[pt] Os fluxos de detritos são perigosos riscos naturais, que afetam países com intensas precipitações e terrenos montanhosos. Tais eventos configuram alto perigo para a vida humana e danificação de infraestrutura, resultando em importantes perdas econômicas. O estudo de fluxos de detritos envolve um mecânismo complexo e suas técnicas de previsão são baseadas na calibração de modelos, que devem ser delimitados por tentativa e erro de eventos anteriores. Tais previsões são ferramentas valiosas para delimitar as potenciais áreas de risco e, dessa forma, projetar medidas de mitigação e convivência. O principal objetivo deste trabalho foi analisar o comportamento de quatro fluxos de detritos deflagrados por precipitações de alta intensidade em regiões tropicais utilizando modelagem numérica em 2D e 3D. Foram analisados os casos de Lajas e Llano de la Piedra na Costa Rica e os casos de Córrego D Antas e Hospital São Lucas no Rio de Janeiro. Os principais parâmetros utilizados, na avaliação do risco deste tipo de movimentos de massa, são: a distância percorrida, a área de impacto, a velocidade e profundidade do fluxo. Os casos foram calibrados utilizando a reologia de Voellmy. A definição dos parametros na calibração é vital, pois oferece a possibilidade de previsões de primeira ordem, feita sobre escorregamentos acontecendo em condições semelhantes. Os resultados da análise dinâmica mostram valores consistentes entre os valores observados e as modelagens numéricas em 2D e 3D para os principais parâmetros avaliados, corroborando o uso destas ferramentas para análises de risco e projeção de medidas de mitigação e convivência. / [en] Debris flows are dangerous natural hazards affecting countries with steep terrains and heavy rainfall. They are associated with serious risks to human lives and infrastructure leading to important economic losses and fatalities. Debris flows involve complex mechanics and prediction techniques that are based on the calibration of models that must be constrained by trial-and-error back-analysis of previous landslides. Such predictions are a valuable tool for outlining potential hazard areas and the development of mitigation strategies and design of protective structures. The main goal of this work was to analyze the behavior of four debris flows triggered by heavy rainfall in tropical regions with numerical modelling. The Voellmy rheology was used to calibrate the cases occurred in Lajas and Llano de la Piedra in Costa Rica, and Córrego D Antas and Hospital São Lucas in Rio de Janeiro. The main parameters used for landslide risk assessment are runout distance, potential impact area, flow velocity and flow depth. The definition of appropriate calibrating parameters is important because it provides the possibility of first order predictions to be made about the motion of future landslides happening under similar conditions. The results of the dynamic analysis showed that consistent values were obtained for the main parameters evaluated in the 2D and 3D runout models, verifying the usefulness of these tools for landslide risk assessment and the project of protection structures.

Compiling comprehensive understanding of all the available natural resources is an important task which should be carried out as it holds a crucial role for the next generation’s lives. In particular, groundwater is considered as one of the vital resources in providing essential drinking water. Krycklan catchment is a well-monitored catchment in Sweden that is characterized with almost 30% of the world’s forest cover and it has a range of data sets stored from 1920. A numerical model with several observational constrains is used in this study to investigate the groundwater flow circulation. The numerical model is developed with Visual MODFLOW Flex 6.1 software to investigate the temporal effects of the climate condition on the groundwater flow of the Krycklan catchment through a transient-state condition. Daily precipitation and daily evapotranspiration data along with stream data are used to represent the climatic boundary conditions. The impact of climatic condition on groundwater flow was investigated using two different metrices: groundwater level, and groundwater flow travel time reaching the stream network. The results clearly indicated the variability in groundwater level due to the impact of climatic condition in which the winter and summer months have the highest and lowest groundwater levels, respectively. In addition, the particles tracing results show that physical characteristics of the stream channel substantially influence the shallow groundwater travel time.

