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Multi-physics Modelling of the Influence of Environmental Conditions on the Hardened Properties of 3D-printed Concrete
No full textInternational audienceAs opposed to massive concrete structures, 3D-printed concrete structures have a high surface-to volume ratio, leading to high water loss after printing. This evaporation is known to cause significant plastic shrinkage shortly after printing [1], which often leads to cracks. We demonstrate experimentally that effects of evaporation are also visible at the hardened state, with a significant impact on the compressive strength of printed parts, evaporation being detrimental to the compressive strength.Based on experimental observations indicating a positive correlation between printed wall thickness and compressive strength at the hardened state, and an increase in the compressive strength when preventing evaporation after printing, we propose a fully coupled thermo-poro-mechanical model [2] to describe the evolution of the printed material, from fresh to hardened state. Cement hydration and associated stiffness and strength build-up, as well as water evaporation at the boundaries, water transport within the printed structure and water consumption due to cement hydration are accounted for. Their effects on temperature, strain, stiffness and compressive strength evolution are studied, and compared with experimental data.Comparisons between model predictions and experimental results demonstrate the model’s validity, enabling estimations of both shrinkage and strength development in 3D-printed cementitious structures in given environmental conditions. Indeed, the findings confirm that, in the absence of protective measures to limit water evaporation, thinner walls suffer from greater plastic shrinkage and lower cement hydration, stiffness and compressive strength than thicker walls. Additionally, experimental and numerical investigations confirm that preventing evaporation enhances compressive strength, reaching that of traditionally cast samples.These results highlight the importance of curing strategies in concrete 3D-printing. The model offers a predictive framework to estimate the efficiency of various curing strategies on several parameters, from short- to long-term after printing, and allows to estimate the hardened properties of printed part given the actual environmental conditions
L'écologie domestiquée : zéro déchet, engagement féminin et écologisation du quotidien.
No full textThis thesis looks at a form of commitment to an individual and largely domestic ecology, which at first glance might appear to escape collective structures, through the case of the zero waste (ZW) approach. How can individual commitment and the ambition for large-scale social change be held together? What definitions of ecology and ecological commitment are being promoted? How do they fit into the ecologist cause social field? How do they relate to the social and gender positions of the people involved?This research explores these questions using a variety of empirical materials: interviews with committed individuals, an ethnographic study in Roubaix, where zero waste has been a public policy since 2014, a quantitative and qualitative study of dedicated Facebook groups, observations in households and analyses of books promoting this approach.Based on a study of the different institutions that prescribe zero waste (books, local and national public policies), the thesis first shows that this ecology, which is close to personal development, is not very concerned to take into account the social relations of class, race and gender that underpin differentiated relations to ecological issues, and promotes a universalist and moral framing that is aimed more at the middle and upper classes. As an everyday ecology, zero waste is also an extension of domestic tasks, and this framing directs it towards a largely female audience.A study of the biographical paths that lead to ZW commitment shows that it is indeed a feminine commitment that echoes gendered dispositions to care, but also socially situated dispositions to asceticism. The thesis proposes to understand this commitment as a commitment of biographical unavailability, likely to attract women who, because of their socially valued professional positions, family responsibilities and heterosexual marital status, would have a lot to lose by committing themselves to other environmentalist modes of action, and find this mode of action preferable as part of the domestic sphere.Exploring the implementation of ecologisation within the home leads to an account of the weight of material resources on this process, of the ways in which tastes, temporal organisation and budgetary assessments are reformed, but also of the family and marital negotiations of this commitment. What emerges is that the greening of everyday life is shaped by class positions and by women's biographical unavailability, particularly its family and marital components, which constrain the reform of ordinary practices.By studying the ambivalent politicisation of zero waste, the thesis shows that the domestic ecology thus promoted and implemented can be read as an ordinary appropriation of ecological ideas and practices, which contributes to their domestication. Familiar, integrated into the domestic space and rendered harmless to the social and gender order, zero waste ecology is a domesticated ecology. Embedded in neoliberal structures, particularly in its conception of social change, it does not threaten the established order, and in fact contributes to the greening of capitalism. Furthermore, because it does not politicise the distribution of the environmental domestic labour (carried out by women), ZW ecology keeps a distance from feminisms and ecofeminisms, and appears to be a polite and conformist ecology that does not politicise