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Green Global Policy Assemblages: The Evolution of Community-Based Natural Resource Management in Response to Climate Change in NamibiaHeffernan, Andrew 28 September 2022 (has links)
Community-Based Natural Resource Management (CBNRM) has emerged in southern Africa as a form of resource governance that is intended to devolve control of natural resources to local populations. CBNRM has produced demonstrable benefits in attaining its three goals of economic development, environmental conservation, and community empowerment, however, over time success has seemingly dwindled which has been documented in the literature. Many scholars argue that it is the third goal of community empowerment that most often fails to be realized. Beyond that, one of the major gaps that exists in the literature is an analysis of the impact of climate change on the CBNRM programs. This dissertation will analyze the challenges and opportunities of climate change while further analyzing to what degree local communities benefit as a result. It builds on existing global assemblage work to develop a composite theoretical approach that analyzes CBNRM as green global policy assemblage in order to account for the evolution of CBNRM in response to climate change. This approach is necessary as CBNRM is highly political and the resultant developing power relations are rearticulating global environmental governance and traditional levels of analysis. What emerges from the case study of Namibia is a policy assemblage that results in power being distributed and enacted in ways that traditional theories of International Relations cannot adequately account for within their state-centric ontology. This dissertation is based on fieldwork conducted in Namibia, a country that is generally recognized as a global leader in CBNRM. My conclusions suggest that CBNRM cannot be viewed as an empowering of Namibian communities and corresponding weakening of the state. Instead, the state maintains its sovereign power however at a distance and it is exercised in a less direct fashion than would have traditionally been the case. Furthermore, by devolving power the state enables NGOs to exert their influence on the ground in assisting communities. However, the actions of NGOs have important political effects based on the complex relations they have with other countries, multilateral institutions, as well as novel hybrid organizations that are increasingly empowered to engage in development actions throughout the Global South. While this proliferation of actors has resulted in continued funding streams for important development initiatives, it also continues the dependence of African communities on global actors. In some ways this is making communities less autonomous and more reliant on others, rather than self-sufficient as CBNRM entails.
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The Role of Physiography in the Relationships Between Land Cover and Stream Fish AssemblagesDeweber, Jefferson Tyrell 01 June 2010 (has links)
Human alteration of the landscape for agricultural and urban land use has been linked to the degradation of streams and stream biota. Natural physical and climatic characteristics, or physiographic template, are important for determining natural land cover and constraining human land use, and are strongly related to stream habitat and stream biotic assemblages. Since the physiographic template differs among watersheds and is an important determinant of the processes being studied, it is important to account for these natural differences among watersheds so that the relationship between land cover and streams can be properly understood. The purpose of this thesis is to develop and assess the utility of a regional framework that classifies watersheds based on physical and climatic predictors of land cover. In Chapter 1, I identified physical and climatic predictors of land cover and classified watersheds into Land cover Distinguished Physiographic Regions (LDPRs) based on these predictors. I was able to identify and create classes based off eight climatic and landform characteristics that determined natural land cover and human land use patterns for both the Eastern and Western U.S. In Chapter 2, I utilized LDPRs to stratify a study region and investigated whether the relationships between land cover and stream fish assemblages varied between these regions. Five commonly used metrics covering trophic, reproductive and taxonomic groupings showed significant variation in their response to agricultural land use across LDPRs. The results suggest that the physiographic differences among LDPRs can result in different pathways by which land cover alterations impact stream fish communities. Unlike other commonly used regional frameworks, the rationale and methods used to develop LDPRs properly accounts for the causal relationship between physiography and land cover. Therefore, I recommend the use of LDPRs as a tool for stratifying watersheds based on physiography in future investigations so that the processes by which human land use results in stream degradation can be understood. / Master of Science
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Institutional Global Maternal Nutrition Communication: Unblackboxing Rhetorical Power Dynamics in Transnational SpacesGanguly, Priyanka 13 May 2024 (has links)
Grounded at the intersection of rhetorics of health and medicine (RHM), technical and professional communication (TPC), and transnational institutional communication, my study aimed to explore the transnational issues of negotiation and power and (mis)articulations within the realm of global maternal nutrition (MN) communication design. Specifically, I sought to demystify the behind-the-scenes interactions and negotiations among funders (in this case, USAID headquarters), contractors (global health designers for a project called "Advancing Nutrition"), and local partners (Global South program implementers).