Sliding isolation bearings are used widely around the world to minimize damage to structures and their contents during earthquakes. Past studies have typically focused on the behavior of sliding isolation bearing under design conditions; however, as the performance-based earthquake engineering advances, it is necessary and critical to understand the ultimate or even failure behavior, of structural systems under extreme conditions. Using a double friction pendulum bearing with non-articulated slider as an example, this thesis comprehensively investigates the extreme behavior of the sliding bearing components as well as steel frame buildings isolated using these bearings. This thesis is comprised of two major parts. The first includes numerical and experimental studies of double friction pendulum bearings at the component-level. Finite element investigation shows that depending on the superstructure mass there are two major failure modes for the double friction pendulum bearings. When the superstructure mass is sufficiently large, the failure mode is dominated by the restraining rim yielding; however, when the mass is relatively small, its failure mode shifts to bearing uplift. A simplified analytical model which can directly simulate the impact and uplift behavior of double friction pendulum bearing is also implemented, comparing well to the finite element analysis. Then, to validate the ability of the models to predict extreme behavior as well as to investigate the effect of the restraining rim design, which varies around the world, an experimental study was carried out. Uplift behavior and significant rim yielding were observed during the shake table tests. Moreover, other response parameters, including uplift and shear forces, are evaluated and compared among different rim designs. It is found the restraining rim design has a substantial influence on the bearing’s extreme behavior. The second part of the thesis investigates the system-level behavior of steel frame buildings isolated with double friction pendulum bearings. It is found that the stiffness of the superstructure largely dictates the system-level failure modes and collapse probability. Initially, bearings with rigid restraining rims are investigated. For flexible moment-resisting frames, the system-level failure modes are mixed: both the bearing uplift and superstructure yielding contribute; also, using current code-minimum design results in acceptably low probability of collapse. However, for stiff concentrically-braced frames, the impact force can impose large ductility demands on the superstructure regardless of its strength. As a result, the system-level failure comes exclusively from superstructure yielding, and only by increasing bearing’s displacement capacity beyond the minimum code allowed can the design meet as acceptably low collapse probability. When flat rims are used instead for the bearing design, the failure modes for both building types are exclusively bearing failure. Furthermore, while it is more apparent for concentrically-braced frames, using flat rims for the bearings can reduce the collapse probability compared to using rigid rims. / Thesis / Doctor of Philosophy (PhD)

Geosynthetic tubes have the potential to replace the traditional flood protection device of sandbagging. These tubes are manufactured with many individual designs and configurations. A small number of studies have been conducted on the geosynthetic tubes as water barriers. Within these studies, none have discussed the dynamics of unanchored geosynthetic tubes. A two-dimensional equilibrium and vibration analysis of a freestanding geosynthetic tube is executed. Air and water are the two internal materials investigated. Three foundation variations are considered: rigid, Winkler, and Pasternak. Mathematica 4.2 was employed to solve the nonlinear equilibrium and dynamic equations, incorporating boundary conditions by use of a shooting method. General assumptions are made that involve the geotextile material and supporting surface. The geosynthetic material is assumed to act like an inextensible membrane and bending resistance is neglected. Friction between the tube and rigid supporting surface is neglected. Added features of viscous damping and added mass of the water were applied to the rigid foundation study of the vibrations about the freestanding equilibrium configuration. Results from the equilibrium and dynamic analysis include circumferential tension, contact length, equilibrium and vibration shapes, tube settlement, and natural frequencies. Natural frequencies for the first four mode shapes were computed. Future models may incorporate the frequencies or combinations of the frequencies found here and develop dynamic loading simulations. / Master of Science

Energy piles are deep foundation elements designed to utilize near-surface geothermal energy, while at the same time serve as foundations for buildings. The use of energy piles for geothermal heat exchange has been steadily increasing during the last decade, yet there are still pending questions on their thermo-mechanical behavior. The change in temperature along energy piles, resulting from their employment in heat exchange operations, causes axial displacements, thermally induced axial stresses and changes in mobilized shaft resistance which may have possible effects on their behavior. In order to investigate these effects, an extensive field test program, including conventional pile load tests and application of heating-cooling cycles was conducted on three energy piles during a period of six weeks. Temperature changes were applied to the test piles with and without maintained mechanical loads to investigate the effects of structural loads on energy piles. Moreover, the lengths of the test piles were determined to represent different end-restraining conditions at the toe. Various sensors were installed to monitor the strain and temperature changes along the test piles. Axial stress and shaft resistance profiles inferred from the field test data along with the driven conclusions