Many different Flexible AC Transmission System (FACTS) devices have been studied in recent years in order to control the flow of power through transmission lines and reduce the overall burden on the power grid. The net results of these devices are decreased utility costs, increased system stability, and improved system flexibility. The main issues with most currently available FACTS controllers are the high costs of installation, and operation. The Sen Transformer (ST) is a new FACTS device that decreases these costs by using relatively inexpensive and industry familiar transformer technology to independently control the active and reactive power in a transmission line.<p> This thesis introduces the first full transient model for the ST developed in an ElectroMagnetic Transients Program (EMTP) using a hybrid transformer modeling approach. This technique handles all the non-linearities of the core, including losses and saturation effects, as well as inter-phase coupling, and zero sequence effect with an attached topographically correct core model. This new model can be used in a variety of power system studies such as transient and dynamic simulations, and protection analysis. The flexibility of the hybid ST model allows for different core and winding configurations as well as response to very fast transients with little modification. Fault analysis studies are presented to showcase the capabilities of the transient ST model developed.<p> The first ST transient model using the Finite Element Analysis (FEA) technique is also created for comparison with the hybrid ST model. This method uses Maxwells equations, material non-linearities and coupled electric circuits to obtain a precise transient solution for the ST. There is good agreement between the two models in a test system for multiple types of fault scenarios. The hybrid ST model is therefore the preferred model to use for fault analysis since it reduces simulation time drastically when compared to the FEA ST model.<p> The hybrid ST model is then used to develop and test differential, and ground protection schemes that ensure device safety during faulted scenarios. The protection schemes are analyzed and compared with analogous Phase Angle Regulator (PAR) schemes that have been implemented for many years.

Diffraction Enhanced X-ray Imaging (DEI) uses synchrotron X-ray beams prepared and analyzed by perfect single crystals to achieve imaging contrast from a number of phenomena taking place in an object under investigation. The crystals used in DEI for imaging requires high precision positioning due to a narrow rocking curve. Typically, the angular precision required should be on the order of tens of nanoradians.<p>One of the problems associated with DEI is the inability to control, set, and fix the angle of the analyzer crystal in relation to the beam exiting the monochromator in the system. This angle is used to interpret the images acquired with an object present and the usual approach is to determine where the image was taken after the fact. If the angle is not correct, then the image is wasted and has to be retaken. If time or dose is not an issue, then retaking the image is not a serious problem. However, since the technique is to be developed for live animal or eventually human imaging, the lost images are no longer acceptable from either X-ray exposure or time perspectives.<p>Therefore, a mechanical positioning system for the DEI system should be developed that allows a precise setting and measurement of the analyzer crystal angles. In this thesis, the fundamental principles of the DEI method, the DEI system at the National Synchrotron Light Source (NSLS) and the sensitivity of the DEI system to vibration and temperature has been briefly studied to gain a better understanding of the problem. The DEI design at the NSLS was analyzed using finite element analysis software (ANSYS) to determine the defects in the current design which were making the system dimensionally unstable. Using the results of this analysis, the new analyzer support was designed aiming to eliminate the problems with the current design. The new design is much stiffer with the natural frequency spectrum raised about eight times. <p> This new design will improve the performance of the system at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory, New York, USA and should assist in the development of a new DEI system for the Bio-Medical Imaging and Therapy (BMIT) beamline at the Canadian Light Source (CLS), Saskatoon, CANADA.

