Дисертації з теми "Clot structure"
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1
Pan, Xiaoxi. "Fibrin clot structure alterations after particulate matter exposure." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/14310/.
Анотація:
Particulate matter (PM) as an important part of ambient air pollution has been associated with increased risks of cardiovascular diseases. Fibrin clot structure alteration is an emerging risk factor of many cardiovascular diseases, especially thrombosis. Therefore, the aim of this study was to investigate whether and how air particulate matter affects fibrin clot structure and endothelial cell behaviour. Turbidity assay, turbidity lysis assay and laser scanning confocal microscopy were used to analyse clots formed from normal pooled plasma or purified fibrinogen, in the presence of varying concentrations of PM. It was found that clots formed from plasma with higher concentrations of particles led to prolonged lysis time compared to control. No differences were seen for clots formed from fibrinogen. In a study of clots formed from plasma samples collected as part of a previous study on the effects of air pollution on deep vein thrombosis (DVT), alterations were observed in clots formed from plasma of DVT patients exposed to high levels of PM compared to those exposed to low levels, but the same differences were not observed in clots formed from plasma of control subjects. To investigate the potential role of venous endothelial cells in moderating clot structure following exposure to PM, human umbilical vein endothelial cells (HUVEC) were treated with PM for 24 hours and clots subsequently formed on the cells. Clots formed from plasma on the treated cells were altered compared to controls. RT-PCR and ELISA results showed increased gene expression of tissue factor (TF), protein expression of von Willebrand Factor (VWF) and plasminogen activation inhibitor-1 (PAI-1) and decreased thrombomodulin mRNA expression which were consistent with changes observed in clot structure. Engineered SiO2 nanoparticles caused denser clot structure in clots formed from normal pooled plasma. The gene expression of thrombomodulin was inhibited by SiO2 nanoparticles, but there were no significant difference in the TF mRNA expression between control and treated cells. Silica NPs caused increased concentrations of VWF, but not PAI-1 produced by endothelial cells. The results presented here show that PM can induce changes to clot structure and function, and that changes in gene expression induced in endothelial cells may be a mechanism by which a prothrombotic state is induced in response to PM exposure. Furthermore, some, but not all, similar changes were observed in clots and cells exposed to SiO2 nanoparticles, raising the possibility that such engineered nanoparticles may also have the potential to contribute to cardiovascular toxicity.
2
Alzahrani, Saad Hassan S. "Cardiometabolic risk factors, clot structure and the effects of therapies in individuals with diabetes." Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540551.
3
Jalal, Mohammed Mansour. "Statins exert antithrombotic action on platelet function and modulate clot formation structure and stability." Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=235575.
Анотація:
Statins are 3-hydroxy, 3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, which block the cholesterol biosynthetic pathway to lower total serum levels and LDL-cholesterol. The cholesterol pathway also provides a supply of isoprenoids (farnesyl and geranylgeranyl) for the prenylation of signaling molecules, which include the families of Ras and Rho small GTPases. Prenyl groups provide a membrane anchor that is essential for the correct membrane localisation and function of these proteins. Statins deplete cells of lipid geranylgeranyl diphosphate (GGPP) thereby inhibiting progression of the mevalonate pathway and prenylation of proteins. Two such proteins are Rab27b and Rap1, small GTPase proteins that are involved in the secretion of platelet granule and integrin activation. We hypothesise that statins can impair prenylation of Rab27b and Rap1a in platelets and thereby attenuate platelet function. The specific aims of the project were to analyse the impact of statins on the prenylation status of Rab27b and Rap1a in platelets. As Rab27b and Rap1a are known to be involved in secretion of platelet granules a secondary aim was to analyse the downstream effects of statins on this process following activation. Finally, we assessed the impact of treatment of platelets with statins on thrombus formation, stability and resistance to fibrinolysis. Platelets incubated with statins overnight were separated into cytosolic (aqueous) and membrane (detergent) components and visualised by Western blot. An accumulation of Rab27b and Rap1a was observed in the cytosolic compartments of statins treated platelets compared to untreated platelets, thus indicating indirect evidence that statins attenuate prenylation of Rab27b and Rap1a in platelets. The most effective statin in attenuating prenylation of Rab27b and Rap1a was atorvastatin (ATV). The inhibitory effect of statins on prenylation was recovered by GGPP, indicating that the mechanism of inhibition involved the mevalonate pathway. Release of ADP from platelet dense granules was significantly impeded following overnight treatment with ATV. In line with the inhibition of prenylation of Rab27b and Rap1a by ATV, addition of GGPP rescued the release of ADP from platelet dense granules. This suggests that attenuation of dense granules release by ATV occurs via interference in the mevalonate pathway and the inhibition of Rab27b prenylation. Furthermore, ATV significantly attenuates α-granules release in thrombin stimulated platelets, which was visualised as impaired accumulation of endogenous P-selectin, PAI-1 and fibrinogen on the activated membrane. Changes in the activation of α₁₁bβ₃ integrin on the stimulated platelet surface, observed as defective binding of exogenous fibrinogen and PAC-1, were also evident following treatment of platelets with ATV. In addition, ATV treatment of platelets reduced binding of CD41a, indicating that the copy number and activation of α₁₁bβ₃ integrin on stimulated platelets was significantly reduced. Statins were also found to significantly inhibit thrombin-induced platelet aggregation following incubation of platelets overnight with therapeutic concentrations of statins. Surprisingly GGPP did not rescue platelet aggregation indicating that different mechanisms are involved in inhibition of platelet responses by statins. Incubation of whole blood with ATV overnight significantly altered several haemostatic parameters. Using thromboelastography we demonstrated a delay in the coagulation time and clot formation time. Maximum clot firmness was also significantly reduced in the presence of statins compared to the control. The effect on clot firmness generally arises from platelet dysfunction and/or a change in fibrinogen concentration and function; the latter was ruled out using a Fibtem test, which shows no difference between treated and untreated whole blood. Similarly, formation of platelet-rich plasma clots was significantly delayed following pre-treatment with ATV overnight. These clots also exhibited lower maximal absorbances, which could represent differences in the fibrin network structure. In line with the reduction in fibrinogen binding defective clot retraction was also observed in platelet-rich plasma pre-treated with ATV overnight. Similar clot retraction results were observed with tirofiban and CytoD, suggesting that the inhibitory effect of ATV may involve modulation of α₁₁bβ₃ integrin activation. Platelet-rich plasma clots formed post-treatment with statins were visualised by confocal microscopy and revealed significant alterations in clot structure; observed as thinner fibrin fibres and fewer platelet aggregates. Additionally, we demonstrated that statins modulate clot stability and shorten time to lysis. Clots formed from platelet rich plasma that was subjected to incubation with ATV overnight revealed faster lysis by tPA compared to the absence of statin. These findings are also in agreement with the lysis of Chandler model thrombi formed from overnight incubated whole blood with ATV, which demonstrated faster lysis rate mediated by tPA. Furthermore, statins were shown to change the clot thrombodynamics as assessed by HemaCore analyser, which shows that stains implicate both clot growth in response to TF-coated comb and spontaneous clot lysis by tPA. In conclusion, statins directly inhibit Rab27b and Rap1a prenylation in platelets and down-regulated dense granules release. Inhibition of Rab27b and Rap1a prenylation, and dense granules release was recovered by GGPP, indicating that these effects are mediated through the mevalonate pathway. Impairment of platelet aggregation by statins resulted via multiple mechanisms as GGPP did not recovered the inhibition of aggregation by ATV. Statins also modulate fibrinogen binding, α-granules release, clot retraction and clot formation and stability in vitro. Together these results suggest that statins may directly attenuate the platelet response in vivo. The pleotropic effect of statins on platelets may contribute to the protective function of these class of drugs in cardiovascular diseases.
4
Sauls, Derrick Lamonte. "A RABBIT MODEL OF HYPERHOMOCYSTEINEMIA: THE EFFECT OF HOMOCYSTEINE ON BLOOD CLOT STRUCTURE AND STABILITY." NCSU, 2003. http://www.lib.ncsu.edu/theses/available/etd-03252003-183839/.
Анотація:
Hyperhomocysteinemia(Hhcys) is a condition that several epidemiological studies have shown to be associated with atherosclerosis and thrombosis, due to an elevation of plasma homocysteine levels. Plasma homocysteine(hcys) levels have a tendency to rise with age and changes in nutrition. Hcys can affect coagulation proteins, altering the formation of blood clots. The mechanism(s) by which hcys might cause modification of coagulation proteins "in vivo" is not understood. My hypothesis is that adult and juvenile animals could respond differently to chronic administration of hcys, and elevated plasma levels of hcys might lead to modification of fibrinogen "in vivo". Methodology: Six months old (juvenile, n=6) and 12 month old (adult, n=6) New Zealand White rabbits were divided into control (n=3) and homocysteine-treated (hcys-trt) (n=3) groups and injected for seven weeks; afterwards, they were given a bolus injection of hcys. Blood was drawn to evaluate plasma clearance of hcys. At the end, rabbits were exsanguinated by cardiac puncture and blood was collected for coagulation studies. Results: Juvenile hcys-trt rabbits adapted to chronic administration of hcys, however, adult hcys-trt rabbits developed Hhcys. Adult hcys-trt rabbits had higher levels of malonaldehyde in liver tissue, which is evidence of oxidative stress. Juvenile hcys-trt rabbits had similar malonaldehyde levels as juvenile control rabbits. Plasma elimination of hcys was impaired in adult hcys-trt rabbits. Adult hcys-trt rabbits had increased fibrinogen levels, longer reptilase times, and shorter thrombin clotting times versus adult control rabbits. Clots formed from purified fibrinogen obtained from hcys-trt rabbits lysed slower than comparable clots formed from control rabbits purified fibrinogen. Some congenital dysfibrinogenemias have clots that are abnormally resistant to fibrinolysis due to alterations in fibrinogen structure, and lead to recurrent thrombosis. Clotting results for adult hcys-trt rabbits suggest that hyperhomocysteinemia leads to a similar acquired dysfibrinogenmia. Therefore, the prolonged reptilase times and formation of clots that are abnormally resistant to fibrinolysis could directly contribute to increased risk of thrombosis in hyperhomocysteinemia.
5
Wang, Xin. "Manipulating fibrin structure of hematomas enhances large bone defects healing." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/100030/1/Xin_Wang_Thesis.pdf.
Анотація:
Hematomas (blood clots) are known important factors in early stages of fracture repair. This project characterized the differences in hematomas between normal healing and delayed healing in bone defects. It was found that manipulation of the hematoma structure can significantly improve bone healing and result in significantly increased bone formation. This project will lead to the development of innovative treatment of large bone defects, fractures, and bone non-union.
6
Garcia, gonzalez Xabel. "Influence de la nature du fibrinogène sur la structure et la mécanique du caillot de fibrine." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI076/document.
Анотація:
La formation du caillot de fibrine, processus clé de la coagulation sanguine, implique la polymérisation des monomères de fibrine en un réseau de fibres. Ce réseau contrôle les propriétés mécaniques du caillot et constitue le squelette sur lequel se base la cicatrisation. Si l’influence des conditions de réaction (pH, concentration, …) est bien connue, le rôle de la composition du fibrinogène sur la structure de la fibrine est inexploré. Cet aspect pourrait être important pour les pathologies cardiovasculaires qui présentent toutes une structure de fibrine anormale.Nous avons étudié la relation entre la composition de plusieurs fibrinogènes et les propriétés structurelles nano- et micro-métriques ainsi que la mécanique des caillots de fibrine. La composition en protéines co-purifiées de ces fibrinogènes a peu d’influence, alors que le profil de polydispersité contrôle la structure multi-échelle de la fibrine. Des mesures de diffusion des rayons x, de spectrophotométrie multi-longueur d’ondes et de microscopie confocale ont mis en évidence que les fibres provenant des fibrinogènes monodisperses sont quasi-cristallines, droites et rigides. Les fibres provenant de fibrinogènes polydisperses sont, elles, beaucoup moins organisées, courbées, avec un module de rigidité faible. Enfin, les propriétés mécaniques de la fibrine ont montré que la réponse des caillots aux déformations, aussi que les scenarios de rupture, sont directement liés à sa structure et donc significativement dépendants du profil de polydispersité des fibrinogènes. Ces résultats ouvrent de nouvelles perspectives dans plusieurs domaines, que ce soit pour l’utilisation optimale des fibrinogènes pour les dysfibrinogénémies et hémorragies, mais également pour la reconstruction tissulaire, ainsi que la compréhension du lien entre la structure anormale des caillots et les maladies cardiovasculairesFibrin clot formation is one of the major processes leading to blood clotting. It involves the polymerization of fibrin monomers into a network of fibrin fibres. This network controls the mechanical properties of the clot and serves as a skeleton for wound healing. Environmental factors (pH, concentration, …) have been proved to influence polymerization, however the role of fibrinogen composition on the structure of fibrin remains unexplored. This aspect might be important for the case of cardiovascular pathologies, which present abnormal fibrin structures.We have determined the relation between different sources of fibrinogen with the nano- and micro-metric structural and mechanical properties of fibrin clots. The composition in co-purified proteins of the fibrinogens has no significant importance, however the polydispersity profile controls the multiscale properties of fibrin. Indeed, x-ray scattering, multi-wavelength spectrophotometry and confocal microscopy measurements have proved that fibres from monodisperse fibrinogens are quasi-crystalline, straight and rigid. Fibres from polydisperse fibrinogens are less organised, curbed and less rigid. Finally, the mechanical properties of fibrin showed that the response of clots to deformation, as well as the scenarios of rupture are closely related to the structure, and consequently related to the profiles of polydispersity. This opens outstanding perspectives in many fields such the optimisation of fibrinogen’s use on dysfibrinogenemias or haemorrhages, tissue regeneration or the understanding between the abnormal structure of clots and cardiovascular diseases
7
Lim, Bernard Boon Chye. "Effects of coding polymorphisms of the coagulation factor XIII and fibrinogen genes on fibrin clot structure-function." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424056.
8
Lau, Yee Cheng. "The prothrombotic state in atrial fibrillation : observations on fibrin clot structure and the relationship to renal dysfunction." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7163/.
Анотація:
Atrial fibrillation (AF) is the most common arrhythmia and is closely associated with chronic kidney disease. The mainstay pharmacological agent to prevent AF-related stroke and thromboembolism is the use of oral anticoagulants, but may result in an increased risk of haemorrhage. Therefore, this MD research thesis is a comprehensive study of the changes in thrombogenesis and fibrin clot structure related to AF and CKD, as well as the potential impact of exposure to different classes of oral anticoagulant.
