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The work deals with issues of evaluation of the shear properties of timber structural materials, particularly CLT elements. The work contains an overview of extensive research so far presented scientific studies dealing with the characteristic shear properties of wood. In the practical part was carried out the experiment dealing with the failure mode of transverse lamellae of CLT elements that were exposed to shear stress. There were observed individual effects that this may affect the material properties. In the first part of the experiment were performed numerical models using FEM. In the second part, the test specimens were tested in three point bending. Here, attention was paid to the influence of macroscopic properties of wood on the distribution of stress cracks and shear strength, the tests were recorded using DIC system.

This thesis is intended to identify the mode I and mode II fracture toughness to characterize the thin laminate interface by using the Double Cantilever Beam test (DCB) and End Notched Flexure test (ENF). This study’s thin laminate was Polyethylene Terephthalate and Low-Density Polyethylene (PET-LDPE), which is mostly used by packaging industries in the manufacturing of packages to store liquid food. As PET-LDPE film is very flexible and difficult to handle, DCB and ENF tests cannot be performed directly so, sheet metal (Aluminium) was used as carrier material. PET-LDPE film is placed between two aluminum plates to reduce the flexibility and perform the tests. Therefore, the Aluminium plate was also studied to find the constitutive parameters (young’s modulus (E) and mixed hardening parameters (Plastic properties)) under the tensile test and three-point bending test. From the test response, energy release rate calculation has been done for different Pre-crack lengths to validate the DCB and ENF experimental setup, study the different Pre-crack lengths, and characterize the laminate interface. Finite Element simulation (FE simulation) for those tests were carried out in AbaqusTM2020. When needed, the force versus displacement response from FE simulation was optimized against experimental response to find the required constitutive parameters (Young’s modulus, Hardening parameters, and PET-LDPE material properties). Implementing of optimization algorithm and automated simulation has been done with the help of MATLAB code. In contrast, MATLAB works as a server, and Abaqus works as a client and connected two interfaces to run the optimization. The results obtained from experiments and FE simulations were compared to the results found in the literature.

Corrosion of steel reinforcement has been identified as one of the major problems facing many existing reinforced concrete structures including bridges. The exposure to aggressive environmental conditions such as those with high concentrations of chloride ions due to the use of de-icing salt in cold regions or high concentrations of carbon dioxide due to increased greenhouse gas emissions, accelerate the initiation process of corrosion. As corrosion initiates, the structural performance in terms of load-carrying capacity, ductility, and service life deteriorate over time. Coupling the effect of reinforcement corrosion with service loads may further weaken the structural performance of reinforced concrete bridges due to the presence of transverse load-induced cracks. Accordingly, a research program was conducted to evaluate the structural performance of reinforced concrete beams subjected to coupled effects of service loads and reinforcement corrosion. The research project consisted of combined experimental and numerical investigations. The experimental phase consisted of tests of nine small-scale beams and six large-scale beams. The beams were designed, constructed, instrumented, and loaded under a four-point load test. The primary test variables were the applied corrosion current density, level of corrosion, and level of sustained loading as percentage of beam ultimate capacity (0% Pu, 40% Pu, and 60% Pu). The corrosion level of steel reinforcement was quantitatively assessed using gravimetric weight measurements and three-dimensional laser scanner technique. Test results indicated that failure of corroded RC beams was brittle due to premature rupture of corroded steel bars, which was attributed to the development of localized corrosion at the sections with flexural cracks in beams. Furthermore, it was found that beams subjected to higher levels of service loads, experienced further reductions in ultimate load capacity and ductility. In addition, tensile tests were used to evaluate the effect of corrosion on the mechanical performance of steel bars retrieved from the corroded beams. It was found that the tensile strength of corroded steel bars, based on nominal sectional area, was reduced with the increase of corrosion levels. In contrast, the tensile strength, based on minimum sectional area, was not influenced by the non-uniform distribution and localization of corrosion. In fact, there was a slight increase in strength with the increase of corrosion levels. The numerical phase consisted of finite element analyses of beams using DIANA FE analysis software. A simplified approach was implemented to introduce the damage induced by corrosion into two-dimensional nonlinear FE models, based on the experimental testing of corroded beams and corroded steel bars. The analyses were reasonably accurate in predicting cracking patterns, residual load capacity, residual ductility, and failure modes of corroded beams. Subsequently, the validated model was used to conduct a parametric study on the level of service loads, level of corrosion, strength of concrete, and tensile reinforcement ratio. It was found that the FE model of corroded beams was strongly influenced by the level of service loads, level of corrosion, and tensile reinforcement ratio.