To achieve this goal, I conducted a rhetorical analysis of twenty-eight publicly available Advancing Nutrition MN artifacts, including program guides, worksheets, toolkits, and multimedia discourses. Additionally, I performed fifteen episodic narrative interviews with key informants from the Advancing Nutrition team, USAID, and local implementing agencies in India, Kyrgyz Republic, and Ghana. Through the theoretical lenses of power as assemblage and articulation, my findings suggested a continual flux of (re)articulation tension within global MN communication design.
This tension stemmed from power assemblages—a confluence of historical-political-ideological forces at the production site in the Global North and the rigid socio-cultural framework at the implementation site in the Global South—in transnational content creation spaces. This tension manifested in maternal-child nutrition indicators, temporally bound MN program design, community narratives in local implementation sites, and an emphasis on normative views of women's nutrition.
Despite the power differentials among funders, contractors, and implementers, global health designers employed tactical technical communication approaches, including coalitional actions and reconstructive moves, to empower women and mothers in the Global South. Thus I conclude that technical and health communication scholars can help global institutional actors create socially-inclusive communication design and foster intentional community-engaged interventions by both attuning themselves to and exposing globalized power structures in the context of public health document creation. / Doctor of Philosophy / Situated at the crossroads of health and medical rhetoric, technical and professional communication, and cross-border institutional interaction, my research set out to delve into the complexities of negotiation, power dynamics, and communication challenges in the global arena of maternal nutrition. Specifically, I aimed to shed light on the behind-the-scenes dealings and discussions among key players such as funders (like USAID headquarters), contractors (working on projects such as "Advancing Nutrition"), and local partners (implementing programs in the Global South).
To accomplish this, I conducted a detailed analysis of twenty-eight publicly available materials related to the Advancing Nutrition initiative, including program guides, worksheets, toolkits, and multimedia presentations. Additionally, I conducted fifteen interviews with individuals from the Advancing Nutrition team, USAID, and local agencies in India, Kyrgyz Republic, and Ghana. Using the theoretical frameworks of power dynamics and articulation, my findings revealed a continual tension in how maternal nutrition communication is (re)shaped and understood on a global scale.
This tension arises from a blend of historical, political, and ideological forces influencing content creation in the Global North, juxtaposed with the socio-cultural realities at the implementation sites in the Global South. It is evident in various aspects such as maternal-child nutrition metrics, the design of time-sensitive nutrition programs, local community narratives, and the portrayal of women's nutrition.
Despite the inherent power imbalances among funders, contractors, and implementers, those involved in global health initiatives employed strategic communication methods, including collaborative efforts and reconstructive strategies, to empower women and mothers in the Global South. As a result, I argue that scholars in technical and health communication have a vital role to play in fostering inclusive communication design and facilitating community-focused interventions by both understanding and exposing global power dynamics in the realm of public health document creation.
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The Fellowship of a Map : How maps affect the imaginary geography of fantasy worldsJohansson, Henrik January 2024 (has links)
By utilizing theories surrounding assemblages, the principle of minimal departure, maps, and world-architecture,the thesis has tried to understand how maps and narrative affect each other in creating an imaginary geography infantasy literature as well as what role maps in fantasy have for the individuals reading them. With a focus on hownarrative, map, and other actors interacted, the thesis, having used two methods, a close reading of the book AWizard of Earthsea, and online content analysis of forum posts regarding fantasy maps, has achieved a deeperunderstanding of maps role in creating an imaginary geography. The thesis has found that when reading a fantasybook using a map, the map serves the role of both limiting what can and cannot be imagined while also bridgingthe assemblages of actual and secondary truth values which aid in interpreting the fantasy world. Furthermore, thethesis has found that for average readers of fantasy, the map can serve two roles: Clarifying spatialities andAugmenting abilities.