9
Dassi, Carhel. "La fibrinographie : une méthode multi-longueurs d’ondes pour la détermination de la structure du caillot en plasma." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAS028.
Анотація:
Le rôle physiologique du caillot est d’éviter un épanchement excessif de sang en présence d’une brèche vasculaire. Une fois cette fonction remplie, il doit pouvoir être facilement détruit, afin qu’il ne passe pas dans le système veineux et ne gêne la circulation sanguine. La formation d’un caillot de fibrine et sa lyse, processus clés de l’hémostase, impliquent à la fois la polymérisation des monomères de fibrinogène en un réseau de fibres de fibrine, et la résorption du réseau de fibres de fibrine constitué. Bien que ce réseau contrôle l’ensemble des propriétés physiques et mécaniques du caillot, sa structure aux échelles inférieures au micron est très mal caractérisée. Le principal verrou à la caractérisation physique du caillot en environnement clinique est l’absence de méthode de mesure quantitative, fiable, sensible et reproductible. Il est donc nécessaire de produire une méthode de mesure adéquate, couplée à un système de mesure sensible. Nous avons démontré dans ce travail, grâce à notre méthode utilisant plusieurs longueurs d’onde, que l’analyse du spectre de lumière visible transmis à travers un caillot permet de déterminer simultanément, quantitativement et en conditions quasi-physiologiques, plusieurs paramètres essentiels de structure du caillot de fibrine, à savoir le nombre de protofibrilles par fibre de fibrine, le rayon et la densité de ces fibres, ainsi que les temps de formation et de lyse du caillot. Cette technique a été validée via les résultats avec des CV inférieurs dans l’ensemble à 6% sous plusieurs conditions de tests et différents profils plasmatiques : normaux, hypo/hyper coagulants et hypo/hyper fibrinolytiques, attestant de la robustesse et de la fiabilité de la technique de mesure aussi bien pour le suivi de la coagulation que de la lyse. Cette méthode de spectrophotométrie a pu être implantée sur un automate modifié à des fins de diagnostic et à vocation hospitalière pour des plasmas de patients présentant des troubles de l’hémostase. Les informations cliniques et intérêts attendus de ce nouveau test, concernent à la fois la qualité du réseau de fibrine, sa lyse accélérée ou sa résistance à la fibrinolyse ainsi que la résultante de la balance coagulo-lytiqueThe physiological role of the clot is to avoid excessive bleeding in the presence of a vascular breach. Once this function is filled, the clot must be able to be easily destroyed, so that it is not transported in the venous system and does not hamper blood circulation. The formation of a fibrin clot and its lysis are key processes of hemostasis, implying simultaneously the polymerization of the fibrinogen monomers in a fibrin fibers network, and the destruction of this constituted network.Although this network controls the physical and mechanical properties of the clot, its structure at scales smaller than the micron is poorly characterized. The main problem in the physical characterization of clot in clinical settings is the current absence of a quantitative, sensitive and reproducible measurement method.We demonstrated in this work, thanks to our method using several wavelengths, that the analysis of the visible spectra of light transmitted through a clot allows to determine simultaneously, quantitatively and in quasi-physiological conditions, several essential parameters of structure of the fibrin clot, namely the number of protofibrils per fibrin fibers, the radius and the density of fibers, and various times of clotting and lysis of the clot. This method was validated by the results with CV inferior to 6 % under all test conditions and various plasmatic profiles: normal, hypo / hyper coagulant and hypo / hyper fibrinolytic. This demonstrates the robustness and reliability of the measurement method when measuring both clotting and clot lysis.This spectrophotometric method was implemented on a modified automaton dedicated to diagnosis of patients presenting hemostatic disorders. The clinical information and the interests expected from this new test concern at the same time the quality of the fibrin network, its accelerated lysis or its resistance to fibrinolysis, and the resultant of the coagulo-lytic balance
10
Seyve, Landry. "Analyse de la structure du caillot en conditions physiologiques et pathologiques." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAS027.
Анотація:
Physiologiquement, le caillot sanguin a pour fonction l’arrêt d’un saignement consécutif à une brèche vasculaire. Dans un premier temps, ce sont les plaquettes sanguines qui stoppent l’épanchement sanguin, rapidement soutenues par la formation d’un réseau de fibres de fibrine qui consolide et confère au caillot les propriétés nécessaires pour résister à la pression sanguine et à la fibrinolyse. Le fibrinogène est l’élément de base du réseau de fibrine. Lors d’une brèche vasculaire, la libération de facteur tissulaire entraine le déclenchement de la cascade de coagulation qui aboutit à la transformation du fibrinogène en monomères de fibrine par l’action de la thrombine. Ceux-ci s’agrègent longitudinalement pour former des protofibrilles, puis latéralement pour former un réseau de fibres de fibrine.A ce jour, de nombreuses étapes de formation du caillot ont été décrites en détail dans la littérature, cependant les mécanismes et les forces motrices de l’agrégation latérale des protofibrilles sont encore mal compris.Lors de ce travail, nous avons étudié différents profils de coagulation : de l’hypo-coagulant à l’hypercoagulant, en passant par le profil normal et en utilisant un panel varié de techniques : génération de thrombine, génération de plasmine, Fibrinographie, Fibrinographie en mode « fibrinolyse », microscopie confocale, thromboélastométrie et diffraction des rayons X aux petits angles.Nous avons mis en évidence la relation entre la quantité de thrombine présente lors de la formation d’un caillot et la structure de celui-ci. En effet, Plus il y a de thrombine, plus le nombre de protofibrilles par fibre est faible et plus le nombre de fibres est important. De plus, nous avons corrélé le temps d’initiation de l’agrégation latérale des fibres en Fibrinographie avec l’initiation de la génération de plasmine. Nous avons ainsi mis en évidence la production d’une structure du caillot de fibrine anormale en présence de dabigatran, grâce à l’utilisation combinée de la microscopie confocale et de la Fibrinographie.Cette analyse multimodale de la structure du caillot dans différentes conditions apporte des informations supplémentaires à la communauté scientifique, pour permettre de mieux comprendre les mécanismes de formation des caillots de fibrinePhysiologically, the blood function of the clot is to stop bleeding following a vascular breach. Initially, platelets stop blood flow, quickly supported by the formation of a fibrin fibers network that strengthens and gives properties to resist the blood pressure and fibrinolysis. Fibrinogen is the basic element of the fibrin network. During a vascular breach, the release of tissue factor triggers the coagulation cascade that results in the conversion of fibrinogen to fibrin monomers by the action of thrombin. These aggregate longitudinally to form protofibrils, then laterally to form a network of fibrin fibers.To date, many stages of the clot formation have been described in detail in the literature, however the mechanisms and driving forces of the lateral aggregation of protofibrils are still poorly understood.During this work, we studied different coagulation profiles: from hypo-coagulant to hyper-coagulant, through the normal profile and using a varied range of techniques: thrombin generation, plasmin generation, Fibrinography, Fibrinography in "fibrinolysis" mode, confocal microscopy, thromboelastometry and X-ray diffraction at small angles.We have highlighted the relationship between the amount of thrombin present during clot formation and the clot structure. Indeed, the more thrombin there is, the lower the protofibrils number per fiber and the greater the number of fibers. In addition, we correlated the initiation time of lateral fibers aggregation in Fibrinography with the initiation of plasmin generation. We have thus demonstrated the production of an abnormal fibrin clot structure in the presence of dabigatran, thanks to the combined use of confocal microscopy and Fibrinography.This multimodal analysis of the clot structure under different conditions provides additional information to the scientific community to better understand the mechanisms of fibrin clot formation
11
Sefiane, Thibaud. "Vers une meilleure compréhension des mécanismes moléculaires régissant l'action des thérapies non-substitutives dans l'hémophilie A et comparaison avec le facteur VIII." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASQ004.
Анотація:
L'hémophilie A est une maladie hémorragique liée à un déficit en une protéine plasmatique de la coagulation : le FVIII. Le traitement standard a longtemps consisté en un remplacement du FVIII manquant par un FVIII exogène mais l'apparition d'inhibiteurs contre le FVIII rend les thérapies substitutives inefficaces chez 30 % des patients. Récemment l'anticorps bispécifique emicizumab anti-FIX/anti-FX mimant l'action cofacteur du FVIII est arrivé sur le marché. L'objectif de ma thèse a été d'étudier comment l'emicizumab se compare au FVIII au niveau de ses propriétés moléculaires et fonctionnelles.Nous avons d'abord analysé le cas d'un patient sous prophylaxie avec emicizumab. Suite à l'apparition d'une hémarthrose après 6 mois de traitement, des anticorps anti-emicizumab ont été identifiés, entraînant une diminution de la concentration plasmatique d'emicizumab sans affecter directement son activité. Une analyse approfondie a permis de révéler le premier cas de patient traité par emicizumab avec des anticorps provoquant une clairance accélérée de l'emicizumab.Dans une seconde partie, nous nous sommes intéressés à l'impact du FVIII/FVIII-Fc vs emicizumab sur la formation et la stabilisation du caillot ainsi que sur sa structure. Des études in vitro limitées par l'absence des composants cellulaires ont été rapportées menant àdes conclusions variables. Nous avons développé un modèle murin de saignement qui a permis de montrer que l'emicizumab altère la cinétique de formation du caillot, pouvant expliquer les saignements observés chez 5% chez des patients traités par emicizumab. L'analyse microscopique de la structure des caillots indique que le FVIII et le FVIII-Fc impactent de manière similaire la structure du caillot, tandis que l'emicizumab, avec son mode d'action unique, induit des différences morphologiques significatives.Enfin, nous nous sommes intéressés à l'utilisation des modèles de saignements murins dans la détermination de l'équivalence entre les thérapies non-substitutives (emicizumab et anti-TFPI) et le FVIII. En effet, la question centrale liée à l'utilisation de ces thérapies concerne la détermination d'une éventuelle équivalence avec le FVIII. Les données issues des tests d'activités in vitro ne permettant pas de répondre à la question, nous nous sommes proposés d'évaluer in vivo cette équivalence en utilisant un panel de modèles de saignements murins. Les résultats ont permis de déterminer des équivalences variables selon la sévérité du modèle et nous ont menés à proposer qu'une équivalence absolue était illusoire et qu'il serait plus réaliste de parler d'un intervalle d'équivalence en terme d'activité FVIIIHemophilia A is a bleeding disorder linked to a deficiency in plasma coagulation protein FVIII. For a long time, the standard treatment consisted in replacing the missing FVIII with exogenous FVIII, but the emergence of inhibitors against FVIII has made replacement therapies ineffective in 30% of patients. Recently, the bispecific anti-FIX/anti-FX antibody emicizumab, which mimics the cofactor action of FVIII, was approved. The aim of my thesis was to study how emicizumab compares with FVIII in terms of its molecular and functional properties.First, we analyzed the case of a patient undergoing prophylaxis with emicizumab. After 6 months of treatment, the patient developed hemarthrosis and anti-emicizumab antibodies were identified, leading to a decrease of emicizumab plasma concentration without directly affecting its activity. Further analysis revealed the first clinical case treated by emicizumab with antibodies causing accelerated clearance of emicizumab.In a second part, we investigated the impact of FVIII/FVIII-Fc vs emicizumab on clot formation, stabilization and structure. The previously reported in vitro studies were limited by the absence of cellular components, therefore leading to contradicting results.We developed a murine bleeding model which demonstrated that emicizumab alters the kinetics of clot formation, which could explain the bleeding observed in 5% of patients treated with emicizumab. Microscopic analysis of clot structure indicates that FVIII and FVIII-Fc have a similar impact on the clot structure, while emicizumab, with its unique mode of action, induces morphological differences.Finally, we investigated the potential use of murine bleeding models to determine equivalence between non-factor therapies (emicizumab and anti-TFPI) and FVIII. Indeed, the important question linked to the use of these therapies concerns the determination of possible equivalence with FVIII. As the data from in vitro activity tests did not answer this question, we proposed to assess this equivalence in vivo using a panel of murine bleeding models. The results showed that equivalence varied according to the severity of the model and led us to propose that absolute equivalence was unrealistic. Indeed, it would be more realistic to talk about an equivalence range in terms of FVIII activity
12
TAMAGNONE, GABRIELE. "Numerical modelling and design methods for CLT structures." Doctoral thesis, Università degli Studi di Trieste, 2019. http://hdl.handle.net/11368/2991040.
Анотація:
Dalla sua concezione a metà degli anni novanta, il legno lamellare a strati incrociati, anche noto come CLT o X-Lam, ha raggiunto grande popolarità tra i materiali da costruzione grazie alle numerose innate qualità, gli sforzi a livello mondiale per costruire strutture affidabili in zone a rischio sismico e la necessità di costruire un ambiente più eco-sostenibile.
Molti test sono stati fatti negli ultimi 15 anni, volti a comprendere meglio il comportamento delle connessioni in edifici in CLT, di parti strutturali o di intere strutture in CLT, in modo da fornire regole affidabili per i progettisti per progettare strutture in CLT sotto ogni condizione di carico.
Sulla base di questi test, molti sono stati i modelli numerici che sono stati suggeriti negli anni. Questi rappresentano uno strumento fondamentale per la progettazione di strutture in CLT quando insorgono specifiche problematiche ed un approccio analitico da solo non è sufficiente.
Nonostante i molti anni di sforzi, non esistono ancora affidabili metodologie di progetto nella quasi totalità dei codici a livello mondiale e ancora molte sono le incognite relative al comportamento delle strutture in CLT a molti livelli (connessioni, parti strutturali, strutture).
Questa tesi riassume tre anni di ricerche numeriche, le quali hanno affrontato diversi problemi relativi al comportamento di elementi strutturali e strutture in CLT sotto azioni dinamiche. Durante la prima parte di questo percorso l’attenzione è stata posta sulla continuazione di un precedente studio, portato avanti durante la tesi di laurea magistrale, il quale era incentrato sulla formulazione di un metodo semplificato per la costruzione di un dominio resistente sforzo normale-momento flettente per pannelli in CLT connessi alla base da connessioni tipo hold-down e angle bracket.