the domestic space and the relations of gendered domination that play out there.Cette thèse porte sur un mode d’engagement dans une écologie individuelle et largement domestique qui, de prime abord, pourrait sembler échapper aux structures collectives, à travers le cas de la démarche zéro déchet (ZD). Comment tiennent ensemble engagement individuel et ambition d’un changement social de grande ampleur ? Quelles définitions de l’écologie et de l’engagement écologique sont ainsi promues ? Comment s’insèrent-elles dans l’espace de la cause écologiste ? En quoi dépendent-elles des positions de classe et de genre des personnes qui s’y engagent ?La thèse explore ces questions à partir de matériaux empiriques variés : entretiens avec des personnes pratiquant le zéro déchet, enquête ethnographique à Roubaix où une politique publique « zéro déchet » est mise en œuvre depuis 2014, enquête quantitative et qualitative sur des groupes Facebook dédiés, observations dans les foyers et analyses de livres de promotion de la démarche.À partir de l’étude des différentes instances de prescription du zéro déchet (livres, politiques publiques locales et nationales), la thèse montre d’abord que cette écologie proche du développement personnel est peu soucieuse de prendre en compte les rapports sociaux de classe, de race et de genre qui traversent les rapports différenciés aux enjeux écologiques, et promeut un cadrage universaliste et moral qui s’adresse davantage aux classes moyennes et supérieures. En tant qu’écologie du quotidien, le zéro déchet est aussi inscrit dans le prolongement des tâches domestiques et ce cadrage l’oriente vers un public largement féminin.L’étude des parcours biographiques qui mènent à l’engagement ZD confirme qu’il s’agit effectivement d’un engagement féminin qui fait écho à des dispositions genrées au care, mais aussi à des dispositions socialement situées à l’ascétisme. Dans une perspective attentive aux rapports sociaux de classe et de genre et à leurs intersections, la thèse propose de saisir l’écologisation du quotidien comme un engagement de l’indisponibilité biographique, susceptible d’attirer des femmes qui, par leurs positions professionnelles socialement valorisées, leurs responsabilités familiales et leur inscription dans la conjugalité hétérosexuelle, auraient beaucoup à perdre à s’engager dans d’autres modes d’action écologistes, et trouvent préférable ce mode d’action inscrit dans la sphère domestique.Explorer le déploiement de l’écologisation au sein du foyer amène à rendre compte du poids des ressources matérielles sur ce processus. Il s’agit aussi d’objectiver les manières dont les goûts, l’organisation temporelle et les évaluations budgétaires se trouvent réformées, ainsi que les négociations familiales et conjugales de cet engagement. Il en ressort que les composantes familiales et conjugales de l’indisponibilité biographique des femmes viennent poser des limites à la réforme des pratiques.En étudiant les politisations ambivalentes du zéro déchet, la thèse montre enfin que l’écologie domestique ainsi promue et mise en œuvre peut être lue comme une appropriation ordinaire des idées et pratiques écologistes, qui contribue à leur domestication. Familière, intégrée à l’espace domestique et rendue inoffensive pour l’ordre social et de genre, l’écologie zéro déchet est une écologie domestiquée. Inscrite dans les structures néolibérales, en particulier dans sa conception du changement social, elle ne menace pas l’ordre établi, contribuant du reste au verdissement du capitalisme. En outre, ne politisant pas la répartition du travail domestique ni du travail d’écologisation (réalisé par les femmes), l’écologie ZD se tient à distance des féminismes et des écoféminismes. En définitive, elle apparait comme une écologie policée et conformiste, qui ne politise pas l’espace domestique et les rapports de domination genrée qui s’y jouent
Damage behaviour of MX80 bentonite pellet in mixture under suction-controlled oedometer compression
No full textInternational audienceIn order to investigate the damage behaviour of MX80 bentonite pellet in mixture, suction-controlled oedometer tests were conducted using vapor equilibrium technique (VET). After wetted to different suctions (113 to 4.2 MPa) at a given vertical stress σv of 0.1 MPa, MX80 bentonite pellet/powder mixtures were loaded in steps till different σv values (0.1, 3.2 and 12.8 MPa), then instantaneously unloaded. The damage behaviour was studied on pellets using Micro-Computed Tomography (micro-CT) and Mercury Intrusion Porosimetry (MIP), due to the difficulty of extruding loose bentonite mixture as a whole at high suctions. MIP results showed that significant cracks occurred during wetting (suction decreasing), while cracking evolution during loading was more complex due to the coupled effects of suction and loading. At high suctions (s≥57 MPa), cracks continuously propagated during loading, as opposed to the consistent crack closure at low suction (4.2 MPa). For intermediate suctions between 38 and 9 MPa, cracks propagated in the low stress range (0.1 to 3.2 MPa), while closed in the low stress range (3.2 to 12.8 MPa). In addition, micro-CT images revealed that due to wetting thin cracks preferentially occurred in the marginal area of pellets because wetting started from this area. By contrast, loading mainly generated extended cracks in pellets, which propagated from the centre to the border. Based on the experimental results, a damage coefficient D proposed to quantify the wetting- and loading-induced damage. This coefficient was defined as the ratio of the macro-pore volume to the total volume in pellet. It appears that D increased with the decrease of suction. During loading, D consistently increased at high suctions (s≥57 MPa), as opposed to the lowest suction (4.2 MPa). However, at medium suctions (38 to 9 MPa), D increased at the low stress level, but decreased at the high stress level