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Suburban Succession and Stream Dynamics: An Investigation of Source Organic Material Dynamics in Areas Experiencing Rapid DevelopmentMcGillewie, Sara B. 12 1900 (has links)
Increasingly higher numbers of people are moving into urbanizing environments, yet our understanding of ecosystem consequences of rapid urbanization is still in its infancy. In this dissertation, I assessed dynamics of residential landscapes during suburban succession and consequences for ecosystem functioning. First, I used a space-for-time approach to quantify more than a century of suburban succession in the Dallas – Fort Worth metroplex (DFW). Attributes of residential landscape plant diversity and habitat complexity were quantified for 232 individual properties nested within 14 neighborhoods constructed between 1906 and 2020. Suburban succession progressed from simple turf lawns with limited habitat complexity to landscapes dominated by deciduous trees and high habitat complexity, but homeowner decisions related to landscape management affect the rate of that transition and the number of plants and taxa present. Next, I used the novel spatial construct of "neighborhoodsheds" to test for effects of suburban succession on carbon export, and found that the proportion of carbon derived from C3 vs. C4 plants was affected by neighborhood plant community structure (i.e. greater proportion of trees and shrubs primarily in later stages of suburban succession). Finally, I conducted a mesocosm experiment to test effects of changes in allochthonous inputs during suburban succession on aquatic ecosystem functioning. The proportion of carbon from C3 vs. C4 sources interacted with time to affect abundance of emergent mosquitoes and chironomids. This work sets the stage for further research on urban ecology in DFW and provides conceptual advances for the study of urban ecosystems more broadly.
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Développement de solutions industrielles pour le traitement de surface par texturation laser permettant l'amélioration de l'adhésion de joints d'aluminiumVeilleux, Catherine 25 March 2024 (has links)
Titre de l'écran-titre (visionné le 7 août 20223) / L'industrie automobile est un domaine manufacturier repoussant constamment les méthodes de fabrication des composants. Avec une production d'environ 91 millions de véhicules par an, le rythme de production et la qualité des pièces fabriquées sont critiques, et les procédés industriels utilisés pour faire ces pièces doivent progresser en conséquence. L'une des méthodes d'assemblage couramment utilisée est le collage de joints métalliques par adhésifs, qui nécessite une bonne préparation des surfaces pour assurer la durabilité du joint. D'autre part, la présence de lasers à fibre dans l'industrie est grandissante, que ce soit pour couper, souder, marquer ou nettoyer les composants. Cette technologie est plus durable, moins énergivore et plus verte que les procédés traditionnels. Ce projet de maîtrise, en partenariat avec la compagnie Laserax, vise à développer des solutions industrielles rapides, répétables et versatiles pour effectuer la préparation des surfaces d'aluminium avant collage à l'aide d'un laser haute puissance. D'abord, une revue de littérature est réalisée afin d'établir une base de connaissance sur le sujet en cause et de comprendre les avancés effectuées jusqu'à présent sur la préparation de surfaces au laser. Un laser à fibre pulsé et monomode transverse générant une puissance moyenne de 500W est ensuite utilisé afin de réaliser une texturation rapide et efficace des surfaces métalliques. Les joints collés sont soumis à des essais de résistance en force et à des cycles de vieillissement pour simuler les conditions réelles d'utilisation. De plus, la morphologie et la composition chimique des surfaces traitées sont analysées afin de démontrer la formation d'oxydes surfaciques qui favorisent l'adhésion. Au terme de ce projet, un ensemble de configurations de texturation laser ayant supporté avec succès un cycle de vieillissement rigoureux est présenté.