In mancanza di risultati di test di interesse, la concentrazione è stata rivolta ancora alla formulazione di metodi semplificati per la progettazione di elementi strutturali in CLT. È stato analizzato il problema delle connessioni pannello-pannello all’interno di una stessa parete. In particolare, è stata studiata la rigidezza di queste connessioni in relazione al comportamento ribaltante di pareti a due pannelli attraverso l’analisi di test a scala reale indipendenti e analisi numeriche agli elementi finiti. Una formula per il calcolo di queste connessioni è stata dapprima proposta e poi, dopo ulteriori analisi, rivista e corretta.
Per estendere l’analisi e considerare elementi strutturali più complessi, è stata investigata, a livello di analisi numerica, l’influenza del solaio e delle connessioni parete-solaio superiore sul comportamento ribaltante delle pareti, prendendo in considerazione configurazioni con e senza solaio, variando diversi parametri di modo da ottenere risultati statisticamente significativi.
Nell’estate del 2017 il candidato ha partecipato attivamente al NHERI TallWood Project, una ricerca statunitense intesa a testare strutture in CLT per fornire regole di progettazione per tali strutture nei futuri codici nazionali. Sponsorizzato dalla Colorado State University, nella persona del Prof. John W. van de Lindt, il candidato ha collaborato alla preparazione di un edificio con due orizzontamenti fuori terra testato sulla tavola vibrante della UCSD a San Diego (California)
Per valutare il più corretto valore di smorzamento per strutture in CLT sotto l’azione di eventi sismici di bassa intensità, sono stati riprodotti numericamente ed analizzati i test su tavola vibrante del progetto SOFIE a 0,15 g. Ulteriori considerazioni sono state fatte sul ruolo dell’attrito su questo tipo di strutture e sul problema delle analisi lineari per strutture in CLT (risposta non simmetrica di connessioni caricate in tensione-compressione).Since its conception in the mid 90’s, cross-laminated timber, known also as CLT or X-Lam, has achieved a great popularity as construction material thanks to its numerous intrinsic qualities, worldwide effort to build reliable structures in seismic-prone areas and necessity to build a more eco-friendly environment. Many tests have been carried out in the last 15 years, aimed to better understand the behavior of connections in CLT buildings, CLT assemblies and CLT structures in order to provide reliable rules for designers to design structures made of CLT in any loading condition. Based on these tests, many numerical models have been suggested through the years. They represent a fundamental tool for the design of CLT structures when specific design problems arise. Despite many years of efforts, reliable design rules are still missing in almost every code worldwide and many are still the unknown related to CLT structures behavior at many levels (connections, assemblies, structures). This thesis summarizes three years of numerical investigations, which have faced different problems related to the comprehension of CLT assemblies and structures behavior under dynamic loading conditions. The first part of this path focused on the continuation of a previous study made within the Master Degree thesis, which was the formulation of a simplified method to obtain an axial-load/bending moment limit domain for a CLT panel connected to the supporting surface through hold-down and angle bracket connections. Without test results of interest, the focus of the study returned to be the formulation of simple methods for CLT assemblies design. The problem of panel-to-panel connections was investigated. In particular, the stiffness of such connections related to the rocking behavior of 2-panel wall assemblies was studied through full-scale tests and FE numerical analyses. A formula for the design of these connections was firstly suggested and then, after further analyses, revised and corrected. In order to extend the analyses and consider more complex assemblies, the influence of diaphragm and wall-to-diaphragm connections stiffness on the rocking behavior of wall assemblies was numerically investigated, taking into account configuration with and without diaphragm, varying several parameters to obtain statistically significant results. In the summer of 2017 the candidate actively participated to the NHERI TallWood Project, an American research project intended to test CLT structures in order to provide design rules for these structures in the future US codes. Sponsored by the Colorado State University, in the person of Professor John W. van de Lindt, the candidate collaborated to the setup of a 2-story CLT building that was tested on the UCSD shaking table located in San Diego (California). In order to assess the most proper value of damping for CLT structures under low-intensity seismic events and to better investigate the potential of the component approach for the modelling of CLT structures, the 0,15 g shaking table tests of the 3-story building within the SOFIE Project were reproduced and analyzed. Further considerations on the role of friction for this type of structure have been made together with the problem of linear analyses for CLT structures (non-symmetric response for tension-compression loaded connections).
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Jeantroux, Myriam. "La structure du huis clos dans le théâtre de Samuel Beckett : un "art d'incarcération"." Besançon, 2004. http://www.theses.fr/2004BESA1027.
Анотація:
La scène beckettienne se donne à voir tantôt comme un petit espace clos, tantôt comme un vaste espace béant, ces deux propositions inverses étant les lectures complémentaires d'un même huis clos que les personnages semblent impuissants à quitter alors que rien ne les retient véritablement prisonniers. Notre étude de l'œuvre théâtrale de Beckett - qu'enrichissent douze manuscrits dramatiques inédits -, entend révéler l'existence et la cohérence d'une structure du huis clos sur laquelle se fonde à la fois l'espace matériel de la scène, l'ambivalence du personnage, et l'accomplissement esthétique de l'écriture beckettienne. Une topographie de ce(s) huis clos scénique(s) permet d'abord de démontrer le paradoxe d'une claustration qui neutralise les tensions théâtrales dans une scénographie géométrique de la réduction, de la fragmentation et de l'épuisement des possibilités spatiales et dramatiques. Le huis clos est alors envisagé comme un espace de l'intervalle où s'annule la dialectique de l'ici et de l'ailleurs. C'est dans cet impossible lieu que tente en vain de s'incarner le personnage, lui-même paralysé entre la présence intolérable et l'absence refusée, entre l'émergence du soi et le refus du moi, entre l'obligation de dire et l'impossibilité de se dire. La structure du huis clos apparaît finalement comme une mise en abyme de l'écriture beckettienne qui se fait et se défait elle-même entre le texte et la scène, entre l'anglais et le français, dans cette création paradoxale d'un espace replié sur son propre vide : le huis clos théâtral, figure exemplaire de cet "art d'incarcération" défini par Beckett, représente un véritable accomplissement esthétique de l'écritureBeckett's stage can be seen as a small closed space or as a large wide-opened space. Those two opposite readings prove to be two complementary facets of the same huis clos structure which Beckett's characters are unable to exit despite a lack of any form of entrapment. This study of Beckett's theatre - including twelve unpublished manuscripts - aims at showing that the physical space of the stage, the ambivalence of the characters and the aesthetic completion of Beckett's writing are all based on the very existence and coherence of a huis clos structure. A topography of the(se) stage huis clos shall first prove the paradox created by a confinement that encapsulates and neutralizes dramatic tensions by means of a geometrical stage strategy of reducing, fragmenting and exhausting of spatial and dramatic possibilities. Huis clos is then to be considered as a space of the "in-between" that invalidates the dialectics of the "here and there". Beckett's characters desperately try to take shape in that impossible space where they are frozen between constraining presence and seductive absence, between the coming out of the self and the rejection of the "I", between the compulsion to say anything and the impossibility to tell something. The huis clos structure appears finally as a mise en abyme of Beckett's writing which is constructed and deconstructed between the text and the stage, between the French and the English language, and within the paradoxical creation of a space hinged on its own vacuum. The dramatic huis clos, as it is considered as the embodiment of what Beckett coined the "art of incarceration", may thus represent the very aesthetic completion of Beckett's writing
14
Harmachova, Karolina. "Vibration performance of hybrid steel-CLT floors." Thesis, KTH, Byggnadsmaterial, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192475.
Анотація:
In the light of today’s effort to achieve sustainable future of the planet, timber as building material makes a comeback on the construction market. Since the requirements on the buildings and the internal comfort increase, there is a need for finding new solutions and products; one of them is cross-laminated timber (CLT), which has the potential to be used for high-rise buildings due to its mechanical properties. The aim of this work was to study the vibration performance of CLT floors as it is often the governing factor in design of CLT structures unlike for other common building materials. The orthotropic mechanical properties of CLT were determined by the shear analogy method and verified with a finite element (FE) model of a simply supported beam compared to hand calculations of shear forces, bending moments and deflections. The properties based on Timoshenko’s approach were evaluated as less precise regarding the deflection. The non-composite structural behaviour of a steel-CLT hybrid floor structure was predicted for FE dynamic analysis based on a comparison between modelling exercise and hand calculations. Two different methods, the Concrete Society (SC) and Steel Construction Institution (SCI) methods, both seemed to be applicable for determination of the response factor first since the mechanical properties are not used as input in the calculations. These two methods differ in certain aspects, and based on FE analysis of simply supported slab even the resulting response factor for the CLT differs significantly. Moreover, the hand calculation results were similar to those of the FE analysis for the CS method, but in less agreement for the SCI method. Nevertheless, it is not recommended to reject the latter method based on this study and further studies should be performed on real structures with response factor known from on-site measurements. A part of the first floor of Canary Wharf College was modelled and analysed, and previous measurements of the frequency and response factors enabled a validation of some assumptions. The SCI approach showed to be inadequate for this type of structure and therefore only the CS method was applied further. Analysis of the floor structures supported by walls demonstrated similar results from both the measurements and the dynamic analysis. However, if the floor slab was supported by beams, the response factor was significantly overestimated although on the conservative side. This difference suggests that the modelling of such conditions are not satisfactory. The CS method appears to assess correctly the magnitude of the response factor for CLT floors supported by walls but overestimates it in case of beam supports. The first finding shall be confirmed through analysis of other structures and a more extensive research should focus on the latter one to determine more exact behaviour of the model under different conditions.
15
Rousset, Jean-Luc. "Contribution expérimentale à l’étude de l'interaction sol-clou dans un massif renforce en cours de réalisation." Lyon, INSA, 1993. http://www.theses.fr/1993ISAL0021.
Анотація:
La présente étude expérimentale, contribue à une meilleure connaissance du comportement d'interaction sol-clou dans un massif de soutènement renforcé par des barres métalliques, et ce au cours des phases de réalisation par terrassements successifs. Un bref rappel précise les principaux modèles décrivant le comportement d'interaction sol-clou, ainsi que les connaissances expérimentales disponibles, L'essentiel de l'apport est constitué par deux campagnes expérimentales menées chacune avec un mode différent de simulation du terrassement. Les essais consistent à simuler en semi-grandeur la réalisation d'un soutènement cloué dans un sol parfaitement homogène et pulvérulent ; les efforts et déplacements apparents sont mesurés ainsi que les sollicitations des clous à l'intérieur du massif. Parallèlement, sont réalisées les essais de caractérisation géotechniques du sol par cisaillement linéaire et par mesures pressiométriques. Des essais d'arrachement complètent la connaissance de l'interaction de frottement sol-clou, L'ensemble des données ainsi recueillies sont comparées aux résultats fournis par les méthodes de calculs les plus répandues pour le clouage, Ceci nous amène à cerner les effets des diverses interactions sur le comportement global de l'ouvrage. L'incidence de déformation du sol au-delà de la zone clouée et l'influence de l'interaction sol-parement sur les sollicitations des clous sont finalement mises en évidenceThis experimental study, contributes to a better understanding of soil-nail interaction in reinforce structures, particularly during this construction phase ; The principal theoretical models describing the soil-nail interaction as well as the currently ava1iable literature on experimental methods and analysis are presented. The experimental work undertaken is constituted of two principal groups, one distinguished by the method used for simulating terracing. The experiments consist of using large scale laboratory models for simulating the construction of mail reinforced retaining structure, in a perfectly homogeneous and cohesion-less soil. The efforts and displacements of the structure as well as the tensile and flexural forces of the nails are measured. Geotechnical soil characterisation tests, mainly shear and pressuremeter, were carried out. Extraction tests were also carried out to complement the study of friction at the soil-nail interface, The acquired experimental data were compared ta that obtained from existing soil-nailing analytical models. This provided the basis of comprehending the different interaction effects on the global behaviour of structure ; we observed soil stein beyond the nail zone and the influence of soil-structure facing on the nail action
16
Smith, Josh E. "Mode I Fracture Toughness of Eight-Harness-Satin Carbon Cloth Weaves for Co-Cured and Post-Bonded Laminates." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1138.
Анотація:
Mode I interlaminar fracture of 3k 8-Harness-Satin Carbon cloth, with identical fill and weft yarns, pre-impregnated with Newport 307 resin was investigated through the DCB test (ASTM D5528). Crack propagations along both the fill and weft yarns were considered for both post-bonded (co-bonded) and co-cured laminates. A patent-pending delamination insertion method was compared to the standard Teflon film option to assess its applicability to mode I fracture testing. The Modified Beam Theory, Compliance Calibration method, and Modified Compliance Calibration method were used for comparative purposes for these investigations and to evaluate the validity of the proposed Equivalent Stiffness (EQS) method. Crack propagation, in all specimens, proceeded in a run-arrest manner for both delamination directions. Energy dissipation in the form of transverse yarn debonding, matrix deformation, and out of plane crack growth was witnessed for specimens with delaminations along weft yarns. A complete comparison between post-bonded and co-cured laminates was not achieved. The patent pending delamination insertion method was found to cause fewer instances of non-linear crack initiation behavior than the Teflon insert and, when non-linear behavior did occur, it was less prevalent. The EQS method was found to achieve fracture toughness values within 5% of the other three data reduction methods for 63% of the propagation values and achieved conservative values for over 33% of the propagations. Suggestions for future studies aimed at completing the comparisons above are provided in Chapter 5.
17
Cornet, Jean-François. "Etude cinetique et energetique d'un photobioreacteur. Etablissement d'un modele structure. Applications a un ecosysteme clos artificiel. Fre." Paris 11, 1992. http://www.theses.fr/1992PA112079.
Анотація:
La modelisation du comportement des microorganismes en photobioreacteur necessite la connaissance de phenomenes physiques et biologiques. La theorie des transferts radiatifs appliquee a un photobioreacteur permet d'obtenir des informations cinetiques et energetiques locales, et par la suite conduit a l'obtention des vitesses specifiques de consommation d'energie lumineuse par les microorganismes, ainsi qu'aux bilans enthalpique et entropique. L'ecriture des equations de conservation sur les differentes especes qui constituent le carbone inorganique dissous permet d'apprehender les modifications de comportement des microorganismes, lors de limitations par le transfert de co#2 ou par la source de carbone. L'utilisation de modeles structures biochimiquement conduit a ecrire les relations de conservation des differents transporteurs d'energie que sont l'atp et les cofacteurs. L'analyse du couplage entre la photosynthese, la production et l'utilisation de l'atp par le metabolisme est alors possible, en utilisant les relations de la thermodynamique lineaire des processus irreversibles. Cette approche permet de diminuer le nombre de parametres du modele, et conduit a la determination predictive des rendements de conversion des substrats en produits. L'ensemble de cette demarche a ete applique a la culture de la cyanobacterie spirulina platensis, dans une large gamme de conditions limitantes et pour differents types de photoreacteurs. Les resultats obtenus permettent d'envisager des applications au niveau de l'utilisation de ce microorganisme, dans le compartiment photosynthetique d'un ecosysteme clos artificiel
18
Toral, Vázquez Javier. "Identification et modélisation du comportement des structures composites assemblées par couplage." Toulouse, ISAE, 2009. http://www.theses.fr/2009ESAE0020.
