Dans le cadre du projet d’avion plus électrique entamé depuis quelques années, l’objectif visé est le remplacement des énergies hydraulique et pneumatique par l’énergie électrique. Cette transition technologique drastique nécessite une augmentation de puissance électrique à bord des avions, qui se traduit par une élévation des niveaux de tension du réseau embarqué (+/- 270 VDC et 230 VAC). Dans ces conditions, les phénomènes de décharges électriques doivent être considérés, en particulier pour les systèmes présents dans les zones non pressurisées des appareils. Les travaux de thèse ont porté sur l’étude des décharges partielles dans des connecteurs aéronautiques aujourd’hui exploités et susceptibles d’être mis en oeuvre dans les nouvelles conditions de tension. Une modélisation électrostatique du connecteur a été effectuée dans le but de mettre en évidence les zones où règne un fort champ électrique pouvant être à l’origine de l’apparition de décharges partielles. L’influence de paramètres, tels que la géométrie des conducteurs, la pression et la température, a été examinée d’un point de vue théorique par adaptation de la courbe de Paschen. Des mesures expérimentales, effectuées dans différentes conditions d’alimentation électrique, de pression, de température et d’état de vieillissement des connecteurs, ont permis de déterminer les tensions seuil d’apparition des décharges partielles. Ces mesures ont également permis de localiser les décharges au sein du connecteur, et ainsi d’identifier les points faibles de la structure. Des solutions visant à repousser les seuils d’apparition de décharges partielles sont alors proposées. / The objective of the more electrical aircraft project is the replacement certain of the hydraulic and pneumatic systems by electrical ones. This drastic technological transition will require the increase of the onboard electrical power, which will result in the increase of voltage levels of the embedded networks. Current systems of 28 VDC and 115 VAC (400 Hz) are to be replaced by +/- 270 VDC and 230 VAC (360 to 1000 Hz). These new conditions of voltage levels will have a significant impact on the appearance of partial discharges that were almost absent up until present. Aeronautical grade electrical connectors being one of the major elements of embedded networks, the aim of this thesis is to study the conditions of occurrence of partial discharges in them. In this work, electrostatic modeling is carried out in order to identify the zones within the connectors where there is a strong electric field facilitating the appearance of partial discharges. Also presented are the results of experiments under both DC and AC voltage in which the ignition voltages of partial discharges and their location within the structure of the connector were studied.

No / This paper presents the experimental and numerical investigation into the behaviour of headed shear studs in composite beams with profiled metal deck flooring. A new single-sided horizontal push test arrangement is proposed to evaluate the shear capacity of the headed shear connectors in pairs with metal deck profiled sheeting. The characteristic resistance obtained from the horizontal push test is compared with Eurocode 4. A three-dimensional finite element model was developed using general purpose finite element program ABAQUS/Explicit. The shear connector capacity, load-slip behaviour and failure modes are validated against experimental results and close correlations were obtained.

yes / This paper presents an experimental study on shear strength, stiffness and ductility of demountable shear connectors in metal decking composite slabs through push-off tests. Twelve full-scale push-off tests were carried out using different concrete strength, number of connectors and different connector diameter. The experimental results showed that the demountable shear connectors in metal decking composite slabs have similar shear capacity and behaviour as welded shear studs and fulfilled the minimum ductility requirement of 6mm required by Eurocode 4. The shear capacity was compared against the prediction methods used for the welded shear connections given in Eurocode 4, AISC 360-10, ACI 318-08 and method used for bolted connection in Eurocode 3. It was found that the AISC 360-10 method overestimated the shear capacity while the ACI 318-08 method underestimated the shear capacity of specimens with single shear connector per trough. The Eurocodes method was found to provide a safe prediction for specimens with single and pair demountable connectors per trough. In addition, prediction methods given in both AISC 360-10 and ACI 318-08 for welded shear studs overestimated the shear capacity of specimens with 22 mm diameter demountable connectors that failed in concrete crushing. / PhD work from EPSRC studentship

No

One of the major purposes of this project was to demonstrate optical components which will be used in fibre optic distribution systems. These include the fibre itself, couplers, connectors, splices, sources and detectors. All components used are state-of-the-art, the star coupler and fusion splice technique being developed by the author during the completion of the project. The star coupler has proved to have one of the lowest insertion losses of any such component to date. Although the telephone system demonstrated has only 3 stations, very similar or identical components would be used in an expanded network. / Thesis / Master of Engineering (MEngr)

No description available.

no / Precast concrete floors are widely used in building construction, but there is little detailed design guidance on their application in steel-framed buildings. Traditionally the steel beams have been designed to support the precast slabs on their top flange. However, there are an increasing number of composite frames and slim floor constructions where the precast slabs are designed to interact structurally with the steel frame. Composite action can be developed by welded shear connectors attached to the steel beams and by transverse reinforcement; however, this form of construction is currently outside the provisions of the current codes of practice. This paper discusses some of the particular issues that affect this form of construction, and presents design guidance using the Eurocode methodology.

The objectives of this research were twofold: a) to define the relationship between tooth withdrawal and specific gravity for southern pine lumber and four different plate-to-wood load orientations, and b) to demonstrate how these relationships could be applied to new lumber grades to predict tooth withdrawal performance so that additional testing would not be necessary. The four orientations investigated were: a.) LRAA - plate axis parallel to load and wood grain parallel to load. b.) LREA - plate axis perpendicular to load and wood grain parallel to load. c.) LRAE - plate axis parallel to load and wood grain perpendicular to load. d.) LREE - plate axis perpendicular to load and wood grain perpendicular to load. For the LRAA, LREA, LRAE, LREE orientations, the following sample sizes were respectively: 27, 22, 27, and 29. Results showed specific gravity and embedment gap were excellent predictors of ultimate tooth withdrawal stress for the LRAA orientation. However, neither specific gravity nor percentage of latewood significantly influenced the location of tooth withdrawal. For the LREA orientation, specific gravity alone was a good predictor of ultimate tooth withdrawal stress. Furthermore, the side of the joint test specimen where tooth withdrawal initiated was dependent on the wood piece with the lowest mean specific gravity. For the LRAE orientation, specific gravity was a marginal predictor of ultimate tooth withdrawal stress. For the LREE orientation, specific gravity was a decent predictor of ultimate tooth-withdrawal stress. / Master of Science

The purpose of this research is to evaluate and compare the influence of four types of secondary reinforcement on various component strengths related to composite slabs. These components include the composite slab strength under uniform load, the strength of two types of shear connectors used with composite beams and joists, composite slab strength due to a concentrated load, and the flexural toughness and first-crack strength of fiber-reinforced concrete using ASTM C1018 (1998) standard test. The performance of the specimens reinforced with fibers are compared with that of the specimens reinforced with welded-wire fabric (WWF), with the purpose of determining if fiber-reinforced concrete can be used as an alternative to WWF. / Master of Science

No / In steel-concrete composite construction, headed stud shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface. Present knowledge of the load-slip behavior of the shear stud in composite beam is limited to data obtained from the experimental push-off tests. A finite element model to simulate the structural behavior of headed stud shear connector in steel-concrete composite beam is described in the chapter. The model is based on finite element method and takes into account linear and nonlinear behavior of the materials. The model has been validated against test results and compared with data given in the current Code of Practices, for which both demonstrate the accuracy of the model used. Parametric studies using the model to investigate variations in concrete strength and shear stud diameter are also discussed in the chapter. The model takes into account the linear and nonlinear material properties of the concrete and shear stud. The FE results compare well with the experimental push-off test results and specified data from the codes. The FE model accurately predicts the mode of failure.