Asphalt joints are inevitable parts of every pavement. They are constructed for different reasons. Although much attention is dedicated to the construction joints (hot with hot pavement), a scientific approach for cold joints (cold with hot pavement) with respect to large patch constructions is still missing. This report tries to evaluate existing construction techniques and to suggest new testing methods of tests. Although, indirect tensile tests IDT and direct tension tests DTT are familiar in the field of asphalt pavement characterization, they have not been used for the assessment of joint quality so far. In this report, these two test types are evaluated and the results are analyzed using finite element software ABAQUS. The results of the comparison of joint compaction techniques on a laboratory scale suggest that joints with angles seem to show more promising behavior than vertical joints. Also, starting compaction from the hot side generally produces better results than compaction starting from cold side.

En el presente trabajo se aborda la tesis “Estudio paramétrico con FEM del refuerzo a punzonamiento de losas de hormigón armado”. Se trata de todo lo relacionado con el fenómeno resistente de punzonamiento en estructuras, especialmente en forjados construidos mediante hormigón armado. Se trata de cuatro apartados bien diferenciados. En este, el primero, se desarrolla la síntesis de la tesis, donde se marcan unos objetivos, seguido de una explicación detallada y descripción de este fenómeno mediante su estado del arte, que abarca el grueso de éste primer apartado, en el cual se describen, entre otros aspectos, las diferentes patologías producidas por el punzonamiento y casos de sucesos catastróficos que provocaron, la historia de los forjados y los principales estudios llevados a cabo sobre este fenómeno, y acabando con las principales resultados y conclusiones de la tesis. Después, el segundo y tercer apartado contienen los artículos publicados y no publicados, respectivamente, por capítulos. Por último, se desarrollan las conclusiones en el último y cuarto apartado.

This master thesis analyses stress and strain of iliac artery with atheroma. Model of artery is created as 2D and symmetric about the y-axis. The first part of the thesis deals with a research, which includes obtaining information from medicine, which is necessary fort the right solution of the task. Next part dedicates to nonlinear mechanics, constitutive modeling from the view of biomechanice and computational modeling of arteries. In the next part is made analysis for load on artery by physiological and also by high blood pressure. In the end were specified uncertainties of the used model and evaluated chance of atherosclerotic plaque rupture.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2007. / This thesis is concerned with the simulation of the in vivo biomechanical performance of a cervical disc replacement. A representative (averaged) maximum range of motion (ROM), determined by measurement of 10 student participants (5 male, 5 female), was used as head motion input to a simulation model of the cervical spine containing a disc implant at the C5/C6 intervertebral level. Intradiscal pressure, relative applied force on the C5 vertebrae, bending moments and vertebral rotations were recorded. The force and motion components of the results obtained were critically evaluated against the ISO and ASTM experimental protocol standards, probing the representativeness of these standards to the actual in vivo behaviour of the cervical functional spinal unit. Further, the wear resulting from a lifetime (10 million cycles) of the ISO prescribed -and simulation determined input cycles was simulated using a linear wear model with a triangulation technique for volume lost due to wear, and compared to in vitro results in the literature. The inputs used for the wear model were determined from a validated non-linear static contact finite element method (FEM) model. The simulation “chain” shows great potential as a comparative tool for the preexperimental testing of spinal implant designs and may be used with relative success as an alternative to expensive prototype testing.

