Prévision de résistances d'assemblages bois par organes multiples à l'aide des réseaux de neurones

Du fait de la complexité du dimensionnement des assemblages dans les constructions en bois, nous avons restreint notre étude à la prévision de la résistance ultime des assemblages bois, par organes métalliques multiples, en double cisaillement. L'éventail des configurations possibles, en pratique, rend illusoire toute tentative de détermination réaliste de ces valeurs par voie d'essais. De plus, il existe dans ces assemblages des mécanismes de ruine particuliers que les différents règlements en vigueur ne parviennent à mettre en équation. Ces règlements présentent également des divergences en de nombreux autres points. On s'est donc attaché à modéliser la résistance ultime de ces assemblages par une approche numérique alternative : celle des réseaux de neurones. Pour cela, on a tout d'abord constitué une base de données qui a servi à alimenter le réseau de neurones. La prévision donnée par ces réseaux est très proche des données expérimentales mais il est difficile de mettre en application ce genre de modèle dans un code de calcul. Nous avons donc simplifié le modèle généré par réseau de neurones en employant des modèles quadratiques généralisés, obtenus par des techniques de régression classiques qui prennent en compte les variables d'entrée les plus significatives.In this thesis, we are interested by predicting the load carrying capacity of single or multiple dowel-type connections. When investigating this aspect of design, we find out that current design rules are still inaccurate and that this lack of accuracy cannot be supplemented by mechanical models, especially concerning multiple fasteners connections. Therefore, a numerical approach disconnected from mechanics has been investigated, i.e. the neural network approach. This method shows some benefits since we want to predict a variable, the load carrying capacity, which is highly complex with the respect of input parameters. To reach this goal, the first part of the work was to gather existing data throughout the literature. The results illustrated in the thesis demonstrate that the approach is powerful and could lead us to propose alternative design rules disconnected from Johansen's theory : we propose a simplification of the neural network model, which is quite complex, by using generalized quadratic models in order to implement the model in a design code

Long-Term Deformations and Mechanical Properties of Fine Recycled Aggregate Earth Concrete

Earth-based materials are currently receiving high attention, as they are considered as sustainable. In addition, the reuse of waste materials and more particularly recycled aggregates can boost circular economy while reducing landfilling and mineral resource depletion. Incorporating recycled aggregates in earth concrete can be an innovative way to valorize them. However, investigations are required concerning their long-term behavior. Such an aspect is more important when fine recycled aggregates are considered. In this paper, the vulnerability to long term deformations of natural sand (NS) and recycled sand (RS) earth concrete mixtures is examined under real exposure conditions. Autogenous shrinkage, drying shrinkage, basic creep and drying creep of the different mixtures were monitored for a period of two months. Specimens were then subjected to compressive tests in order to evaluate their residual strength. Furthermore, the destructive tests were monitored in parallel with the acoustic emission (AE) technique. The results show an increase in the rate of drying creep and shrinkage for RS earth concrete mixtures. In addition, NS and RS earth concrete mixtures subjected to drying, with and without loading, reported a strength development in comparison to the reference mixtures. However, the Young’s modulus reported its lowest value for drying shrinkage of both mixtures. Regarding the AE technique, the distribution of its activity reflected the higher rate of damage of dried specimens in the pre-peak region

Turning sunlit rooftops and windy sites into energy assets

International audienc

Prévision de résistances d'assemblages bois par organes multiples à l'aide des réseaux de neurones

Du fait de la complexité du dimensionnement des assemblages dans les constructions en bois, nous avons restreint notre étude à la prévision de la résistance ultime des assemblages bois, par organes métalliques multiples, en double cisaillement. L'éventail des configurations possibles, en pratique, rend illusoire toute tentative de détermination réaliste de ces valeurs par voie d'essais. De plus, il existe dans ces assemblages des mécanismes de ruine particuliers que les différents règlements en vigueur ne parviennent à mettre en e quation. Ces règlements présentent également des divergences en de nombreux autres points. On s'est donc attaché à modéliser la résistance ultime de ces assemblages par une approche numérique alternative : celle des réseaux de neurones. Pour cela, on a tout d'abord constitué une base de données qui a servi à alimenter le réseau de neurones. La prévision donnée par ces réseaux est très proche des données expérimentales mais il est difficile de mettre en application ce genre de modèle dans un code de calcul. Nous avons donc simplifié le modèle généré par réseau de neurones en employant des modèles quadratiques généralisés, obtenus par des techniques de régression classiques qui prennent en compte les variables d'entrée les plus significatives.In this thesis, we are interested by predicting the load carrying capacity of single or multiple dowel-type connections. When investigating this aspect of design, we find out that current design rules are still inaccurate and that this lack of accuracy cannot be supplemented by mechanical models, especially concerning multiple fasteners connections. Therefore, a numerical approach disconnected from mechanics has been investigated, i.e. the neural network approach. This method shows some benefits since we want to predict a variable, the load carrying capacity, which is highly complex with the respect of input parameters. To reach this goal, the first part of the work was to gather existing data throughout the literature. The results illustrated in the thesis demonstrate that the approach is powerful and could lead us to propose alternative design rules disconnected from Johansen's theory : we propose a simplification of the neural network model, which is quite complex, by using generalized quadratic models in order to implement the model in a design code.BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Turning sunlit rooftops and windy sites into energy assets