A combined experimental and analytical program was conducted to investigate the effects of Alkali-Silica Reaction (ASR) and Delayed Ettringite Formation (DEF) on D-regions in reinforced concrete (RC) bridge bents. Four large-scale RC specimens, which represent cantilever and straddle bents in Texas bridges in each specimen, were constructed. The first specimen represented the unexposed control specimen, while the other three were conditioned in the field with supplemental watering to promote ASR/DEF and served as the exposed specimens. The control and two exposed specimens with various levels of ASR/DEF, after eight months and two years of field conditioning, were load tested to failure. The last specimen remains in field with additional exposure to promote ASR/DEF and will be load tested in future studies. The width and length of preload-induced cracks and developing cracks that initiated in the exposed specimens and grew over time, indicating concrete expansion due to ASR/DEF mechanisms, were measured. Petrographic analysis results of concrete cores extracted from the exposed specimens after their load testing confirmed the formation of ASR gel and minimum accumulation of ettringite. The structural testing results showed that the failure mechanism in all three tested specimens was due to a brittle shear failure in the beam-column joint. However, slightly greater stiffness, strength, and ductility were observed in the exposed specimens as a result of the activation of the reinforcing steel in the specimens due to the expansion of the concrete primarily from ASR, which effectively prestressed and confined the core concrete. Sectional analysis and Strut-and-Tie Modeling (STM) of the experimental specimens were applied. Three-dimensional nonlinear Finite Element Analyses (FEA) were also conducted to numerically simulate the overall structural performance, internal response, and out-of-plane behavior of the experimental specimens. The effects of varying constitutive relations of the concrete in tension on models of the specimens were compared with the measured experimental response. A method to mimic ASR/DEF effects on exposed specimens was proposed and incorporated into the FEA approach. As a result, forces that prestress and confine the core concrete were effectively applied through the reinforcing steel prior to subsequent structural loading. The three-dimensional FEA approach was able to simulate the out-of-plane behavior of the beam-column joint and the proposed method yielded comparable results with the measured overall and internal behavior of specimens.

ABSTRACT FINITE ELEMENT ANALYSIS OF CORNERING CHARACTERISTICS OF ROTATING TIRES ErSahin, Mehmet Akif Ph. D., Department of Mechanical Engineering Supervisor: Prof. Dr. Y. Samim &Uuml / nl&uuml / soy September 2003, 157 pages A finite element model is developed to obtain the cornering force characteristics for rotating pneumatic tires which combines accuracy together with substantially reduced computational effort. For cord reinforced rubber sections such as the body plies and breaker belts, continuum elements with orthotropic material properties are used to improve solution times. Drastic reductions in computational effort are then obtained by replacing the continuum elements with truss elements which do not require orientation of element coordinate system to model textile body plies. With these simplifications, new model can be used produce a complete carpet plot of cornering force characteristics in substantially reduced solution times. The finite element model is used to obtain the cornering force characteristics of a tire, simulating the experiments on a tire test rig where the tire rotates on a flywheel. Results from both models are compared with each other and with the experimental results. It is concluded that the model developed provides results at least as accurate as the previously published models with a clear superiority in stability of solution.

Workpieces during cold forging fail basically due to ductile fracture. Ductile fracture can be predicted by damage models. In this study, various damage models such as Cockcroft &amp / Latham, McClintock, Freudenthal, Rice &amp / Tracy, Oyane, Ayada, Brozzo are investigated for their applicability to three workpiece materials: bearing steel (100Cr6), stainless steel (X5CrNiMo1810) and brass (CuZn39). The damage material parameters have been obtained by various tests such as tensile, standard compression, ring compression, compression with flanges and conical compression tests. The characterization has been assisted by finite element simulation of the various tests. It has been shown that the available damage models can predict the location of failure satisfactorily but are no able to predict the onset of failure quantitatively. Keywords: Formability Limit, Failure Criteria, Cold Forming, Surface Cracks, Finite Element Analysis

Many different Flexible AC Transmission System (FACTS) devices have been studied in recent years in order to control the flow of power through transmission lines and reduce the overall burden on the power grid. The net results of these devices are decreased utility costs, increased system stability, and improved system flexibility. The main issues with most currently available FACTS controllers are the high costs of installation, and operation. The Sen Transformer (ST) is a new FACTS device that decreases these costs by using relatively inexpensive and industry familiar transformer technology to independently control the active and reactive power in a transmission line.<p> This thesis introduces the first full transient model for the ST developed in an ElectroMagnetic Transients Program (EMTP) using a hybrid transformer modeling approach. This technique handles all the non-linearities of the core, including losses and saturation effects, as well as inter-phase coupling, and zero sequence effect with an attached topographically correct core model. This new model can be used in a variety of power system studies such as transient and dynamic simulations, and protection analysis. The flexibility of the hybid ST model allows for different core and winding configurations as well as response to very fast transients with little modification. Fault analysis studies are presented to showcase the capabilities of the transient ST model developed.<p> The first ST transient model using the Finite Element Analysis (FEA) technique is also created for comparison with the hybrid ST model. This method uses Maxwells equations, material non-linearities and coupled electric circuits to obtain a precise transient solution for the ST. There is good agreement between the two models in a test system for multiple types of fault scenarios. The hybrid ST model is therefore the preferred model to use for fault analysis since it reduces simulation time drastically when compared to the FEA ST model.<p> The hybrid ST model is then used to develop and test differential, and ground protection schemes that ensure device safety during faulted scenarios. The protection schemes are analyzed and compared with analogous Phase Angle Regulator (PAR) schemes that have been implemented for many years.