Two different soils may be generated from open-pit mining: lumpy soils with a granular structure and clay mixtures, depending on the length of the conveyor belt and the strength of the original soils. Lumpy soils may be created for a high strength of the excavated soils. They are dumped as landfills without any compaction, which permits the water and air flows via the inter-lump voids. As a result, a new structure consisting of the lumps and reconstituted soil within the inter-lump voids can be created. However, if the original soil has a low strength or a long transportation takes place, the material may disintegrate into small lumps and thoroughly mix soils from different layers. Landfills consisting of clay mixtures arise in this way. The stability and deformation of landfills are crucial for design of occupied area and landfill slopes. For this reason, three different landfill materials will be investigated in this thesis: (1) the lumpy granular soil from fresh landfills, (2) the lumpy composite soil corresponding to old landfills and (3) clay mixtures. Firstly, an artificial lumpy soil was investigated. It is a transition form between the reconstituted and natural lumpy soils. Compression, permeability and strength of lumpy materials have been evaluated based on oedometer and triaxial tests. The shear strength of the normally consolidated lumpy specimens lies approximately on the Critical State Line of the reconstituted soil. The reconstituted soil, which exists in the inter-lump voids, plays a crucial role in the behaviour of artificial lumpy materials. Similarly to the artificial lumpy soil, inter-lump voids of the natural lumpy soil are mainly closed above a relatively small stress level, which is induced by the rearrangement of the lumps. However, its limit stress state is located above the Critical State Line of the reconstituted soil, which may be caused by the diagenetic soil structure in the natural lumps. The structure transition of the lumpy granular material can be divided into three possible stages related to the stress level. Firstly, the compressibility of a fresh lumpy is relativity high due to the closure of the inter-lump voids within a low stress range. In this stage, the hydraulic conductivity is mainly controlled by the inter-lump skeleton due to the existence of macro drainage paths, while the shear strength is controlled by the reconstituted soil around the lumps. Afterwards, its compressibility decreases with the consolidation stress and the soil behaves similarly to an overconsolidated soil. The clayfill appears to be uniform visually in this stage, but its structure is still highly heterogeneous and the hydraulic conductivity is higher than that of the reconstituted soil with the same overall specific volume. Finally, the loading reaches the preconsolidation stress of the lumps, and the whole soil volume becomes normally consolidated. Isotropically consolidated drained triaxial shear tests were performed on artificially prepared specimens with parallel and series structures. The laboratory tests show that the specimens with the series structure have the same failure mode as the constituent with the lower strength; the specimens with the parallel structure have a failure plane which crosses both constituents. As a result, the shear strength of the series specimens is only slightly higher than that of the constituent with the lower strength and the strength of the parallel specimens lies between those of the constituents. Afterwards, the behaviour of an artificial lumpy material with randomly distributed inclusions is investigated using the Finite Element Method. The computation results show that the stress ratio, defined as the ratio of the volume-average stress between the lumps and the reconstituted soil within the inter-lump voids, is significantly affected by both the volume fraction and the preconsolidation pressure of the lumps under an isotropic compression path, while the volume fraction of the lumps plays a minor role under a triaxial compression path. Based on the simulation results and analysis of the two basic configurations, a homogenization law was proposed utilizing the secant stiffnesses. The compression behavior of the lumpy composite soil was analyzed within the homogenization framework. Firstly, the volume of the composite soil was divided into four individual components. The inter-lump porosity was introduced to