L’intérêt grandissant suscité par l’utilisation de l’hydrogène en tant que vecteur énergétique a mis en évidence un besoin de données fiables concernant les explosions de mélanges hydrogène-air dans des milieux obstrués et/ou confinés. C’est pourquoi, après une analyse poussée de la littérature, le travail de thèse présenté dans ce mémoire s’est focalisé sur l’accélération de flamme hydrogène-air dans de tels milieux. L’objectif est de proposer une base de données concernant la surpression maximale et la vitesse de flamme maximale dans le cas d’une déflagration de mélange hydrogène-air. Pour parvenir à cet objectif, différentes séries d’expériences menées à l’échelle du laboratoire ont été réalisées. Les séries d’essais entreprises se sont ainsi déroulées selon trois phases : i) validation du dispositif d’acquisition des mesures en utilisant une charge hémisphérique hydrogène-air, ii) essais en milieu obstrué et non confiné, et iii) essais en milieu confiné et obstrué. Les obstacles choisis pour cette étude se présentent sous la forme de couches de grillage ou de plaque. Dans les structures obstruées ainsi créées, la taille de maille, la forme de la maille, la position des différentes couches et l’espace entre couches varient. Ces essais ont notamment montré que des mailles carrées engendraient une surpression plus importante que des mailles rondes dans le cadre d’obstacles de type plaque. Une comparaison des résultats expérimentaux avec ceux obtenus par application des modèles de la littérature a été établie. Cette comparaison porte sur le calcul de la vitesse de flamme maximale en milieu obstrué et le calcul de la surpression maximale en milieu confiné. / The increasing interest created by the use of hydrogen as an energy carrier has underlined a need of reliable data concerning hydrogen-air explosions in obstructed and/or confined area. That’s why, after a detailed literature review, the study presented in this dissertation focused on hydrogen-air flame acceleration in obstructed and/or confined area. The aim of this study is to propose a data base concerning maximal overpressure and maximal flame speed in the case of hydrogen-air deflagration. To achieve this goal, different series of laboratory scale experiments have been realized. The experiments have been performed in three steps: i) validation of measurement set up with hemispherical hydrogen-air charge, ii) experiments in obstructed and unconfined area, and iii) experiments in confined area. The obstacles chosen in this study are layers of wire mesh or plate. In this obstructed structure, the mesh size, the mesh shape, the place of two consecutive layers and the pitch between two consecutive layers can vary. These experiments have notably shown that the square meshes generated more important overpressures than circular meshes in the case of plate obstacles. A comparison has been performed between experimental measurements and results given by the use of analytical models found in literature relations. The comparison was done for the maximal flame speed in obstructed area, and the maximal overpressures in confined area.

Master of Science / Department of Civil Engineering / Asadollah Esmaeily / The accuracy and applicability of the existing stress-strain models for concrete confined by Carbon Fiber Reinforced Polymer (CFRP) were analytically and experimentally explored. This investigation includes major parameters affecting the stress-strain response of confined concrete, including the loading pattern and protocol. It has been observed and reported that the experimentally recorded stress-strain relationship of the same specimen will be different if the loading protocol of the test is switched from displacement control to load control. In the experimental phase of this study, four standard 6" by 12" concrete cylinders were constructed using the same concrete batch for consistency. Three two-inch strain gauges were affixed equally spaced at mid-height on the surface of the specimen in the longitudinal direction, and two two-inch strain gauges were applied in the lateral direction at mid-height opposite each other. CFRP was then impregnated with a two-part epoxy and applied externally in two continuous layers, with an overlap. During the first phase of the experimental program, the tests were conducted with a constant load rate or with a constant displacement rate. The data was collected from externally mounted strain gauges and potentiometers positioned on the opposite sides of the cylinder in the longitudinal direction. Since the capacity of the existing actuator in the structural lab was less than the required failure level of the specimens, a nutcracker-like device was constructed to increase the mechanical advantage of the test frame in the second phase of the experimental program. In this phase, all tests were conducted in displacement control. Various models were selected to be studied from a large number of existing models that propose to determine the stress-strain relationship of concrete. Analytical predictions of the models were compared against the experimental data. Results show that some of the models provide a reasonable prediction of the real performance of the specimen. However, in general, predictions are different from the real performance for most models.