Анотація:
L'optimisation des structures aéronautiques fabriquées en composite a mené EADS-IW à développer une technique d'assemblage par cloutage qui a pour objectif la fabrication à coût réduit de sous ensembles structuraux avec un fort niveau d'intégration. L'objectif de ce travail de thèse est d'étudier le comportement mécanique des assemblages cloutés et de proposer des modélisations associées. Dans le cadre d'une démarche multi-niveau, le comportement des liaisons clou/résine et clou stratifié a d'abord été étudié. Des campagnes expérimentales ont montré l'influence du diamètre du clou et de la profondeur d'enfoncement sur la tenue en arrachement ainsi que des similitudes entre le comportement du clou noyé dans de la résine et implanté dans le stratifié. Une modélisation capable d'estimer la tenue en arrachement d'un clou a été développée. Au niveau éprouvettes technologiques, des éprouvettes cloutées représentatives de structures aéronautiques de type « L » ou « T » ont été testés en sollicitations statiques montrant l'influence des paramètres de conception et les possibles avantages du cloutage. Finalement, des modélisations basées sur les études élémentaires ont permis de simuler le comportement de ces éprouvettes cloutées retrouvé en essai et notamment de prédire leur tenue sous sollicitations différentes validant ainsi la démarche multi-niveau.
19
Benoist, Franck André René. "Théorie des modèles des corps munis d' une dérivation de Hasse." Paris 7, 2005. https://tel.archives-ouvertes.fr/tel-00134889.
20
Blom, Henrik, and Johan Thored. "STABILA HÖGHUS I TRÄ : En analys av infästningars inverkan på accelerationer och utböjningar i ett 15-våningshus av trä." Thesis, Uppsala universitet, Byggteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296929.
Анотація:
In today’s society cities grow increasingly larger, not only on the ground but vertically as well. Utilizing height means taller buildings, which often are large steel- and concrete constructions. Why not construct tall buildings out of timber instead, a material by many believed to be far better from an environmental perspective than steel and concrete? The answer lies in the lack of knowledge regarding tall timber constructions and the stresses they need to withstand. The report was conducted at the construction consulting company Bjerking AB, Uppsala. The focus in this report was to examine accelerations and deformations as an effect of wind loads. The issue at hand was whether the connections between building elements affect the dynamic responses that occur. The chosen model was a 15 storey timber building whose walls and floors consisted mainly of cross laminated timber elements as the load bearing structure. As a large amount of the analyses were complex, the calculations were made in the computer program FEM-Design, which is a finite element program. After performing numerous calculations with different settings, a result emerged. Clear trends could be seen in the connections’ influence on accelerations and deformations. A stiffer connection makes the building more resistant to wind loads. This result has to be considered when constructing tall timber buildings to avoid problems with accelerations and deformations. However, merely adjusting the connections to meet requirements is not sufficient, other measures are also needed.I dagens samhälle växer sig städer allt större, inte bara till ytan utan även på höjden. För att kunna exploatera på höjden krävs högre hus vilka ofta byggs av stora stål- och betongkonstruktioner. Men varför byggs inte höghus istället av trä som av många anses vara mycket bättre ur bland annat miljösynpunkt? Svaret ligger i kunskapsbristen som finns kring hur höga trähus ska konstrueras för att klara de olika påfrestningarna det utsätts för. Arbetet genomfördes i samarbete med konsultföretaget Bjerking AB, Uppsala. En del av de problemen som finns har undersökts, nämligen accelerationer och deformationer som en effekt av vindlaster. Frågeställningen är huruvida infästningarna och dess inspänningsgrad mellan olika byggnadselement påverkar de statiska respektive dynamiska effekterna som uppstår. Den valda modellen, ett 15-våningar högt trähus, bestod i huvudsak av CLT-element, Cross Laminated Timber, i både väggar och bjälklag som hade till uppgift att föra ner lasterna till grunden. Då analysen är komplex utfördes en stor del av beräkningarna i FEM-Design som är ett avancerat beräkningsprogram. För att säkerställa indata samt komplettera kunskapen inom området utfördes en bakgrundsstudie. Efter utförta beräkningar på den bestämda modellen fastslogs resultatet. En tydlig trend kunde följas vid beaktning av accelerationer och deformationer vid olika värden på inspänningen mellan byggnadselementen. Styvare förband gör byggnaden mer beständig gentemot vindlaster. Ett resultat som måste beaktas för att kunna lösa en del av de problem som uppstår med höga hus i trä. Dock räcker det inte att enbart justera inspänningsgraden för att klara gällande krav och normer, utan ytterligare åtgärder krävs.
21
Mezeiro, Rafaela Maria Marques. "Construir em Madeira aplicabilidade de painéis CLT em habitação de média densidade em Portugal." Master's thesis, Universidade de Lisboa, Faculdade de Arquitetura, 2018. http://hdl.handle.net/10400.5/18088.
Анотація:
Dissertação de Mestrado Integrado em Arquitetura, com a especialização em Arquitetura apresentada na Faculdade de Arquitetura da Universidade de Lisboa para obtenção do grau de Mestre.Serve o presente trabalho para estudar a viabilidade da aplicação do sistema construtivo de painéis de madeira de Cross Laminated Timber - CLT, na construção ou recuperação de um edifício de habitação de média densidade em Portugal, na cidade de Lisboa. Os painéis de CLT são peças de madeira associadas a um processo construtivo inovador, com uma considerável capacidade de suportar cargas aplicadas, principalmente quando comparado com sistemas construtivos convencionais. Neste tipo de estruturas de CLT os elementos que a constituem comportam-se como painéis, em que o transporte das forças é feito bidireccionalmente. Considerou-se a elaboração deste trabalho atendendo às preocupações relacionadas com um tema da actualidade, nomeadamente as alterações climáticas. Ao nível da arquitectura, uma das formas de reduzir o impacto ambiental que a construção provoca é por exemplo através da utilização da madeira, que por sua vez tem a capacidade de armazenar dióxido de carbono, um dos principais gases emitidos para a atmosfera com efeito de estufa. Ao potenciar o uso da madeira, está-se por uma lado a dinamizar o sector madeireiro, mas também por outro lado a contribuir para a diminuição da pegada ecológica. Na realidade, com o aumento da utilização da madeira poder-se-á eventualmente, verificar-se uma maior necessidade do aumento da fileira, significando portanto que quantas mais árvores forem plantadas maior a quantidade de CO2 poderá ser retirada da atmosfera, desta forma também poderá surgir a necessidade de criar diferentes políticas de gestão e manutenção florestal com esta utilização em vista. Atendendo às propriedades físicas e mecânicas da madeira considerou-se importante abordar o tema da pré-fabricação de peças de madeira. Por ser um material dúctil, a madeira permite a normalização de vários tipos de produtos que por sua vez podem ser aplicados na construção de casas modulares, em que um dos principais objectivos deste tipo de construção está relacionado com a regularização das dimensões da construção de modo a estabelecer um módulo padrão como unidade de medida de referência, optimizando-se o processo de pré-fabricação e montagem do edifício no local. Por outro lado este é um tipo de construção que obedece a medidas passivas, que por sua vez pressupõe poupanças, ou até mesmo reduções significativas do consumo de energia do próprio edifício.
ABSTRACT: The present work aims to study applicability of the use of the Cross Laminated Timber – CLT construction system for new construction and rehabilitation of medium density housing in Portugal, in the city of Lisbon. The CLT panels are pieces of wood associated with an innovative construction process, with a considerable loading capacity, especially when compared with traditional constructive systems. In this type of CLT structures the elements consist of panels, in which the force transport is made bidirectionally. The elaboration of this work was considered taking into account the concerns related to a current theme, namely climate change. In architecture one of the ways to reduce the environmental impact that the construction causes is for example through the use of wood, since this material has the capacity to store carbon dioxide, a green house effect gas. By enhancing the use of wood, on the one hand, the timber industry could become more dynamic while also contributing to the reduction of green house effect. In fact, with increasing use of wood there will also be a greater need to plant trees, impling that the more trees that are planted the more CO2 that is withdrawn from the atmosphere, this could also create the need to create a different forest management and maintenance policies. Considering the physical and mechanical properties of wood, it was considered important to address the pre-fabrication of wood pieces. Because it is a ductile material, wood allows the standardization of several types of products which in turn can be applied in the construction of modular houses, in which one of the main objectives of this type of construction is related to the regularization of the dimensions of the construction with the purpose to establish a standard module as a reference unit of measurement, optimizing the pre-fabrication and assembly process of the building on site. On the other hand this is a type of construction that obeys passive requirements, which in turn supposes savings, or even significant reductions in the energy consumption of the building itself.
N/A
22
IZZI, MATTEO. "Mechanical characterization of connections in seismic resistant Cross-Laminated Timber structures." Doctoral thesis, Università degli Studi di Trieste, 2017. http://hdl.handle.net/11368/2908192.
Анотація:
Cross-Laminated Timber (CLT) structures are assembled with massive timber panels that are fastened together and to the horizontal elements (the foundations and the intermediate floors) with step joints and mechanical connections. Due to the high in-plane stiffness of CLT, the seismic behaviour of those structures markedly depends upon the connections used.
The mechanical behaviour of lateral load-resisting systems made with CLT panels and typical connection systems was the focus of a large body of research, especially in Europe and North America. Furthermore, full-scale shaking table tests were carried out on several multi-storey buildings, demonstrating a significant ductility and energy dissipation under seismic loading.
In contrast with the significant findings associated to those research projects, specific calculation methods have not yet been included either in Eurocode 5 (static design) or in Eurocode 8 (seismic design). Nowadays, the design is done using simplified calculation methods that neglect the connections stiffness and introduce some simplifications on their mechanical behaviour.
The mechanical characterization of typical connection systems for CLT structures (e.g. with angle brackets and hold-downs, nailed and bolted to the wall and floor panels) is an expensive and time-consuming process, since requires the execution of a large number of tests. Therefore, to limit the need of experimental testing to a minimum, significant effort should be devoted to develop advanced numerical models capable to predict their load-displacement response and failure mechanisms.
In the scope of this thesis, an extensive experimental programme was carried out on nailed steel-to-timber joints in CLT. The experimental results were used as input to assess the reliability of currently available calculation methods and to develop capacity-based design principles for nailed steel-to-timber joints in CLT (i.e. the overstrength factor and the strength degradation factor). In addition, analytical methods and numerical models capable to predict the mechanical properties and energy dissipation at different building levels (single fastener joint, connection, and wall system) were developed. Experimental results obtained during previous research projects served also for calibration of non-linear analyses, which were used to extend the test results to different configurations of technical interest. Outcomes of the parametric studies provided better understanding of the seismic behaviour and energy dissipation of typical connection systems for CLT buildings.
It was concluded that the numerical models presented within this thesis are a sound basis to investigate the seismic behaviour of CLT buildings. However, future research is required to further verify and improve these predictive models.
23
El, Amrani Bouchta. "Analyse structurale de nouveaux conducteurs organiques : influence de la composition (TMTTF)₂ (SbF₆)₁-ₓ(AsF₆)ₓ ou de la température (DMtTSF)₂-ClO₄". Bordeaux 1, 1986. http://www.theses.fr/1986BOR10601.
Анотація:
CARACTERISATION DES SOLUTIONS SOLIDES (TMTTF)₂ (SbF₆)₁-ₓ(AsF₆)ₓ PAR ANALYSE DES STRUCTURES ET A PARTIR DE LA NOTION DE TENSEUR DE DEFORMATION COMPOSITIONNELLE. LA MISE AU POINT D'UNE CHAMBRE DE DIFFRACTION DE LAUEE, FONCTIONNANT A TRES BASSE TEMPERATURE PERMET LA MISE EN EVIDENCE D'UN CHANGEMENT STRUCTURAL POUR LE SEL (DMTTSF)₂ CLO₄ DONT LA DESCRIPTION FAIT INTERVENIR SUR UNE GAMME REDUITE DE TEMPERATURE UNE PHASE PROBABLEMENT CHAOTIQUE
24
SANTONI, Andrea. "Sound Radiation and Sound Transmission in Building Structures: Numerical Modelling and Experimental Validation." Doctoral thesis, Università degli studi di Ferrara, 2017. http://hdl.handle.net/11392/2488167.
Анотація:
The radiation efficiency is an important acoustic descriptor, frequency dependent, that characterises the capability of a vibrating structure to radiate sound, and it is required as input data in many prediction models. Several analytical or approximated formulations have been proposed, by different authors, to evaluate the radiation efficiency of isotropic elements, as an alternative to numerical method. However, orthotropic structures have not been investigated as thoroughly. In this dissertation different models specifically developed to evaluate the radiation efficiency of orthotropic building structures, such as cross-laminated timber (CLT) plates, are presented.
Even though CLT panels' dynamics is sometimes investigated by using high order theories, like in structural analysis for example, in the vibro-acoustic investigations presented in this dissertation, they have been treated as thin orthotropic plates, under the assumption of small displacements.
The nature of the external excitation strongly influences the radiation behaviour, therefore either a mechanical force or an incident sound field have been considered acting on the plate surface.
A non-destructive experimental procedure, based on wave analysis, has been developed, in order to evaluate the direction dependent dynamic stiffness properties of orthotropic structures, obtaining reliable input data. The prediction models for orthotropic panels are finally validated with the experimental radiation efficiency evaluated for a CLT plate.
A standard procedure to experimentally determine the radiation efficiency of a structure is not currently available. Since this acoustic descriptor is not directly measurable, it has to be evaluated form other quantities, such as the total radiated sound power, and the mean square velocity of the vibrating surface. Therefore different methods to experimentally determine these quantities have been compared, highlighting advantages, limitations and their influence on the radiation efficiency.
Acoustically excited building elements are usually analysed in terms of sound transmission loss. It is computed from the transmission coefficient, defined as the ratio of the sound power incident on the excited surface, to the sound power transmitted through the partition and radiated in the receiving side. Sound transmission through different materials can be modelled by means of the transfer matrix method. The transmission loss of a CLT panel has been evaluated modelling the structure as an equivalent orthotropic thin plate. The results are validated with experimental data.