River flow amplification under climate change: attribution and climate-driven storylines of the winter 2023/24 UK floods
No full textInternational audienceClimate change is expected to alter the magnitude and frequency of river floods. Post-event analyses often assess the rarity of events from historical observations and a growing number of studies attempt to attribute the event's severity to anthropogenic warming. Recent studies also advocate for the creation of "what-if" event storylines to explore consequences if an observed event turned out worse. However, few studies have harmonised these different approaches when conducting retrospective analyses of hydrological extremes. Climate change attribution including river flows also remains rare. Here, a framework for post-event analyses of hydrological extremes is demonstrated using the winter half-year 2023/24 UK river flooding as a case study. Persistent high river flows were observed across the UK and Western Europe, following on from notable winter floods in 2013/14, 2015/16 and 2019/20. The 'ClimaMeter' analogue-based attribution suggests that a 6-month period with similar atmospheric circulation patterns to the observed winter half-year 2023/24 has become warmer and wetter (by an average 8.8%) in 1945-2021 compared 1850-1925. Monthly river flow reconstructions extended back to 1850 show that river flows during the analogue periods in the recent past have also become 13.5% higher. Applying the UNSEEN approach by pooling seasonal hindcasts show the potential for river flows to be 46% higher than the baseline in a worst-case storyline. Finally, hydrological simulations driven by a single model initial-condition large ensemble suggest that when accounting for internal variability, a robust climate signal in winter half-year river flows have emerged for some areas but may remain concealed until mid-21st century and beyond. Our results contribute to the use of storyline approaches in postevent analysis and highlights the changing risk of winter UK flooding. This framework can be applied to future hydrological extremes both in the UK and elsewhere to inform long-term planning for climate adaptation
Climate Change, Natural Resources, and Conflict
No full textThis paper examines how climate change and natural resource dynamics contribute to conflict, with a focus on the implications of the green transition. It reviews empirical evidence showing that extreme weather events-such as droughts, floods, and heatwaves-are linked to increased violence, particularly through economic disruptions, reduced agricultural productivity, and displacement. The analysis also explores the mechanisms through which climate shocks influence conflict, including opportunity costs, resource competition, and behavioral responses to environmental stress. The discussion then turns to the role of natural resource exploitation, especially in the context of rising demand for minerals essential to low-carbon technologies. The paper highlights how resource price and availability shocks can trigger conflict, often depending on the type of resource, extraction method, and local governance. It also addresses the overlap between climate-and resource-driven conflict risks, emphasizing that their interaction may amplify instability. Throughout, the paper identifies open research questions related to prediction, the effects of long-run environmental changes, and the design of policy responses. These include insurance schemes, climate adaptation strategies, infrastructure investment, and regulatory frameworks for resource governance. The findings point to the need for research that integrates climate and conflict dynamics, with the goal of informing policies that can mitigate the risks associated with environmental change and resource pressures
Total hip arthroplasty, associated rehabilitation care and the COVID-19 pandemic in France
No full textInternational audienceThis study investigates the Total Hip Arthroplasty (THA) activity and the associated rehabilitation care in France over the period 2013-2022, with particular attention to the COVID-19 pandemic. In 2020, scheduled THA activity was 17% lower than predicted based on the 2013–2019 trend (−19,000 THAs). In 2022, this activity was close to the pre-2019 trend, but there has been no catch-up of scheduled THAs that did not occur in 2020 and 2021. There is no obvious explanation for this absence of catch-up. In addition, in 2020, THA activity for recent trauma was only 3.1% lower than predicted based on the 2013–2019 trend. Activity in 2022 shows a return to the pre-2019 trend, without any catch-up effect, as would be expected in such a case. Finally, the proportion of scheduled THAs followed by an associated rehabilitation stay declined sharply in 2020 (−4 percentage points compared to 2019) whereas the downward trend in this proportion had previously been much slower (−10 percentage points from 2013 to 2019). These results underscore the major effect of the COVID-19 pandemic on surgical activity, though further investigation is needed to fully understand the long-term effects on patients' health and life expectancy
Construire le courbe: Apports méthodologiques à la conception des structures