account for the evolution of the volume fractions of the constituents, and it was formulated as a function of the overall porosity and those of its constituents. A homogenization law was then proposed based on the analysis of the lumpy structure together with a numerical method, which gives a relationship for tangent stiffnesses of the lumpy soil and its constituents. Finally, a simple compression model was proposed for the composite lumpy material, which incorporates both the influence of the soil structure and the volume fraction change of the reconstituted soil. Furthermore, a general framework for the consolidation behaviour of the lumpy composite soil was proposed based on the double porosity concept and the homogenization theory. To describe the behaviour of lumps with low stress level, a new failure line was proposed with help of the equivalent Hvorslev pressure and critical state concept. The structure effect was incorporated into the nonlinear Hvorslev surface within sensitivity framework and the generalized Cam clay model proposed by McDowell and Hau (2003) was adopted on the wet side of the critical state. A secant stiffness, defined as the ratio between the deviatoric stress and deviatoric strain, was used in the homogenization law. Finally, a simple model for the natural lumpy soil was proposed within the homogenization framework. The physical properties, compression behaviour and remolded undrained shear strength of clay mixtures were investigated by reproducing the soils artificially in the lab. Afterwards, the models for the compression and undrained shear strength of clay mixtures were proposed. The model for the strength of the clay mixture originated from simplifying the structure of a clay mixture, in which the elements of the constituents are randomly distributed in a representative elementary volume. By defining a water content ratio (the ratio of water contents between the constituents), the undrained shear strength of each constituent was estimated separately and then combined together with corresponding volume fractions. A homogenization law was proposed afterwards based on the analysis of the randomly arranged structure. A simple compression model considering $N$ constituents was proposed within the homogenization framework, which was evaluated by a mixture with two constituents. / In einem Tagebau können die feinkörnigen Böden in unterschiedlichen Zustandsformen entstehen. Dies sind zum einen klumpige Böden mit einer granular ähnlichen Struktur (Pseudokornstruktur) und einer hohen Konsistenzzahl und zum anderen Mischungen aus mehreren Tonen oder Schluffen mit niedriger Konsistenzzahl. Der Zustand wird dabei massgebend von dem Transport (z.B. Länge des Förderbandes) und dem Ausgangszustand (z.B. der Anfangsscherfestigkeit) beeinflusst. Klumpige Böden entstehen bei der Abbaggerung des natürlichen Materials auf der Abbauseite, welches eine hohe Festigkeit besitzt. Alle Böden werden normalerweise ohne Verdichtung verkippt, so entstehen bei der Verkippung von klumpigen Böden grosse Makro-Porenräume zwischen den Klumpen, welche sehr luft- bzw. wasserdurchlässig sind. Nach einiger Zeit entsteht eine neue Struktur aus den Klumpen und dem Material des sich von aussen auflösenden Klumpens, welches das Füllmaterial bildet. Wenn die Festigkeit des Ausgangsmaterials niedrig ist oder lange Transportwege stattfinden, zerfallen die Klumpen. Zudem werden die Böden von verschiedenen Schichten der Abbauseite unter einander gemischt, wodurch die Tongemische entstehen. Sowohl für die Dimensionierung und Berechnung der aus den Verkippungen entstehenden Tagebaurandböschungen sowie für eine spätere Nutzung des ehemaligen Tagebaugebietes ist die Kenntnisüber das Deformations- und Verformungsverhalten von Kippenböden notwendig. Daher wurden in dieser Arbeit Tagebauböden und ihr zeitlich veränderliches Verhalten untersucht. Dabei werden diese, bezugnehmend auf den Anfangszustand, in drei typische Materialien unterschieden: (1) der frisch verkippte klumpige Boden, (2) eine Mischung aus Klumpen und Füllmaterial, welche höhere Liegezeiten repräsentiert und (3) Mischungen von feinkörnigen Ausgangsböden. Zunächst wurden künstlich hergestellte klumpige Böden untersucht. Sie bilden eine Übergangsform zwischen aufbereiteten und natürlichen klumpigen Böden. Das Kompressions- und Scherverhalten sowie die Durchlässigkeit wurden an Ödometer und Triaxialversuchen bestimmt. Das