In this thesis, basic concepts of populational models are studied from a theoretical point of view, especially the long term behaviours. All models are at least time dependent with additional age structure, spatial structure. The last model which is an extension of the von Foerster equation, is dependent on all o f these structures and have a long-term solution for large values of time. Modeling population is a frequent subject in modern biology. It is hard to create a model that appears as realistic as possible. First one might consider that a population size is governed by the current size of the population, along with rates of how each individual contributes (give birth), so that the population increases. and how frequent an individual dies, causing the population to decrease in size. However these sort of models can only describe the size of population in a shorter span of time.

There are numerous experiments for the exploration of the corium spreading behaviour, but comparable data have not been available up to now in the field of the long term behaviour of a corium expanded in a core catcher. The difficulty consists in the experimental simulation of the decay heat that can be neglected for the short-run course of events like relocation and spreading, which must, however, be considered during investigation of the long time behaviour. Therefore the German GRS, defined together with Battelle Ingenieurtechnik a benchmark problem in order to determine particular problems and differences of CFD codes simulating an expanded corium and from this, requirements for a reasonable measurement of experiments, that will be performed later. First the finite-volume-codes Comet 1.023, CFX 4.2 and CFX-TASCflow were used. To be able to make comparisons to a finite-element-code, now calculations are performed at the Institute of Safety Research at the Forschungszentrum Rossendorf with the code ANSYS/FLOTRAN.For the benchmark calculations of stage 1 a pure and liquid melt with internal heat sources was assumed uniformly distributed over the area of the planned core catcher of a EPR plant. Using the Standard-k-e-turbulence model and assuming an initial state of a motionless superheated melt several large convection rolls will establish within the melt pool. The temperatures at the surface do not sink to a solidification level due to the enhanced convection heat transfer. The temperature gradients at the surface are relatively flat while there are steep gradients at the ground where the no slip condition is applied. But even at the ground no solidification temperatures are observed. Although the problem in the ANSYS-calculations is handled two-dimensional and not three-dimensional like in the finite-volume-codes, there are no fundamental deviations to the results of the other codes.

There are numerous experiments for the exploration of the corium spreading behaviour, but comparable data have not been available up to now in the field of the long term behaviour of a corium expanded in a core catcher. The difficulty consists in the experimental simulation of the decay heat that can be neglected for the short-run course of events like relocation and spreading, which must, however, be considered during investigation of the long time behaviour. Therefore the German GRS, defined together with Battelle Ingenieurtechnik a benchmark problem in order to determine particular problems and differences of CFD codes simulating an expanded corium and from this, requirements for a reasonable measurement of experiments, that will be performed later. First the finite-volume-codes Comet 1.023, CFX 4.2 and CFX-TASCflow were used. To be able to make comparisons to a finite-element-code, now calculations are performed at the Institute of Safety Research at the Forschungszentrum Rossendorf with the code ANSYS/FLOTRAN.For the benchmark calculations of stage 1 a pure and liquid melt with internal heat sources was assumed uniformly distributed over the area of the planned core catcher of a EPR plant. Using the Standard-k-e-turbulence model and assuming an initial state of a motionless superheated melt several large convection rolls will establish within the melt pool. The temperatures at the surface do not sink to a solidification level due to the enhanced convection heat transfer. The temperature gradients at the surface are relatively flat while there are steep gradients at the ground where the no slip condition is applied. But even at the ground no solidification temperatures are observed. Although the problem in the ANSYS-calculations is handled two-dimensional and not three-dimensional like in the finite-volume-codes, there are no fundamental deviations to the results of the other codes.

Intresset för användning av KL-trä som byggnadsmaterial har ökat kraftigt sedan tekniken introducerades i Sverige under 1990-talet. Med ökande användning av KL-trä i konstruktioner finns behov av att undersöka hur materialet beter sig under längre tid. Förband är generellt sett en svag punkt i en konstruktion, och det är därför viktigt att närmare undersöka långtidsbeteendet hos förband i KL-trä. Syftet med arbetet är att utveckla metoder som kan användas för att ge större insikt i hur effekterna av belastning under lång tid påverkar konstruktioner i KL-trä. I den här studien undersöks vilka tidigare utförda studier som behandlat långtidsbeteende hos trä i allmänhet och hos KL-trä i synnerhet. Utifrån dessa studier har två förslag på testmetoder tagits fram: ett test för förband utsatt i skjuvning, och ett utdragstest. / The interest for the use of CLT as a building material has increased dramatically since the technology was first introduced in Sweden during the 1990s. With increasing use of CLT in constructions there is a need to investigate the material’s long-term behaviour. Connections are generally a weak point in a construction, and it is therefore important to investigate the long-term behaviour of connections in CLT. The purpose of this project is to develop methods that can be used to provide greater insight into how the effects of long-term loading affect the behaviour of CLT designs. This study examines previously conducted studies involving long-term behaviour of wood in general and CLT in particular. Following this investigation, two proposals of test set-ups have been developed: one test for joints subjected to loading in shear, and one withdrawal test.