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis provides an approach to incorporate natural composites like Flax Fiber using a resin with 30% bio-content to enhance the packaging boxes made of corrugated cardboard. The objective of introducing natural composite skins is to reduce/eliminate the compressive loading subjected to the boxes while stacking in warehouses.

In order to satisfy the mechanical requirements for space structures, achieving lightweight designs is of the greatest significance. The primary focus of this study is the utilization of Kelvin cell core in the design of sandwich structures for space applications. The research encompasses a variety of production techniques, analyzes, and tests related to the design of sandwich structures with Kelvin cells as the core material. While a variety of configurations are evaluated in a general sense, particular configurations are examined in greater extensive detail. In this context, the structure's bending stiffness, compression stiffness, and vibration characteristics are analyzed. The analytical procedure begins with a simplified structure analysis, followed by the modeling of the actual geometry. According to applicable standards, stiffness values are calculated based on the deflection results of the analyzes. However, it is important to note that the tests performed on the modeled structures are conducted in a laboratory environment using additively manufactured samples. This permits a comparison between the obtained test results and the findings of the analyzes, shedding light on the effect of the manufacturing method. This study demonstrates that the honeycomb sandwich structure is superior in terms of overall stiffness. In addition, a specially designed reinforced Kelvin Cell structure possesses exceptional bending rigidity properties. In light of these findings, it is clear that the combination of Kelvin Cell core and specific reinforcement strategies has the potential to improve the mechanical performance of sandwich structures. In addition, the deformation results revealed by the analyzes showed that the structure can be deformed in large amounts in directions other than the direction of the force it is exposed to. This situation is of great importance for damping in space applications. As a result of vibration analyzes and tests, the effect of stiffness and mass increase in a certain direction on natural frequencies has been revealed, and with 3-point bending tests, the facing elastic modulus and core shear modulus values of the structure have been determined separately and its effect on the sandwich structure has been shown. Accordingly, this study examined and evaluated many aspects of the possible role of the Kelvin Cell in space applications. / För att tillgodose de mekaniska kraven på rymdkonstruktioner är det av största vikt att uppnå lätta konstruktioner. Det primära fokuset för denna studie är utnyttjandet av Kelvin-Cellkärna vid design av sandwichstrukturer för rymdtillämpningar. Forskningen omfattar en mängd olika produktionstekniker, analyser och tester relaterade till design av sandwichstrukturer med Kelvin-Celler som kärnmaterial. En mängd olika konfigurationer utvärderas generellt, medan vissa specifika konfigurationer undersöks mer utförligt på detaljnivå. I detta sammanhang analyseras strukturens böjstyvhet, kompressionsstyvhet och vibrationsegenskaper. Den analytiska proceduren börjar med en förenklad strukturanalys, följt av modellering av den faktiska geometrin. Enligt gällande standarder beräknas styvhetsvärdena baserat på strukturanalysens resultat. Det är dock viktigt att notera att de tester som utförs på de modellerade strukturerna utförs i en laboratoriemiljö med hjälp av additivt tillverkade prover. Detta möjliggör en jämförelse mellan de erhållna testresultaten och resultaten av analysen, vilket belyser effekten av tillverkningsmetoden. Denna studie visar att sandwichstrukturen honeycomb är bäst när det gäller total styvhet. Dessutom har en specialdesignad förstärkt Kelvin-Cellstruktur exceptionella böjstyvhetsegenskaper. I ljuset av dessa fynd är det tydligt att kombinationen av Kelvin-Cellkärna och specifika förstärkningsstrategier har potential att förbättra den mekaniska prestandan hos sandwichstrukturer. Dessutom visade deformationsresultaten från analyserna att strukturen kan deformeras till hög grad i andra riktningar än den kraft som den utsätts för. Denna iaktagelse är av stor betydelse för dämpning i rymdapplikationer. Som ett resultat av vibrationsanalyser och tester har effekten av styvhet och massökning i en viss riktning på naturliga frekvenser upptäckts, och med 3-punkts böjtester har konstruktionens elasticitetsmodul och skjuvmodulsvärden bestämts separat och dess effekt på sandwichstrukturen har visats. Följaktligen undersökte och utvärderade denna studie många aspekter av Kelvin-Cellens möjliga roll i rymdtillämpningar.