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Aboutage de l'érable à sucre pour la fabrication de produits de bois d'ingénierie structurauxDagenais, Christian 13 April 2018 (has links)
Le bois abouté est souvent utilisé dans la fabrication de produits de bois d’ingénierie structuraux tels que le lamellé-collé et la poutrelle en I. Au Québec, les fabricants de produits de bois d’ingénierie utilisent principalement du bois du groupe Épinette-pin-sapin (EPS) qui comporte des essences de résineux acceptées dans les normes canadiennes. Étant un bois de feuillus, l’érable à sucre n’est pas une essence prescrite dans les normes de fabrication par contre, en théorie, ce bois peut offrir une alternative intéressante aux bois résineux compte tenu de sa résistance mécanique supérieure. Une revue de la littérature démontre qu’il existe plusieurs recherches sur l’aboutage par entures multiples, mais que celles portant sur l’aboutage de bois de feuillus sont plutôt rares. Plusieurs paramètres d’usinage doivent être contrôlés afin de fournir de belles surfaces de collage et d’optimiser le procédé d’aboutage. Ce projet vise à définir un intervalle de paramètres d’usinage pour l’aboutage structural par entures multiples de l’érable à sucre afin de développer les meilleures résistances mécaniques que ce bois peut potentiellement offrir. Plus spécifiquement, ce projet étudie la résistance en traction parallèle au fil en variant la vitesse de coupe ainsi que l’avance par couteau (chip-load). Des deux paramètres étudiés, la vitesse de coupe semble être le paramètre ayant le plus d’effet sur la résistance en traction parallèle au fil de l’érable à sucre. Les meilleures résistances furent atteintes avec une vitesse de coupe de 2726 m/min et une avance par couteau de 0,60 mm. La vitesse de coupe de 2726 m/min semble être la meilleure afin d’atteindre les meilleures résistances en traction parallèle au fil, et ce, peu importe l’avance par couteau. Finalement, les résultats obtenus nous permet de croire que l’érable à sucre abouté possède un bon potentiel pour des applications structurales dont la fabrication de produits de bois d’ingénierie structuraux. / Finger-jointed softwood lumber is often used in manufacturing of structural engineered wood products such as glued laminated (glulam) beams and prefabricated wood I-joists. In Québec, producers of engineered wood products utilize generally wood species of Spruce-pine-fir (SPF) group, which includes softwood species recognized in Canadian standards. As hardwood species, sugar maple is not listed in the product standards, although, presumably, it can offer an interesting alternative to softwoods from the view point of strength. Literature review shows that there are many studies on finger-jointing but there are few on finger jointing of hardwoods. Certain machining parameters have to be controlled in order to produce suitable gluing surfaces and to optimize the finger-jointing process. The main objective of this study was to evaluate the effect of machining parameters on the ultimate tensile strength parallel to grain (UTS) of finger-jointed sugar maple dimension lumber. Three different chip-loads and three cutting speeds were used as variables. Based on test results, the cutting speed appeared to influence the UTS the most. The best UTS (47.1 MPa) of finger-jointed sugar maple specimens were achieved with a chip-load of 0.60 mm and a cutting speed of 2726 m/min (rotation speed of 3250 RPM and feed speed of 11.7 m/min). Finally, results of the study show that finger-jointed sugar maple possesses a good potential for structural applications including fabrication of structural engineered wood products.
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Effet de la teneur en humidité du bois sur la performance des assemblages bois boulonnés de pin grisDorval Legras, Baptiste 16 April 2018 (has links)
Ce projet porte sur la problématique de l’influence de l’humidité sur la performance des attaches boulonnées des charpentes en bois. Afin d’améliorer la justesse des règles de calcul des charpentes en bois présentées dans la norme canadienne CSA-O86, nous vérifions, dans cette étude, la pertinence du coefficient de service (KSF) appliqué aux attaches dans des teneurs en humidité (TH) variables. Pour ce faire, nous utilisons cinq types d’attaches assemblées de bois sec (TH ≈ 12%) et humide (TH ≥ 19%) et testées en trois conditions d’humidité (TH ≈ 8%; TH ≈ 12%; TH ≥ 19%). Toutes les attaches sont constituées d’une membrure de pin gris (Pinus banksiana) de 89 mm d’épaisseur et de plaques de jonctions en acier de 6,4 mm d’épaisseur, le tout assemblé de boulons de 12,7 mm de diamètre de grade 2 et, dans certains cas, de grade 5. Les attaches sont à un, deux et six boulons; pour ce dernier, on fait varier l’espacement entre les rangées et entre les boulons. Chaque série inclut six éprouvettes, avec un joint à chacune des deux extrémités, pour un total de 198 tests de traction parallèle au fil du bois en double cisaillement. Les paramètres suivants sont déterminés pour chaque test : la limite de proportionnalité, le seuil de plasticité, la charge maximale, la rigidité, la ductilité et le mode de rupture. Les résultats de cette étude révèlent que c’est l’humidité du bois lors du test et non pas lors du montage qui est plus importante pour la performance des attaches. La rigidité