Le malaxage est une étape clé de la fabrication des bétons. Il consiste à distribuer de façon homogène et à mouiller tous les constituants présents dans le malaxeur. Ce travail de thèse a été réalisé en utilisant des matériaux modèles (billes de verre), des matériaux de référence présent dans la composition du béton (calcaire, ciment, sable) et différents liquides (eau, isopropanol, glycérol). Cette étude a permis d’identifier les leviers d'optimisation de l’opération de malaxage, et de clarifier la notion de bonne ou mauvaise malaxabilité d'un système granulaire. D’autre part, il a apporté des éléments de compréhension pour réduire la dépense énergétique et la durée du malaxage. Nous avons montré que le comportement du milieu granulaire en cours de malaxage (résistance au cisaillement, cinétique de mouillage, compacité), est très largement affecté par les propriétés du mélange et les caractéristiques du malaxeur, particulièrement lors de la transition “granulaire sec / granulaire humide”. Une étude (paramétrique) a permis de hiérarchiser ces grandeurs qui ont été classifiées parmi les propriétés individuelles des poudres (taille, forme), les propriétés collectives (empilement), les propriétés du liquide mouillant (viscosité, tension superficielle, présence d’un adjuvant), les propriétés d’interface liquide/solide (angle de contact), et les paramètres opératoires (mode d’addition du liquide). Deux niveaux d’analyse complémentaires ont été utilisés pour étudier l'impact de ces différents paramètres. Le régime dynamique (utilisation d’un malaxeur planétaire de laboratoire) a permis de caractériser le comportement du milieu granulaire malaxé grâce à la mesure de la dépense en intensité. Le régime quasi-statique (cellule annulaire de Schulze) a été utilisé afin de réaliser une approche du malaxage et des contraintes locales de façon simplifiée ( plan de cisaillement de surface connue et vitesse très faible). Ce système a permis de distinguer les parts frictionnelles et cohésives mises en jeu au cours du malaxage. Parallèlement, la porosité du lit granulaire a été mesurée en cours de malaxage. Cette porosité évolue avec la quantité de liquide additionnée, et conditionne en grande partie l’évolution de la résistance au malaxage. / Mixing is an important operation in the elaboration of concrete. It creates a homogeneous distribution of solids and liquid. This work was carried out with model materials (glass beads), reference materials present in the concrete composition (calcite, cement, sand) and different liquids (water, isopropanol, glycerol). This study allowed us to optimize the mixing operation, and to clarify the difference between good and bad mixing. Moreover, the study offered informations allowing to reduce the energy consumption and the mixing time. We showed that the granular medium behaviour during the mixing (shear resistance, wetting kinetic, compacity), is affected a lot by the granular medium properties and by the mixer parameters, particularly during the “dry granular medium / wet granular medium” transitional period. A systematic study allowed us to classify these parameters among the individual powders properties (size, shape), the collective properties (packing), the wetting liquid properties (viscosity, superficial tension, liquid with an adjuvant), the liquid/solid interface properties (contact angle), and the process parameters (liquid addition method). Two complementary analysis levels were used to study the influence of these different parameters. The dynamic regime (using of a laboratory planetary mixer) allowed us to characterise the granular medium behaviour during the mixing, using the intensity consumption measure. The quasi-static regime (Schulze annular shear cell) was used in order to achieve a simplified approach to the mixing and to the local stresses (shear plan with a known surface and low velocity). This system allowed us to distinguish the frictional and cohesive interactions that take place during the mixing. In addition, the porosity of the granular medium was measured during the mixing. This porosity changes with the added liquid amount, and is partially responsible of the shear resistance modifications.

The aim of the dissertation is to compare different analysis of the interaction continuous welded rail and bridge in the domestic and foreign literature and to compare the provisions of the prescription S3 Permanent way structure and ČSN EN 1991-2 (73 6203) Eurocode 1: Actions on structures - Part 2: Traffic loads on bridges.