El objetivo principal de la presente investigación es idear un sistema que logre disminuir el costo y el tiempo de elaboración de muros no portantes de albañilería confinada. Para lograrlo se ha diseñado un sistema de bloques de arcilla apilables en seco y autoencajables que cumple con todas las normas imputables. Para determinar el rendimiento del sistema diseñado se fabricaron las piezas y se construyó un muro con medidas típicas. Los resultados para dicho caso de estudio se resumen en un ahorro de 17% en el costo directo (considerando todo el muro en su conjunto) y 76% en el tiempo empleado (solo en el asentado de bloques). / The principal objective of this research is to design a system that manage to reduce the cost and time in the construction of non-structural masonry walls. To achieve this, it has been designed a Mortarless Dry-Stacked Interlocking Masonry Clay Bricks which verifies all the imputable codes. To determine the performance of the system, the bricks were made and a wall with typical measurements was built. The results for this study are 17% of reduction in the direct cost (considering the whole wall) and 76 % less time used (alone in the brick seating). / Tesis

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / The aim of this article is to use artificial neural networks (ANN) to perform the structural design of confined masonry buildings. ANN is easy to operate and allows to reduce the time and cost of seismic designs. To generate the artificial neural network, training models (traditional confined masonry designs) are used to identify the input and output parameters. From this, the final architecture and activation functions are defined for each layer of the ANN. Finally, ANN training is carried out using the backpropagation algorithm to obtain the matrix of weights and thresholds that allow the network to operate and provide preliminary structural designs with a 10% margin of error, with respect to the traditional design, in the dimensions and reinforcements of the structural elements.

No description available.

A passive treatment alternative for the removal of metal and organic contaminants from runoff and effluent in CDFs was evaluated in this study. Activated carbon impregnated curtains have been used for different remediation projects; however, very little research has been conducted to understand its sorption behavior, breakthrough time, and exhaustion time of contaminants under high flow rates characteristic of CDF runoff and effluent. The major objectives of this study were to evaluate the efficiency of the curtain in removing contaminants from a synthetic effluent in a flow through regime and estimate the expected life of the curtains. Equilibrium tests, batch sorption tests and column tests were conducted to evaluate the feasibility of this alternative. The copper column tests showed that the curtain is not efficient in the removal of metals; whereas, the Aroclor1016 column tests showed that the curtains could potentially be used as a treatment alternative for organic contaminants.

Concrete is among the most common materials utilized to construct protective elements in hardened structures. Subsequently, understanding how a concrete member will respond to explosively driven fragment or projectile impact is critical to the protective design process. Explosively driven fragments can have many different shapes and sizes depending on the event that resulted in their creation. These geometric variations can include a high-aspect, or width to thickness, ratio; however, impact from fragments with elevated aspect ratios on hardened concrete has not been extensively studied. Therefore, reinforced concrete specimens were subjected to impact from fragments with different aspect ratios to illustrate and quantify the effect of fragment characteristics, protective element features, and experimental target size on local impact performance. A novel experimental technique was developed to allow for high-aspect ratio fragment impact on concrete slabs to be evaluated. The same concrete materials were also impacted with lower aspect ratio fragments for comparative purposes. Data collected from these two experimental series were utilized to analyze the effects of compressive strength, thickness, and fiber reinforcement on impact performance. The accuracy of existing penetration and spall prediction methodologies were evaluated for both fragment types. The kinetic energy required to cause reinforced concrete to present a breached condition due to the high-aspect ratio fragment was also analyzed. Modifications were made to existing contact charge equations to account for differences between the contact charge energy required to cause a breach condition and that required from fragment impact to produce a breach condition. The breach envelope defined by these relationships was further evaluated using a computational model calibrated specifically for this impact scenario. Finally, the effect of impact specimen geometry and confinement type on target performance was numerically evaluated. Artificial and inertial confinement were examined through varying target diameter to projectile diameter ratio with and without artificial circumferential confinement. Given the minimal data associated with local effects of high-aspect ratio fragment impact and the many factors that can influence concrete impact resistance, the information and relationships learned along with the analysis techniques developed herein can be utilized to improve the state of the art of protective design.

No description available.