augmente en proportion de la diminution de l’humidité en dessous du point de saturation des fibres, qui est accompagnée par une transition du mode de rupture de ductile à fragile. Les attaches assemblées et testées humides (TH > 19%) sont les plus faibles, mais les plus ductiles. Le séchage du bois a un plus grand effet sur les attaches avec un espacement plus petit entre connecteurs : en plus de la rupture fragile, leur résistance est réduite 15% en condition très sèche (TH ≈ 8%). La diminution de la résistance d’attaches en conditions très sèches est observée; néanmoins, pour les modes de rupture fragiles, le coefficient de service (KSF) est jugé trop conservateur. Des propositions sont faites et justifiées pour le remplacement du KSF par le coefficient de service en cisaillement et en traction longitudinale (KSv et KSt) dans les cas de rupture fragile, comme il est couramment recommandé dans la norme américaine National Design Specification. / This research is focused on the effect of moisture on the performance of bolted connections in timber structures. To improve the accuracy of the engineering design of timber structures based on the Canadian standard CSA-O86, we studied the relevance of the service factor (KSF) as applied to the lateral resistance of fastenings in different moisture conditions (MC). To reach this goal, we used five connection configurations assembled with seasoned (MC ≈ 12%) and unseasoned (MC ≥ 19%) timber and tested at various moisture conditions: wet (MC ≥ 19%), dry (MC ≈ 12%) and very dry (MC ≈ 8%). All connections were 89-mm thick jack pine (Pinus banksiana) sawn lumber and 6.4-mm thick steel side plates assembled with 12.7-mm diameter bolts of grade 2 and, in some cases, of grade 5. The joints included one, two or six bolts; in the latter, the fasteners were installed in two rows with various spacing between the rows and between the bolts in a row. Each series consisted of six specimens, with a joint at both ends, with a total of 198 tests in tension parallel to grain of wood in double shear. The following parameters were determined from each test: proportional limit, yield point, maximum load, stiffness, ductility and failure mode. Results of the study revealed that it was moisture content at test and not at the time of assembly that influenced the performance of the tested connections the most. The stiffness increased in direct proportion with the decrease of moisture content below the fibre saturation point, which was accompanied with a transition from ductile to brittle failure. Connections assembled and tested unseasoned (MC > 19%) were the weakest but the most ductile. Seasoning had the highest effect on the connections with the minimum spacing of fasteners within and between the rows: not only were they the most brittle, their load capacity was reduced 15% in very dry conditions (MC ≈ 8%). The reduction of load capacity of connections in very dry conditions was observed; yet for brittle failure modes, the service factor KSF was found to be overly conservative. Proposals are put forward and justified to replace the KSF by service condition factors in longitudinal shear and tension (KSv and KSt) in case of brittle failure modes, which is the current recommended practice in the US National Design Specification.
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Spécificités physiques et enjeux de la performance énergétique du CLT en milieu nordiqueMartin, Ulysse 19 April 2024 (has links)
Le bois a été l’un des premiers matériaux utilisés par l’homme et possède encore aujourd’hui beaucoup de potentiel dans la construction. En effet, de nombreux matériaux d’ingénierie ont été développés à partir du bois, comme les panneaux de bois lamellé-croisé (CLT). Ces matériaux permettent d’être compétitifs avec le béton ou l’acier en termes de performance, de coût et d’empreinte environnementale. L’extraction des ressources, la fabrication de matériaux de construction et la construction elle-même (transport et machinerie) sont énergivores et à l’origine d’importants dégagements de gaz à effet de serre. Le bois est une ressource renouvelable qui a l’avantage de fixer du carbone lors de sa croissance et de le conserver une fois en service. Durant sa vie utile, un bâtiment va aussi consommer de l’énergie pour le chauffage / la climatisation et l’éclairage. C’est pourquoi la recherche de l’efficacité énergétique est nécessaire. Le CLT est un matériau d’ingénierie qui a le potentiel de démocratiser les bâtiments de moyenne hauteur en bois. En cela le CLT est avantageux pour la performance énergétique, puisque les panneaux font un effet barrière à l’air, à la vapeur et à la chaleur. Dans le système constructif en CLT, les jonctions avec les autres panneaux et les percements sont les principaux chemins de fuites pour l’air. Les infiltrations/exfiltrations vont être responsables d’importantes pertes thermiques. De plus, les exfiltrations peuvent induire une humidité excessive en présence de chaleur dans le mur, provoquant la croissance de moisissure et de pourriture du bois. La résistance des matériaux et la santé des occupants peuvent être compromises à moyen et long terme. Le but de ce projet est d’évaluer l’impact des tolérances d’assemblages, en présence d’une fuite d’air, sur la performance énergétique et la durabilité du mur afin de vérifier si les tolérances d’assemblages