This thesis presents the results of a series of undrained cyclic triaxial tests carried out on four lime-cement stabilized specimens and clay specimen. The shear resistance degradation rate of lime-cement column subjected to cyclic loading simulated from heavy truck was investigated based on stress-controlled test. The influence of lime and cement on the degradation rate was investigated by comparing the behavior of stabilized kaolin and unstabilized kaolin with similar initial condition. The results indicate an increase in degree of degradation as the number of loading cycles and cyclic strain increase. It is observed that the degradation index has approximately a parabolic relationship with the number of cycles. Generally adding lime and cement to the clay will increase the degradation index which means lower degree of degradation. The degradation parameter, t has a hyperbolic relationship with shear strain, but it loses its hyperbolic shape as the soil getting stronger. On the other hand, for unstabilized clay an approximate linear relationship between degradation index and number of cycles was observed and the degradation parameter has a hyperbolic shape with the increase number of cycles. It was also observed that the stronger the material was, the lesser pore pressure developed in the lime-cement stabilized clay.

No description available.

Several regions of the Western United States utilize statistical binary classification models to predict and manage debris flow initiation probability after wildfires. As the occurrence of wildfires and large intensity rainfall events increase, so has the frequency in which development occurs in the steep and mountainous terrain where these events arise. This resulting intersection brings with it an increasing need to derive improved results from existing models, or develop new models, to reduce the economic and human impacts that debris flows may bring. Any development or change to these models could also theoretically increase the ease of collection, processing, and implementation into new areas. Generally, existing models rely on inputs as a function of rainfall intensity, fire effects, terrain type, and surface characteristics. However, no variable in these models directly accounts for the shear stiffness of the soil. This property when considered with the respect to the state of the loading of the sediment informs the likelihood of particle dislocation, contractive or dilative volume changes, and downslope movement that triggers debris flows. This study proposes incorporating shear wave velocity (in the form of slope-based thirty-meter shear wave velocity, Vs30) to account for this shear stiffness. As commonly used in seismic soil liquefaction analysis, the shear stiffness is measured via shear wave velocity which is the speed of the vertically propagating horizontal shear wave through sediment. This spatially mapped variable allows for broad coverage in the watersheds of interest. A logistic regression is used to then compare the new variable against what is currently used in predictive post-fire debris flow triggering models. Resulting models indicated improvement in some measures of statistical utility through receiver operating characteristic curves (ROC) and threat score analysis, a method of ranking models based on true/false positive and negative results. However, the integration of Vs30 offers similar utility to current models in additional metrics, suggesting that this input can benefit from further refinement. Further suggestions are additionally offered to further improve the use of Vs30 through in-situ measurements of surface shear wave propagation and integration into Vs30 datasets through a possible transfer function. Additional discussion into input variables and their impact on created models is also included.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Structural design standards based on the principles of structural reliability are gaining worldwide acceptance and are fast becoming the new basis of structural safety verification. The application of these principles to establish a standardised basis for structural design using partial factor limit states design procedures is done in the European Standard for the Basis of Structural Design EN 1990 from which it is adapted to the South African Basis of Design Standard for Building and Industrial Structures SANS 10160-1. The basis of design requirements stipulated in EN 1990 and SANS 10160-1 apply to all aspects of structural design: This includes reliability levels of structural performance and their differentiation and management; identification of various limit states and design situations; the specification of all the basic variables; separate treatment of actions and material-based resistance. However, application of these requirements is then primarily focused on actions whilst the provision for structural concrete is then left to the materials based design standards. This two-part thesis describes a systematic assessment of the degree to which the application of the reliability framework presented in the basis