments accordingly. The objective of the present thesis is to promote and enhance the NBS implementation in cities, focused on solutions for stormwater management and control. Based on the analysis of their contribution to urban resilience, the potential to meet environmental, social, and economic challenges and to adapt across diverse urban scales and contexts is demonstrated. In this sense, a Resilience Assessment Framework (RAF) to assess the NBS contribution to urban resilience was developed. This framework aims to assess the NBS contribution to urban resilience. Moreover, a Guidance for the RAF application in cities with different resilience maturity was developed, which involved the RAF validation by seven cities (from a national and international context), that participated voluntarily in this phase. In this context, the developed RAF is comprehensive and multidimensional. It is driven by the definition of objectives, criteria, and metrics, according to the proposed structure for assessing the water supply and wastewater system service performance in the framework of the ISO 24500 standards of the International Organization for Standardization. For an oriented assessment of the criteria, qualitative and quantitative metrics were defined, considering data from different sources and complexity. Reference values were also identified and metrics' classifications were defined. In this classification, each answer is associated with a resilience development level, intending to assess the NBS contribution to urban resilience on a normalized scale. To support the RAF application to cities with different resilience maturity (in terms of resilience and available information), three analysis degrees (essential, complementary, and comprehensive) and a set of metrics were proposed, which are pre-defined in the guidance for the RAF application. To support the selection of the analysis degree more adequate to any city, a structure to characterize the city's profile was developed. This complementary profile also supports the interpretation of the RAF results, both at the city and at the level of specific NBS. To conclude, the application of the RAF essential analysis degree to the seven participating cities, with different challenges regarding urban resilience and NBS, and of the comprehensive analysis degree (complete RAF) to Porto´s urban area, through an assemble assessment at the city and NBS levels, were presented.
Ano: 2021
Autor(es): Beceiro, P.
Keywords: Urban resilience; Stormwater management; Resilience assessment framework; Nature-Based Solutions (NBS)
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Proposal and validation of a performance assessment framework for urban storm water systems
Over the past two decades, performance assessment (PA) has been one of the areas show-ing the greatest advancement in the water sector. PA aims to measure effectiveness and/or efficiency of an activity or process using performance metrics, supporting the decision-making process and the continuous improvement of water utilities. Despite the potential benefits, few projects, and initiatives on PA have been undertaken regarding storm water systems (SWS). The present thesis aims to develop a performance assessment framework (PAF), applicable to both conventional SWS and sustainable urban drainage systems (SUDS), objective driven and focused on systems
Ano: 2021
Autor(es): Santos, L.F.
Keywords: Water utilities; Storm water systems; Indicators; Performance metrics; Framework; Performance assessment
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Towards a better urban water infrastructure asset management by condition assessment and cost modelling
Infrastructure asset management (IAM) has been increasingly becoming a key topic in the mind-set shift of the water sector managers and policy makers, allowing to assist in the operational, tactical and strategic decision-making in urban water infrastructures. Nevertheless, IAM implementation by the water utilities is still far from needed and not widespread, due to several challenges and constraints, mainly associated with limited human, technological and financial resources. The current research aims at enhancing urban water infrastructure asset management through an integrated decision-making approach, that includes novel methodologies for condition assessment, service life prediction and cost modelling. This approach can be applied at three assessment levels
Ano: 2021
Autor(es): Cabral , M.
Keywords: Urban water assets; Decision-making; Cost modelling; Service life prediction; Condition assessment; Infrastructure asset management
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A New Approach for the Maintenance Management of Transportation Infrastructures using Machine Learning
Transportation infrastructures are vital to our society. These infrastructures naturally tend to deteriorate over time. A set of activities is then required to manage existing assets in accordance with sound management principles. These activities are usually integrated into systems that manage infrastructures according to technical, social and economic aspects. This research aims to examine the potential of applying machine learning techniques to current transportation infrastructure management systems. Machine learning is an application of artificial intelligence enabling systems to automatically learn and improve from experience (data), arriving at solutions not explicitly programmed. Powered by algorithms that can learn from data, machine learning leads to efficient and effective systems that improve over time. Over the last few years, the application of machine learning has transformed several industries and could do so for transportation infrastructure as well.To achieve the research objectives, a set of studies was performed. Each of these studies had a specific objective, the set of which can be expressed as follows: to define combined performance indicators for pavement condition assessment using machine learning; to develop machine learning models for pavement performance prediction; to formulate machine learning solutions to overcome pavement data issues, such as missing data; to integrate machine learning techniques into decision support systems for pavement maintenance management. Together these studies explored the development of machine learning applications for solving some standard pavement management problems, providing insights into the application of machine learning to transportation infrastructure management systems. The studies successfully demonstrated the potential of machine learning applications for pavement management systems. It showed that machine learning is applicable to various transportation asset management problems, such as condition assessment, performance prediction, and decision support, and that it is able to outperform some of the analytical techniques currently used. Overall, this research work finds that machine learning is a promising tool for transportation infrastructure management systems.
