The diploma thesis deals with problems of identification and specification of insurmountable impairments with a focus on moisture. The aim of my work is generally explain what the fault and failure, what is their cause, and the overall approach in this area. Next determine the difference between removable and irremovable defect. Part of this work is a chapter devoted to surveys of buildings, which are an integral part in detecting defects, failures and their root structures. Another section is devoted to the main subject of work - moisture, approach this issue and the problems caused by moisture in the structure. At the end of this chapter is about ways of reducing the moisture in structures. The last section is on the case (the object affected moisture) approach procedure for identifying and assessing these impairments in practice.

La modélisation numérique de la multi-fissuration et son influence sur les ouvrages du Génie Civil reste un sujet ouvert et nécessite le développement de nouveaux outils numériques de plus en plus performants. L’approche retenue dans cette thèse est basée sur l’utilisation des concepts des équations intégrales de Galerkin accélérées par la méthode multipôle rapide. Les méthodes intégrales sont bien connues pour leur souplesse à définir des géométries complexes en 3D. Elles restent également très performantes en mécanique de la rupture, lors de la détermination des champs singuliers au voisinage des fissures. La Méthode Multipôle Rapide, quant à elle, permet via une judicieuse reformulation des fonctions fondamentales propres aux formulations intégrales, de réduire considérablement le coût des calculs. La mise en œuvre de la FM-SGBEM a permis de pallier les difficultés rencontrées lors de la phase de résolution et ce lorsqu’on traite de domaines de grandes tailles par équations intégrales de Galerkin pures. Les présents travaux, viennent en partie optimiser et renforcer cette phase dans les environnements numériques existants. D’autre part, des adaptations et des développements théoriques des formulations FM-SGBEM pour prendre en compte le caractère hétérogène des domaines en Génie Civil qui en découlent, ont fait l’objet d’une large partie des travaux développés dans cette thèse. La modélisation du phénomène de propagation de fissures par fatigue a également été étudiée avec succès. Enfin, une application sur une structure de chaussée souple a permis de valider les modèles ainsi développés en propagation de fissures par fatigue dans des structures hétérogènes. De réelles perspectives d’optimisations et de développements de cet outil numérique restent envisagées. / The modeling of cracks and its influence on the understanding of the behaviors of the civil engineering structures is an open topic since many decades. To take into consideration complex configurations, it is necessary to construct more robust and more efficient algorithms. In this work, the approach Galerkin of the boundary integral equations (Symmetric Galerkin Boundary Element Method) coupled with the Fast Multipole Method (FMM) has been adopted. The boundary analysis are well-known for the flexibility to treat sophisticated geometries (unbounded/semi-unbounded) whilst reducing the problem dimension or for the good accuracy when dealing with the singularities. By coupling with the FMM, all the bottle-necks of the traditional BEM due to the fully-populated matrices or the slow evaluations of the integrals have been reduced, thus making the FM-SGBEM an attractive alternative for problems in fracture mechanics. In this work, the existing single-region formulations have been extended to multi-region configurations along with several types of solicitations. Many efforts have also been spent to improve the efficiency of the numerical algorithms. Fatigue crack propagations have been implemented and some practical simulations have been considered. The obtained results have validated the numerical program and have also opened many perspectives of further developments for the code.