The thesis describes the study of slow dynamics of confined polymers and soft colloids. We study the finite size effect on the dynamics of glassy polymers using newly developed interfacial microrheology technique. Systematic measurement have been performed to address the issue of reduction of glass transition under confinements. Slow and heterogeneous dynamics are the underlined observed behavior for dynamics in confined glassy polymers. The slow relaxation dynamics and dynamical heterogeneity in polymer grafted nanoparticles (PGNPs) systems were studied using advanced X - ray photon correlation spectroscopy (XPCS) techniques. Our studies presented in this thesis on dynamics of polymer grafted nanoparticle systems in melts and solution are the first attempt to study them experimentally. Thus our work shed the light about new technique to study confined system more accurately and explore new soft colloidal system to study fascinating dynamics and interesting phase behavior. In Chapter 1, we provide the theoretical background along with brief review of the literature for understanding the results presented in this thesis. The details of the experimental set up and their operating principle along with the details of the experimental conditions are provided in Chapter 2. In Chapter 3 we present our newly developed technique (interfacial microrhelogy) and its consequences to study the complex fluids at interface. Chapter 4 discusses the concentration and temperature dependent glassy dynamics in confined glassy polymers. In Chapter 5 we provide the structural and dynamical study of polymer grafted nanoparticles in melts and solutions. We provide the summary of our result and the future prospective of the work in Chapter 6. Chapter-1 provides the ground work and theoretical aspects for understanding the results presented in this thesis. It starts with the discussion about the slow dynamics of complex fluids and transit to dynamic behavior of polymer in confinement, glassy dynamics in confinements . This also discusses the basic aspects of studying viscoelastic properties using rheology, interface rheology, microrheology, interface microrheology techinques. In continuation it discusses structure and dynamics of different soft colloids investigated for last decade and then theoretical aspects of XPCS is discussed. Towards the end of this Chapter, we discuss the procedure to explain and understand systems dynamical heterogeneity near glass like phase transition. Chapter-2 contains the details of the experimental techniques which has been used for the study of confined polymers and soft colloids. Brief introduction to basic principles of the measurements followed by details of the material and methods have been provided. Chapter-3 we discuss the interafacial microrheology of different complex fluids and advantages of the techniques is discussed in Chapter 3. This includes discussion about the technique sensitivity at the surface using quantum dots (QDs) as a probe and about the configuration of the QDs at/on monolayer. Later on establishment of the technique has been demonstrated through easurements on arachidic acid, poly(methylmethacrylate) (PMMA), poly(vinylacetate) (PVAc), poly(methylacrylate) (PMA) monolayers. The extracted subdiffusive nature of QDs in on monolayers through mean square displacement has been explained using fractional Brownian motion model. Towards the end of the chapter we discuss about the extraction of real and imaginary elastic modulus from mean square displacement data using generalized Stokes-Einstein relation for the quasi two dimensional systems and explains about the possible viscoelastic transition in the different monolayers. The concentration and temperature dependent glassy dynamics of confined polymers (PMMA) are discussed in Chapter-4. We demonstrate the microscopic nature of spatio-temporal variation of dynamics of glassy polymers confined to a monolayer of 2 3 nm thickness as a function of surface density and temperature. It illustrates the systems dynamical heterogeneity and explain the observed large reduction of glass transition temperature in confined system through finite size effect. In Chapter 5 we discuss the result based on systematic studies of dynamics of PGNPs in melts and solutions. In addition it also illustrates the structural anisotropy and anomalous dynamical transitions in binary mixture of PGNPs and homopolymers in good solvent condition. It provides temperature and wave vector dependent XPCS measurements on polymer grafted nanoparticles with the variation of functionality. The functionality ( f ) dependent nonmonotonic relaxation in melts of PGNPs and solvent quality dependent non monotonic relaxation of PGNPs system have been elaborated in the continuation. We present possible phase behavior of PGNPs system in good solvent with addition of homopolymer of two different molecular weight. Chapter 6 contains the summary and the future perspective of the work presented.

Master of Science / Department of Civil Engineering / Asadollah Esmaeily / Realistic strength assessment of reinforced concrete structural elements, especially columns in bridges and tall buildings is a critical need not only at design time, but also when an accurate evaluation of the strength is needed for decisions such as retrofit or replacement of an existing structure. Assessment of the flexural strength of a column under a specific axial load level is usually done by constructing the axial force-bending moment interaction response curve of the section. This assessment can be done using the code procedure. However, the code does not consider the confinement effect, and is based on the “stress block” assumption for a pre-assumed failure strain for concrete. It has been shown by various experimental and analytical studies that the performance of a reinforced concrete section is affected by different factors such loading history and material behavior. A realistic performance assessment should consider not only proper models for the monotonic and cyclic response of the material, but also analytical methods and procedures that can capture the effects of loading pattern and provide realistic predictions of the section capacity. Accuracy of the analytical methods in strength assessment of reinforced concrete sections was explored in a comparative study. These methods were compared and validated against the existing experimental data. The factors considered in these analytical procedures, included the effect of confinement, and the method employed in assessment of the axial-force-bending moment interaction response of a column section. The experimental data were collected from tests conducted on circular and rectangular columns under a constant axial load. It has been shown that the axial force-bending moment interaction curve, constructed based on the moment-curvature response of a section using a more detailed analytical method such as fiber-model, considering the confining effect of the lateral reinforcement, represents the most realistic and optimal response of a cross section.