Ano: 2020
Autor(es): Marcelino, P.
Keywords: Pavement Management Systems.; Decision Support Systems; Prediction Models;; Machine Learning; Transportation Infrastructure Asset Management
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Displacement measurement through InSAR geodesy for structural health monitoring
Interferometric synthetic aperture RADAR is an applied geodesy technique, which enables displacement measurement through satellite images. A literature review of the technique principles and of previous studies regarding its application to structural health monitoring allowed the identification of a few bottlenecks to the operational usage of this cost-effective technology for monitoring purposes.Three research lines were defined. First, a data mining strategy was developed to extract structural behaviour information from displacement time series from thousands of points on the region of interest, with tens of observation epochs each. Second, displacements from this technique were integrated into a previously existing monitoring system and were used to expand it to a larger number of points on the structure and to its surroundings. Third, an experimental infrastructure was deployed in order to perform several tests for displacement validation and uncertainty assessment. The infrastructure included a new model of artificial reflector to the satellite signals, purposefully developed in the scope of this study.The developed methods enabled the successful monitoring of different types of civil and geotechnical structures. Slope behaviour around water reservoirs was assessed during both the reservoir first impoundment and regular operation. Differential displacements were detected on building-blocks at a cultural heritage urban area and concrete arch dam responses to temperature loads were identified. The experimental work showed the achieved displacements agreed with those of other geodetic techniques and uncertainties around 2 mm were obtained for the measurements.In conclusion, interferometric synthetic aperture RADAR is a promising technique, able to provide useful information for structure monitoring, such as aiding in the planning of in situ monitoring activities and in identifying space-time patterns in structural behaviour. Thanks to its spatial coverage, observation period of a few days and achieved displacement uncertainty, it is advantageous to complement existing monitoring systems with data from this technique.
Ano: 2020
Autor(es): Roque, D.
Keywords: Uncertainty analysis; Data mining; Interferometric synthetic aperture RADAR; Geodesy; Structure monitoring systems
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Formulation of an advanced effective stress based constitutive model for unsaturated soils
The main purpose of the thesis is to show that it is viable the use of a correct effective stress framework to model the behaviour of unsaturated soils, with the development of an adequate effective stress model being an essential factor. One of the main advantages of this methodology is the separation between the solid skeleton mechanical constitutive models, which can be those developed for saturated soils, and the effect of the partial saturation on the behaviour of the soil, being only influenced by the effective stress model. The effective stress framework consists on the solid skeleton mechanical, the soil-water retention and the effective stress models. An isotropic effective stress model is proposed based on the main characteristics of the effective stress evolution in cubic spheres arrangements, incorporating hysteretic behaviour between drying and wetting paths and the dependency of specific volume and temperature, and being a function of the degree of saturation. A soil-water retention model is also proposed incorporating the hysteretic behaviour existent in drying and wetting paths, its dependency of specific volume and the incorporation of unsaturated states with zero suction. A rate-dependent (viscoplastic) and a rate-independent (elastoplastic) mechanical constitutive models, formulated with the subloading concept and the same hardening laws, was presented. The mechanical models can reproduce the cyclic, anisotropic and structured behaviour. Additionally, it is presented their expansion to nonisothermal conditions and the convergence of the response of the viscoplastic model to the elastoplastic model, when dealing with rate-independent soil behaviour (the elastoplastic model being more efficient). A generalised mixed stress-strain control for both viscoplastic and elastoplastic models in non-isothermal conditions is given. The effective stress framework constituted by the proposed mathematical models can reproduce with success diverse and complex unsaturated laboratory tests, reproducing the main aspects of the unsaturated soils behaviour. It is concluded that with an adequate effective stress model, it is not necessary to modify the mechanical constitutive models, previously formulated for saturated soils, introducing dependence of several model parameters on suction, degree of saturation or other similar variables. Also, it is shown that with an adequate evolutionary algorithm, the number of parameters is no longer a relevant issue restraining the use of these complex constitutive models. A newversion of the Differential Evolution method is developed to calibrate constitutive models for the laboratory tests.
Ano: 2020
Autor(es): Pereira, C.
Keywords: Differential evolution method; Non-isothermal constitutive models; Micromechanical models of spheres; Effective stress model; Unsaturated soils
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