184 research outputs found
Analyse de la vulnérabilité sismique des structures à ossature en bois avec remplissage : essais expérimentaux - modélisation numérique - calculs parasismiques
The seismic vulnerabilty is an important issue in the design of a building. The seismicresistant behavior of timber-framed structures is particularly relevant. Two types of timberframedstructures can be distinguished : the timber-framed structures using industrial products,such as wood-products panels used to brace the structure or metal fasteners, and traditionaltimber-framed structures included infill made of natuarl materials (earth or stones masonry).The seismic resistant behavior efficiency of traditional structures remains poorly recognizedbecause of the lack of research results on this kind of construction.Therefore, the thesis aims at improving the seismic behavior knowledge of timber-framedmasonry. Based on the assumption that their behavior is driven by the response of the metalfasteners connections, a multi-scale approach is proposed. It couples experimental and numericalstudies. At the scale 1 of the connection, at the scale 2 of the elementary constitutive cell ofwalls, at the scale 3 of structural elements such as shear walls and finally at the scale 4 of theentire building.In regards to the experimental work, this method allows, on the one hand, to perform parametricstudies and to analyze the influence of each element (wood member, nails, steel strip,infill, bracing, openings) on the local behavior (scales 1 and 2) and on the global behavior(scales 3 and 4) of the structure. On the other hand, it allows to provide a database to validatethe numerical modeling at each scale.In regards to the numerical work, this multi-scale approach allows to take into account thehysteretic behavior of joints in the development of a macro-element at the scale 2. Thus, thanksto a simplified finite element modeling (macro-element assembly), the computational cost islimited and it allows to take into account the local phenomena. The model is able to predictrelatively accurately the dynamic behavior at the scale 4 of the building, tested on a shakingtable.The study, presented herein, is one of the pioneer work that deals with the analysis of theseismic vulnerability of timber-framed structures with infill panels. This study provides outlookfor the analysis of this type of buildings. It confirms that the timbered masonry structures havea relevant seismic resistant behavior.Les sĂ©ismes constituent une source dâalĂ©as importante pour lâĂ©tude de la vulnĂ©rabilitĂ© dâunbĂątiment. Le comportement parasismique des bĂątiments Ă ossatures en bois est particuliĂšrementintĂ©ressant. Deux familles de structure Ă ossature en bois peuvent ĂȘtre distinguĂ©es : les ossaturesutilisant les produits industriels que sont les panneaux en bois reconstituĂ© servant Ă contreventerla structure et les connecteurs mĂ©talliques, et les ossatures traditionnelles avec remplissage reposantsur des techniques de construction anciennes et dĂ©pendantes du contexte local. LâefficacitĂ©du comportement parasismique des bĂątiments Ă ossature en bois traditionnels avec remplissagereste encore peu reconnue en raison du manque de rĂ©sultats issus des travaux de recherche.Les travaux prĂ©sentĂ©s dans cette thĂšse visent ainsi Ă amĂ©liorer les connaissances sur le comportementparasismique de cette typologie constructive. Partant de lâhypothĂšse selon laquellece comportement est gouvernĂ© par la rĂ©ponse des assemblages par connecteurs mĂ©talliques, uneapproche multi-Ă©chelles, couplant Ă©tudes expĂ©rimentales et Ă©tudes numĂ©riques est dĂ©veloppĂ©e.Elle dĂ©taille lâanalyse Ă lâĂ©chelle 1 de la connexion, en passant par lâĂ©chelle 2 des cellules Ă©lĂ©mentaires,constitutives des murs, par lâĂ©chelle 3 des murs de contreventement pour se finaliserĂ lâĂ©chelle 4 du bĂątiment dans son ensemble.Sur le plan expĂ©rimental, cette approche permet dâune part, de rĂ©aliser des Ă©tudes paramĂ©triqueset ainsi dâapprĂ©hender lâinfluence de la rĂ©ponse de chaque Ă©lĂ©ment (bois, clous, feuillard,remplissage, contreventement, ouvertures) sur le comportement local (Ă©chelles 1 et 2) et global(Ă©chelles 3 et 4) de la structure. Dâautre part, elle permet de fournir une base de donnĂ©es pourla validation des modĂ©lisations numĂ©riques aux diffĂ©rentes Ă©chelles.Sur le plan de la modĂ©lisation numĂ©rique, cette approche multi-Ă©chelles est fondĂ©e sur la priseen compte du comportement non-linĂ©aire hystĂ©rĂ©tique des assemblages Ă lâĂ©chelle supĂ©rieure, parlâintermĂ©diaire dâun macro-Ă©lĂ©ment, dĂ©veloppĂ© dans la cadre de la mĂ©thode des Ă©lĂ©ments finis.Ainsi, grĂące Ă une modĂ©lisation simplifiĂ©e (assemblage des macro-Ă©lĂ©ments), le calcul est rapide,aussi bien Ă lâĂ©chelle du mur quâĂ celle du bĂątiment, et intĂšgre les phĂ©nomĂšnes non-linĂ©aire locaux.Le modĂšle peut ainsi prĂ©dire de maniĂšre relativement prĂ©cise le comportement dynamique de lastructure complĂšte Ă lâĂ©chelle 4, testĂ©e sur table vibrante.LâĂ©tude prĂ©sentĂ©e dans ce manuscrit fait partie des travaux prĂ©curseurs relatifs Ă lâanalysede la vulnĂ©rabilitĂ© sismique des ossatures bois avec remplissage. Cette Ă©tude dĂ©bouche sur denombreuses perspectives pour lâanalyse de cette typologie constructive. Elle confirme que les bĂątimentsĂ ossatures en bois avec remplissage ont un comportement parasismique trĂšs performant
La optimizaciĂłn de la dieta individual en adultos franceses muestra que las alternativas vegetales a los lĂĄcteos pueden complementar los lĂĄcteos en dietas sostenibles
Deriving Personalized Recommendations for Fish Intake Using Mathematical Optimization Methods
How low can dietary greenhouse gas emissions be reduced without impairing nutritional adequacy, affordability and acceptability of the diet? A modelling study to guide sustainable food choices
Role of Young Child Formulae and Supplements to Ensure Nutritional Adequacy in U.K. Young Children
The European Food Safety Authority (EFSA) states that young child formulae (YCFs) âcannot be considered as a necessity to satisfy the nutritional requirementsâ of children aged 12â36 months. This study quantifies the dietary changes needed to ensure nutritional adequacy in U.K. young children who consume YCFs and/or supplements and in those who do not. Dietary data from 1147 young children (aged 12â18 months) were used to identify, using linear programming models, the minimum changes needed to ensure nutritional adequacy: (i) by changing the quantities of foods initially consumed by each child (repertoire-foods); and (ii) by introducing new foods (non-repertoire-foods). Most of the children consumed neither YCFs, nor supplements (61.6%). Nutritional adequacy with repertoire-foods alone was ensured for only one child in this group, against 74.4% of the children consuming YCFs and supplement. When access to all foods was allowed, smaller food changes were required when YCFs and supplements were initially consumed than when they were not. In the total sample, the main dietary shifts needed to ensure nutritional adequacy were an increase in YCF and a decrease in cowâs milk (+226 g/day and â181 g/day, respectively). Increasing YCF and supplement consumption was the shortest way to cover the EFSA nutrient requirements of U.K. children
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