Stone column technique is mostly used to reinforce soft cohesive soils. Settlements are decreased under foundations and bearing capacity is increased. This study initially focuses on a comprehensive review of literature about stone column reinforced soils. Afterwards, numerical modeling of stone column reinforced soft clays is done. Three different cases are chosen on different foundation soils mainly soft clays. Parametric studies are done to determine influence of parameters on settlement reduction ratio under three different foundation conditions. Analyses are converted to two dimensional conditions and this conversion is also compared within the scope of this study. Settlement reduction ratio response to variation in parameters revealed similar results under three different foundation conditions.

Femoroacetabular impingement (FAI) is recognized as a pathomechanical process that leads to hip osteoarthritis (OA). It is hypothesized that mechanical stimuli are prominent at higher range of motions in hips with cam FAI (aspherical femoral head-neck deformity). Adverse loading conditions can impose elevated mechanical stimuli levels at the articulating surfaces and underlying subchondral bone, which plays a predominant mechanical role in early OA. The aim of this research was to determine the levels of mechanical stimuli within the hip, examining the effects of severe cam impingement on the onset of OA, using patient-specific biomechanics data, CT data, and finite element analysis (FEA). Patient-specific hip joint reaction forces were applied to two symptomatic patient models and two control-matched models, segmented from patient-specific CT data. The finite element models were simulated to compare the locations and magnitudes of mechanical stimuli during two quasi-static positions from standing to squatting. Maximum-shear stress (MSS) was analyzed to determine the adverse loading conditions within the joint and strain energy density (SED) was determined to examine its effect on the initiation of bone remodelling. The results revealed that peak mechanical stimuli concentrations were found on the antero-superior acetabulum during the squatting position, underlying to the cartilage. The MSS magnitudes were significantly higher and concentrated for the FAI patients (15.145 ± 1.715 MPa) in comparison with the MSS magnitudes for the control subjects (4.445 ± 0.085 MPa). The FAI group demonstrated a slight increase in peak SED values on the acetabulum from standing (1.005 ± 0.076 kPa) to squatting (1.018 ± 0.082 kPa). Insignificant changes in SED values were noticed for the control subjects. Squatting orients the femoral head into the antero-superior acetabulum, increasing the contact area with the cartilage and labral regions, thus resulting in higher peaks behind the cartilage on the acetabulum. The resultant location of the peak MSS and SED concentrations correspond well with the region of initial cartilage degradation and early OA observed during open surgical dislocation. Due to the relatively low elastic modulus of the articular cartilage, loads are transferred and amplified to the subchondral bone. This further suggests that elevated stimuli levels can provoke stiffening of the underlying subchondral plate, through bone remodelling, and consequently accelerating the onset of cartilage degradation. Since mechanical stimuli results are unique to their patient-specific loading parameters and conditions, it would be difficult to determine a patient-specific threshold to provoke bone remodeling at this stage.

No description available.

The analysis and design of bracing systems for complex frame geometries typically found in metal buildings can prove to be an arduous task given current methods. The American Institute of Steel Construction's Appendix 6 from the 2010 Specification for Structural Steel Buildings affords engineers a means for determining brace strength and stiffness requirements, but only for the most basic cases. Specifically, there are a number of aspects of metal building systems that place their designs outside the scope of AISC's Appendix 6 (Stability Bracing for Columns and Beams). Some of the aspects not considered by Appendix 6 include: the use of web-tapered members, the potential for unequally spaced or unequal stiffness bracing, combination of bracing types including panel and flange diagonal bracing, and the effects of continuity across brace points. In this research, an inelastic eigenvalue buckling procedure is developed for calculation of the ideal bracing stiffness demands in general framing systems. Additionally, the software provides a method of calculating the elastic lateral-torsional buckling load of members with generally stepped and tapered cross-sections, which satisfies an important need for rigorous design assessment. Extensive benchmarking to load-deflection simulations of geometrically imperfect systems is performed and recommendations are developed for determining the required design stiffness and strength of the bracing components based on the use of this type of computational tool.