représentent un risque à prendre en considération ou non. Des thermographies d’une jonction en angle de murs en CLT prises lors d’une dépressurisation du bâtiment ont permis d’identifier une fissure. Un travail de modélisation de la fissure en fonction des températures observables a ensuite permis de dimensionner la fissure (0,72 mm traversant l’isolation) en considérant une tolérance d’assemblage pour le CLT de 2 mm. Cette fissure « modèle » a ensuite été transposée dans le cas d’un mur plat, afin que ne soit pas considéré le pont thermique lié à l’angle. Une analyse de l’impact sur la performance énergétique de tolérances d’assemblages variables a été réalisée par simulation informatique, pour une infiltration et une exfiltration. La simulation a également permis d’analyser l’impact sur la durabilité, en termes de développements fongiques et de risque de condensation, d’une exfiltration sur notre fissure « modèle ». La simulation a montré que l’impact d’une infiltration sur la performance énergétique est 1,62 fois plus grand que pour une exfiltration, qui est elle-même 1,37 fois plus énergivore qu’un mur sans fissure. L’influence de la largeur de la tolérance d’assemblage est minorée par la dimension de la fissure dans le reste du mur. La simulation des échanges hygriques dans la fissure a montré que la croissance de moisissure est à craindre en surface, lorsque l’humidité relative de l’air est de 40 % et plus. La zone touchée est principalement l’isolation, mais s’étend jusqu’au CLT à mesure que l’humidité relative de l’air exfiltré augmente. L’humidité de l’air condense à proximité de la sortie de l’exfiltration, ce qui peut mener à une accumulation de givre sous le revêtement extérieur. Le résultat de ces simulations permet de mettre l’accent sur l’importance de la continuité du pare-air et de la mise en place de mesures pour éviter qu’une tolérance d’assemblage soit un chemin libre pour l’air. L’utilisation de joints adhésifs souples pouvant épouser la découpe irrégulière du CLT et amortir les variations dimensionnelles permettrait de réduire les risques liés aux fuites d’air. / Wood is one of the first material mankind used to work with and is still full of potential for building sector. Many engineering materials have been developed from wood, such as the cross-laminated timber (CLT). Wooden engineering materials are as performant as steel and concrete but are also cost effective and have a lower environmental footprint. Resources extraction for the manufacture of building materials and the building phase itself require a lot of energy, and generate or release important amount of greenhouse gaz. Wood is a sustainable resource that has the benefit of being able to capture carbon during its growing phase and to preserve it. In service, buildings will have heating and cooling loads, depending of their energy efficiency, high energy efficiency is required to lower the overall energy footprint of buildings. CLT has the potential to be a greener substitute to reinforced concrete in the mid-rise building. CLT helps to reach energy efficiency because wood panels act as a barrier for air, vapor and heat. In CLT building system, junctions between panels and with other elements (ducts, wiring, etc) are the main leakage paths through the envelope. Infiltrations and exfiltrations are responsible for important heat losses. Exfiltrations can also lead to excessive moisture accumulation in the walls, resulting in mold and rot growth. Structural integrity and air quality can be jeopardized on the average/long term. The aim of this project was to assess the impact of gaps between CLT panels, in case of air leakages, on the energy efficiency and durability of the wall. A real case of infiltration in a corner of a CLT building was used to size an air leakage area in the insulation (0.72 mm through the insulation considering a 1 m high wall), intended an assembly tolerance or gap of 2 mm. The gap was then extrapolated to a flat wall, to exclude the thermal bridge effect of the corner. An energy efficiency assessment was done using simulations for both cases of infiltration and exfiltration, with variable assembly gap. Simulation also permits to assess the impact on durability, on mold growth risks, of the exfiltration for variable exfiltrated air relative humidity. Results show that infiltration has a greater impact (1.62 times) than exfiltration, which is itself 1.37 times more energy-consuming than a perfect wall. The impact of the assembly gap variations in the CLT is restricted by a maximum flow rate dicted by the air leakage path in the insulation. Simulation of moisture transfer shows that mold growth is to fear on the gap surface through the wall, when the exfiltrated air relative humidity exceeds 40 %. The first mold development should primarily affects the insulation, but extends to the CLT as the relative humidity of the exfiltrated air increases. Condensation occurs in the insulation near the outlet of the exfiltration, leading to an accumulation of ice behind the external cladding. Results of simulations show how important it is to keep the air barrier continuous, and to avoid that assembly gaps in the CLT act as shortcut for eventual air leaks. The use of flexible adhesive joints, which can match the irregular cut of the CLT and dampen the dimensional variations would reduce the risks of air leakage.