of design requirements has been achieved in the present generation of structural concrete design standards. More importantly, attempts are made to identify ways in which the process can be advanced. Special attention is drawn to issues that are specific to South African conditions and practice in structural concrete. Part One of the thesis focuses on the key elements of the reliability framework presented in EN 1990 and traces to what extent the requirements have been propelled through the design stipulations of the Eurocode Standard for Design of Concrete Structures EN 1992-1-1. The implications of the different reference level of reliability between the Eurocode default value of ß = 3.8 and that characteristic of South African practice ß = 3.0 through various issues are highlighted. The use and advantage of explicit treatment of reliability performance on reliability management related to some aspects of quality control are explored. A critical aspect is the shear prediction model providing unconservative estimates of shear resistance. Part Two of the thesis focuses on characterising the model factor of the EN 1992-1-1 shear prediction model for members requiring design shear reinforcement. This is done by a comparison to a compiled experimental database with special focus on situations with high reinforcement ratios. The significance of the modelling uncertainty in shear prediction is verified by this comparison. The use of the more conceptually rational modified compression field theory (MCFT) to improve on the quality of shear predictions is investigated and proves to yield more precise values with lower scatter hence making it a more reliable tool for predicting shear. The MCFT can then be used as reference for the reliability calibration and possible improvement for the Eurocode procedure. / AFRIKAANSE OPSOMMING: Strukturele ontwerpstandaarde gebaseer op die beginsels van strukturele betroubaarheid verkry wêreldwye aanvaarding en word vinnig die nuwe basis van strukturele veiligheid bevestiging. Die toepassing van hierdie beginsels om ʼn gestandaardiseerde basis vir strukturele ontwerp is bevestig deur gebruik te maak van gedeeltelike-faktorbeperkende stadiums ontwerpprosedures in die Europese Standaard vir die Basis van Strukturele Ontwerp EN 1990 waarvandaan dit herbewerk is na die Suid-Afrikaanse Basis van Ontwerp Standaarde vir Bou en Industriële Strukture SANS 10160-1. Die basis van ontwerpvereistes bepaal in EN 1990 en SANS 10160-1 is van toepassing op alle aspekte van strukturele ontverp: Dit sluit inbetroubaarheidsvlakke van struktureele prestasie en hul diversifikasie en bestuur; identifikasie van verskeie beperkende state en ontwerpsituasies; die spesifikasie van al die basiese veranderlikes; afsonderlike behandeling van aksies en materiaal-gebaseerde weerstand. Desnieteenstaande, die toepassing van hierdie voorwaardes is dan hoofsaaklik gefokus op aksies terwyl die voorsiening van strukturele beton is dan gelaat op die materiaalgebaseerde ontwerpstandaarde. Hierdie tweeledige verhandeling beskryf ʼn stelselmatige beoordeling van die graad waartoe die toepassing van die betroubaarheidsraamwerk aangebied word in die basis van ontwerpvereistes bereik in die huidige generasie van strukturele beton-ontwerp standaarde is. Meer belangrik, pogings is aangewend om die maniere hoe die proses bevorder kan word te identifiseer. Spesiale aandag word gevestig op kwessies wat spesifiek op Suid-Afrikaanse toestande en praktyke in strukturele beton toepaslik is. Deel Een van die verhandeling fokus op die sleutel-dele van die betroubaarheidsraamwerk aangebied in EN 1990 en skets die mate waartoe die vereistes aangespoor word deur die ontwerp voorskrifte van die Eurocode Standard for the Design of Concrete Structures EN 1992-1-1. Die implikasie van die verskillende verwysingsvlakke van betroubaarheid tussen die Eurocode standaardwaarde van ß = 3.8 en die eienskap van Suid-Afrikaanse praktyk ß = 3.0 deur verskillende kwessies word uitgelig. Die gebruik en voordeel van spesifieke behandeling van betroubaarheidsuitvoering op betroubaarheidsbestuur verwantskap met sekere aspekte van kwaliteit kontrole word ondersoek. ʼn Kritiese aspek is die model vir die voorspelling van skuif-weerstand wat die onkonserwatiewe beramings vir skuif-weerstand gee. Deel Twee van die verhandeling fokus op karakterisering die modelfaktor van die EN 1992- 1-1 skuif-weerstand voorspellings-model. Dit word gedoen deur ʼn vergelyking na ʼn saamgestelde eksperimentele databasis met spesifieke fokus op situasies met hoe herbevestigingsvergelykings. Die oorheersing van die modellering- onsekerheid in skuifweerstand voorspelling is bevestig deur hierdie vergelyking. Die gebruik van ʼn meer konseptuele rasionele gemodifiseerde druk-veld teorie (bekend as MCFT) om die kwaliteit van skuif voorspelling te verbeter is ondersoek en verskaf ‘n meer presiese waarde met laer verspreiding wat lei tot ʼn meer betroubaree instrument om skuif mee te voorspel. Die MCFT word dan gebruik as verwysing vir die betroubaarheid-samestelling en moontlike verbetering van die Eurocode prosedures.

