Développement d'un connecteur Rigide-Ductile-Économique pour dalles composites en bas lamellé-croisé et béton pour les bâtiments multiétages

Les structures en bois sont une bonne solution pour la construction de bâtiments multiétages. Le bois est reconnu pour son aspect architectural, pour son empreinte écologique faible ainsi que pour sa résistance mécanique. L’ajout d’une mince couche de béton connectée à l’aide de connecteurs de cisaillement sur une pièce de bois lamellé-collé ou bien un CLT permet d’augmenter considérablement la rigidité du plancher. Il est donc possible de construire sur une plus longue portée tout en respectant les critères de flèche d’État Limite de Service (ELS) et de résistances aux États Limites Ultimes (ELU). Ces solutions innovantes sont aussi moins sensibles aux vibrations puisqu’elles sont plus rigides. Le confort des usagers est donc amélioré. Cette thèse se concentre sur le développement d’une connexion de type entaille peu profonde adaptée aux dalles composites. Cette connexion est conçue afin d’obtenir un comportement initial rigide, puis une grande ductilité. Ceci est possible en utilisant le caractère ductile en compression du bois. Plusieurs configurations sont testées dans le CLT et dans le bois lamellé-collé. La profondeur de l’entaille varie. L’influence de la présence d’un isolant acoustique entre le bois et le béton est aussi quantifiée. Les premiers tests de cisaillement sur les différentes configurations ont montré de très bons résultats et des dalles CLT-BHP ont été coulées pour une portée de 8 m. Les dalles de CLT-BHP ont été conçues selon une approche multicritère afin de respecter les normes du Code National du Bâtiment du Canada et de maximiser certains facteurs considérés importants par le milieu de la construction tels l’épaisseur du plancher, le poids du plancher, le coût, etc.Wooden structures are a good solution for building multi-story buildings. Wood is known for its architectural appearance, low footprint and mechanical strength. The addition of a thin layer of concrete connected using shear connectors to a piece of glued-laminated timber (GLULAM) or a Cross-Laminated Timber (CLT) considerably increases the rigidity of the floor. It is therefore possible to build longer span in building while respecting the Serviceability Limit States (SLS) deflection criteria as well as the Ultimate Limit States (ULS) bearing capacity. These innovative solutions are also less sensitive to vibrations since they are more rigid. The comfort of users is improved. This thesis focuses on the development of a shallow notch type connection suitable for composite slabs. This connection is designed to obtain a rigid initial behavior, followed by a big ductility. This is possible by using the compressive ductile nature of the timber. Several configurations are tested in CLT and GLULAM. The depth of the cut varies from 20 mm to 35 mm. The influence of the presence of an acoustic insulation between the timber and the concrete is also quantified. The first shear tests on the different configurations showed very good results. Three 8 m single span CLT-HPC slabs were cast. The CLT-HPC slabs were designed with a multi-criteria approach to meet the National Building Code of Canada (NBCC) standards and to maximize certain factors considered important by the building industry such as floor thickness, floor weight, the cost, etc

Lightweight and slender timber-concrete composite floors made of CLT-HPC and CLT-UHPC with ductile notch connectors

Cross-Laminated Timber (CLT) structures have been emerging worldwide for residential floors in multi-storey buildings thanks to their lightness, fast construction and low ecological footprint. This work aims at fostering this application, which is often limited by vibrational and deflection limits, by investigating composite slab floors made of CLT and High-Performance Concrete (HPC) slab as well as CLT and Ultra High-Performance Fiber Reinforced Concrete (UHPFRC). Firstly, the composite floors CLT-HPC and CLT-UHPFRC with a span of 8 m were designed by considering a multicriteria analysis. To assure a certain structural ductility, previously developed ductile notch connectors were employed. As an economic choice, no shear reinforcement in the concrete slab was employed. Then, fullscale composite beams were fabricated in order to verify the predicted flexural behaviour and natural frequency. A numerical analysis was carried out to verify the connectors could effectively yield before the timber collapse. The comparison between the numerical simulation and the slip measurements confirmed that about 50% of the notch connections fully yielded and underwent inelastic deformation which favors the structural ductility. In the case of the CLT-HPC floor, a reduction of the notch contact surface due to the use of plastic sheet waterproofing as well as shear cracks developing in the concrete close to the notch corner both reduced the expected structural stiffness. Finally, the CLT-UHPFRC floor is endowed with outstanding values of slenderness ratio (~35) and lightness (~2 kPa), while eliminating the use of shear reinforcement and sheet waterproofing

Changes in hair cortisol and self-reported stress measures following mindfulness-based stress reduction (MBSR) : a proof-of-concept study in pediatric hematology-oncology professionals

Background and purpose Little data is available on the effect of mindfulness amongst pediatric hematology-oncology professionals. The purpose was to further document change in biological and psychological stress following a mindfulness-based stress reduction (MBSR) program. Materials and methods We led two pre-post interventional studies (n = 12 and n = 25) and measured changes on hair cortisol concentrations, perceived stress, psychological distress and burnout. Results Professionals did not change on biological stress (d = 0.04), but improved on self-reported measures (median d = 0.58). Effects were maintained over 3 months for psychological distress, anxiety, depression, and burnout (median d = 0.66). Effects were larger if trainees participated to the retreat and if they reported higher baseline perceived stress. Conclusion In pediatric hematology-oncology professionals, an MBSR program was related with improvements in self-reported stress over 3 months. Components of the program and characteristics of trainees may influence the impact of MBSR

Étude de formation de cycles à dix membres par voie directe : étude de la réaction de Diels-Alder transannulaire de triènes macrocycliques à quatorze et à quinze membres : vers une synthèse de l'aphidicoline

La première partie de cette thèse décrit les résultats obtenus pour la préparation de cycles à dix membres insaturés utilisant la réaction de déplacement interne d'un halogénure par l'anion malonate comme méthode de cyclisation. Les propriétés conformationnelles des produits obtenus y sont discutées. La seconde partie traite de la cycloaddition[4+2] transannulaire. Dans la première section, les résultats d'une étude générale de la cycloaddition de triènes macrocycliques à quatorze membres sont présentés. La section suivante décrit l'étude modèle d'un triène macrocyclique à quinze membres en vue d'une synthèse totale de l'aphidicoline par la stratégie transannulaire

Le nid de l'aigle

See French abstract

Engineering ductile notch connections for composite floors made of laminated timber and high or ultra-high performance fiber reinforced concrete

Different kinds of ductile connectors have been lately developed for enhancing the structural ductility of TimberConcrete Composite (TCC) structures. In particular, ductile notch connections can be designed by favoring the local compression failure of wood fibers. This work aims at further developing economic and ductile notch connector by considering different floor systems made of Glulam Laminated Timber (GLT) beam or Cross Laminated Timber (GLT or CLT) slab connected with a High Performance Concrete (HPC) slab or a Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) slab. Firstly, the geometry of the notch connector was suitably designed for favoring a ductile hierarchy of collapse modes. Then, a wide campaign of push-out tests was carried out to characterize the shear behaviour of 14 connection configurations by varying the notch geometry, the concrete type and the possible presence of acoustic insulation. Finally, based on the experimentally identified connection shear law, an example of design is presented for a TCC slab of 9 m span. The insulation layer was found to reduce the connection stiffness, but to increases the structural stiffness thanks to the enhanced lever arm of the composite action. For plastically designed TCC structures, the connection ductility allows increasing the structural ductility for both GLT-(U)HPC and for CLT-(U)UPC floor systems