This study deals with the hydro-mechanical behaviour of compacted bentonite-based materials used as sealing materials in high-level radioactive waste repositories. The pure MX80 bentontie, mixtures of MX80/crushed claystone and MX80/sand were used in the investigation. An experimental study on the swelling pressure of the bentonite-based materials was first performed. The results evidenced the effects of water chemistry, hydration procedure and duration, pre-existing technological void and experimental methods. Emphasis was put on the relationship between the swelling pressure and the final dry density of bentonite. Afterwards, the water retention test, hydration test and suction controlled oedometer test were conducted on samples with different voids including the technological void and the void inside the soil. By introducing the parameters as bentonite void ratio and water volume ratio, an overall analysis of the effects of voids on the hydro-mechanical response of the compacted material was performed. To get better insight into the seal evolution in case of technological void, the effects of final dry density and hydration time on the microstructure features were also characterized. Then, the hydraulic properties under unsaturated state were investigated by carrying out water retention test and infiltration test as well as the microstructure observation. The results obtained allowed relating the variation of hydraulic conductivity to the microstructure changes. A small scale (1/10) mock up test of the SEALEX in situ experiment was also performed to study the recovery capacity of bentonite-based material with consideration of a technological void. The results were used for interpreting the in-situ observations. With a reduced time scale, it provides useful information for estimating the saturation duration and sealing effectiveness of the field design. Finally, the experimental data obtained in the laboratory on bentonite/sand mixture were interpreted in the framework of the Barcelona Expansive Model (BExM). By comparing the model with the experimental results, the performance and limitation of the model were analyzed

The assessment of ageing tunnels requires a deeper understanding of the long-term behaviour of twin tunnels, whilst lack of permeability data limits the accuracy of long-term predictions. This thesis therefore investigates long-term twin-tunnel behaviour through finite-element parametric analyses, and provides additional pereability data through laboratory studies. Permeability tests are performed on fissured London Clay, exploring the effect of isotropic stress cycles on the permeability of fissures. A model explaining the permeability-stress relationship is proposed to explain irrecoverable changes observed in fissure permeability, and is formulated mathematically for numerical implementation. Laboratory investigations are performed on grout from the London Underground tunnels, investigating permeability, porosity, microstructure and composition. A deterioration process is proposed to explain observations, consisting of acid attack and leaching. The deterioration had appeared to transform the grout from impermeable to permeable relative to the soil. The change in grout permeability with time would strongly influence long-term movements. The long-term behaviour of single tunnels is investigated in a finite-element parametric study. A new method is formulated to predict long-term horizontal and vertical surface displacements after excavation of a single tunnel, and incorporates an improved measure of relative soil-lining permeability. The study also predicts significant surface movements during the consolidation period, contradicting the lack of further building damage observed in the field. A further parametric study also investigates the long-term behaviour of twin tunnels. Key interaction mechanisms are identified, leading to the postulation of the long-term interaction behaviour under different tunnelling conditions. Long-term interaction is found to be complex and significant, and should be accounted for in numerical simulations.

<p>The research contained in this thesis is concerned with longterm behaviour of drilled piers socketed in weak rock. The experimental work involved testing of two steel and seven concrete model piers. The 25.4 mm (1.0 in) diameter steel piers had relatively smooth socket walls (RF = 0.033) and were socketed into pseudo-rock material. The concrete piers were 76.2 mm (3.0 in) in diameter and were socketed into weak rock (Queenston Shale). The concrete piers were of two types: conventional socketed piers with relatively smooth socket walls (RF = 0.025) and grooved piers with relatively rough socket walls (RF = 0.081 and 0.303).</p> <p>The piers were tested under two condition of load support, shaft resistance only and combined shaft resistance and end-bearing support conditions.</p> <p>In case of steel piers, electrical resistance strain gauges were mounted on the pier shaft to measure the load distribution along the shaft of the piers. For concrete piers under combined shaft resistance and end-bearing support conditions, flat jack load cells with Marsh and Budenberg pressure gauges and/or electrical pressure transducers were used to measure the load transfer at the base.</p> <p>All model piers were axially loaded in the laboratory using load frames designed and fabricated for this purpose. The axial loads were iii applied by the air cylinders and held constant throughout the period of testing using a regulated air pressure supply.</p> <p>The test results confirmed that performance of socketed piers can be significantly improved by increasing the roughness of the pier-rock interface. Both the primary creep rate and the load transfer with time were larger for piers with small shaft roughness.</p> <p>A second stage of creep having a much lower creep rate was observed for all model tests. The time to the end of primary creep was found to depend on the roughness of the socket wall. The primary and secondary creep rate appeared to be dependent on the stress level, shaft roughness, compressive strength of weak rock and support conditions.</p> <p>The results of the model tests are compared with available test data and with values predicted using methods based on viscoelastic analysis. This method of analysis for piles in clay soils has been modified for application to socket piers in weak rock. It is suggested that the modifications can be used to estimate the long-term settlement of socket piers in weak rock</p> / Master of Engineering (ME)