<p>Maize is one of the top sources of food starch. Industrial use of starch is mostly in its native form and used due to their functional and structural properties. Native starch properties and functionalities have been altered using chemical. An alternative for the development of native starch substituents with desirable starch properties is the use of mutagenesis techniques to increase genetic variation in maize kernels. With this approach, a highly diverse library of native starches with different properties are produced. Traditional analysis of the functional and structural properties requires generous amounts of material as well as a time-consuming and costly breeding process to obtain enough kernels. To address this difficulty, high-throughput techniques are proposed for studying starch properties and functions which includes a 1) single kernel sampling method for the isolation of milligrams of starch, and techniques for studying starch based on functional properties, 2) retrogradation and 3) shear resistance, using low-volume low-concentration starch pastes.</p><p>First, three mechanical approaches were evaluated for the collection of endosperm samples from individual kernels: razor blade, 1.5 mm drill bit, and trephine bur. Furthermore, two methods for the isolation of crude starch from endosperm samples (steeping method and combination of proteases and sonication) were compared. In this study, the mechanical approaches were evaluated using the recovery rate, throughput, and germination rate of sampled kernels. Moreover, yield determination, particle size distribution, and morphological evaluation using a light microscope were performed on crude starch isolated from the endosperm samples. The use of trephine bur to collect endosperm samples and isolation of crude starch using protease digestion and sonication showed the best combination for a high-throughput setting. </p><p>Second, a high-throughput technique using milligram sample for the screening of retrogradation-resistant starch was evaluated by comparing two spectrophotometric techniques: turbidity method and molecular rotor (MR). MRs are fluorescent probes with high sensitivity to the viscosity of their environment, polarity of the media, molecular crowding, and free volume. After excitation, MRs relax through rotational movement and reduces the emission of fluorescence. In this study, hydroxypropylated waxy corn starch (WCS) and hydroxypropylated normal corn starch (NCS) were used and their retrogradation kinetics was compared with retrogradation kinetics of native WCS and NCS. </p><p>It was found that the molecular rotor 9-(2-carboxy-2-cyaovinyl)-julolidine (CCVJ) was effective to sense changes during slow retrogradation of amylose-containing starch pastes. Development of elastic modulus of retrograded NCS pastes obtained from dynamical rheology showed high correlation with the development of fluorescence intensity of the CCVJ. Furthermore, rate of retrogradation using fluorescence intensity was affected by the introduction of a retrogradation inhibitor, hydroxypropyl groups. Accelerated retrogradation of low-concentration WCS pastes was measured using the turbidity method and fluorescence intensity of CCVJ in a microplate. Accelerated retrogradation was performed by subjecting the low-concentration WCS pastes to six freeze-thaw cycles of -20 ºC for 1 hour and 30 ºC for 1 hour. Overall, development of turbidity resulted in the more sensitive technique to detect rate of retrogradation of amylopectin-containing starch. </p><p>The last part of this research studied the use of CCVJ as a technique to identify shear-resistant starch in starch slurries using milligram sample. For this purpose, WCS was cross-linked with sodium trimetaphosphate (STMP) and phosphoryl chloride (POCl₃). Low-volume starch slurries having CCVJ were prepared ranging from 0.5% to 1% starch concentration in a 96-well PCR plates and subjected to heat and shear treatments. It was found that fluorescence intensity measured in native WCS pastes were the lowest. Furthermore, fluorescence intensity of the CCVJ in the gelatinized starch increased as the amount of cross-linker increased in the cross-linked WCS. After shear treatments, the same trend in fluorescence intensity increase was recorded in all the crosslinked WCS. Results obtained using fluorescence intensity were compared with rapid viscosity analyzer (RVA) and images from microscope. Results obtained from both techniques corroborated the findings using fluorescence intensity.</p><p>In general, the findings of this research provide new insights into the possibilities of developing a high-throughput screening platform of milligram starch sample based on their physical properties. </p>