are presented herein for all three test piles. It is inferred from the field test results that changes in temperature results in thermally induced compressive or tensile axial stresses along energy piles, the magnitude of which increases with higher restrictions such as structural load on top or higher toe resistance. Moreover, lower change in shaft resistance is observed with increasing restrictions along the energy piles. In addition to the design, deployment, and execution of the field test, a thermo-mechanical cyclic numerical model was developed as a part of this research. In this numerical model, load-transfer approach was coupled with the Masing's Rule in order to simulate the two-way cyclic axial displacement of energy piles during temperature changes. The numerical model was validated using the field test results for cyclic thermal load and thermo-mechanical load applications. It is concluded that the use of load-transfer approach coupled with the Masing's Rule is capable of simulating the cyclic thermo-mechanical behavior of energy piles. / Ph. D. / Global energy demands are increasing rapidly, along with depleting natural resources. Of equal importance, the consumption of fossil fuels pose a great threat to the environment. Hence, there is an urgent need to find alternative energy resources, such as near surface geothermal energy. Energy piles are one of the ways of exploiting near surface geothermal energy. In this system, the piles that are already required for structural support are equipped with geothermal loops, for heat exchange operations. With the use of energy piles, the heat energy can be extracted from the ground to heat the buildings during winter. Similarly, the heat energy can be withdrawn into the ground, in order to cool the buildings during summer. Energy piles provide an environmental friendly way of heating and cooling of the buildings. However, there are several effects of the heat exchange operations on the behavior of energy piles. During winter, because of heat extraction, the temperature of the energy pile decreases, which causes the tendency of contraction of the pile. On the other hand, during summer, the heat injection into the ground increases the temperature of the energy piles, which results in a tendency of elongation of the energy pile. Depending on the level of restriction from the surrounding soil or the building on top, some of the expansion or contraction tendency of the energy piles actually take place, which results in axial displacements and changes in shaft resistance. The restricted part of the contraction or expansion causes axial stresses along the piles. The primary role of the piles, which is structural support, should not be jeopardized by these effects of heat exchange operations. In this doctoral research, the effects of temperature change on the behavior of energy piles are investigated. For the experimental investigation, a full-scale field test on three energy piles was performed, where temperature changes were applied to the test piles, to evaluate their effects. In addition, a numerical model was developed, and it is validated by using the field test results. This numerical model can be used for different soil profiles, pile characteristics and temperature changes, in order to estimate the behavior of various scenarios of energy piles during their design.

This thesis focuses on solutions of reactive transport problems in porous media. The principle mechanisms of flow and reactive mass transport in porous media are investigated. Global implicit approach (GIA), where transport and reaction are fully coupled, and sequential noniterative approach (SNIA) are implemented into the software OpenGeoSys (OGS6) to couple chemical reaction and mass transport. The reduction scheme proposed by Kräutle is used in GIA to reduce the number of coupled nonlinear differential equations. The reduction scheme takes linear combinations within mobile species and immobile species and effectively separates the reaction-independent linear differential equations from coupled nonlinear ones (i.e. reducing the number of primary variables in the nonlinear system). A chemical solver is implemented using semi-smooth Newton iteration which employs complementarity condition to solve for equilibrium mineral reactions. The results of three benchmarks are used for code verification. Based on the solutions of these benchmarks, it is shown that GIA with the reduction scheme is faster (ca. 6.7 times) than SNIA in simulating homogeneous equilibrium reactions and (ca. 24 times) in simulating kinetic reaction. In simulating heterogeneous equilibrium mineral reactions, SNIA outperforms GIA with the reduction scheme by 4.7 times. / Diese Arbeit konzentriert sich auf die numerische Berechnung reaktiver Transportprobleme in porösen Medien. Es werden prinzipielle Mechanismen von Fluidströmung und reaktive Stofftransport in porösen Medien untersucht. Um chemische Reaktionen und Stofftransport zu koppeln, wurden die Ansätze Global Implicit Approach (GIA) sowie Sequential Non-Iterative Approach (SNIA) in die Software OpenGeoSys (OGS6) implementiert. Das von Kräutle vorgeschlagene Reduzierungsschema wird in GIA verwendet, um die Anzahl der gekoppelten nichtlinearen Differentialgleichungen zu reduzieren. Das Reduzierungsschema verwendet Linearkombinationen von mobilen und immobile Spezies und trennt die reaktionsunabhngigen linearen Differentialgleichungen von den gekoppelten nichtlinearen Gleichungen (dh Verringerung der Anzahl der Primärvariablen des nicht-linearen Gleichungssystems). Um die Gleichgewichtsreaktionen der Mineralien zu berechnen, wurde ein chemischer Gleichungslaser auf Basis von ”semi-smooth Newton-Iterations” implementiert. Ergebnisse von drei Benchmarks wurden zur Code-Verifikation verwendet. Diese Ergebnisse zeigen, dass die Simulation homogener Equilibriumreaktionen mit GIA 6,7 mal schneller und bei kinetischen Reaktionen 24 mal schneller als SNIA sind. Bei Simulationen heterogener Equilibriumreaktionen ist SNIA 4,7 mal schneller als der GIA Ansatz.

