Global ETD Search

21	Numerical Analysis of Cracking in Concrete Pavements Subjected to Wheel Load and Thermal Curling Aure, Temesgen W. January 2013 (has links) No description available. Civil Engineering Pavement analysis Curling Load transfer Concrete fracture Cohesive zone Crack propagation
22	Curling dynamics of naturally curved surfaces : axisymmetric bio-membranes and elastic ribbons Albarrán Arriagada, Octavio Eduardo, Albarrán Arriagada, Octavio Eduardo 20 December 2013 (has links) (PDF) Curling deformation of thin elastic surfaces appears in numerous natural and man-made structures where a spontaneous curvature is present. In this thesis, we couple theoretical approaches and macroscopic experiments on elastic ribbons to understand the dynamics of curling of opened bio-membranes, motivated by the need to better understand recent microscopic observations during egress of Malaria infected red blood cells (MIRBC) and bursting of artificial polymersomes.In a first part, we study theoretically pore stability and curling propagation of an initially opened spherical bio-membrane. We model geometrically curling deformation as the revolution of a decentered Archimedean spiral, leading to a prescribed toroidal wrapping of the membrane. In this configuration, we show how the stability of a pore to curling depends strongly on both line-tension and shear elasticity and we discuss these results in relation to the curling of MIRBCs membranes. Moreover, taking into account viscous dissipations, the consequent dynamics we calculate agrees quantitatively well with experimental data obtained during opening of MIRBCs. Our approach shows in particular how the membrane dissipation resulting from the surface redistribution dominates curling dynamics over outer viscous dissipation.However, the complexity of the spherical geometry and the lack of detailed images in microscopic observations hamper the development of more accurate models where the coupling between flow and deformation is fully understood. Subsequently, we study in a second part the curling deformation of macroscopic naturally curved elastic ribbons in different viscous media and elastic conditions. At high Reynolds numbers, due to the tendency of ribbons to localize bending deformations when a curling front travels down the material, we show that curling reaches rapidly a constant propagating velocity. In this regime, the ribbon wraps itself into a compact roll whose size is predicted through the solitary wave solution of the associated Elastica. At low Reynolds numbers, however, closer to the hydrodynamic conditions of curling in microscopic membranes, we show that the strong lubrication forces induce a non-compact curling. The overall size of the spiraling ribbon increases in time leading to a temporal decrease of the released elastic power and therefore a consequent decrease in velocity. We discuss how such discovery sheds a new light on the modeling of curling in MIRBCs and polymersomes. Curling Ribbon Membrane Malaria Spontaneous curvature Dynamics
23	Evaluation of Rigid Pavement Rehabilitation Methods Using an Unbonded Concrete Overlay Ambrosino, Joel D. 24 July 2007 (has links) No description available. Unbonded concrete overlay Rigid pavement rehabilitation PCC instrumentation JRCP JPCP Interstate 86 I-86 Strain Deflection Curling Thermal Gradient Pavement Temperature Loss of support Fracturing techniques Rubbilize Rubbilization
24	Response of concrete pavements under moving vehicular loads and environmental effects Darestani, Mostafa Yousefi January 2007 (has links) The need for modern transportation systems together with the high demand for sustainable pavements under applied loads have led to a great deal of research on concrete pavements worldwide. Development of finite element techniques enabled researchers to analyse the concrete pavement under a combination of axle group loadings and environmental effects. Consequently, mechanistic approaches for designing of concrete pavements were developed based on results of finite element analyses. However, unpredictable failure modes of concrete pavements associated with expensive maintenance and rehabilitation costs have led to the use of empiricalmechanistic approach in concrete pavement design. Despite progressive knowledge of concrete pavement behaviour under applied loads, concrete pavements still suffer from deterioration due to crack initiation and propagation, indicating the need for further research. Cracks can be related to fatigue of the concrete and/or erosion of materials in sub-layers. Although longitudinal, midedge and corner cracks are the most common damage modes in concrete pavements, Austroads method for concrete pavement design was developed based on traditional mid-edge bottom-up transverse cracking introduced by Packard and Tayabji (1985). Research presented in this thesis aims to address the most common fatigue related distresses in concrete pavements. It uses comprehensive finite element models and analyses to determine the structural behaviour of concrete pavements under vehicular loads and environmental effects. Results of this research are supported by laboratory tests and an experimental field test. Results of this research indicate that the induced tensile stresses within the concrete pavement are significantly affected by vehicle speed, differential temperature gradient and loss of moisture content. Subsequently, the interaction between the above mentioned factors and concrete damage modes are discussed. Typical dynamic amplifications of different axle groups are presented. A new fatigue test setup is also developed to take into consideration effects of pavement curvature on fatigue life of the concrete. Ultimately, results of the research presented in this thesis are employed to develop a new guide for designing concrete pavements with zero maintenance of fatigue damage. dynamic analysis dynamic amplification finite element analysis finite element model static analysis axle group loads critical axle group configuration critical position of axle groups tyre pavement interaction stress distribution fatigue failure concrete pavement distresses corner cracking longitudinal cracking transverse cracking top-down cracking bottom-up cracking boundary conditions debonding layer temperature effects loss of moisture contents shrinkage effects curling induced stress warping stress pavement curvature field test laboratory text experimental study truck load JPCP JRCP CRCP SAST SADT TAST TADT TRDT QADT

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