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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
171

Moment-rotation characteristics of semi-rigid, high-tensile bolted connections.

Mathison, William. January 1959 (has links)
Moment rotation characteristics are obtained for a standard web connection for a 12 inch deep beam using high tensile bolts. Variables were 1) initial pre-tension 2) thickness of angle 3) ratio moment shear. The results obtained are compared with existing information. The rotation is found to be due to angle deformation and column deformation. The effect or the column flange stiffness on the connection characteristics are analyzed. The effect of the history of the connection is shown also. The determination or pre-tension in the bolts is described as well as the complete instrumentation and behaviour during test.
172

Hydrologic regime of Lake Hertel, Mont St. Hilaire, P. Q.

Goswami, Santosh. R. January 1962 (has links)
The objective of the investigation was to establish the hydrologic regime of the drainage basin of the Lake Hertel giving proper considerations to the various phases of the hydrologic cycle. Constructional features included two measuring weirs for inflow to and a measuring weir for outflow from the Lake. Installation of a class "A" evaporation pan with all instrumentations were done to register all parameters to compute water surface evaporation. These were compared with results from empirical formulae. Comparative calculations concerning applicability of meteorological data of McGill University and St. Hubert Air Base meteorological stations were made. Rainfall - runoff relations were analysed measuring inflow by the two measuring weirs taking into account base flow and surface runoff. From such observational findings the derivation of a runoff coefficient for this area was aimed at. Complete computations for all phases of the analysis were tabulated in the text of the thesis.
173

Comparisons of player calibers and skate models during an ice hockey explosive transitional maneuver

Forget, Samuel January 2014 (has links)
The ground (ice) reaction force and the plantar foot pressure variables were measured during an explosive transitional maneuver, stop and go, skating task on ice using: 1) regular hockey skate and 2) a modified skate with an altered tendon guard and eyelet configuration which allows for increased dorsiflexion and plantarflexion. The objective of this study was to describe the differences in skating mechanics and kinetics between high and low caliber skaters and between the two different skate models during the specific explosive transitional, stop and go, skating task. Both the left and right skates were instrumented with a calibrated strain gauge force transducer system to measure the ground (ice) reaction force and with an insole system used to measure the plantar foot pressure variables during the stop and go skating task. Similar CoP and vertical force results were observed between the two skate models; however, high caliber skaters showed a reduction of 10.7 (inside skate) and 15.2 (outside skate) mm in total antero-posterior CoP excursion during the stop phase (p<0.05). In conclusion, specific postural control patterns were observed between high and low caliber skaters. However, a full body kinematic study might be needed in order to study the exact biomechanical changes. / Les variables de la force de réaction du sol (glace) et de la pression plantaire du pied ont été mesurées pendant une manœuvre de transition explosive, "stop and go", de patinage sur glace. 1) à l'aide de patins de hockey standard et 2) des patins de hockey modifiés avec un protecteur du tendon d'Achille plus flexible et une configuration différente des œillet pour lacets permettant une plus grande flexion dorsale et plantaire de la cheville. Le but de cette étude était d'illustrer les différences de la mécanique du patinage et la cinétique entre les patineurs de haut et bas calibre et entre les deux modèles de patins pendant la tâche de patinage spécifique du "stop and go". Tant les patins de gauches et de droites ont été instrumentés avec un système d'estimation de la force calibré et avec un système de capteurs de pression en dessous de la semelle pour mesurer les variables de la pression plantaire du pied pendant la tâche de patinage du "stop and go". Les deux modèles de patin ont démontré des résultats similaires quant aux variables du Centre de Pression (CdP) et de la force verticale. Toutefois, les patineurs de haut calibre ont démontré une réduction de 10,7 (patin intérieur) et 15.2 (patin extérieur) mm concernant le déplacement total du CdP antéro-postérieur pendant la phase d'arrêt (p <0,05). En conclusion, des modèles spécifiques du contrôle postural ont été observées entre les patineurs de haut et de bas niveau. Néanmoins, une étude cinématique exhaustive du corps humain serait manifestement nécessaire afin d'étudier les changements biomécaniques exacts.
174

Computational modeling for stress analysis of overhead transmission line stranded conductors under design and fretting fatigue conditions