Résumé : Plusieurs tremblements de terre passés ont montré que face aux séismes, les ponts peuvent être les points faibles d’un réseau de transport. Néanmoins, les retours des expériences postsismiques ainsi que les études théoriques et expérimentales effectuées par les chercheurs et les ingénieurs de la pratique ont permis de faire évoluer les règles de l'art relatives au comportement sismique des ponts. Un des résultats de cette évolution est le dimensionnement basé sur la performance sismique (DBPS). En bref, le DBPS tente de concevoir des structures qui atteindront un état limite de performance déterminé lorsqu’ils sont soumis à un séisme d’une intensité donné. Toutefois, dans l'optique du DBPS, il est primordial de situer les états limites des composantes principales des ponts, principalement des piliers, de manière mesurable plutôt que phénoménologique. Lors du développement de courbes de fragilité des ponts au Québec, il est apparu que les états limites des piliers de ponts n'étaient pas clairement définis. Un programme de recherche expérimental a donc été conçu pour déterminer les états limites des piliers de pont en béton armé. Le projet comprend l’essai d’un poteau en béton armé à échelle réelle soumis à des cycles de chargement latéral en plus d’une charge axiale constante représentative du niveau de chargement réel. Le poteau reproduit les propriétés exactes des piliers du pont Chemin des Dalles (Trois-Rivières, Québec). Ce projet de recherche vise à améliorer l’évaluation de la fragilité sismique des ponts actuels du réseau routier québécois et à optimiser le dimensionnement sismique des futures structures selon l’approche basée sur la performance sismique. En particulier, le projet cherche à répondre aux incertitudes importantes qui subsistent sur la description quantitative des états limites des piliers de ponts en béton armé, particulièrement au niveau des déformations associées. / Abstract : Several past earthquakes have shown that bridges can be the weak points of a transport network. Nevertheless, returns of the post-seismic experiences as well as theoretical and experimental studies made by researchers and practice engineers allowed the art rules evolution related to the seismic behavior of bridges. One result of this evolution is the seismic performance based design (DBPS). In brief, the DBPS tries to design structures which will reach a certain limit state of performance when they are submitted to an earthquake of a given intensity. However, in the optics of the DBPS, it is essential to define the limit states of the main components of bridges, mainly for columns, in a measurable way rather than phenomenological. During the development of the fragility curves of bridges in Québec, it seemed that the limit states of the bridges columns were not clearly defined. An experimental research program was thus designed to determine the limit states of the reinforced concrete bridge columns. The project includes the testing of a large-scale reinforced concrete bridge column submitted to lateral cycles load in addition to a constant axial load which represented the real dead load level. The column reproduces the exact properties of the Chemin des Dalles bridge columns (Trois-Rivières, Québec). This research project aims to improve the evaluation of the seismic fragility of existing bridges of Québec road network and optimize the seismic design for future structures according to the performance based seismic approach. In particular, the project seeks to address the significant uncertainties which remain on the quantitative description of the limit states of the reinforced concrete bridge columns, particularly at the associated deformations level.