La majorité des bâtiments existant aujourd'hui ne respectent pas les réglementations thermiques actuelles. Pour répondre aux exigences environnementales il est impossible, dans ce contexte, d'envisager une politique globale de démolition-reconstruction. Des campagnes de réhabilitation doivent être mises en place. Une solution innovante de réhabilitation énergétique est proposée permettant d'exploiter les ressources énergétiques urbaines, peu utilisées actuellement. Elle consiste à rajouter autour du bâtiment une enveloppe extérieure qui aurait pour fonction principale le captage d'énergie solaire. Un outil d'optimisation de la géométrie de l'enveloppe et de la distribution spatiale de panneaux capteurs à sa surface est développé. Sa validation est effectuée sur des cas simples, puis il est appliqué aux situations présentant de forts contrastes : optimisation pendant la période d'hiver ou d'été, à Oslo ou à Tunis, avec des obstacles proches masquant le Soleil. Afin de réaliser les formes complexes obtenues, il est proposé d'utiliser les gridshells comme système constructif. Ces structures obtenues par déformation élastique d'une grille de poutres en matériau composite initialement planes posent la question de la durabilité de ces matériaux soumis au chargement permanent. Pour étudier le comportement à long terme (fluage et rupture différée) de ces matériaux composés de fibres de renfort et matrice polymère viscoélastique, un modèle micro-mécanique est développé. Ce modèle de type shear-lag permet d'étudier l'influence des propriétés mécaniques des constituants sur la durée de vie du composite soumis à un chargement en traction et traction-cisaillement combinés / The majority of existing buildings does not follow present energy efficiency regulations. In order to fulfill environmental requirements it seems impossible, in this context, to consider a global demolition-reconstruction policy. Renovation programmes need to be implemented. An innovative energy efficiency improvement solution is proposed, enabling to explore urbain energy ressources presently underexploited. The concept is to add, around the building, an external envelope whose main function would be to collect energy. An optimization tool aiming at finding the optimal geometry and collectors' spatial distribution on the envelope's surface, is developed. Its validation is carried out on simple cases, it is then applied in situations showing strong contrasts: optimization during summer and winter, in Oslo and in Tunis, with close obstacles partially masking the Sun. In order to build the emerging complex geometries, the use of gridshell structures is proposed. These structures are obtained through elastic deformation of an initially plane grid made of composite material slender beams. This raises the problem of composite materials durability under sustained loading. In order to study the long-term behavior (creep and creep rupture) of these materials composed of reinforcing fibres and a polymeric viscoelastic matrix, a micromechanical model is developed. This shear-lag type model allows studying the influence of the constituents' mechanical properties on the lifespan of the composite under permanent pure traction or combined shear and traction loadings