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Performance au feu des vis auto-taraudeuses dans les bâtiments en bois de grande hauteurLétourneau-Gagnon, Mathieu 27 January 2024 (has links)
Les bâtiments et les matériaux de construction doivent avoir un degré de résistance au feu suffisant pour prévenir l'effondrement prématuré de la structure et fournir des moyens sécuritaires d'évacuation des occupants tels qu'exigés dans le Code National du bâtiment au Canada. Jusqu'à maintenant, l'Annexe B de la norme CSA O86 « Règles de calcul des charpentes en bois » fournit une méthode de calculs afin de déterminer la résistance au feu des éléments structuraux en bois massif. Toutefois, cette méthode ne considère pas l'effet du temps, le mode de rupture et l'interaction entre les différents matériaux en situation incendie. Ce projet de recherche étudie la performance au feu des assemblages utilisant des vis auto-taraudeuses pour les constructions massives en bois au Canada. Dans un premier temps, des essais expérimentaux combinés à des résultats d'articles scientifiques fourniront une représentation du comportement mécanique d'assemblages vissés utilisés dans la construction massive en bois. Dans un second lieu, ces données expérimentales viendront valider un modèle thermique par la méthode des éléments finis prédisant le transfert thermique en situation incendie. Puis, les résultats expérimentaux pourront être comparés avec les valeurs caractéristiques prédites par calculs selon la méthode de conception de la norme la norme CSA O86 « Règles de calcul des charpentes en bois » utilisée au Canada. Les résultats présentent la grande performance de feu de l'utilisation de vis auto-taraudeuses utilisées dans les assemblages en bois lamellé-collé sous longue durée d'exposition. Étant généralement de plus petit diamètre et plus élancées que les boulons et les goujons, les vis auto-taraudeuses limitent la conduction thermique le long de la section transversale et maintiennent la température le long de l'attache relativement faible. Principalement influencée par la réduction de la résistance du bois à des températures élevées, l'étude présente de nouveaux principes de conception pour prédire les profils de température le long de l'attache non protégée avec l'influence de la zone chauffée thermiquement du bois afin de déterminer la longueur de pénétration résiduelle qui fournira la résistance résultante. Lors du maintien d'une capacité structurale adéquate des fibres du bois, la capacité des vis auto-taraudeuses a été peu influencée par une augmentation de la durée d'exposition. La méthode de conception présentée ici permet de calculer la résistance résiduelle des vis auto-taraudeuses non protégées exposées au feu jusqu'à deux heures. / Buildings and building materials are required to provide sufficient fire-resistance to prevent collapse and safe means of evacuation to the occupants based on requirements set forth in the National Building Code of Canada. Annex B of the Canadian standard for wood engineering design provides a design methodology to calculate structural fire-resistance of large cross-section timber elements. However, it does not address failure modes, interactions between materials and reduced capacities under fire. This project addresses the connection design using self-tapping screw in mass timber construction in Canada. First, a test program combined with several researcher results were carried out to provide a good representation of the mechanical behavior of screw connections commonly used in mass timber construction. Secondly, the test results are used to validate a three-dimensional transient heat transfer model using the finite element method and to predict the heat transfer when exposed under fire conditions. Then, the test results were compared with the predicted characteristic and average withdrawal resistance values according to the design methodology in the Canadian standard for wood engineering design used in Canada. The results present the great fire performance of using self-tapping screws under long time exposure on connections in mass timber construction. The smaller heated behavior has limited thermal conduction along the cross-section area and maintained the temperature profiles relatively low along the self-tapping screw shanks for long fire exposures. Based on the heat affected area, the study presents new design principles to determine the residual length of penetration that would provide adequate load-capacity of the fastener under fire conditions. When maintaining adequate structural capacity of the surrounding wood fibers, the capacity of the self-tapping screw was not influenced with an increase of exposure duration. The design method presented herein allows calculating the residual capacity of unprotected STS exposed to fire up to 2-hours.
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