Les matériaux à changement de phase (MCP) constituent une alternative prometteuse pour l'amélioration de l'inertie thermique des matériaux de construction. Grâce à leur chaleur latente, ces matériaux permettent de stocker des quantités importantes d'énergie thermique, ce qui permet de réduire la consommation d'énergie liée au chauffage et à la climatisation. Cependant, leur incorporation dans les matériaux cimentaires entraine une baisse de la résistance mécanique du nouveau matériau composite ainsi obtenu. Durant ces dernières décennies, les composites MCP/bétons ont suscité un grand intérêt conduisant à un grand nombre de travaux expérimentaux. Cependant, les modèles théoriques et numériques pour prédire les comportements de ces matériaux complexes sont aujourd'hui très peu développés en raison de la complexité du comportement thermique avec changement de phase, de la séparation d'échelle et de la difficulté que représente la prédiction de l'endommagement par fissuration à l'échelle des hétérogénéités microscopiques. L'objectif de cette thèse est précisément de développer des outils de modélisation numériques pour prédire le comportement thermomécanique effectif du matériau en vue de calculs de structures. Pour cela, des modèles numériques sont développés pour simuler le transfert de chaleur, le comportement mécanique, la fissuration ainsi que la fuite du MCP liquide à travers les fissures, à l'échelle d'un Volume Elémentaire Représentatif du matériau. Après avoir étudié les effets des changements de phase dans le MCP sur le comportement mécanique effectif, une approche multi-échelle (méthode EF²$) est proposée afin de réaliser des calculs de structures en tenant compte des phénomènes à l'échelle des micro capsules. Des caractérisations expérimentales thermo-physiques sont menées afin de prouver l'utilité des MCP dans les matériaux de construction et de faire des comparaisons avec les outils d'homogénéisation développés. Enfin, nous proposons une étude dans le but de comprendre et d'évaluer les effets du MCP dans la dégradation des propriétés mécaniques de ces nouveaux matériaux / A promising way to enhance thermal inertia of buildings is the use of phase change materials (PCMs). Thanks to their high latent heat, PCMs can be used to store a significant amount of thermal energy in order to reduce energy consumption related to air conditioning. However, their use leads to a decrease in the mechanical strength of the obtained composites. During the last decades, the incorporation of PCMs in concrete has been of great interest leading to many experimental works. However, theoretical and numerical models to predict the behavior of such complex materials are not developed so far, due to the complexity of the phase change behavior, the scale separation and issues associated to the damage which is mainly induced by microcracking at the scale of microstructural heterogeneities. The objective of this thesis is precisely to develop numerical modeling tools to predict the effective thermomechanical behavior of the material with aim of structural calculations. For this purpose, numerical tools based on microstructures at the scale of microencapsulated PCM are developed to simulate heat transfer, mechanical response, cracks propagation as well as leakage of liquid PCM through cracks. After studying the effects of phase changes in the PCM on the effective mechanical response of the composites, a multi-scale approach (FE² method) is proposed to carry out structural calculations taking into account phenomena at micro scale. Thermo-physical experimental characterizations are carried out to show the usefulness of PCMs in building materials and to make comparisons with the developed homogenization tools. Finally, we propose a study to understand and evaluate the effects of PCMs in the degradation of the mechanical properties of these new materials

Problematik med moderna putsfasader rörande hållbarhet har på senare år uppenbarat sig. Trots modern byggnadsteknik är skaderisken idag större än den var med äldre byggnadsteknik. Sprickbildningar, missfärgningar, mikrobiella angrepp, frostsprängningar, mögelangrepp m.m. är alla exempel på skador som kan uppstå. Rapporten syftar till att identifiera risker och problem med dagens putsfasadkonstruktion, samt undersöka hur dessa problem kan avhjälpas byggnadstekniskt och arkitektoniskt.   Projektet avgränsas till fasader på nybyggda flerbostadshus i svenskt klimat. Fokus ligger på att undersöka putsade fasader. Vägguppbyggnaden avgränsas till utfackningsväggar av regelkonstruktion då det är en vanlig ytterväggskonstruktion.   