International audienceAt the core of renewable energy project development is the work of turning things (roof, site) into productive assets (solar roof, wind power site) through the siting of material devices (turbines, PV panels). The resulting assets convert an untamed flow (sun, wind) into electricity dubbed ‘renewable’ and eligible to stable remuneration (‘feed-in’ tariff). They are valued (tradable projects/portfolios) and they produce value (marketable electricity). Assembling productive-enough assets implies engaging things in hybrid agencements by requalifying their pre-existing usages and/or users.Our contribution starts from two case studies of politically engaged project developments: a mutualised PV project carried out by farmers (Fermes de Figeac, Lot, France), and a wind farm repowering in a European migratory corridor involving bird watchers and a wind power developers (Narbonnaise, Languedoc-Roussillon, France). These cases allow us to describe the socio-technical and economic reconfigurations through which sunlit rooftops and a windy site are turned into assets, and made to generate revenue streams. We further look at what these reconfigurations produce, which allows us to discuss the forms of rentierships entailed and the way in which we define assets.As these processes take place at the junction with financial valuation, conveyed by developers business models (project/portfolio TRIs, relation with banks), they additionally make the case for discussing the relation between capitalisation (TRI requirements) and asset making

Feed-in tariffs in the European Union - Renewable energy policy, the internal electricity market and economic expertise

International audienceThis book retraces the history of feed-in tariffs in relations with the European Union renewable energy policy from a sociological perspective. Feed-in tariffs are one of the most widespread instruments for promotion renewable electricity. By following their trajectory since their emergence in the late 1970s, the book explores evolving conceptions of renewable energy policy in the European Union at the intersection between environmental objectives, technological change and the ambition to liberalise the internal electricity market. The book is structured according to a chronology punctuated by key EU directives relevant to renewable energy policy. From this account, conclusions are drawn on the relationships between markets and policy-making as it is instituted in the European Union, as well as on the interplay between the implementation of a European vision on energy and national politics

Turning sunlit rooftops and windy sites into energy assets

International audienceAt the core of renewable energy project development is the work of turning things (roof, site) into productive assets (solar roof, wind power site) through the siting of material devices (turbines, PV panels). The resulting assets convert an untamed flow (sun, wind) into electricity dubbed ‘renewable’ and eligible to stable remuneration (‘feed-in’ tariff). They are valued (tradable projects/portfolios) and they produce value (marketable electricity). Assembling productive-enough assets implies engaging things in hybrid agencements by requalifying their pre-existing usages and/or users.Our contribution starts from two case studies of politically engaged project developments: a mutualised PV project carried out by farmers (Fermes de Figeac, Lot, France), and a wind farm repowering in a European migratory corridor involving bird watchers and a wind power developers (Narbonnaise, Languedoc-Roussillon, France). These cases allow us to describe the socio-technical and economic reconfigurations through which sunlit rooftops and a windy site are turned into assets, and made to generate revenue streams. We further look at what these reconfigurations produce, which allows us to discuss the forms of rentierships entailed and the way in which we define assets.As these processes take place at the junction with financial valuation, conveyed by developers business models (project/portfolio TRIs, relation with banks), they additionally make the case for discussing the relation between capitalisation (TRI requirements) and asset making

Organizing policy relevant Expertise on Climate Action: the Community of Integrating Assessment Modelling,

International audienc

Organising Policy-Relevant Knowledge for Climate Action: Integrated Assessment Modelling, the IPCC, and the Emergence of a Collective Expertise on Socioeconomic Emission Scenarios

Greenhouse gas emission scenarios are key in analyses of human interference with the climate system. They are mainly produced by one category of computer models: Integrated Assessment Models (IAMs). We analyse how IAM research organised into a community around the production of socio-economic scenarios during the preparation of the IPCC AR5 (2005-2014). We seek to describe the co-emergence of a research community, its instruments, and its domain of applicability. We highlight the role of the IPCC process in the making of the IAM community, showing how IAMs worked their way to an influent position. We then survey three elements of the repertoire that served to organise collective work on scenarios in interaction with the IPCC and the European Union, and which now frames the community and its epistemic practices. This repertoire needs to articulate epistemic practices with the pursuit of policy relevance, which shows how epistemic communities and patterns of co-production materialise in practical arrangements