Füllmaterial, welches die Makroporen zwischen den Klumpen füllt, spielt eine entscheidende Rolle für das Materialverhalten. Ähnlich wie bei den künstlich hergestellten klumpigen Böden schliessen sich auch bei den Böden im Tagebau die Makroporenschen bei niedrigen Spannungen. Dabei werden die Klumpen umgelagert. Allerdings befindet sich die Grenze des Spannungszustandes oberhalb der Critical State Line des Füllmaterials, was möglicherweise mit den unter Diagenese entstandenen Bodenstrukturen erklärt werden kann. Die Strukturänderung der klumpigen Böden kann aufgrund des Spannungsniveaus in drei mögliche Stufen unterteilt werden. Am Anfang ist die Kompressibilität der frischen verkippten Klumpen hoch, da sich die Makroporen bereits bei geringen Spannungen schliessen. Zu diesem Zeitpunkt sind auch die Durchlässigkeiten in erster Linie von den grossen Porenräumen der Makroporen, welche als Entwässerungspfade dienen, beeinflusst. Die Scherfestigkeit hingegen, wird durch die aufgeweichten Böden an den Oberflächen der Klumpen massgebend beeinflusst. Bei höheren Konsolidationspannungen sinkt die Kompressibilität und der Boden verhält sich wie einüberkonsolidierter Boden. Obwohl die Struktur aufgrund der veränderten Klumpenoberflächen zu diesem Zeitpunkt homogener wirkt, ist die Struktur noch heterogen und die Durchlässigkeit ist höher als bei einem aufbereiteten Boden mit gleichem spezifischem Volumen (Porenzahl). Letztendlich erreicht der aktuelle Spannungszustand den derüberkonsolidierten Klumpen und der gesamte Boden verhält sich wie ein normal konsolidierter Boden. Des Weiteren wurden isotrop konsolidierte drainierte Triaxialversuche an künstlich aus zwei Ausgangsmaterialien hergestellten Proben mit parallelen und seriellen Strukturen durchgeführt. Die Laborversuche zeigten, dass die Proben mit seriellem Aufbau dieselben Gleitflächen haben, wie der Ausgangsboden mit der niedrigeren Scherfestigkeit. Die Gleitfläche der Proben mit parallelen Strukturen verlief durch beide Materialien. Es wurde festgestellt, dass die Scherfestigkeit der seriell aufgebauten Proben geringfügig höher, als die des Bodens mit der niedrigeren Scherfestigkeit ist. Die Scherfestigkeit der parallel aufgebauten Proben liegt zwischen den beiden Ausgangsmaterialien. Danach wurde das Verhalten der künstlich erzeugten klumpigen Böden mit zufällig verteiltem Füllmaterial mit Hilfe der Finiten Elemente Methode verglichen. Die Simulationen zeigten, dass unter einer isotropen Kompressionsbelastung das Spannungsverhältnis, definiert aus dem Verhältnis der Spannung des Volumendurchschnitts zwischen den Klumpen und dem Füllmaterial, deutlich durch die Volumenanteile und die Vorkonsoliderungsspannung der Klumpen beeinflusst wird. Während das Volumenverhältnis eine untergeordnete Rolle in den in Triaxialzellen unter Scherung belasteten Proben spielt. Aus den Simulationsergebnissen und den Laborversuchen der beiden Grundkonfigurationen wurde ein Homogenisierungsgesetz abgeleitet, welches die Sekandensteifigkeiten verwendet. Das Kompressionsverhalten der Mischungen aus Klumpen und Füllmaterial wurde mit Blick auf die Homogenisierung analysiert. Zunächst kann das Volumen der Mischungen in 4 individuelle Komponentenanteile zerlegt werden. Die Makroporosität zwischen den Klumpen wurde zur Entwicklung der Volumenanteile des Füllmaterials eingeführt. Sie wurde als eine Funktion der totalen Porosität und der Materialien formuliert. Auf Grundlage einer theoretischen Analyse an klumpigen Böden und unter Zuhilfenahme einer numerischen Methode wird ein Gesetz zur Homogenisierung vorgeschlagen. Dieses enthält eine Beziehung zwischen der Tagentensteifigkeit der Klumpen und seinem Füllmaterial. Abschliessend wird ein einfaches Kompressionsmodel für die Mischung aus Klumpen und Füllmaterial vorgeschlagen, welches den Einfluss der Bodenstruktur und der Änderung des Volumenanteils des Füllmaterials berücksichtigt. Darüber hinaus wurde eine allgemeine Formulierung für das Konsolidationsverhalten der klumpigen Böden mit Füllmaterial vorgeschlagen, welche sich auf das Konzept der doppelten Porosität (Klumpen und Füllmaterial) und eine Homogenisierungstheoerie bezieht. Um das Verhalten der Klumpen bei niedrigen Spannungen zu beschreiben, wird eine neue Grenzbedingung unter Zuhilfenahme der äquivalenten Hvorslev-Spannung und des Criticial State Konzeptes vorgeschlagen. Der Struktureffekt für sensitive Böden wurde in die nichtlineare