La présente étude concerne le comportement hydromécanique des matériaux compactés à base de bentonite pour le stockage des déchets radioactifs en grande profondeur. Trois matériaux candidats ont été étudiés : la bentonite (MX80) pure, le mélange bentonite/argilite broyée et le mélange bentonite/sable. Une étude expérimentale sur la pression de gonflement du mélange bentonite/argilite a été premièrement réalisée. Cette étude a mis en évidence l'effet de la salinité de l'eau, de la procédure et la durée d'hydratation, du pré-existant vide technologique et des méthodes expérimentales. Une importante relation entre la pression de gonflement et la densité sèche finale de la bentonite a été élaborée. Ensuite, des essais de rétention d'eau, des essais d'hydratation et des essais oedométriques à succion contrôlée ont été réalisés sur des échantillons à différentes porosités tout en considérant la présence du vide technologique. En introduisant les paramètres comme indice des vides de la bentonite et le ratio volume d'eau, une analyse globale des effets des vides sur la réponse hydromécanique de la barrière ouvragée a été effectuée. Pour obtenir un meilleur aperçu de l'évolution de l'étanchéité dans le cas de vide technologique, l'effet de densité sèche finale (densité après fermeture de vide technologique) et du temps d'hydratation sur la microstructure a été, de même, étudié. La perméabilité de ce matériau à l'état non saturé a été ensuite étudiée en réalisant des essais de rétention d'eau et d'infiltration ainsi que par des observations de la microstructure. Les résultats obtenus ont permis de relier la variation de la conductivité hydraulique non saturée aux changements de la microstructure. Une expérimentation en modèle réduit reproduisant à une échelle 1/10ème les essais in-situ (SEALEX) a été effectuée, et cela pour étudier la reprise des vides à long terme d'un mélange compacté bentonite/sable, tout en considérant la présence d'un vide technologique. Les résultats ont été utilisés pour interpréter les observations de l'essai in situ. A une échelle de temps réduite, cette étude fournit des informations utiles pour estimer la durée et l'efficacité de la conception en place. Finalement, les données expérimentales obtenues dans le laboratoire sur le mélange bentonite/sable ont été interprétées dans le cadre du modèle de Barcelone (BExM). Après comparaison des résultats expérimentaux avec le modèle, les performances et les limitations du modèle ont été analysées / This study deals with the hydro-mechanical behaviour of compacted bentonite-based materials used as sealing materials in high-level radioactive waste repositories. The pure MX80 bentontie, mixtures of MX80/crushed claystone and MX80/sand were used in the investigation. An experimental study on the swelling pressure of the bentonite-based materials was first performed. The results evidenced the effects of water chemistry, hydration procedure and duration, pre-existing technological void and experimental methods. Emphasis was put on the relationship between the swelling pressure and the final dry density of bentonite. Afterwards, the water retention test, hydration test and suction controlled oedometer test were conducted on samples with different voids including the technological void and the void inside the soil. By introducing the parameters as bentonite void ratio and water volume ratio, an overall analysis of the effects of voids on the hydro-mechanical response of the compacted material was performed. To get better insight into the seal evolution in case of technological void, the effects of final dry density and hydration time on the microstructure features were also characterized. Then, the hydraulic properties under unsaturated state were investigated by carrying out water retention test and infiltration test as well as the microstructure observation. The results obtained allowed relating the variation of hydraulic conductivity to the microstructure changes. A small scale (1/10) mock up test of the SEALEX in situ experiment was also performed to study the recovery capacity of bentonite-based material with consideration of a technological void. The results were used for interpreting the in-situ observations. With a reduced time scale, it provides useful information for estimating the saturation duration and sealing effectiveness of the field design. Finally, the experimental data obtained in the laboratory on bentonite/sand mixture were interpreted in the framework of the Barcelona Expansive Model (BExM). By comparing the model with the experimental results, the performance and limitation of the model were analyzed

Dieser Beitrag bietet einen Überblick über die in zwölf Jahren Forschungsarbeit am Institut für Textilmaschinen und Textile Hochleistungswerkstofftechnik (ITM) erzielten Ergebnisse auf dem Gebiet textiler Betonbewehrungen unter Einsatz der Nähwirktechnik. Standen zunächst die Weiterentwicklung der Nähwirk- bzw. Multiaxial-Kettenwirktechnik und die Integration zusätzlicher Prozessschritte im Mittelpunkt, so wurde dies mit der Einführung neuer Faserwerkstoffe durch die Beantwortung grundlegender Fragen zum Materialverhalten von Glas- und Carbonfasern unter verschiedensten Belastungsszenarien ergänzt. Aufbauend auf den gewonnen Erkenntnissen stehen heute Multiaxialgelege als Bewehrung für Beton zur Verfügung, die ein weites Anforderungsspektrum abdecken können, mit hoher Qualität und Produktivität herstellbar sind und damit den praktischen Einsatz des Textilbetons auf breiter Basis ermöglichen. / This paper provides an overview on the results of textile concrete achieved in twelve years of research at the Institute of Textile Machinery and High Performance Material Technology (ITM) in the field of textile reinforcements for concrete based on the multiaxial stitch-bonding technology. During the early years the research focused on the development of the textile manufacturing process and the integration of additional functions in stitch-bonding machines. With the introduction of new fiber materials this was shifted towards the description of the material behavior of glass and carbon fibers under different load scenarios. Based on the results of this research, multiaxial multi-ply fabrics are available now as reinforcements for concrete, covering a broad range of applications. These fabrics can be produced with high quality and productivity and enable the practical usage of textile reinforced concrete.