Qi, Gang January 2014 (has links)
While great efforts have been made in the electrical utility industry to engineer various stranded conductors with enhanced strength and vibrational characteristics, research devoted to understanding the complex mechanical behavior of complete conductors has been scarce, especially from a computational mechanics perspective. In the meanwhile, the long-lasting problem of conductor fretting fatigue becomes increasingly critical for overhead line design and maintenance, especially with the world-wide aging of electrical transmission grids. Aging of conductors contributes to significant degradation of their local fatigue strength, leading to drastic reduction of their service life. However, the complex mechanical response of stranded conductors cannot be well predicted by either experimental testing or simplified theoretical models, owing to the physical complexity introduced by their multi-layer stranded geometry, nonlinear material properties, substantial frictions among the wires and between the wires and hardware clamping systems, as well as the comprehensive contact interactions amongst their components. Simplified beam models and coarse 3-D models of earlier computational studies also fail to calculate the accurate stress variations inside a conductor strand and capture the stress gradients near the contact interfaces. Moreover, the estimations of fretting fatigue life are very dependent on the high accuracy of the stress predictions in the conductor wires. Therefore, reliable high-fidelity computational models have been long expected for a better understanding of the contact damage of transmission line conductors under both design and fretting fatigue conditions. The main objective of this thesis is to study the complex stress states and relevant influencing factors of stranded electrical conductors, using finite element analysis approaches. The research was carried out in three stages. First of all, a study focused on the finite element (FE) modeling of an optical ground wire (OPGW) cable strand for its detailed stress analysis. A refined 3-D FE model including all essential nonlinear characteristics was successfully constructed. As a result, a high-fidelity physics-based macroscopic modeling methodology was developed for detailed and accurate computational stress analysis of stranded conductors. A 795 kcmil Drake ACSR conductor was then selected as a benchmark conductor to investigate the tensile strength and critical stress states of a complete conductor under extreme design conditions. Furthermore, a sensitivity study explored the relative importance of friction effects among conductor wires on the mechanical response.A large scale 3-D FE stress analysis model with comprehensive nonlinearities was developed and implemented to simulate an actual ACSR fretting fatigue test. The computational results showed good agreement with some experimental measurements and field observations reported in the open literature. Based on the accurate stress analysis, a practical multi-axial fatigue lifing methodology was developed to estimate local fretting fatigue strength of electrical conductors. Subsequently, a parametric study was performed to examine the influence of fretting amplitudes on the mechanical response of the conductor-clamp system.In conclusion, this research shows the reliability and significance of using reliable FE modeling in predicting the complex response of stranded conductors, which has contributed to fill some of the current knowledge gaps. Furthermore, the computational modeling and lifing approaches developed in this thesis provide a different perspective from existing practices and may become a starting block of further exploration of the mechanisms of conductor fretting fatigue and future development of improved fatigue lifing methods for the increasingly aging overhead transmission line conductors. / Malgré les efforts déployés par l'industrie des lignes de transport d'électricité pour la conception de conducteurs toronnés de haute résistance mécanique, la recherche dédiée à la compréhension physique du comportement mécanique des conducteurs s'est faite plus rare, surtout du point de vue de la mécanique computationnelle. Le problème du vieillissement des conducteurs de lignes aériennes à haute tension, en particulier celui de l'usure en fatigue des brins et torons, n'est toujours pas complètement compris ni donc résolu. Le vieillissement des conducteurs se manifeste par une dégradation importante de leur résistance locale à l'usure en fatigue, réduisant par le fait même leur vie utile et la robustesse mécanique de l'ensemble de la ligne. Il faut reconnaître que les études expérimentales et les modèles théoriques simplifiés ne peuvent pas prédire le comportement mécanique détaillé des conducteurs toronnés à cause de la complexité physique de ces câbles: torons et brins multicouches, matériaux inélastiques non-linéaires, effets des frictions substantielles entre les brins, torons et les surfaces des accessoires d'attache, ainsi que les interactions de contact entre ces éléments.Les travaux rapportés dans la thèse procèdent en trois étapes principales, décrites ci-après. La première partie consiste à préparer un modèle de section de câble de garde à fibre optique (CGFO) de construction complexe et d'en faire l'analyse détaillée sous déplacement axial contrôlé. Cette étape a servi à établir les bases de la méthodologie proposée, lesquelles sont discutées de manière exhaustive. La deuxième partie de la recherche porte sur la modélisation raffinée du conducteur de ligne ACSR 795 kcmil qui porte le nom de code « Drake », sélectionné comme cas de référence pour étudier la résistance en traction et les états de contraintes complexes du conducteur sous des conditions de conception extrêmes de conception. sensibilité a également exploré l'importance relative des effets frictionnels entre les brins du câble sur les contraintes calculées par le modèle. Finalement, un modèle détaillé 3-D est créé pour simuler les conditions précises d'un essai typique de fatigue en flexion pour le conducteur « Drake » jumelé à une pince de suspension. Le modèle retient toutes les non-linéarités du problème d'un point de vue mécanique. l'auteur suggère une méthode pratique pour évaluer la résistance locale en fatigue multiaxiale des conducteurs du type ACSR au droit des points de contact des pinces de suspension. Cette méthode est relativement simple d'application (une fois les analyses de contraintes disponibles) et donne des résultats en accord avec les valeurs recommandées par les manufacturiers pour le câble « Drake ». Par la suite, une étude paramétrique est faite pour vérifier l'influence de l'amplitude des mouvements de glissement sur les états de contraintes déterminés dans le conducteur dans la région de contact avec la pince sous l'effet d'un cycle complet de chargement flexionnel. En conclusion, cette recherche démontre la faisabilité et la pertinence de l'usage des méthodes computationnelles avancées pour l'analyse des contraintes d'un problème complexe comme celui des conducteurs toronnés multicouches. La méthodologie de construction des modèles est une contribution scientifique importante qui permet d'améliorer notre compréhension du comportement mécanique des conducteurs sous charges extrêmes ou dans des conditions de fatigue flexionnelle. La méthode proposée pour l'estimation de la résistance à l'usure en fatigue est également utile pour l'industrie des lignes de transport et pour les manufacturiers de câbles et il est envisageable que cette recherche servira de tremplins à plusieurs autres études computationnelles pertinentes sur les conducteurs de lignes afin d'améliorer leur fiabilité et leur robustesse mécanique.
175