Underlaget till rapporten baseras på litteraturstudier, tekniska rapporter och rådgivning från handledare och yrkeskunniga experter. Fördjupningsstudier görs inom putsfasader för att reda ut det bästa lösningsförslaget för hållbara putsfasader.   Resultatet av rapporten pekar på att det inte finns en enkel lösning till problematiken. Förebyggs ett problem uppstår ett annat. Det finns dock vissa parametrar som bör tas i anspråk. Ytterväggen bör tvåstegstätas för att förebygga mögelrisk i konstruktionen. Grovkornigt putsbruk bör användas för att förebygga sprickbildning och eventuellt minska adsorption. Vattenavvisande detaljer i det arkitektoniska formspråket bör finnas för att minska vattenbelastningen. Ytfärgen bör vara oorganisk och alkalisk för att ytterligare förebygga uppkomsten av mikrobiella angrepp.   För vidare studier föreslås att putsprovväggskonstruktionen konstrueras och testas i praktiken. Faktorer som kornstorlek, vattenavvisande detaljer, adsorption bör vara fokus. Konstruktionernas RF i ytskiktet studeras därefter för att ge en idé över vilken konstruktion som förebygger skador effektivast. / In recent years, sustainability problems with regards to contemporary stucco facades have revealed themselves. Despite modern construction techniques, the risk of damage today is greater than it was with older techniques. Damage such as cracks, discoloration, microbial attacks, frost damage, mold, etc. are all examples of risk factors.   The report aims to identify the risks and problems of today's plaster facade construction, as well as explore how these problems can be remedied through constructional and architectural solutions.   The project is constrained to facades of newly constructed apartment buildings in the Swedish climate. The focus is to examine the plastered facades. Wall construction is constrained to pre-fabricated wall panels of regulatory structure as it is the most common exterior wall construction in Sweden.   The basis for the report is based on literature studies, technical reports and guidance from supervisors and skilled experts. In-depth studies have been performed on plaster facades to find the best recommendations for durable plaster facades.   The results of the report indicate that there is no simple solution to the problem. However, there are some guidelines that should be followed. The outer wall should be “two way sealed” to prevent the risk of mold in the construction. Coarse plaster should be used to prevent cracking and to reduce adsorption. Water repellent details should be implemented to reduce the water load on the walls. The surface paint should be inorganic and alkaline in order to further prevent the development of microbial attacks.   For further study, the report suggests that a stucco sample wall structure is tested in practice.   Factors such as particle size, water repellent details and adsorption properties should be the focus. The RH in the surface layer should thereafter be studied to give an idea of which structure that prevents damage most efficiently.

Byggnader med grundkonstruktioner under mark blir allt vanligare. Att bygga långt ner i marken innebär ofta att man måste handskas med det fluktuerande grundvattnet. Konstruktioners beständighet och livslängd beror många gånger på vattenbeständigheten. Det byggs en mängd olika betongkonstruktioner som är utsatta för ensidigt vattentryck. Kravet på vattentätheten varierar beroende på syfte och användning av byggnaden. Det kan för ett parkeringsdäck vara acceptabelt med vattenläckage medan det i kommersiella byggnader inte tillåts vatteninträngning överhuvudtaget. Denna uppsats utreder hur man fuktsäkrar husgrunder under grundvattenytan. Vattentätheten i grundkonstruktioner beror framförallt på tre faktorer. Det får inte existera breda genomgående sprickor i betongen. Gjutfogar och rörelsefogar bildar diskontinuiteter i grundkonstruktioner som måste tätas. Vidare måste anslutande element såsom fundament och pålar tätas. Hänsyn bör tas till faktorerna för att slippa läckage och att behöva efterbehandla grundkonstruktioner som innebär stora kostnader i förhållande till en tät byggnad från första början. Syftet med examensarbetet var att för svenska konstruktörer presentera hur man projekterar en fuktsäker grundkonstruktion under grundvattenytan. På uppdrag av Sweco har rapporten utrett de tekniker som finns, vad dessa har för egenskaper och begränsningar samt när dessa är lämpliga. Utredningen baseras på en omfattande litteraturstudie och en intervjustudie med involverade parter vid nybyggnation. Målet med rapporten var att presentera hur man framgångsrikt projekterar och bygger vattentäta betongkonstruktioner under grundvattenytan. Rapporten