Further, a general model to predict sound transmission through multilayer elements considering the presence of mechanical connections has been developed within the transfer matrix framework. The model, based on the decoupled approach, takes into account airborne and structure-borne transmission paths as independent additive contributions. The model can be applied to layers of different nature: elastic solid, orthotropic thin plate, fluid, and poroelastic. The different radiation mechanisms associated to excitations of different nature play a key role in this approach.
A homogenisation technique, specifically developed for masonry brick wall but generally valid for any kind of wall, has been proposed to obtain the equivalent elastic properties of the partition, that one has to know in order to implement the transfer matrix method. The elastic properties of an equivalent homogeneous element are derived by means of a numerical procedure, based on a minimisation algorithm, as a function of the measured transmission loss.
The decoupled model is finally validated with the experimental transmission loss measured on an External Thermal Insulation Composite System (ETICS), constituted by a masonry wall clad with high-density mineral wool slabs. Moreover, its applicability to lightweight structures, such as double-wall systems, is verified.L'efficienza di radiazione è un importante descrittore, dipendente dalla frequenza, necessario come dato di input nella maggior parte dei modelli di calcolo; questo parametro caratterizza la capacità di una struttura di convertire l'energia vibrazionale in energia sonora nel fluido circostante. Diversi autori hanno presentato formulazioni analitiche o approssimate per valutare l'efficienza di radiazione, di strutture omogenee isotrope, alternative all’utilizzo di metodi numerici. Tuttavia, le strutture ortotrope non sono state studiate così approfonditamente. In questa dissertazione sono presentati due diversi modelli di calcolo, appositamente sviluppati per determinare l'efficienza di radiazione di strutture edilizie ortotrope, come i pannelli in legno cross-laminato (CLT). I meccanismi di radiazione sonora da parte di una struttura vibrante sono fortemente influenzati dalla natura della forzante che induce il campo vibrazionale. Pertanto, sono stati considerati sia l'azione di una forzante meccanica agente sul pannello, sia un campo acustico incidente. Utilizzare dei dati di input affidabili per l'implementazione dei modelli è fondamentale per ottenere dei risultati accurati. Inoltre è stata sviluppata una procedura sperimentale non distruttiva per determinare la rigidezza flessionale dinamica di una piastra ortotropa, in funzione della direzione di propagazione dell'onda vibrazionale, ottenendo così dati di input affidabili necessari a una corretta modellazione. I metodi previsionali per una piastra ortotropa sono stati validati attraverso i dati ottenuti da misure sperimentali su pannelli in CLT. Al momento non esiste una procedura standardizzata per la determinazione sperimentale dell'efficienza di radiazione. Inoltre, questo descrittore acustico non è direttamente misurabile, ma deve essere determinato da altre grandezze: la potenza sonora totale irradiata e la velocità quadratica media di vibrazione del pannello. Pertanto è stata investigata la determinazione di queste grandezze secondo diversi approcci, evidenziandone vantaggi, limitazioni e come influenzano l'efficienza di radiazione. Le strutture eccitate da un campo acustico incidente sono generalmente analizzate in termini di isolamento acustico, invece che radiazione sonora. L'isolamento acustico viene calcolato in funzione del coefficiente di trasmissione, definito come il rapporto tra la potenza sonora incidente sulla superficie eccitata e la potenza sonora irradiata nell'ambiente ricevente. La trasmissione sonora attraverso diversi materiali può essere modellata con il metodo delle matrici di trasferimento. Questo metodo è stato implementato per determinare l'isolamento acustico fornito da un pannello in CLT, modellato come una piastra sottile ortotropa e validando i risultati confrontandoli con i dati ottenuti sperimentalmente. Inoltre, è stato sviluppato un modello generale, implementato con il metodo delle matrici di trasferimento, per simulare la trasmissione sonora attraverso delle strutture multistrato, tenendo in considerazione la presenza di connessione meccaniche. Il modello può essere applicato a strati di diversa natura: solidi elastici, piastre sottili ortotrope, fluidi e materiali poroelastici. I diversi meccanismi di radiazione sonora, associati al tipo di eccitazione esterna, giocano un ruolo chiave in questo approccio. Il modello è stato validato confrontandone i risultati con i dati sperimentali misurati su un sistema ETICS (External Thermal Insulation Composite System). Viene proposta una tecnica di omogeneizzazione, sviluppata per pareti in muratura, ma potenzialmente applicabile a qualunque partizione, per determinazione delle proprietà meccaniche, necessarie per una corretta modellazione dell’elemento con il metodo delle matrici di trasferimento, in funzione dell'isolamento acustico sperimentale.
25
MITSUMATSU, Sawako, Takeshi FURUHASHI, Tomohiro YOSHIKAWA, Akira ITO, 佐和子 光松, 武. 古橋, 大弘 吉川 та 晃. 伊藤. "階層的可視化手法を用いたアソシエーション分析によるプロファイリング". 日本感性工学会, 2011. http://hdl.handle.net/2237/20697.
26
Massari, Milena <1986>. "Seismic Behavior of Cross laminated Timber (CLT) Structural Systems: from Traditional Steel Connections to Low-Damage Solutions." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/8167/1/PhD_Thesis_MilenaMassari.pdf.
Анотація:
Timber buildings have always showed great performances, even if past timber structural systems are no longer adequate to fulfil modern building standards. The key aspect of CLT buildings, as for timber constructions in general, are the connection systems.
Nowadays, design of CLT wall connections is based on the hypothesis that hold-down connection is subjected only to tension, while angle bracket only to shear. Nevertheless, experimental highlighted that the two types of connection may be subjected to significant displacements in both directions, thus to coupled actions.
The first part of this study presents results from an extensive experimental campaign conducted on traditional connections for CLT buildings using a specific setup that allowed to impose prescribed levels of displacements in secondary direction, varying at the same time the main direction displacement in a cyclic and monotonic manner. A total of fifteen specimens, for each connection type, are presented and critically discussed in terms of load-displacement curves, strength, stiffness, energy dissipation, strength degradation and ductility.
The second part of the thesis focuses on an experimental and numerical investigation of a two storey 2/3 scaled CLT hybrid rocking wall. The applicability and the response of this relatively new low-damage solution has been studied for the first time applied on a CLT shear wall. The CLT wall included post-tensioned bars to provide self-centring capabilities and replaceable external steel dissipaters to accommodate energy dissipations. Furthermore, an experimental solution for the dissipater-wood panel link has been implemented. Results are presented in terms of achieved lateral force, overturning moment capacity, variation in the post-tension force, oscillation of the neutral axis depth and energy dissipation. Lastly, a numerical simulation accompanied experimental evidences, to examine the response of the rocking system for higher level of drifts, going beyond test limits.
27
Le, Pevelen Delphine. "Analyse structurale des matériaux soumis simultanément à haute pression et basse température : conception et réalisation de l'appareillage de diffraction des rayons X, application au diagramme de phases de deux conducteurs organiques : (TMTSF)₂ClO₄ et (TSeT)₂Cl." Bordeaux 1, 1999. http://www.theses.fr/1999BOR10566.
Анотація:
Ce travail de thèse présente la conception et la réalisation, pour la première fois au plan international, d'un ensemble de diffraction X (diffractomètre à incidence normale et chambre Weissenberg verticale) permettant le couplage des contraintes pression et température, ce qui rend désormais possible l'accès d'un point de vue structural à n'importe quel point d'un diagramme de phases P-T. Ce nouvel équipement a été utilisé avec succès pour étudier le comportement structural de deux conducteurs organiques : (TMTSF)₂ClO₄ et (TSeT)₂Cl. Pour chacun d'entre eux, est décrite de manière détaillée l'évolution des caractéristiques structurales sous contraintes avec en particulier la détermination de leur structure cristalline à (5 kbar, 7 k). Ces résultats cristallographiques ont permis de calculer les structures de bandes et surfaces de Fermi, d'établir des corrélations avec les propriétés physiques en expliquant notamment les transitions décelées précédemmentThe work presented in this thesis deals with the design and the achievement, for the first time at the international level, of an X-Ray diffraction instrumentation (normal beam diffractometer and vertical Weissenberg camera) allowing the coupling of the pressure and temperature constraints, which makes possible the access, from a structural point of view, to any point of a P-T phase diagram. This new apparatus has been successfully used to study the structural behaviour of two organic conductors: (TMTSF)₂ClO₄ and (TSeT)₂Cl. For each of them, the pressure and temperature dependence of the structural parameters has been described in detail, with in particular the determination of the crystal structure at (5 kbar, 7 K). Owing to these crystallographic results, the band structures and the Fermi surfaces have been calculated and some correlations have been established with the physical properties, leading to an explanation of the transitions previously detected
28
PERGOLINI, MARIANNA. "Experimental Study of Alternative Solutions for Integrated Energy and Structural Buildings Retrofits." Doctoral thesis, Università Politecnica delle Marche, 2019. http://hdl.handle.net/11566/263616.
Анотація:
Un approccio olistico nella progettazione di interventi è fortemente favorito dalle recenti Calls Europee sull’efficienza energetica per promuovere una riqualificazione degli edifici più sostenibile ed efficiente in termini di costi. Risolvere tutte le carenze dell’edificio con un’unica soluzione è fortemente incoraggiato, ma il tema è ancora poco affrontato dalla comunità scientifica. La presente tesi illustra una ricerca sperimentale di soluzioni alternative per il retrofit energetico e strutturale di edifici in legno.
Il primo obiettivo dello studio affronta l’ottimizzazione energetica di edifici in legno lamellare incrociato (CLT), che successivamente sarà implementata anche con una ottimizzazione strutturale. Il secondo obiettivo riguarda una soluzione integrata energetica e strutturale per edifici con telaio in legno (PF) attraverso l’utilizzo di una muratura in blocchi di terra cruda sul lato interno ed esterno della struttura per ottimizzarne il comportamento complessivo a taglio e risposta energetica.
La metodologia si è basata su: campagne di monitoraggio su un caso studio in diverse stagioni e condizioni operative, attraverso studi simultanei comparati di differenti finiture interne ed esterne; tests meccanici su muretti in terra cruda, utilizzando la tecnica della correlazione digitale delle immagini (DIC).
In primo luogo, i risultati hanno dimostrato che, per un edificio in CLT, nel clima Mediterraneo, l’adozione di uno strato di finitura interno massivo, garantisce la migliore prestazione termica annuale, sotto differenti condizioni operative. Inoltre, una facciata ventilata con una massa termica esterna è la scelta migliore poiché limita i flussi termici provenienti dall’esterno in estate e inverno.
In secondo luogo, per quanto riguarda la strategia di retrofit in PF, è stato verificato sperimentalmente che il blocco in terra cruda ha un buon comportamento termico, indipendentemente dall’uso dell’impianto di raffrescamento, e il beneficio di giunti a coda di rondine per migliorare il comportamento a taglio di tamponature di strutture intelaiate in legno.A holistic approach in the design of interventions is strongly boosted by recent Horizon Calls on energy-efficiency to perform a more sustainable and cost-effective building rehabilitation. Solving all building deficiencies at once with a unique solution is highly promoted, but the topic is still seldom addressed by the scientific community. The present thesis outlines an experimental research on alternative solutions for energy and structural retrofits strategies for wooden buildings. The first objective of the study deals with the energy optimization of cross laminated timber (CLT) buildings, that will eventually be implemented with a structural rehabilitation. The second objective focuses on an integrated energy and structural alternative solution for platform frame (PF) buildings by means of a masonry wall, made of unbaked earth blocks, on the internal and external sides of the structure, to optimize its global shear behavior and thermal responsiveness. The methodology comprised: extensive monitoring campaigns on a case study in different seasons and operative conditions, by means of simultaneous comparative studies of different internal and external linings; mechanical testing on unbaked masonry wallettes by means of digital image correlation (DIC) technique. Firstly, the outcomes demonstrated that, for CLT buildings, in the Mediterranean climate, the adoption of a massive innermost layer guarantees the best thermal performance on annual basis under different indoor operative conditions. Moreover, a ventilated technology, with an outer thermal mass, is the best choice yearly, being beneficial for minimizing the incoming heat fluxes through the envelope. Secondly, regarding the retrofit strategy of PF buildings, it was experimentally verified that the earth block masonry has a good thermal performance, regardless of the switching on/off of the cooling system, and that the presence of the dovetail joints improve the overall shear behavior of masonry veneer walls in wooden light-framing structures.
29
Abrahamsson, Jenny, and Fleur Filip la. "The impact of connection stiffness on the global structural behavior in a CLT building : A combined experimental-numerical study." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-105166.
Анотація:
Cross Laminated Timber (CLT) has in recent years become a more important building material. This means that the demand for accurate calculation methods in building standards such as Eurocode 5 has increased. There is limited knowledge about the connections in CLT buildings which is an important part of a CLT structure. This thesis was therefore focused on investigating a wall-floor-wall type connection commonly found in platform type buildings. An experimental and numerical study on typical wall-floor-wall connections was carried out in this thesis. In the experimental part 60 tests with 8 different configurations were conducted to investigate the influence of different parameters on the connection, moment capacity and rotational stiffness. During the tests the deformation of the specimens under four load levels were investigated. Compression tests were also performed on the specimens to determine the compressive strength and stiffness of the elements. In the numerical part two different models for the connection were created. One simplified model with rotational springs and one more complex model with compression springs. With these models the influence from the number of stories, span and thickness of the wall on the global behavior of a structure was investigated. The result from this thesis shows that there is both moment capacity and rotational stiffness in the wall-floor-wall type connection that can be utilized in the design phase of a structure. This was proven by both the experimental and the numerical study. The parameters that influence the behavior of the connection most were the load level applied on the wall and the wall thickness. The model created in the numerical study showed great potential regarding the replication of the connection behavior observed in the experimental study.
30
FRANCO, LUCA. "Numerical modelling strategies and design methods for timber structures." Doctoral thesis, Università IUAV di Venezia, 2020. http://hdl.handle.net/11578/283196.
Анотація:
Over the last years timber constructions are gaining back a primary role in the building industry after decades in which they were almost abandoned in favor of concrete and steel structures. A sign of this change is the appearance in the last years in many Italian universities of courses dedicated to the design of timber structures. One of the main reasons behind this success must be sought in the development of new engineered timber materials, such as glued-laminated and cross-lam timber, that allowed to wooden structures to reach structural potentialities that until some decades ago were prerogative of concrete or steel building materials. Tests recently carried out on full-scale buildings have also proven the excellent capabilities of these new timber technologies in providing reliable and highly-performant multi-storey building able to withstand high seismic intensities.