No full textThis thesis provides an overview of my research activities in the field of structural design. Based on René Motro's idea that this discipline is a constant search for compromise between form, force, structure, material, and technology, I detail various projects to which I have contributed and endeavor to show how this work encompasses the entire spectrum of design. Its title is borrowed from an intensive workshop at the École des Ponts that I have been running since 2010 on double-curved structures, which are among the most mechanically efficient structures and for which new digital technologies promise a new boom. However, the tools and methods developed to actually build curvature are not limited to architectural applications alone and, as we shall see, are relevant to understanding the mechanical behavior and design of lightweight and slender structures of all kinds, in particular rockfall protection nets. Two aspects are explored in depth: the first focuses on a specific object of study or type of structure, elastic gridshells, and provides a rich array of approaches and methods for analysis and exploration; the second focuses on a particular discipline, constructive/architectural geometry, illustrating the value of detailed geometric knowledge for the study and design of a multitude of structural objects. Finally, architect Félix Candéla and his work are discussed in conclusion to offer some perspectives on this work.Le présent mémoire propose une synthèse de mes activités de recherche autour de la conception des structures. Partant de l’idée de René Motro que cette discipline est une recherche de compromis permanent entre forme, force, structure, matériau et technologie, j’y détaille différents projets auxquels j’ai pu contribuer et m’attache à montrer en quoi ces travaux embrassent l’ensemble du spectre de la conception. Son titre est emprunté à un atelier intensif de l’École des Ponts que j’anime depuis 2010 autour des structures à double courbure qui sont mécaniquement parmi les plus efficaces qui soient et pour lesquelles les technologies numériques nouvelles promettent un nouvel essor. Les outils et méthodes développés pour construire le courbe ne sont cependant pas limités aux seules applications architecturales et, comme on le verra, sont pertinents pour la compréhension du comportement mécanique et la conception des ouvrages légers et élancés en tout genre, en particulier les filets pare-blocs. Deux aspects sont néanmoins approfondis : le premier centré sur un objet d’étude ou une typologie de structure particulière, les gridshells élastiques, permet de brosser un éventail riche d’approches et de méthodes d’étude et d’exploration ; le second centré sur une discipline particulière, la géométrie constructive, illustre quant à lui l’intérêt d’une connaissance géométrique fine pour l’étude et la conception d’une multitude d’objets structurels. Enfin, l’architecte Félix Candéla et son œuvre sont évoqués en conclusion pour proposer quelques perspectives à ce travail
Ballot Richness and Information Aggregation
No full textWhen voters have different information quality, voting rules with richer ballot spaces can help voters better aggregate information by endogenously allocating more decision power to better-informed members. Using laboratory experiments, we compare two polar examples of voting rules in terms of ballot richness: majority voting (MV) and continuous voting (CV). Our results show that CV outperforms MV on average, although the difference is smaller than predicted, and that CV has more support than MV in treatments where it is expected to perform better. We also find that voters with intermediate information overestimate the importance of their votes under CV
An investigation on the impact of intermittency on wind Lidar profiler data utilizing a Universal Multifractal framework
No full textInternational audienceThe intermittent nature of turbulence introduces significant variability and extreme events, which profoundly complicates efforts to accurately measure, model, and predict its behavior. In the context of the atmospheric boundary layer, this intermittent turbulence can lead to localized bursts of wind shear, which poses risks to wind energy operations. These fluctuations directly impact the operational efficiency and structural integrity of wind turbines. Specifically, turbulence influences fatigue loads on the turbines and is essential for accurately modeling wake effects that occur within wind farms, which can affect the performance of adjacent turbines and forecasting energy production. Research suggests that a multifractal framework characterized by complex patterns across various scales enables one to properly model the intermittency of turbulence. To investigate this phenomenon, the present study analyzes wind data collected using a state-of-the-art lidar (Light Detection and Ranging) system profiler. This profiler was deployed on an offshore measurement mast situated near an offshore wind farm located 13 kilometers off the coast of Fécamp, France. Employing a universal multifractal (UM) framework, this study seeks to simulate and analyze the extreme variability inherent in the collected data. In the first step, The UM framework will be used to quantify the effects of intermittency on standard metrics such as turbulence intensity (TI) and spectral slopes, also accounting for the resolution at which they are computed and the frequency of data. Empirical estimates of TI and spectral slope in homogeneous turbulence often deviate from theoretical scaling, which can be theoretically and empirically quantified. In the second step, the results of the UM analysis of the measured time series will be discussed. Additionally, this study will delve into the instrumental biases introduced by the lidar instrument used in the measurement of turbulence. These biases can significantly impact the accuracy of data interpretation and reliability of results, making it essential to explore and address them thoroughly. This research not only addresses the theoretical aspects of turbulence but also has practical implications for optimizing wind energy operations in the face of unpredictable environmental conditions. Finally, the authors would like to acknowledge the partial financial support of the French Government, managed by the Agence Nationale de la Recherche under the Investissements d’Avenir program, with the reference ANR-10-IEED-0006-34. This work was carried out in the framework of the NEMO project