ska ge en överskådlig introduktion samt underlätta för de som eftersträvar ingående förståelse inom ämnet. Den riktar sig framförallt till projektörer men även övriga parter med en betydande roll skall kunna följa rapporten för en bättre förståelse och kännedom. Befintliga lösningar utvärderas genom en omfattande litteraturstudie och en kvalitativ intervjustudie med konstruktörer, entreprenörer och leverantörer av tätningstekniker. Samtliga aktörers kompetens och erfarenhet sammanfördes för att identifiera förbättringspotentialen i projektering- och produktionsfasen av vattentäta grundkonstruktioner. Kompetensen finns i branschen men återkopplingen och feedbacken är synnerligen begränsad. Åsikter och kunnigheter är utspridda mellan många källor vilket gör att en enhetlig bild saknas. Sammanfattningsvis visar studien dels att man som konsult tillsammans med entreprenör bör göra en ny risk- och konsekvensanalys inför varje projekt. Olika tätningsalternativ bör övervägas för att medvetandegöra varje parts del av riskhanteringen. Vidare bör man som konstruktör leverera isometriska perspektiv alternativt digitala 3D ritningar för att tydliggöra komplicerade och kvalitetskritiska detaljer. Slutligen bör hantverkare på byggarbetsplatsen vara utbildade och se mervärdet av en sprickminimerad betong och väl utförd tätning av fogar och anslutande element. Konsulter och entreprenörer bör tillsammans efter varje projekt utvärdera valda tätningstekniker för att tillsammans driva de framåt i utvecklingen. / Buildings with foundations below ground is becoming increasingly common. Building far below the ground level means that you have to deal with the fluctuating groundwater. A variety of concrete structures are subjected to one-sided water pressure. Structures' durability and longevity many times depends on the water resistance. The requirement considering waterproofing varies depending on the purpose and use of the building. It can for example be acceptable with some water leakage in a parking deck, while it can be unacceptable for commercial buildings. This paper investigates how to waterproof building foundations below the groundwater level. The water tightness of foundations is mainly depending on three factors. Wide thoroughgoing cracks cannot exist in the concrete. Construction joints and expansion joints forming discontinuities in the foundation must be sealed. Furthermore, connecting elements such as mat-slabs and pile heads must be sealed. These three factors should all be considered to avoid leaks and to avoid the need of after-treatment which means high costs in relation to a waterproof foundation in the first place. The aim of the thesis was to present for Swedish designers how you waterproof foundations below the groundwater level. On behalf of Sweco the report investigated the existing techniques, which properties and limitations they have and when they are suitable. The study is based on an extensive literature review and interviews with involved parties during construction. The goal of the report was to present how to successfully project and build water-proof concrete structures below the groundwater level. The report should give a clear introduction to the subject and facilitate for those who aspire a thorough understanding of the subject. It is primarily aimed to designers, other parties with a significant role can also follow the report for a better understanding and awareness. Existing solutions are evaluated through an extensive literature review and qualitative interviews with designers, contractors and suppliers of sealing techniques. All participant’s skills and experiences were brought together to identify potential for improvement in project planning and production phase of waterproof foundations. The expertise is available in the industry, but the feedback is exceedingly limited. The opinions and skills are sprawled among many sources, which means that a uniform image is missing. In summary, the study shows that consultants and contractors together should make a new risk and impact assessment ahead of each project. Various waterproofing options should be considered, to raise the awareness of each parts share of the risk management. Furthermore the designer should deliver isometric perspectives or digital 3D drawings to clarify complex and quality-critical parts. Finally, craftsman on the construction should be educated and aware of the additional value of a crack minimized concrete and well executed sealing of joints and connecting elements. Consultants and contractors should evaluate the waterproofing techniques after each project to jointly push the technologies forward.