This present thesis comprise two major parts both experimental and numerical study which have been conducted in four distinct steps as following: (1) Design, construction, and evaluation of control and hydrodynamic of a bioreactor system. (2) Visualization of fluid flow perfusion in the hollow fibre membrane bioreactor (HFMB) using a biomedical noninvasive imaging technique, i.e. positron emission tomography (PET). (3) Development of a mathematical model for analyzing a hybrid hollow fibre membrane bioreactor (hHFMB) and (4) Development of a dynamic and two-porous media model for analyzing the HFMB with the aid of computational fluid dynamics (CFD), specifically for bone tissue engineering application. The experimental part includes the steps 1 and 2. In the step 1, the flow perfusion bioreactor system has been designed and constructed. The experimental evaluations of hydrodynamic, and control were performed. In this system, mean pressure, mean flow rate, frequency and waveform of the pulsatile pressure and flow rate can be modulated and controlled over the time to simulate both physiological and non-physiological conditions. The temperature, dissolved oxygen, and pH can be controlled.This bioreactor system can be applied to a variety of scaffold configurations, geometries, and sizes as the cell/tissue culture chamber is adjustable in length.This system is autoclavable, and compatible with noninvasive medical imaging techniques. Designing of the inlet and outlet manifold of the bioreactor were performed according to data obtained from CFD simulation of the flow distribution to achieve high efficiencies in the uniformity of flow perfusion. In the second step, PET was proposed for the very first time and a small animal PET system was used to obtain new information about steady and pulsatile flow patterns in the HFMB for tissue engineering applications. The non-homogeneous tracer distribution, as found with PET imaging, implies the occurrence of non-efficient regions with respect to mass transfer. In steady inlet flow condition, a non-uniform distribution of radioactive tracer was obtained. In contrast, the pulsatile inlet flow generated more uniform perfusion than that of steady flow. Further, it was found that in the case of pulsatile flow, the accumulation of the tracer within the bioreactor was efficiently less than that of steady inlet flow at the same condition. Therefore, in one hand these findings have the potential to improve bioreactor design and in the other hand can explore a very important rout to employ PET in developing bioreactors for tissue engineering applications. The numerical part includes the step 3 and 4 in which the numerical study has been performed for 3-D bone tissue growth in HFMB as a case study for large-scale tissue culture. In the step 3, the feasibility of utilizing newly proposed hHFMB for the growth of mesenchymal stem cells (MSCs) to form bone tissue was investigated using numerical simulations. To this aim, a mathematical model using a CFD code was developed to optimize the design and operation parameters of hHFMB for the growth of MSCs. The volume averaging method was used to formulate mass balance for the nutrients and the cells in the porous extracapillary space (ECS) of the hHFMB. The cell-scaffold construct in the ECS of the hollow fibres and membrane wall were treated as porous medium. Cell volume fraction dependent porosity, permeability, and diffusivity of mass were used in the model. The simulations allowed the simultaneous prediction of nutrient distribution and nutrient-dependent cell volume fraction. In addition, this model was used to study the effects of the operating and design parameters on the nutrient distribution and cell growth within the bioreactor. The modeling results demonstrated that the fluid dynamics within the ECS and transport properties and uptake rates in hHFMB were sufficient to support MSCs required for clinical-scale bone tissue growth in vitro and enabled to solve nutrition difficulties because of high cell density and scaffold size. In the step 4, the new dynamic and two-porous media model has been used for analyzing the nutrient-dependent MSCs growth in order to form the bone tissue in the HFMB. In the present model, hollow fibre scaffold within the bioreactor was treated as a porous domain. The domain consists of the porous lumen region available for fluid flow and the porous ECS region, filled with collagen gel containing cells, for growing tissue mass. Furthermore, the contributions of several design and process parameters, which enhance the performance of the bioreactor, were studied. In addition, the dynamic evaluation of cell growth, oxygen and glucose distributions were quantitatively analyzed. The obtained information can be used for better designing of the bioreactor, determining of suitable operational conditions and scale up of the bioreactor for engineering of clinical-scale bone tissue.--Résumé abrégé par UMI.