Supercritical flow in curved channels.

Anand, Tilakraj. R. January 1954 (has links)
The importance of study of super-critical flow in open channels is recognized by present day hydraulic engineers. The subject is so vast and the mechanics of such flow is so complex that in spite of considerable work having been done in this field during the past twenty years, the final word has still to be said, especially regarding the beat remedial measures available. The writer found an article "Model Study Aids Designers of Spillway for Lyman Run Dam" in September 1951 issue of "Civil Engineering".
176

Some effects of cation exchange on Leda clay.

Coates, Donald. F. January 1954 (has links)
Most engineers interested in soil problems now recognize that for progress to be made analysis must be in terms of more fundamental physical and chemical concepts. The nature of the exchangeable cation is an example of an important chemical factor contributing to the properties of many clays. Experimental work has shown that in some soils swelling due to frost action can be dramatically reduced by changing the exchangeable cation./47 Other work indicates that the bearing capacity of piles may be increased by promoting cation exchange./47 At the Golden Gate Exposition the permeability of a lagoon was reduced 90% as the result of cation exchange./37
177

Flow of granular material through orifices.

Ahmed, Syed. I. January 1959 (has links)
This study introduces and investigates a general method for measuring the flow of granular material through orifices. During the last decade or so, the phenomenon of the mechanization of material handling in modern industry has developed into immense proportions. But the problem of the handling of granular material through orifices lies, obviously, at the very root of this tremendous development. The present study is an attempt to contribute to the solution of this problem. Laboratory investigations were conducted with Ottawa Sand, glass bins, sand-paper bins and circular orifices. The effect of head, diameter of bin, diameter of orifice, roughness of bin walls and vibrations on the flow were studied. Graphs were plotted and the flow constants ascertained.
178

Plastic steel design with semi-rigid connections.

Nitkin, Irving. M. January 1961 (has links)
Note: Missing Page 55. / This thesis is concerned with the effect of connections of the semi-rigid type on the Plastic methods of structural steel design. The basic principles of Plastic Design are presented, illustrating the formation of plastic ''hinges", and their rotational properties. The beam line method for semi- rigid connections, originated by C. Batho, is shown, and a theory presented using this beam line to find the required semi- rigid connection which will transfer the hinge rotation from the beam to the connection. Experiments are described in which this theory was verified. Two connections were tested to obtain their moment-rotation characteristics. Then two statically indeterminate structures using the same types of connections were tested to demonstrate that all plastic hinges formed at the same load. Finally, the advantages of this method are discussed.
179

Seismic response of steel beams coupling concrete walls

Harries, Kent A. (Kent Alexander) January 1992 (has links)
Ductile coupled flexural walls are critical lateral load resisting systems of many structures. The coupling beams of these structures must exhibit excellent ductility and energy absorption ability. To achieve better ductility and energy absorption than previously possible, the use of steel link beams with their ends embedded in the reinforced concrete walls is proposed. Preliminary experimental results are reported for two full-scale reversed cyclic loading tests of portions of ductile flexural walls coupled with steel link beams. The excellent performance, together with the ease of construction, demonstrate the feasibility of this alternative form of construction. In order to ensure ductile response, design and detailing guidelines for both the clear span and embedded portions of the link beams and the reinforced concrete embedment region are presented. An assessment, based on comparisons with other structural systems, of this novel type of construction is presented.
180

Some fundamental considerations in the mechanics of frozen soils.

Yong, Raymond. N. January 1960 (has links)
The behaviour of frozen soil under loading conditions has been studied in terms of fundamental factors contributing to the strength of the soil. Electro-chemical theories based upon forces of interaction between charged particles have been applied by considering fine-grained soils as platelets with unbalanced charges. It has been shown that the quantity of water remaining unfrozen in a soil-water system is directly related to the surface potential and the potential halfway between two adjacent charged plates. Unfrozen water content is dependent on the original water content, temperature, clay content, charge density, and electrolytic concentration.

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