The report aims to investigate the influence of chemical reactions on comb crack formation and propagation in coated cemented carbide milling inserts with different compositions. A series of novel experimental techniques have been developed and applied to understand oxidation and corrosion effects on comb cracks. Furthermore microstructure changes in the region of the comb cracks on worn milling inserts were studied by high resolution microscopy. It has been observed that the main effect of the oxidation and corrosion on comb cracks is connected to an attack of the binder phase, affecting its composition, distribution and morphology. Different comb crack types for dry and wet milling have been observed. In the presence of cooling media (wet machining) inserts present lateral cracks (fatigue induced) connected to the principal comb crack, which form at regions where the binder has been strongly corroded. Despite the addition of Cr and (Ta,Nb)C enhance both the oxidation and corrosion attack resistance have a minor effect on the formation and propagation of comb cracks. Schematic models based on the experimental results and scientific discussions are presented to understand the influence of oxidation and corrosion in the formation and propagation of comb cracks.

I Sverige produceras varje år grovt uppskattat ca. 1,5–2,0 miljoner m2 industrigolv av betong [1]. Resultaten är varierande och det vanligaste felet hos dessa golv är sprickor [2]. I sprickorna letar sig vatten och i vissa fall klorider ned och förorsakar armeringskorrosion. Armeringen expanderar pga. korrosionen och spränger sönder betongen. Golvet blir inte längre estetiskt tilltalande samtidigt som livslängden förkortas avsevärt och golvytan blir ojämn vilket försvårar eventuell trucktrafik. Sprickor uppkommer främst pga. tvångskrafter som uppstår när betongen krymper. Storleken på sprickorna avgörs av betongens benägenhet att krympa, armerings-innehåll och graden av tvång. DynaMate som bygger och underhåller Scanias serviceverkstäder och industrilokaler upplever stora problem med sprickbildning hos industrigolven. Sprickorna medför stora kostnader i form av driftstopp, rivning, reparation och eventuell nyproduktion [3]. Föreliggande rapport baseras framförallt på litteraturstudier utifrån en rad rapporter, artiklar och handböcker men även normer. Intervjuer har genomförts med sakkunniga personer för att ta del av deras erfarenheter och åsikter. För att även få bättre insikt i utförandeskedet har författarna närvarat vid två olika gjutningar av industrigolv. För att minska sprickrisken i betonggolv, orsakad av betongens fria krympning, krävs en betongsammansättning som minimerar den fria krympningen, ett armeringsinnehåll som överstiger minimiarmering, fogar som tillåter rörelser i plattan och en långsam uttorkning. Det har upplevts att problem med sprickor i betonggolv beror på okunskap, olika viljor och slarv bland involverade aktörer. Därför är det även viktigt med tydliga mål och bra kommunikation mellan alla aktörer. På uppdrag av DynaMate har ett förslag till åtgärdsprogram för minskad sprick-bildning tagits fram. Detta kan ligga till grund för framtida golvprojekt och på sikt minska de stora kostnader som underhåll och reparationer medför. / Roughly estimated 1,5–2,0 million m2 of industrial concrete floors are produced in Sweden every year [1]. The results vary and the most common matter/failure among these floors is cracks [2]. Water finds its way down in the cracks and in some cases chlorides, which causes corrosion of the reinforcement. The reinforcement expands due to the corrosion and makes the concrete burst. The floor is no longer esthetically appealing. At the same time the lifetime is shortened substantially and the floor surface becomes uneven which complicates any truck traffic. Cracks arise due to restraint forces that develop because of concrete shrinkage. The width of the cracks is determined by the concretes tendency to shrink, reinforcement content and the extent of restraint forces. DynaMate builds and maintains Scania service centers and industrial facilities. They are experiencing major problems with cracking in industrial floors. The cracks bring large costs in terms of downtime, demolition, repair and any new production. The present report is based mainly on literature research from reports, articles and handbooks but also norms. Interviews were performed with qualified persons to share their experiences and opinions. To receive even more knowledge the authors attended two different castings of industrial floors. A reduction of cracking in concrete floors caused by the free shrinkage requires a concrete composition which minimizes the free shrinkage, reinforcement content in excess of minimum reinforcement, a slow drying and joints that allow movements. It was believed that the problem with cracks in concrete floors is due to ignorance, different wills and carelessness among the involved actors. Consequently it is also important to have clear objectives and good communication between all actors. On behalf of DynaMate a proposal for actions to reduce cracking was prepared. That proposal can form the basis for future flooring projects and ultimately reduce the significant costs due to maintenance and repairs.