Permeable Friction Course (PFC) is a layer of porous asphalt pavement with a thickness of up to 50 millimeters overlain on a conventional impervious hot mix asphalt or Portland cement concrete roadway surface. PFC is used for its driver safety and improved stormwater quality benefits associated with its ability to drain rainfall runoff from the roadway surface. PFC has recently been approved as a stormwater best management practice in the State of Texas. The drainage properties of PFC are typically considered to be governed primarily by two hydraulic properties: porosity and hydraulic conductivity. Both of these hydraulic properties are expected to change over the life of the PFC layer due to clogging of the pore space by trapped sediment. Therefore, proper measurement of the hydraulic properties can be problematic. Laboratory and field tests are necessary for accurately determining the hydraulic conductivity of the PFC layer in order to ensure whether the driver safety and water quality benefits will persist in the future. During testing, PFC experiences a nonlinear flow relationship which can be modeled using the Forchheimer equation. Due to the two-dimensional flow patterns created during testing, the hydraulic conductivity cannot be directly measured. Therefore, numerical modeling of the two-dimensional nonlinear flow relationship is required to convert the measureable flow characteristics into the theoretical flow characteristics in order to properly determine the isotropic hydraulic conductivity. This numerical model utilizes a new scalar quantity, defined as the hydraulic conductivity ratio, to allow for proper modeling of nonlinear flow in two-dimensional cylindrical coordinates. PFC core specimens have been extracted from three different roadway locations around Austin, Texas for the past four years (2007 to 2010). Porosity values of the core specimens range from 12% to 23%, and the porosity data suggest a statistical decrease over time due to trapped sediment in the pore space. A series of constant head tests used in the laboratory and a falling head test used in the field are recommended for measurement of PFC hydraulic characteristics using a modified Forchheimer equation. Through numerical modeling, regressions equations are presented to estimate the hydraulic conductivity and nonlinear Forchheimer coefficient from the measureable hydraulic characteristics determined during experimental testing. Hydraulic conductivity values determined for laboratory core specimens range from 0.02 centimeters per second (cm/s) to nearly 3 cm/s. Field measurements of in-situ hydraulic conductivity vary over a range from 0.6 cm/s to 3.6 cm/s. The results of this research provide well-defined laboratory and field methods for measurement of the isotropic hydraulic conductivity of PFC experiencing two-dimensional nonlinear flow and characterized by the Forchheimer equation. This methodology utilizes a numerical model which presents a proper solution for nonlinear flow in two-dimensions. / text

This thesis focused on investigating flow, coherent structures, and mechanisms leading to scour around a series of three submerged groynes in a high curvature (radius of curvature (R)/channel width (B)=1.5) channel bend using a Large Eddy Simulation Numerical (LES) model. Flow was investigated during both an initial and a later stage of scour. The results showed that the groynes appeared effective in keeping the main core of high streamwise velocity away from the outer bank wall in the region where they were installed, although high potential still existed for local scour around the groynes. During the initial stage of scour, horseshoe vortices (HVs) showed the greatest propensity to induce scour immediately upstream of the groyne tips. During the later stage of scour, the HV in front of the first upstream groyne (G1) induced very high mean pressure fluctuations on the outer bank wall. Scour was also of very great concern around the tip of G1 due to severe mean bed pressure fluctuations. Downstream of the groyne field, the presence of a counter-rotating outer bank cell was capable of endangering the stability of the outer bank. The second focus of this thesis was to investigate flow in a 135° channel bend using both Reynolds Averaged Navier Stokes (RANS) and LES numerical models. The RANS study examined the effects of curvature ratio (R/B), and aspect ratio (B/H, where H is the inlet flow depth), on secondary circulation strength, and bed shear stresses. The study revealed that a decrease in R/B was associated with an increase in secondary circulation strength and peak bed shear stress. A change in B/H also substantially affected cross stream circulation strength. The LES study was conducted in a 135° (R/B = 1.5) bend flume with a fixed bed corresponding to near equilibrium scour conditions, and the results were compared to a similar high curvature 193° bend numerical study. Inner bank vortices and shear layers were present in both cases although their characteristics were substantially different. Distributions of boundary friction velocities, and turbulence were also quite different for each case.