Hvorslev-Oberfläche eingebaut. Das allgemein gültige Cam-Clay-Model von McDowell und Hau (2003) wurde um die nasse Seite des Critical State Konzeptes erweitert. Eine Sekandensteifigkeit, definiert aus dem Verhältnis zwischen der Deviatorspannung und der Deviatordehnung, wurde für das Homogenisieurungsgesetz ebenfalls verwendet. Abschliessend wird ein Modell für natürliche klumpige Böden vorgestellt, welches auch eine Homogenisierung beinhaltet. Die physikalischen Eigenschaften, das Kompressionsverhalten und die undrainierten Scherfestigkeiten von aufbereiten Tongemischen wurden im Labor unter Herstellung künstlicher Bödengemische untersucht. Anschliessend wurde ein Kompressions- und Schermodell für aufbereitete Tongemische vorgeschlagen. Das Modell der Scherfestigkeit der Tongemische entstand aus der Vereinfachung der Tongemischstruktur, in welcher die Elemente der Ausgangsmaterialien zufällig in dem Einheitsvolumen verteilt sind. Werden Wassergehaltsverhältnisse (das Verhältnis der Wassergehalte der Ausgangsmaterialien) definiert, kann die undrainierte Scherfestigkeit für alle Bestandteile separat geschätzt werden und dannüber die Volumenanteile bestimmt werden. Ein Homogenisierungsgesetz wurde auf Grundlage der theoretischen Analyse von zufällig angeordneten Strukturen entwickelt. Ein einfaches Kompressionsmodell, welches N-Ausgangsmaterielien bzw. Tone und eine Homogenisierung enthält, wird vorgeschlagen, und an einer Mischung aus 2 Bestandteilen im Labor validiert.

Most of the today’s concrete structures are older than tenyears, and the need to strengthening existing structures is growing steadily. This is due to various reasons such as degradation due to ageing, environmentally induced degradation, poor initial design or construction and lack of maintenance, to name a few. Among the benefits of strengthening existing structures are; less impacts on the environmental and financial benefits. Therefore, there is a need to find alternative ways to strengthen concrete structures more effectively. For the past decades, several different strengthening methods have been studied. Two examples are externally bonded reinforcement (EBR) and near surface mounted reinforcement (NSM). The outcome of these studies has shown a significant enhancement to the structures. Steel plates and rebar have been used to strengthen concrete structures and have shown good increases in flexural capacity. For this purpose, resins have been used to implement the steel plates and rebar, e.g. shotcrete and epoxy. Due to the weight of steel and its sensitivity to corrosion, new materials have been sought. A promising material for this use is the fiber reinforced polymers (FRP). There are several types of FRP such as, carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP) and aramid fiber reinforced polymer (AFRP). These new material has shown a better performance, due to their light weight, resistance to corrosion,etc. NSM and EBR perform extremely well in practice as long as sufficient anchorage is provided. However, a premature debonding has been observed by several researchers. This report will study an alternative method to reinforce existing concrete structures called “Side Near Surface Mounted Reinforcement (S-NSMR)” in association with a project run by Gabriel Sas at Luleå University of Technology. This is compared to Bottom Near Surface Mounted Reinforcement (B-NSM), which is a well-established method. It is assumed that the fiberutilisation will increase in NSM applied on the side of the beam. If this hypothesis is proven correct, the proposed method will also solve a major constrain in the utilisation of the NSM technique. In certain cases, the bottom of a beam is not fully accessible for strengthening using bottom Applied NSM techniques due to e.g. partition walls or beam-column joints. To test the effect of S-NSMR seven concrete beams, one reference beam with no fiberreinforcement and two sets of three, for S-NSMR and B-NSMR respectively with different CFRP-rebar length, were tested in the laboratory. An analytical calculation has also been carried out. In this thesis, a parametric study is performed with FEM software Atena. The thesis begins with a study of the failure phenomena occurring in the earlier mentioned strengthening method. A benchmark model is then modelled with a good comparison to the experimental results. An idealised model of the steel reinforcement in the