El concreto es uno de los materiales más utilizados en el mundo de la construcción, de las cuales cada material en la mezcla depende de la resistencia que se requiera de acuerdo al análisis estructural. Dentro del proceso de producción de concreto debemos garantizar que el cemento reaccione químicamente y desarrolle la resistencia para la cual fue diseñada, para esto es importante mantenerlo hidratado en ese tiempo mediante el proceso de curado. Una técnica aún no tan conocida es el auto-curado del concreto, por lo cual es una necesidad saber cuál es su influencia en el desarrollo de la resistencia y en la disminución del porcentaje de agrietamiento del concreto en estado plástico. El objetivo de esta tesis es determinar la influencia que tiene el reemplazar un cierto porcentaje de ladrillo triturado como reemplazo del agregado grueso; evaluando la resistencia a la compresión, resistencia a la flexión, y el agrietamiento por contracción plástica del concreto. Se desarrolló con 3 diferentes porcentajes de reemplazo de ladrillo triturado que son: 15%, 21%, 27% del peso del agregado grueso para la resistencia a la compresión (f’c) de 280 kg/cm2. Se concluyó que reemplazo del agregado grueso por ladrillo triturado es efectivo cuando es usado hasta un máximo de 21%. Los resultados obtenidos son óptimos y viables en el tiempo, mostrándonos un aumento en la resistencia a la compresión, resistencia a la flexión y la disminución del porcentaje de fisuras en estado plástico. / Concrete is one of the most used materials in the world of construction, of which each material in the mixture depends on the strength required according to the structural analysis. Within the concrete production process, we must ensure that the cement reacts chemically and develops the resistance for which it was designed, for this it is important to keep it hydrated at that time through the curing process. A technique not yet so well known is the self-curing of concrete, so it is a necessity to know what its influence is in the development of resistance and in the reduction of the percentage of cracking of concrete in the plastic state. The objective of this thesis is to determine the influence of replacing a certain percentage of crushed brick as a replacement for coarse aggregate; evaluating the compressive strength, flexural strength, and cracking by plastic shrinkage of concrete. It was developed with 3 different percentages of crushed brick replacement that are: 15%, 21%, 27% of the weight of the coarse aggregate for the compressive strength (f’c) of 280 kg / cm2. It was concluded that replacement of coarse aggregate with crushed brick is effective when used up to a maximum of 21%. The results obtained are optimal and viable over time, showing an increase in compressive strength, flexural strength and a decrease in the percentage of cracks in the plastic state. / Tesis

L’objectif principal de ce travail de thèse est de consolider et rendre opérationnelle l’extension du cadre multi-modèles et multi-échelles Arlequin à la modélisation et la simulation (par éléments finis) en élasto-dynamique, en faisant l’hypothèse de localisation des ondes hautes fréquences, tenant ainsi compte de phénomènes physiques dissipatifs divers.Parmi les applications visées par ces travaux, citons i) la propagation dans le sol d’ondes sismiques et leurs impacts sur des infrastructures critiques, ii) l’analyse multi-résolutions du comportement dynamique d’une structure impactée ou encore la propagation de fissures en dynamique dans des matériaux.Les contraintes que l’on s’impose dans ce travail sont doubles. La première est que l’on s’interdit de polluer la ou les zones critiques localisées. La seconde est que l’on souhaite aussi approcher le plus correctement possible le comportement des champs mécaniques dans les zones approchées plus grossièrement. Une étude de l’ensemble des paramètres Arlequin est menée. Des préconisations pratiques sont fournies, en étant étayées par des simulations 1D et une simulation 2D. Une attention toute particulière est portée à l’opérateur de couplage Arlequin en volume (dont on rappelle et