Since the employment of timber to build multi-storey buildings in seismic-prone areas is quite recent, many aspects relating the understanding of their structural behavior and their correct design are still to be sought, as demonstrated by the lack of provisions in current building codes and standards and the still ongoing great amount of research activity on seismic behavior of timber structures.
Modern timber technologies also allow to cover very large spans with long glued-laminated timber beams, satisfying the need of large open spaces and architectural flexibility required by modern building design approaches. These bulky big-size elements anyway result quite expensive in production, transportation and installation phases undermining the economic competitiveness of timber structures. To cope with this problem, the prototype of an innovative timber-steel composite beam consisting of sub-elements assembled on-site to create longer members has been ideated at KTH Royal Institute of Technology of Stockholm in Sweden.
One of the objectives of this thesis is therefore to provide an advance in the state of knowledge of timber building technology adopted for seismic-prone areas, focusing in particular on both numerical modelling strategies and design methods for cross-laminated timber buildings, illustrated respectively in the first and second part of the thesis. The other goal is the development of an analytical tool for the enhancement and the investigation of the structural performances of the innovative composite beam ideated at KTH Royal Institute of Technology, and it will be exposed in the third and last part of the thesis.
31
Eriksson, Jennifer. "Horizontal natural frequency in a 10 story building : A comparison between CLT and concrete using estimate calculations." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-152131.
Анотація:
Tall slender buildings are easily set in motion by wind and earthquakes but by estimating the buildings horizontal natural frequencies in the design phase, these motions can be kept within acceptable boundaries. There are many parameters that decides the natural frequency of a building and it can therefore be difficult to calculate it. There are a few ways though to estimate horizontal natural frequencies of tall buildings and two methods have been tested in this report. Both methods give the frequency of a clamped-free cantilever but one of them requires a single degree of freedom system whilst the other handles a multi degree of freedom system. The methods are called SDOF method and MDOF method in this report. A fictional building was created for this project to be the reference object in the comparison between the two methods SDOF and MDOF. The walls and floors of the building was designed with the support of both an acoustic engineer and a structural engineer to create a realistic building. A building’s natural frequency is dependent of the self-weight, stiffness and height of the building and it was therefore important to design these components with care. The fictional building is called House 1 and is a 10 story, almost square building about 20 m wide and broad and 30 m high. This report does not only compare the natural frequencies obtained from the two different calculation methods, but it also shows the difference in frequency in timber and concrete structures. Shear walls constitutes the horizontal stabilization system of the fictional building and both a CLT core and a concrete core is designed and compared. It is only the walls that comes in two different versions, the floorings consist of CLT boards for both structures tested. The horizontal natural frequencies of House 1 were about 2 Hz and 3 Hz for the CLT version and concrete version respectively. It was expected to get frequencies within that range considering the height of House 1. The CLT core having a lower frequency than the concrete core was also expected since concrete is a stiffer material than wood. To be able to make a fair comparison between the SDOF method and the MDOF method, House 1 was designed with the same dimensions and stiffness on all floors because the SDOF method requires that. The results from the two methods are almost identical with only 0.3 Hz and 0.4 Hz difference for the concrete and CLT respectively. For a shear wall structure with a consistent stiffness, weight and dimension, any of the two methods can be used to estimate the horizontal natural frequency. However, it is not realistic for a building of 30 m or higher, to have the same dimensions on the load bearing structure on all floors which makes the MDOF method more accurate in more cases than the SDOF method.Höga slanka byggnader kan sättas i svajande rörelser av vind och jordbävningar, men genom att uppskatta byggnadernas horisontella egenfrekvenser i den tidiga konstruktionsfasen kan dessa rörelser hållas inom acceptabla gränser. Det är många parametrar som bestämmer byggnadens egenfrekvens och det kan därför vara svårt att beräkna den. Det finns dock några sätt att uppskatta horisontella egenfrekvenser hos höga byggnader och två metoder har testats i denna rapport. Båda metoderna ger frekvensen av en fast inspänd konsolbalk men en av dem kräver ett enfrihetsgradsystem medan den andra kan hantera ett system med flera frihetsgrader. Metoderna kallas SDOF-metoden och MDOF-metoden i denna rapport. En fiktiv byggnad skapades i detta projekt för att vara referensobjekt i jämförelsen mellan de två metoderna SDOF och MDOF. Byggnadens väggar och golv konstruerades med stöd av både en akustiker och en konstruktör för att skapa en realistisk byggnad. Byggnadens egenfrekvens är beroende av byggnadens egenvikt, styvhet och höjd och det var därför viktigt att utforma dessa komponenter med omsorg. Den fiktiva byggnaden kallas House 1 och är en 10 vånings-, nästan fyrkantig byggnad ca 20 m lång och bred och 30 m hög. Denna rapport jämför inte bara egenfrekvenserna erhållna från de två olika beräkningsmetoderna, den visar även skillnaden i frekvens i trä- och betongkonstruktioner. Skjuvväggar utgör det horisontella stabiliseringssystemet för den fiktiva byggnaden och både en KL-kärna och en betongkärna har utformats och jämförts. Det är bara väggarna som skiljer de två olika versionerna åt, bjälklagen består av KL-skivor i båda fallen. De horisontella egenfrekvenserna hos House 1 var ca 2 Hz och 3 Hz för KL-version respektive betongversion. Frekvenser inom detta område var väntade med tanke på höjden av House 1. Att KL-kärnan skulle ha en lägre frekvens än betongkärnan förväntades också eftersom betong är ett styvare material än trä. För att kunna göra en rättvis jämförelse mellan SDOF-metoden och MDOF-metoden, var House 1 utformad med samma dimension och styvhet på alla våningsplan eftersom SDOF-metoden kräver det. Resultaten från de två metoderna är nästan identiska med endast 0,3 Hz och 0,4 Hz skillnad för betong respektive KL. För en skjuvväggskonstruktion med en kontinuerlig styvhet, vikt och dimension kan båda de två metoderna användas för att uppskatta den horisontella egenfrekvensen. Det är dock inte realistiskt för en byggnad på 30 m eller högre att ha samma dimensioner på den lastbärande konstruktionen på alla våningar vilket gör MDOF-metoden mer korrekt i fler fall än SDOF-metoden.
32
Nold, Michael George. "Draped Interiors." Kent State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=kent1461599487.
33
Sidén, Marja. "KL-träbjälklag i kombination med stålstommar : Teknisk utvärdering och utveckling av lösningar för förband och längre spännvidder." Thesis, Luleå tekniska universitet, Byggkonstruktion och -produktion, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-61828.
Анотація:
En i dagsläget vanlig byggteknik i Sverige är användandet av en stålstomme i kombination medprefabricerade betonghåldäck. Detta arbete grundar sig på frågeställningen om KL-träbjälklag skullekunna vara ett reellt alternativ till betongbjälklag i en sådan konstruktion, i kombination medhattbalkar. Som ett första steg skisserades en typkonstruktion för att ha en väl definierad utgångspunkt för enanalys. Utgångspunkten för denna typkonstruktion var främst en studie av två tidigare konstruktioner,konstruerade med stålstomme med hattbalkar och håldäcksbjälklag. Litteraturstudien fokuserade påbakomliggande teorier i relation till bjälklagets funktion i konstruktionen. Ett antal områdendefinierades som utgångspunkt för en teknisk utvärdering. Dessa områden var spännvidder,dimensionering i brottgränstillståndet, dimensionering i bruksgränstillståndet, knutpunkter,dimensionering för olyckslaster, akustik och byggbarhet. Utgående från ovanstående områdenutvärderades så tekniska förutsättningar för användandet av KL-träbjälklag i den aktuellakonstruktionstypen. Det konstaterades att det på många områden finns väl fungerande lösningar ochatt det finns många positiva aspekter med ett lätt och lättmonterat KL-träbjälklag. De problemområdensom hittats kan sammanfattas som: 1. Begränsad spännvidd 2. Ökade horisontella deformationer i bjälklaget 3. Beräkning av svängningar med hänsyn till upplag på stålbalkar 4. Förband mellan bjälklag och hattbalkar 5. Akustisk dimensionering Två av dessa områden valdes för vidare analys; förband mellan bjälklag och hattbalkar samt denbegränsade spännvidden. För förbandet utvecklades en lösning med en klack på hattbalkens fläns ikombination med en slits i KL-träskivan som enkelt ska kunna hakas på vid montage. För att ta krafterlängs balkens längd måste dock lösningen sedan kompletteras med ett skruvförband genombalkflänsen. Förhoppningen är att en enklare lösning för att ta dessa förhållandevis små krafter skakunna utvecklas som komplement till det primära förbandet med klack och slits. Handberäkningarutfördes för det utvecklade förbandet och det konstaterades att det är möjligt att utforma ett sådantförband, med rimliga dimensioner, för alla verkande laster. Som den sista delen av arbetet studerades lösningar för att kunna uppnå längre spännvidder, för ettplattbjälklag är spännvidden begränsad till något mindre än 7,7m. Olika typer av samverkansbjälklagstuderades och det konstaterades att samverkan med ett prefabricerat betongbjälklag med en limmadförbindelse skulle kunna vara en lämplig lösning. Limmade förbindelser studerades så mer ingåendeoch det konstaterades att en limmad förbindelse mellan trä och prefabricerad betong medför storstyrka och styvhet. Upp mot 100% samverkan har observerats för samverkansbjälklag med denna typav förbindelse. En osäkerhetsfaktor är dock långtidseffekter, där fler studier behöver hittas ellerutföras för att få en större kunskap på området. Handberäkningar utfördes enligt teorin i SS-EN 1995-1-1 på två typer av samverkansbjälklag med ett antal olika dimensioner. I beräkningarna medräknades100% samverkansgrad. Det konstaterades att 9m spännvidd skulle kunna uppnås med en kombinationav KL-trä och betong, medan 12m spännvidd kan uppnås med hjälp av mellanliggande träreglar. Andraberäkningsmodeller för svängningar där egenfrekvensen inte är den begränsande faktorn skulle kunna leda till bättre resultat för denna typ av samverkansbjälklag.A currently common building technology in Sweden is the use of a steel structure in combination withprefabricated HD/F concrete slabs. This work is based on the issue of whether CLT slabs could be asuitable alternative to concrete slabs in such a structure, in combination with the type of weldedplated beams that are often called hat beams. As a first step a type-structure was sketched to have a well-defined starting point for an analyze. Thebasis for this structure was mainly a study of two designs constructed with steel structures composedof hat beams and HD/F slabs. The literature study was focused on underlying theories in relation to theslabs function in the structure. A number of areas were defined as a basis for an evaluation of thebuilding type. These areas where spans, design in the ultimate limit state, design in the serviceabilitylimit state, joints, design for accidental actions, acoustics and constructability. Based on the above,technical conditions for the use of CLT slabs in the building type in question were evaluated. It wasfound that in many areas there were working solutions, and that there are many positive aspectsrelated to the use of a light and easily mounted CLT slab. The issues that were found can be concluded as: 1. Limited span lengths 2. An increase of horizontal deformations in the slab 3. Calculations of vibrations with respect to the flexible support 4. Joints between slabs and hat beams 5. Acoustic design Two of these issues were chosen for further analysis: joints between slabs and beams and the limitedspan length. A solution was developed for the joint, composed of a heel on the flange of the steelbeam in combination with a slit in the CLT slab. The joint is supposedly easy to mount during assembly.To be able to handle the forces along the length of the beam the solution must however becomplemented with a secondary screw joint through the flange of the beam. The hope is that a simplersolution to handle these relatively small forces can be developed, as complement to the primary jointmade up of the heel and slit. Calculations were performed by hand for the developed joint and it wasfound that it is possible to design such a joint, with reasonable dimensions, for all the acting loads. As the last part solutions to achieve longer spans were studied, for a flat CLT slab the span length islimited to somewhat less than 7,7m. Different types of composite slabs were studied and it was notedthat a composite with a prefabricated concrete slab and a glued connection could be a suitablesolution. Glued connections were then studied more closely, and I was found that a glued connectionbetween wood and prefabricated concrete entails great strength and rigidity. About 100% unitedaction has been observed for this type of connection. An uncertain factor is however long-term effectswhere further studies need to be found or performed to achieve more knowledge. Hand calculationswere performed using the theory in SS-EN 1995-1-1 on two types of composite slabs for a couple ofdifferent dimensions. In the calculations 100% united action was used. It was found that 9m span couldbe achieved with the combined action of CLT and concrete, while 12m could be achieved using woodenstuds for spacing. Other theories for the calculations where the natural frequency isn’t the limiting factor could lead to better results for this kind of composite slabs.
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Rapin, Jean-Philippe. "Synthèse et étude cristallochimique de quelques aluminates et ferrites calciques hydratés de formule [Ca2 M(OH)6]+, [X,nH2O]- avec X=Cl, Br, I, ClO4, 1/2CO3 1/2CrO4 et 1/2SO4 et M=Al et Fe." Nancy 1, 2001. http://docnum.univ-lorraine.fr/public/SCD_T_2001_0124_RAPIN.pdf.
Анотація:
Ce travail porte sur la synthèse et l'étude cristallographique de quelques aluminates et ferrites de calcium hydratés de formule structurale [Ca2Al1-xFex(OH)6]+ [X, nH2O]-, appelés "phase AFm" par les cimentiers. Ces composés appartiennent à la famille des hydroxydes doubles lamellaires (HDL) et sont formés par l'empilement de feuillets rigides chargés positivement, entre lesquels diverses espèces anioniques peuvent être insérées. La transition structurale de la phase AFm-Cl, a pour origine une organisation du réseau de liaisons hydrogène. Les structures cristallographiques de nombreuses phases, AFm-(Cl, Br), AFm-(Cl, CO3), AFm-(Cl, SO4) et AFm-(CrO4) ont été résolues. Une application de la phase AFm-Cl comme détecteur d'iodure par voltampérométrie a été réalisé. L'étude des ferrites de calcium a montré qu'une solution solide Al et Fe existe. Cependant la substitution de Al3+ par Fe3+ engendre des perturbations structurales mises en évidences par spectrométrie Mössbauer et EXAFSThis work deals with the synthesis and the crystallographic study of some calcium aluminate and calcium ferrite with structural formulae [Ca2Al1-xFex(OH)6]+ [X, nH2O]-, commonly named "AFm phases" by the cement workers. These compounds belong to the layered double hydroxide (LDH) family and are composed by the stacking of positively charged main layers, and negatively charged interlayers. It was shown that the structural transition of the AFm-Cl phase is due to an ordering of the hydrogen bonds network. The crystallographic structures of several phases, AFm-(Cl, Br), AFm-(Cl, CO3), AFm-(Cl, SO4) and AFm-(CrO4) are given. An application of AFm-Cl like iodide sensor by voltammetric detection is detailed. Finally, calcium ferrite study has shown that a solid solution between aluminium and iron exists. However the substitute of Al3+ by Fe3+ gives some structural modifications, which are clearly emphasised by Mössbauer spectrometry and EXAFS
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Llerena, Pillaca Wilder Leoncio, and Gomez Abel Paco. "Evaluación de las propiedades mecánicas de la madera laminada cruzada (CLT) mediante ensayos de resistencia para mejorar el comportamiento estructural de muros de madera elaborados con una especie de mediana densidad." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/652156.