This thesis helps develop a material model for a novel Fiber Core SandwichSheet construction. A test method was used to determine the mechanicalproperties of the sandwich material. Standard three point bendingtests coupled with digital image correlation was used. Results wereextracted from the digital image data. These results supplemented thedevelopment and tuning of an FE model of the sandwich material. Conclusionswere drawn about the feasibility of the method in studying sucha material. / Denna avhandling genomfördes mot utvecklingen av en homogeniseradmaterialmodell för en ny sandwich-konstruktion med fiberkärna. En testmetodanvändes för att bestämma de mekaniska egenskaperna hos sandwichmaterialet.Testmetoden involverade trepunkts i kombination meddigital bildkorrelation. Resultaten extraherades från den digitala bilddatanvid genomförande av trepunkts. Dessa resultat användes utvecklingenav en FE-modell av sandwichmaterialet. Slutsatser drogs om tillämplighetenav metoden för att studera ett sådant material.

L’objectif de ce travail est d’établir des relations entre chimie d’interface et propriétés mécaniques dans les assemblages bimétalliques. Il met en évidence que les mécanismes qui contrôlent le développement d’une interface entre alliage Al-Si et renfort ferreux ou titane ont une influence majeure sur les propriétés mécaniques de cette interface. La caractérisation mécanique des interfaces est réalisée par un test de flexion 4 points sur des lames bimétallique élaborées par aluminiage au trempé sur lesquelles un raidisseur est rapporté par collage ou surmoulage. L’évolution de la chimie de la zone de réaction interfaciale est provoquée par un traitement thermique à 535°C à différents temps. La caractérisation des zones de réaction ainsi que des chemins de fissuration est réalisée par diffraction des rayons X et microsonde électronique. Pour les interfaces Fe/A-S7G03 brutes d’élaboration, avant traitement thermique, l’analyse des essais mécaniques conduit à l’obtention d’une valeur du taux de restitution d’énergie de 23 J/m2 qui correspond à la propagation d’une fissure dans la phase η−Al5Fe2(Si). En ce qui concerne les interfaces Ti/A-S7G03, leur force n’a pas permis la propagation d’une fissure dans les conditions de l’essai. A la suite d’un traitement thermique à 535°C, les interfaces Fe/A-S7G03 sont fragilisées par le mécanisme de croissance de la couche de réaction interfaciale qui conduit à l’apparition de porosités Kirkendall en son sein. A l’inverse, dans le cas des interfaces Ti/A-S7G03, aucun affaiblissement de l’interface n’est associé au traitement thermique en raison d’un mécanisme de croissance différent. / The objective of this work is to establish the relationships between interface chemistry and mechanical properties in bimetallic assemblies. It proves that the mechanisms which control the development of an interface between Al-Si alloy and titanium or ferrous reinforcement have a major influence on the mechanical properties of this interface. The mechanical characterization of these interfaces is performed by a 4-point bending test on the bimetallic plates elaborated by hot dip aluminizing on which a stiffener is joined by bonding or overmolding. The chemistry evolution of the interfacial reaction zone is induced by a heat treatment at 535 °C at different reaction times. The characterization of reaction zones and the crack paths is performed by X-ray diffraction and electron probe microanalysis. Before heat treatment, the analysis of mechanical tests performed on Fe/A-S7G03 interfaces leads to a value for the energy release rate of 23 J/m2 which corresponds to a crack propagation in the η- Al5Fe2 (Si) phase. As regards the Ti/A-S7G03 interfaces, their strength did not allow a crack propagation under the test conditions. After a heat treatment at 535°C, the Fe/A-S7G03 interfaces are weakened by the growth mechanism of interfacial reaction layer which leads to the appearance of Kirkendall voids within it. Conversely, in the case of Ti/A-S7G03 interfaces, the heat treatment is not associated with any weakening of the interfacial zone because of a different growth mechanism.