The scope of the presented Diploma thesis was the establishment of calculation model for shear design of textile reinforced concrete members with rectangular cross-section. To accomplish this task, it was necessary to acquire the knowledge of the principles of shear design for steel reinforced concrete and existing design methods for textile reinforced concrete. Based on these principles, an experiment was designed as 3-point bending test to obtain values of acting shear force in textile reinforced concrete beams. These beams were filled with textile reinforcement made of carbon and alkali resistant glass and cast in the laboratory of the Solidian Company. An important factor for the experiment design was the a/d ratio which was constant for all tested beams. The value of acting shear force as well as of concrete compressive strength was obtained from each experiment. These values were used for the optimization of mathematical equation for the shear design of textile reinforced concrete members with rectangular cross-section. This equation was first analyzed to gain the knowledge of every influential factor. After, the coefficient CRm,c was determined from the experimental data using the methods of optimization. The problem statement resulted in the formula for shear design of textile reinforced concrete members with rectangular cross-section which may be applied with respect to the conditions of usability of the shear model.

The diploma thesis deals with processing of determining the shear strength of concrete structures reinforced with composite reinforcement, subjected to shear force, according to five different design approaches. The theoretical part of the thesis is closely related to the project FW01010520 - "Development of bent composite reinforcement for environmentally exposed concrete constructions", which is realized at the Institut of Concrete and Masonry Structures, Faculty of Civil Engineering, Brno University of Technology. The project deals with the shear strength of concrete beams reinforced with steel and composite reinforcement in various combinations. Then the load-bearing results gained within the project are compared with the values obtained by calculations according to the solved design approaches and computer software Atena Science. The second part of the diploma thesis deals with the static design and assessment of the cell structure. The cell is designed as a room inside of the medical building, where is placed device of magnetic resonance which is the reason why the cell is reinforced with non-magnetic composite reinforcement.

In der vorliegenden Arbeit wurde die Ringfuge einer Tübbingschale hinsichtlich der Möglichkeit einer Reibungskopplung zur Übertragung von Scherkräften, wie sie bei relativen Ringversätzen auftreten können, untersucht. Ein Schwerpunkt lag dabei in der Ermittlung von Scherwiderständen an unterschiedlich profilierten Betonprobekörpern mit direktem Betonkontakt bzw. mit Verwendung einer Zwischenlage. Neben diesen Scherversuchen wurde zudem die Entwicklung der Normalkraft in der Ringfuge untersucht. Dabei wurden zur Verfügung gestellte Messdaten eines In-situ-Versuchs am Neuen Schlüchterner Tunnel ausgewertet. Weitere Erkenntnisse lieferte ein unter Laborbedingungen durchgeführter Bauteilversuch an Originaltübbings. Letztere wurden mittels Spanngliedern über einen Zeitraum von drei Jahren verspannt. Der Spannkraftverlust infolge von Kriechen und Schwinden des Betons sowie der Relaxation der Dichtungsprofile und der Spannglieder wurde kontinuierlich ermittelt