Анотація:
La presente investigación corresponde a la evaluación de las propiedades mecánicas de la madera contralaminada (CLT) elaborados con una especie de mediana densidad mediante ensayos de resistencia para mejorar su comportamiento como muros estructurales en edificaciones. La aplicación de la madera laminada cruzada denominada también CLT (Cross Laminated Timber) como material estructural en la construcción de edificaciones permitiría un mejor aprovechamiento del potencial forestal de muchos países, haciendo que este sector sea más sostenible. Esta aplicación es factible siempre en cuando el material a emplear cumpla con las solicitaciones de resistencia que demanda su uso estructural y su proceso industrial sea compatible con las condiciones y la oferta existente en el entorno. Para lograr este propósito, se elaboraron prototipos de paneles CLT con madera Cachimbo, especie de mediana densidad denominado científicamente como Cariniana doméstica perteneciente a la familia Lecythidaceae. Se realizaron ensayos para determinar las propiedades mecánicas de resistencia a esfuerzos de compresión perpendicular y paralela a las fibras de las capas exteriores, esfuerzo de flexión y resistencia al corte. Los procedimientos fueron realizados siguiendo normativas de madera contralaminada como la española EN16351, el EC5 y la E.010 de madera. Los resultados obtenidos dan cuenta que los paneles CLT elaborados con Cachimbo son capaces de resistir los requerimientos de carga que podría demandar una edificación de mediana altura y cumple con los requisitos básicos especificados en las normativas. Las resistencias alcanzadas son similares a las obtenidas con maderas de tipo coníferas en estudios realizados en otros países, siguiendo los mismos criterios y normatividad.The present investigation corresponds to the evaluation of the mechanical properties of the Cross Laminated Timber (CLT) made with medium density species by means of resistance tests to improve its behavior as structural walls in buildings. The application of the cross laminated wood also called CLT (Cross Laminated Timber) as structural material in the construction of buildings would allow a better use of the existing forest potential in many countries, making this sector more sustainable. This application is feasible as long as the material to be used complies with the stresses of resistance that its structural use demands, and its industrial process is compatible with the conditions and the existing offer in the environment. To achieve this purpose, prototypes of CLT panels were made with Cachimbo wood, a medium-density species scientifically called Carinianadomestic belonging to the Lecythidaceae family. Tests were carried out to determine the mechanical properties of resistance to perpendicular and parallel compression stresses to the fibers of the outer layers, bending stress and shear strength. The procedures were carried out following norms of contra-laminated wood such as the Spanish EN16351, the EC5 and the Peruvian E.010 wood regulations. The results obtained show that the CLT panels made with Cachimbo can withstand the load requirements that a medium-height building could demand and meets the basic requirements specified in the regulations. The strengths achieved are similar to obtained with coniferous woods in studies carried out in other countries, following the same criteria and regulations.
Trabajo de investigación
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Bui, Tuan Anh. "Experimental and numerical uncertain vibration analysis of multilayered timber structures assembled using compressed wood dowels." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0202.
Анотація:
Cette thèse présente une étude expérimentale et numérique sur les aptitudes en service en ce qui concerne le comportement vibratoire de planchers réalisés en bois d’ingénierie sans colle (AFEWP), à savoir les poutres en bois lamellé sans adhésif (AFLB) et les panneaux en bois lamellé-croisé sans adhésif (AFCLT), assemblés par des tourillons en bois densifié (CWD). Les analyses modales expérimentales ont été réalisées en conditions libres-libre à l'aide d'un marteau instrumenté. Les fréquences naturelles, les modes propres et les coefficients d'amortissement ont été évalués expérimentalement. De plus, des poutres en bois lamellé-collé similaires ont été fabriquées et testées à des fins de comparaison. Un modèle EF 3D a été développé et validé par comparaison avec des données expérimentales, puis utilisé pour prédire le comportement vibratoire d'un système de plancher à grande échelle réalisé avec un panneau AFCLT mesurant 4,5 m x 5,5 m. Une étude paramétrique a été réalisée en utilisant le modèle EF pour identifier les paramètres qui influent sur la rigidité et les fréquences propres du plancher. Les résultats obtenus ont été analysés au regard des critères de conception exigés par Eurocode 5 en ce qui concerne le confort vibratoire des planchers bois. Un modèle EF simplifié a ensuite été développé pour réduire les coûts de calcul. Le niveau de variabilité des résultats des AFEWP a été également étudié et discuté. La variabilité numérique des fréquences des AFEWP a été étudiée en utilisant la méthode MSP (Modal Stability Procedure). Les résultats de la méthode MSP ont d'abord été comparés aux résultats EF dans le cas nominal. Les résultats statistiques (valeur moyenne, écart type, coefficient de variation et distribution) obtenus par la méthode MSP ont été confrontés aux résultats de simulation directe de Monte Carlo ainsi qu’aux données expérimentales. Une estimation rapide des erreurs entre la méthode MSP et la simulation directe de Monte Carlo a été développée. Enfin, la variabilité (moyenne et écart-type des fréquences) du comportement vibratoire du système de plancher à grande échelle a été étudiée en utilisant la méthode MSPThis study presents an experimental and numerical investigation on the vibrational serviceability performance of novel adhesive free engineered wood products (AFEWPs), namely adhesive free laminated timber beams (AFLB) and adhesive free cross-laminated timber panels (AFCLT), assembled through thermo-mechanically compressed wood dowels (CWD). The experimental modal analyses were carried out under free-free conditions using a hammer impact. Natural frequencies, mode shapes, and damping ratio were assessed experimentally. In addition, similar glued timber beams (conventional glulam) were manufactured and tested for comparison purpose. A 3D FE model was developed and validated by comparison against experimental data and then used to predict the vibrational behavior of a realistic flooring system made with AFCLT panel measuring 4.5 m x 5.5 m. A parametric study was performed on the FE model to maximize the floor stiffness. The predicted FE results were discussed with regard to the Eurocode 5 vibrational serviceability design requirements showing acceptable vibrational performance. A simplified FE model was then developed to reduce computational cost. The variability level of the results for the AFEWPs was also studied and discussed. The numerical variability of frequencies of the AFEWPs was investigated based on the development of the Modal Stability Procedure (MSP). The MSP result was first compared with the FE result in the nominal case. Then, the statistic results (mean value, standard deviation, coefficient of variation and distribution) obtained from the MSP were compared with the results from the classical method (direct Monte Carlo simulation) and experimental results. A quick error estimation between the MSP and the direct Monte Carlo simulation was developed. Finally, the mean and standard deviation of the frequencies of the realistic AFCLT flooring system were predicted by the MSP
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Hezard, Pauline. "Modélisation de la croissance des plantes supérieures pour les systèmes de support-vie : conception d'un modèle global et simulation des transferts de masse et d'énergie à l'échelle de la plante." Thesis, Clermont-Ferrand 2, 2012. http://www.theses.fr/2012CLF22250/document.
Анотація:
Les missions spatiales habitées de longue durée nécessitent des systèmes de support-vie efficaces recyclant l’air, l’eau et la nourriture avec un apport extérieur minimum en matière et énergie. L’air et l’eau peuvent être recyclés par des méthodes purement physico-chimiques, tandis que la production de nourriture ne peut être faite sans la présence d’organismes vivants. Le projet Micro-Ecological Life Support System Alternative (MELiSSA, alternative de système de support-vie micro-écologique) de l’Agence Spatiale Européenne inclut des plantes supérieures cultivées dans une chambre close contrôlée, associée à d’autres compartiments microbiens. Le contrôle à long terme de la chambre de culture et du système de support-vie entier requiert des modèles prédictifs efficaces. Le bouclage du bilan massique et la prédiction de la réponse de la plante dans un environnement extraterrestre inhabituel mettent en avant l’importance de modèles mécanistes basés sur le principe des bilans de matière et d’énergie.Une étude bibliographique poussée a été réalisée afin de lister et analyser les modèles de croissance de plantes supérieures existants. De nombreux modèles existent, ils simulent la plupart des processus de la plante. Cependant aucun des modèles structurés globaux n’est suffisamment mécaniste ni équilibré en terme d’échange de masse pour une application dans un système de support-vie clos. Ainsi, une nouvelle structure est proposée afin de simuler tous les termes du bilan massique au niveau de la plante, en incluant les différentes échelles de l’étude : les processus généraux, l’échelle de l’organe et l’échelle de la molécule. Les résultats d’une première approche utilisant des lois physiques mécanistes simples pour les échanges de matière et d’énergie, une stoechiométrie unique pour la production de biomasse et quelques lois empiriques pour la prédiction des paramètres architecturaux sont illustrés et comparés avec des résultats expérimentaux obtenus dans un environnement contrôlé. Une analyse mathématique du modèle est réalisée et tous ces résultats sont discutés afin de proposer les prochaines étapes de développement. Ceci est décrit en détail pour l’inclusion de modèles de processus plus complexes dans les futures versions du modèle ; les expériences qui devraient être réalisées ainsi que les mesures nécessaires sont proposées. Ceci conduit à la description d’une nouvelle conception de chambre de culture expérimentaleFor long-term manned space missions, it is necessary to develop efficient life support systems recycling air, water and food with a minimum supply of matter and energy. Air and water can be recycled from purely physico-chemical systems; however food requires se presence of living organisms. The Micro-Ecological Life Support System Alternative (MELiSSA) project of the European Space Agency includes higher plants grown in a closed and controlled chamber associated with other microbial compartments. The long-term control of the growth chamber and entire life support system requires efficient predictive models. The mass balance closure and the prediction in uncommon extraterrestrial environments highlight the importance of mechanistic models based on the mass and energy balances principles.An extensive bibliographic study has been performed in order to list and analyse the existing models of higher plant growth. Many models already exist, simulating most of the plant processes. However none of the global, structured models is sufficiently mechanistic and balanced in terms of matter exchange for an application in closed life support systems. Then a new structure is proposed in order to simulate all the terms of the mass balance at the plant level, including the different scales of study: general processes, organ scale and molecular scale. The results of the first approach using simple mechanistic physical laws for mass and energy exchange, a unique stoichiometry for biomass production and few empirical laws for the prediction of architectural parameters are illustrated and compared with experimental results obtained in a controlled environment. A mathematical analysis of the model is performed and all these results are discussed in order to propose further developments. This is described in detail for the implementation of more complex models of processes in the future model versions; the experiments that should be performed including the main measurements are proposed. This leads to the description of a new design of experimental growth chamber
38
Sorber, Samuel C. "Geologic Map and Structural Analysis of the Twin Rocks 7.5 Minute Quadrangle, Wayne County, Utah." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1352.pdf.
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Kučírek, Josef. "Zahraničně-obchodní politika Brazílie." Master's thesis, Vysoká škola ekonomická v Praze, 2007. http://www.nusl.cz/ntk/nusl-125215.
Анотація:
The thesis examines the trade policy of Brazil and its impact on the international position and trade of the country. Despite having come to the fore of interest of the whole world, both political and business, there are still numerous areas to be improved. The thesis evaluates trade policy tools used by the country to promote exports and limit imports, integration efforts in the region and in the world, and the effects of particular government provisions on the reality of the trade relations and results. The analysis points out structural and systemic failures together with deliberate barriers, such as high level of bureaucracy or complicated tax system. Although Brazil promotes free trade, its trade policy proved to be highly anti-import.
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TORRE, ROBERTO. "Theoretical, numerical, and experimental methodologies for structural analysis of polymeric aeronautical elements produced via additive manufacturing." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2915193.
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Noble, Priscilla Garrido. "Foreign Language Learning in Santo Domingo: Qualitative Case Studies in Two Private Schools." unrestricted, 2007. http://etd.gsu.edu/theses/available/etd-05092007-164942/.
Анотація:
Thesis (Ph. D.)--Georgia State University, 2007.Title from file title page. Philo Hutcheson, committee chair; Gertrude Tinker-Sachs, Joyce E Many, Douglas Davis, committee members. Electronic text (325 p.) : digital, PDF file. Description based on contents viewed Dec. 6, 2007. Includes bibliographical references (p. 292-309).
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Adhikari, Sailesh. "Assessment of Cross Laminated Timber Markets for Hardware Lumber." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/103013.
Анотація:
The goal of this study was to assess the potential of using hardwood lumber in CLT manufacturing. The goal was achieved by addressing four specific objectives. The first objective was to collect CLT manufacturers' perspectives for using hardwood lumber in the current manufacturing setup. The second objective was to determine hardwood sawmills' current ability to produce structural grade lumber (SGHL) from low value logs as a product mix through a survey of hardwood lumber producers in the US. The third objective was to conduct a log yield study of SGHL production from yellow poplar (YP) logs to produce 6'' and 8'' width SGHL to match the PRG 320 requirements. The fourth objective was to determine CLTs' production cost using SGHL and compared it with the CLTs manufactured from southern yellow pine (SYP).
The results suggest that all three CLT industries visited and interviewed had sufficient technology to produce hardwood CLTs. The production of hardwood CLTs was mainly limited by the quality and quantity of lumber available. The hardwood sawmill survey results indicated that, currently, less than 10% of the sawmills had all the resources required to produce SGHL. The current ability of the sawmills was measured based on the resources necessary to begin SGHL production. Forty percent of the sawmills would require an investment in sawing technology to saw SGHL, 70% would require employing a certified lumber grader, and 80% would require a planer to surface lumber. Another significant finding was the sawmills' willingness to collaborate with other sawmills and lumber manufacturers. More than 50% of sawmills were open to potential collaboration with other stakeholders if necessary, which is crucial to commercializing SGHL for a new market.