A reciclagem de pavimentos com adição de cimento Portland é uma técnica que permite reutilizar estruturas degradadas de pavimentos flexíveis na conformação de uma nova camada estabilizada. Seu dimensionamento, no Brasil, tem sido abordado de forma empírica. Entretanto, os métodos racionais desenvolvidos para pavimentos semirrígidos estão baseados principalmente na previsão da vida de fadiga das camadas cimentadas, associada ao nível de deformação atuante na sua fibra inferior. Com o intuito de contribuir no desenvolvimento de um método de dimensionamento de pavimentos com camadas recicladas com adição de cimento, a pesquisa relatada nesta dissertação teve como objetivo principal o estudo laboratorial do comportamento a fadiga de misturas constituídas por fresado asfáltico (20%, 50% e 70%), brita graduada e cimento Portland (teores de 2% e 4%). O programa experimental foi baseado no protocolo para caraterização de materiais cimentados da Austroads (2008; 2012), para ensaios estáticos e de fadiga, além de recomendações para caracterização flexural da JCI (1984), procurando-se avaliar a sua aplicabilidade. Os ensaios de fadiga foram realizados em vigotas com dimensões 10 cm x 10 cm x 40 cm, curadas por pelo menos 28 dias. O modo dos ensaios foi o de tensão controlada como função da resistência à tração na flexão, previamente determinada. O sistema de carregamento é conhecido como fadiga a 4 pontos. Foram obtidos modelos de fadiga em função da tensão de tração atuante, da deformação inicial e da energia dissipada inicial. Os resultados dos ensaios estáticos indicam a predominante influência do teor cimento na resistência a tração na flexão das misturas (valores entre 0,21 MPa e 1,53 MPa), enquanto a porcentagem de fresado tem efeito significativo na deformação de ruptura, tornando as misturas mais dúcteis, e no Módulo de Elasticidade Flexural (que variou entre 1483 MPa e 12800 MPa). No caso dos ensaios de fadiga, os Módulos de Resiliência Flexural iniciais (valores entre 2913 MPa e 7725 MPa) mostraram-se mais dependentes do teor de cimento e independentes do nível de tensão. Nos modelos de fadiga obtidos, os valores dos exponentes de dano por deformação variaram entre 7 e 15, sendo próximos aos relatados pela Austroads para materiais cimentados. Esses modelos foram empregados na modelagem de estruturas de pavimento com camadas de base reciclada, de espessura de 18 cm a 40 cm, visando quantificar o efeito do teor de cimento e da porcentagem de fresado na vida de fadiga, bem como das espessuras da camada reciclada e da nova camada asfáltica sobrejacente. Observou-se que espessuras de camada reciclada inferiores a 30 cm terão curta vida de fadiga. Por outro lado, também ficou evidenciado que a vida de fadiga dessa camada depende significativamente da espessura da nova camada asfáltica sobrejacente, recomendando-se espessuras de no mínimo 10 cm. Finalmente, destaca-se que o volume de dados gerado durante os ensaios de fadiga, e seu processamento por meio de algoritmos desenvolvidos na pesquisa, permitiram abordar conceitos de energia dissipada, como aproximação à definição de critérios de micro e macrofissuração, o que mostrou a utilidade deste tipo de abordagem para futuras pesquisas. / Full-depth reclamation with Portland cement (FDR-C), is a technique allowing the reuse of flexible pavements damaged structures, in order to build a new stabilized layer. In Brazil, pavement design with FDR-C has been determined by empirical approaches. However, mechanistic approach developed for semi-rigid pavements mainly use fatigue relationships based on deformations occurring at the bottom of the cemented layer. In order to develop a pavement design method with FDR-C materials, this research work aimed to study, in laboratory, the fatigue behavior of FDR-C mixtures, for three cement grades (2 %, 4 % e 6 %) and three RAP (Reclaimed Asphalt Pavement) percentages (20 %, 50 % e 70 %).The experimental program was based on the protocol for the characterization of cemented materials of the Austroads (2008; 2012), for static and dynamic tests, and on the recommendations for flexural characterization of concrete reinforced with steel fibers, of the JCI (1984), evaluating the availability of these procedures. Fatigue tests were executed using beams (10 cm x 10 cm x 40 cm), static compacted and with a minimum curing time of 28 days. Stress controlled mode was used, based on flexural strength, previously determined. Loading system was a four-point bending test. Were developed fatigue strain, stress and dissipated energy relationships. Static