concrete beam is used according to Eurocode 2. Material parameters in concrete are calculated according to Atena theory documents. The influence of creep and shrinkage are considered by reducing the elastic modulus of concrete by 25 %, reducing the tensile strength by 50 % and fracture energy accordingly. Thereafter, three additional parameters were chosen to continue the parametric study with Atena, 1) CFRP with E-modulus 160 GPa, 2) two different position in cross-section height of S-NSM and 3) five shorter CFRP-rebar each 100 mm smaller than the previous rebar. The behaviour of the two reinforcing types is then compared. The first parameter is, CFRP with a smaller E-modulus. It could be observed that all beams lost their stiffness, especially after yielding of the steel reinforcement. A small improvement in ductility could also be observed. The utilisation rate of CFRP increased by 13-16% in the case of S-NSM and 18-20% in the case of B-NSM. The second parameter is, different position of CFRP along the height of the beams cross-section in S-NSM beams. The positions of the CFRP was lowered in two steps. In each case an increase in stiffness and a decrease in ductility could be observed. However, the increase of the stiffness was still smaller than the stiffness in the B-NSM, in all cases. The failure mode changed from a ductile (concrete crushing) type to a more brittle kind (peeling-off concrete), due to large flexural cracks at the end of the CFRP-rebar.   The utilisation rate of CFRP-rebar, is decreased in each S-NSM beam except for S-NSM 2 with the height 25 mm. The reduction in the utilisation rate of the CFRP is 7-32 % and in S-NSM 2 with the height H25mm showing an increased in utilisation rate by 7 %. The third is parameter, different length of CFRP-rebar. In the case of S-NSM, the failure mode changed from a ductile failure mode to a brittle failure mode. The utilisation rate decreased with the decrease in CFRP length. In three of five cases, the S-NSM shows a higher ultimate load-displacement relation, and in all five cases the maximum tensile strains in the CFRP were higher in S-NSM than B-NSM. Even though the stiffness in the S-NSM is lower than the B-NSM, it would be more preferable to use the S-NSM than B-NSM, because of its higher ultimate load and lower displacements.

In an attempt to improve the quality in finite element analysis of thermoformed components, a method for predicting the thickness distribution is presented. The strain induced anisotropic material behaviour in the amorphous polymers of concern is also taken into account in the method. The method comprises of obtaining raw material data from experiments, followed by a simulation of the vacuum thermoforming process where hyperelastic material behaviour is assumed. The theory of hyperelasticity that was applied was based on the Ogden model and implemented in the FE-software LS-DYNA. Material behaviour from thermoformed prototypes is examined by experiments and implemented together with the mapped results from the thermoforming simulation in a succeeding FE-model. For the latter, the three-parameter Barlat model was suggested, giving the possibility to account for anisotropic material behaviour based on an initial plastic strain.

No description available.

This master’s thesis deals with structural design of twin heat exchanger with vertically stacked horizontal vessels according to CSN EN 13 445 standard. Brief introduction and basic characteristics of shell and tube heat exchangers is performed in the beginning part of the thesis. Design of the heat exchanger was initially performed using design by formula (DBF), which was verified by specialized software Sant´Ambrogio. Since this approach does not include methods for assessment of the nonstandard connection between the vessels, simulations of significant load states were performed using FEM analyses followed by result evaluation using stress categories.

The diploma thesis deals with the design of the measuring bucket of bucket wheel excavator KR400Nk. The main part of this thesis is the strength analysis of the supporting structure and the measuring bucket, which is done using the finite element method. In addition, examinations of the elements replaced in the finite element model are performed. Appropriate adjustments are proposed based on strength analysis. This diploma thesis was prepared in cooperation with company NOEN, a. s..