The log yield study of yellow poplar helped demonstrate that the mixed grade lumber production method to convert lumber from lower quality zones as SGHL yields higher lumber volume for sawmills and at the same time reduces lower-grade lumber volume. On average, SGHL production increased lumber volume by more than 6% compared to only NHLA grade lumber production when 65% of the lumber was converted to SGHL. The volume of lower lumber grades from 2 common and below decreased from an average of 85% to less than 30% when producing SGHL as a product mix with NHLA grade lumber. This study observed more than 95% of SGHL as Number 3 and better lumber grades. At estimated lumber value, 2x6 and 2x8 SGHL and NHLA grade lumber production as product mix from a log generate higher revenue for all log groups except for the diameter 13" logs. A lower percentage of higher-grade lumber was observed for diameter 13’’ logs than other log groups from this experiment, which resulted in lower revenue.
Production cost of CLTs was determined based on the lumber value to manufacture 40' x 10' plain panels with different combinations by lumber grade of yellow poplar and southern yellow pine lumber alone. Production cost was determined by assuming that lumber value contributes 40% of CLTs' total production cost. The 3- ply CLT panels were manufactured using S. Selects lumber in a major direction, and No 1-grade lumber in the minor direction from YP had a production cost of $662.56 per cubic meter, which cost only $643.10 when SYP lumber was used at referenced lumber value. This study concludes that CLT panels from YP cost 3-7 % more than SYP-CLTs at the referenced lumber values.Ph.D.
This research aims to expand the hardwood lumber consumption in the US by evaluating the opportunity to manufacture cross-laminated timber (CLTs). First, CLT manufacturing industries were visited to know their current capacity to process hardwood lumber. The results suggest that all three CLT industries had sufficient technology to produce hardwood CLTs, and the production was mainly limited by the quality and quantity of lumber available. Commercially hardwood can be used in CLT manufacturing if it can be used for structural application. Hardwood lumber must meet the structural application's minimum requirements to manufacture the structural grade CLTs, so we surveyed the hardwood sawmills to know if they have the required resources to manufacture the structural grade hardwood lumber (SGHL). Only ten percent of the sawmills had required technology to produce SGHL without additional investments. Production of the SGHL also required to generate more revenue for the hardwood sawmills, so we conducted the log yield study to know how the revenue structure of sawmill operation will change from the mixed grade lumber production. At estimated lumber value, 2x6 and 2x8 SGHL and 1-inch National Hardwood Lumber Association (NHLA) grade lumber production as product mix from logs generate higher revenue for all log groups except for the diameter 13" logs. Finally, the production cost of SGHL from the log yield study was evaluated and used to produce CLTs at 40% production cost from lumber at 15% profit margins for sawmills and compare with southern yellow pines CLTs. The results indicate that yellow poplar CLTs cost 3-7 % more than southern yellow pines CLTs at the referenced lumber values. This study concludes that hardwood lumber can be used in CLT manufacturing, so there is an opportunity for hardwood sawmills to expand the market. The first step for commercial production of hardwood CLTs is to produce SGHL on a commercial scale, given that sawmills can benefit from these new products in the current lumber market and meet the minimum requirements of the CLT raw materials.
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Töttrup, Hampus, and Gunnar Renström. "Möjligheter med KL-trä : Hur en betongstomme kan omformas till en KL-trästomme." Thesis, KTH, Byggteknik och design, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231871.
Анотація:
KL-trä är ett stommaterial som blir allt intressantare på marknaden. Kunskapen är hos mångakonstruktörer idag begränsad. Genom att utgå från en betongstomme, där många konstruktörer har goderfarenhet av projektering och dimensionering, kan en jämförelse mellan dessa två stommaterial vara relevant. Frågan som då kan ställas är hur en KL-trästomme dimensioneras enligt Eurokoderna och vadskillnaderna och dess konsekvenser på boarea och byggnadshöjd, i jämförelse med en betongstomme. Genom att för en byggnad göra om dess betongstomme till en KL-trästomme så kunde dessa skillnader undersökas. KL-trä eller korslimmat trä är ett skivmaterial av sammanlimmade brädor, där vartannat lager liggerkorslagt mot föregående lager. Denna uppbyggnad ger KL-träskivan bärförmåga i två riktningar ochkan användas som vägg- och bjälklagselement. KL-trä är ett stommaterial med låg vikt, jämfört medexempelvis betong, och har precis som andra lätta konstruktioner utmaningar med att uppfylla ljudkrav. Trä som utsätts för brand brinner med en konstant hastighet. Då kolskiktet som bildas har enisolerande effekt, brinner det med en låg hastighet. Detta gör det enkelt att dimensionera för brand. KL-trä har mindre fuktbetingade rörelser jämfört med konstruktionsvirke. Handlingar för en referensbyggnad med betongstomme erhölls av Kåver & Mellin. Med målet attbehålla byggnadens ursprungliga arkitektoniska kvaliteter utformades en ny byggnad i KL-trä därhänsyn togs till krav för bärighet, ljud, värmeisolering, brand och fukt. Resultatet som presenteras är en metod för dimensionering av KL-träväggar och -bjälklag. Därefterföljer en uppställning av typdetaljer för väggar och bjälklag, dess ingående material och till vilken gradkraven uppfyllts. Förslag till anslutningar mellan utvalda byggnadsdelar visas. Boarean minskade iförhållande till referensbyggnaden. Byggnadhöjden alternativt rumshöjden påverkas negativt. KL-träbyggnaden visades väga 118 ton mindre än referensbyggnaden. Vid val av KL-trästomme måste hänsyn tas till den ökade tjockleken av lägenhetsskiljande bjälklagväggar som kan leda till minskad area och ökad byggnadshöjd, och dess ekonomiska konsekvenser. Den påtagliga skillnaden i vikt är betydelsefull vid grundläggning och hantering av vindlaster.
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Kociánová, Lenka. "Sportovní centrum Za Lužánkami Brno." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-354991.
Анотація:
Prior to this thesis, there was a specialist course “Sport centre Za Lužánkami Brno”. This project was focused on planning of urbanism-architectural area with a mixture of renovated and new facilities with different functions for sport and leisure, together with professional sport opportunities. The emphasis was on collision-free paths for pedestrians and cyclists, clear transport links around the centre and terrain configuration of the area. The thesis follows on from this project, focusing on development between the hotel Bobycentrum in the South and the Lužánky swimming pool in the North. The idea of the proposal stems from the need to connect the development area to the existing network of pedestrian and cycle paths and the public transport system to minimise the use for individual car travel to the sport centre; and to connect existing and new facilities for leisure and sports. The Sport relax centre was designed with existing buildings in mind and partially follows their ground floor dimensions. The centre creates a barrier from the noisy and busy street and provides a calmer area for outdoor recreation. It fills a gap between the existing buildings and is encircled by a footpath at second level joining to the footbridges over Sportovní Street and the existing terrain in the north-western part. The footpath is ended by passageway between swimming pool and wellness centre. More and more people are looking for sport opportunities in cities however; there are still not enough quality grounds and facilities on offer. The facilities in this development are meant for regular trainings and recreation for the public, including parents with children, groups of friends as well as individual and team sports players, offering a range of day, evening and night activities both indoors and outdoors. Other facilities include outdoor changing rooms and sports equipment rental as well as spaces for meeting friends such as a restaurant, wellness and a dancing-hall.
45
Wachner, Doreen. "Membranen mit integrierter Stützstruktur." Doctoral thesis, Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-115118.
Анотація:
Die vorliegende Arbeit befasst sich mit der Herstellung von porösen Membranen mit integrierter Stützstruktur, wobei ihre Membrandicke geringer als ihr Porendurchmesser ist. Derartige Membranen können unter dem Begriff Mikrosiebe zusammengefasst werden und versprechen ein hohes Anwendungspotential als Filtermedien in industriellen und medizinischen Bereichen. Für die Membranstabilisierung werden Gewebe, extrudierte Gitter und Gewirke eingesetzt und erforscht. Gleichzeitig erfolgt die Weiterentwicklung eines bestehenden Herstellungsverfahrens von Membranen, welche nach dem Prinzip der partikelassistierten Benetzung (PAB) hergestellt werden. Die verschiedenen Stützstrukturen werden direkt bei der Membranherstellung fest in diese integriert. Weiterhin werden verschiedene Herstellungsparameter, wie zum Beispiel das Membranmaterial, die Funktionalisierung der Porenbildner und die leichtflüchtige Komponente gezielt untersucht und optimiert. Somit können mechanisch stabilisierte Membranen hergestellt werden, welche einen Durchmesser von bis zu 10 cm aufweisen. Für die abschließende Charakterisierung werden Filtrationsversuche und Stabilitätsmessungen durchgeführt.
46
Labudek, Lukáš. "Yacht club Hlučín - stavebně technologický projekt." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240368.
Анотація:
The subject of this thesis is a construction technology project object Yacht Club Hlučín. The basis for the elaboration of this work is the diploma thesis from Ing.Radim Kučera - Yacht Club Hlučín. This thesis includes technical report construction technology project, coordinating the situation with the construction of wider relations of routes for transportation of main materials, time and financial plan of the construction according to the technical-economic indicators, drawing building equipment, scheduling, inspection and test plan, technological regulation for the implementation of the gross substructure, itemized budget and the plan for OSH implementation in Yacht club Hlučín.
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Vystrčil, Jan. "Mateřská školka v Jihlavě." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2020. http://www.nusl.cz/ntk/nusl-410113.
Анотація:
In diploma thesis is elaborated project documentation for the construction of an building of kindergarten. The building is situated in peryphery of Jihlava city. The building is two-storey kindergarten building with a basement. There aure two classes for children 3 - 6 years old in the building. In diploma thesis is elaborated architect-building solutions, building – construction solutions, fire safety solutions and physics qualities of constructions.
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Hartman, František. "Energeticky efektivní horská chata." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265229.
Анотація:
This diploma thesis deals with project energy efficient mountain chalet. The building is located in the Krkonoše national park, near by highest Czech mountain named Sněžka. Object is located on plot number 899 in the cadastral Pec pod Sněžkou, on the site of the initial ,,Giant” chalet. The aim of this thesis is proposal of energy efficient mountain chalet in extreme climate conditions, such as in the mountain area, at the elevation 1378 m. Proposal of the chalet emphasis is on achieving maximum energy self-sufficiency. The building consists of two objects SO 01 and SO 02 interconnected by the roof. The total built-up area is 191.39 square meters. The accommodation capacity is 20 people.
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FERIC, NICOLE T. "Interactions of Lipoprotein(a) with the Plasminogen System: Mechanisms and Pathophysiological Consequences." Thesis, 2011. http://hdl.handle.net/1974/6905.
Анотація:
Elevated plasma concentrations of lipoprotein(a) (Lp(a)) are associated with increased risk of atherothrombotic disease. Lp(a) is a unique lipoprotein consisting of a low density lipoprotein-like moiety covalently linked to apolipoprotein(a) (apo(a)), a homologue of the fibrinolytic proenzyme plasminogen. Apo(a) is extremely heterogeneous in size with small isoforms being independently associated with increased cardiovascular risk.
Several in vitro and in vivo studies have shown that Lp(a)/apo(a) can inhibit tissue-type plasminogen activator (tPA)-mediated plasminogen activation on fibrin surfaces, although the mechanism of inhibition by apo(a) remains controversial. Essential to fibrin clot lysis are a number of plasmin-dependent positive feedback reactions that enhance the efficiency of plasminogen activation, including the plasmin-mediated conversion of Glu1-plasminogen to Lys78-plasminogen.
Additionally, abnormal fibrin clot structures have been associated with both an increased risk of cardiovascular disease and elevated Lp(a) levels. Similarly, oxidized phospholipids have been implicated in the development of cardiovascular disease, and are not only preferentially carried by Lp(a) in the plasma but have also been shown to covalently-modify both apo(a) and plasminogen.
In this thesis, we built upon the understanding of the role of apo(a) in plasminogen activation on the fibrin/degraded fibrin surface by determining that: (i) apo(a) inhibits plasmin-mediated Glu1-plasminogen to Lys78-plasminogen conversion and identifying the critical domains in apo(a) responsible for this effect, (ii) apo(a) isoform size does not affect either the inhibition of tPA-mediated plasminogen activation or the inhibition of plasmin-mediated Glu1-plasminogen to Lys78-plasminogen conversion, (iii) apo(a) modifies fibrin clot structure to form more dense clots with thinner fibers and reduced permeability, modifications that enhance the ability of apo(a) to inhibit tPA-mediated plasminogen activation and (iv) the phosphorus content of apo(a) affects its ability to inhibit tPA-mediated plasminogen activation and the phosphorus content of plasminogen affects its ability to be activated by tPA.
By understanding these individual reactions, each of which has the potential to affect the broader fibrin clot lysis process, we have expanded our understanding of the overall effect of Lp(a)/apo(a) in the inhibition of plasminogen activation on the fibrin/degraded fibrin surface and thus broadened our understanding of how Lp(a)/apo(a) may mediate the inhibition of thrombolysis in vivo.Thesis (Ph.D, Biochemistry) -- Queen's University, 2011-12-14 08:26:54.99
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Swanson, Pascale Libront. "Revisiting the antifibrinolytic effect of carboxypeptidase N: novel structure and regulation." Master's thesis, 2010. http://hdl.handle.net/10048/1215.
Анотація:
Carboxypeptidase N (CPN) is a plasma carboxypeptidase that was discovered in the 1960s as a regulator of inflammation and vascular tone. Through the removal of carboxy-terminal basic residues, CPN alters the activity or binding specificity of inflammatory mediators and vasoactive peptides. CPN shares significant homology with carboxypeptidases known to mediate antifibrinolysis through the removal of basic residues from fibrin clots, which would otherwise stimulate fibrinolysis. Despite the similarity of these enzymes, CPN is generally regarded as lacking a role in fibrinolysis. This thesis demonstrates that CPN is indeed a capable antifibrinolytic enzyme, and that the antifibrinolytic activity of CPN was previously undisclosed due to the presence of a circulating CPN inhibitor, which is likely the free CPN2 subunit. This inhibitor is described for the first time here. Furthermore, potential mechanisms of inhibition and mechanisms of enhancing activity of CPN are proposed based upon the additional structural characterization of CPN presented here.