tests results show that cement is the principal influence on the flexural strength of the mixtures (0.21 MPa up to 1.53 MPa), while the RAP have a major effect in the increasing of the tensile strains making it more ductile (flexural elastic modulus were 1483 MPa up to 12800 MPa). In the case of fatigue tests, flexural modulus were more dependent on the degree of cementation (2913 MPa up to 7725 MPa), and not on the applied stress level. About the fatigue models of FDR-C mixtures, strain damage exponents (7 up to 15) were similar to those reported by Austroads. Laboratory models based on strain were used in modeling of pavement structures, with a FDR-C base layer. Results showed benefits of thickness in FDR-C mixtures and asphalt layers (18 cm up to 40 cm), in order to evaluate the effect of the cement and RAP content on fatigue life, and FDR-C new asphalt thickness as well. This model highlights that FDR-C with a thickness inferior than 30 cm will have a shorter fatigue life. On the other side, was showed that the fatigue life of this layer mainly depends on new hot mix asphalt thickness layer (thickness recommended up to 10 cm). Finally, the volume of data generated during the fatigue tests and his processing through algorithms developed in research allowed using dissipated energy criteria as an approximation of the definition of micro and macro-cracking limits which indicate the utility of this methodology for future research. / El reciclaje de pavimentos con adición de cemento Portland es una técnica que permite la reutilización de estructuras degradadas de pavimentos flexibles para la conformación de una nueva capa estabilizada. Su diseño, en Brasil, ha sido abordado de forma empírica. Sin embargo, métodos racionales desarrollados para pavimentos semirrígidos están basados en la vida de fatiga de las capas cementadas, asociada al estado de deformaciones actuante en su base. Con el objetivo de contribuir al desarrollo de un método de dimensionamiento de pavimentos con capas recicladas con adición de cemento, la investigación relatada en esta disertación tuvo como objetivo principal el estudio laboratorial del comportamiento de fatiga de mezclas constituidas por fresado asfáltico (20%, 50% y 70%), base granular y cemento Portland (2%, 4 % y 6 %). El programa experimental fue basado en protocolos de caracterización de materiales cementados de la Austroads (2008, 2012), para ensayos estáticos y de fatiga, además de recomendaciones para caracterización flexural de concreto reforzado con fibras de acero de la JCI (1984), procurando evaluar su aplicabilidad. Los ensayos de fatiga fueron realizados en vigotas con dimensiones de 10 cm x 10 x cm x 40 cm, moldadas estáticamente y curadas por lo menos 28 días. El modo de carga fue de esfuerzo controlado en función de la resistencia de tracción en la flexión, previamente determinada. El sistema de carga es conocido como fatiga 4 puntos. Los resultados de los ensayos estáticos mostraron una influencia predominante del contenido de cemento respecto a la resistencia flexural de las mezclas (valores entre 0,21 MPa y 1,53 MPa), mientras que el material fresado tiene un efecto significativo en la deformación de tracción al tonar más dúctiles las mezclas, afectando módulo de elasticidad flexural (valores entre 1483 MPa y 12800 MPa). En el caso de los ensayos de fatiga, los Módulos de Resiliencia Flexural iniciales (valores entre2913 MPa y 7725 MPa) mostraron ser más dependientes del grado de cementación e independientes del nivel de esfuerzo aplicado. Los valores de los exponentes de daño por deformación en los modelos de fatiga, que variaron entre 7 y 15, fueron próximos a los relatados por la Austroads. Estos modelos fueron usados en la modelación de estructuras de pavimento con capas de base reciclada, de espesor entre 18 cm y 40 cm, buscando cuantificar el efecto del contenido de cemento y de fresado en la vida de fatiga. Se observó que espesores de la capa reciclada inferiores a 30 cm tendrán corta vida de fatiga. Por otro lado, fue evidenciado que la vida de fatiga de esta capa depende significativamente del espesor del nuevo revestimiento asfáltico, recomendándose espesores superiores a 10 cm. Finamente, se destaca que el volumen de datos generados durante los ensayos de fatiga y su procesamiento por medio de algoritmos desarrollados en la investigación permitieron abordar conceptos de energía disipada, como aproximación a la definición de criterios de micro y macro fractura que mostraron la utilidad de este tipo de metodologías para estudios futuros.

Auf der Basis der Bemessungsgrundlagen (DAfStb-Richtlinie „Stahlfaserbeton“, DBV-Merkblatt „Stahlfaserbeton“ und DIN 1045-1) wurden ausgewählte Bauteilversuche mit entsprechenden rechnerischen Überprüfungen der experimentell ermittelten Ergebnisse durchgeführt. Die Untersuchungen konzentrierten sich auf die Ermittlung der Effizienz von ausgewählten Stahlfasern in Betonen mit und ohne Betonstahlbewehrung in durch Biegung ohne Längskraft belasteten Versuchskörpern unter Betrachtung der Grenzzustände der Gebrauchstauglichkeit (GZG) und Tragfähigkeit (GZT). Das Versuchsprogramms umfasste neben der Prüfung ausgewählter Frischbetoneigenschaften die Bestimmung von Festbetonparametern an standardisierten Probekörpern. Des Weiteren wurden 4-Punkt-Biegezugversuche an Balken mit den Abmessungen l/h/b = 70/15/15 cm aus reinem Stahlfaserbeton sowie stahlfaserbewehrtem Stahlbeton, in Anlehnung an das DBV-Merkblatt „Stahlfaserbeton“ und die Richtlinie „Stahlfaserbeton“ vom DAfStb, durchgeführt. Aufbauend auf den Erkenntnissen aus den Materialversuchen im Labormaßstab wurden anschließend Untersuchungen an großformatigen Biegebalken (l/h/b = 420/40/20 cm) durchgeführt. Im Weiteren erfolgten Prüfungen und Auswertungen von Einzelfaserausziehversuchen mit ausgewählten Stahldrahtfasern in Verbindung mit Betonen unterschiedlicher Druckfestigkeit unter Berücksichtigung des Einflusses der Einbindelänge sowie des Einbindewinkels. Im Rahmen des Versuchsprogramms wurden die auf der Grundlage der 4-Punkt-Biegezugversuche ermittelten Ergebnisse analysiert und mit dem derzeit gültigen Bemessungsmodell nach DAfStb-Richtlinie „Stahlfaserbeton“ rechnerisch überprüft. Auf der Basis dieser Ergebnisse erfolgte die Entwicklung eines Ansatzes zur Optimierung der bestehenden Bemessungsansätze. Gegenstand dieser Forschungsarbeit war ebenfalls die Entwicklung eines Fasermodells, mit dem man auf der Grundlage des eingesetzten Fasergehaltes und der Faserart Rückschlüsse auf die Faseranzahl in einer rechteckigen Bruchfläche ziehen kann. Hierbei wurde ein Modell für Rechteckquerschnitte entwickelt, welches es ermöglicht, die durchschnittliche Faseranzahl in einer Bruchfläche, auf der Basis vereinfachter Annahmen, abzuschätzen. Die Verifizierung des Modells erfolgte durch den Vergleich der errechneten Faseranzahl mit zahlreichen experimentellen Versuchsergebnissen. Im letzten Abschnitt dieser Arbeit wurde die Herleitung bzw. Generierung von Bemessungshilfsmitteln zur Biegebemessung von Stahlfaserbeton mit und ohne Betonstahlbewehrung behandelt. Die Ausführungen beziehen sich dabei auf dimensionslose Bemessungstafeln und Interaktionsdiagrammen für Rechteckquerschnitte.