souligne le caractère incontournable pour les problèmes de dynamique multi-échelle ; les couplages en surfaces étant inopérants, pour ces problèmes). Sur ce sujet, un des faits saillants de ces travaux de thèse est le développement d’un nouvel opérateur de couplage Arlequin réduit : tirant profit d’une représentation modale des champs de multiplicateurs de Lagrange, définis dans la zone de couplage, d’une notion de (1-epsilon) Compatibilité de modèles (initiée dans [Ben01b]) et du caractère multi-résolution des champs primaux du problème, dans la même zone de superposition Arlequin, cet opérateur permet de réduire considérablement les coûts des calculs des problèmes dynamiques multi-échelles abordés ici, par rapport à un couplage classique, tout en assurant des transmissions plus précises que celles données par deux autres méthodes de réduction, rappelées et mises en oeuvres dans cette thèse. Ces avantages sont étayés pour une barre élastique, en statique et en dynamique.Les approches développées sont utilisées et validées, par comparaison avec des résultats de la littérature, pour l’application phare de ce travail, consistant à simuler le comportement dynamique d’une structure fissurée, dans le cas d’une fissure fixe et celui d’une fissure propagative, en utilisant l’enrichissement par la fonction Level-Set à la X-Fem dans le modèle grossier et des éléments finis fins au voisinage du fond de fissure. / The main objective of this thesis work is to consolidate and make operational the extension of the multi-model and multi-scale Arlequin framework to modeling and simulation (using finite element) in elastodynamic, by making the hypothesis of localization of high frequency waves, thus taking into account various dissipative physical phenomena. Applications targeted by this work include i) ground propagation of seismic waves and their impact on critical infrastructures, ii) multi-resolution analysis of the dynamic behavior of an impacted structure or iii) the dynamic propagation of cracks.The constraints imposed on this work are twofold. The first is that one is prohibited from polluting the localized or critical areas. The second is that we also want to approach as accurately as possible the behavior of the mechanical fields in the coarsly approximated areas. A study of all dynamic Arlequin parameters is conducted. Practical recommendations are provided and supported by 1D and 2D simulations. Particular attention is paid to the volume Arlequin coupling operator (whose essential character for coupling in multi-scale dynamic problems is recalled and underlined; surface couplings being inoperative in this context). On this subject, one of the highlights of these thesis works is the development of a new reduced Arlequin coupling operator: taking advantage of a modal representation of the Lagrange multiplier fields defined in the coupling zone, a concept of (1- epsilon)-Compatibility of models (initiated in [Ben01b]) and the multi-resolution character of the overlayed primal fields, this operator makes it possible to reduce considerably the computational costs of the multiscale dynamic problem discussed here (when compared to a classical coupling) while ensuring transmissions more accurately than those given by two other reduction methods, recalled and implemented in this thesis. These benefits are supported by an elastic bar test, both in static and dynamic regimes.The developed approaches are used and validated, in comparison with results of the literature, for the flagship application of this work consisting of simulating the dynamic behavior of a cracked structure in the case of a fixed crack and that of a propagative crack using enrichment by the Level-Set function à la X-Fem in the coarse model and fine finite elements near the crack tip.

Fatigue-crack-growth-rate tests were conducted on compact tension specimens made of 7050-T7451 aluminum alloy and 9310 steel. Compact tension specimens were tested over a wide range of load ratios (0.1 less than, or equal to R less than, or equal to 0.9) to generate crack-growth-rate data from threshold to near fracture. Three methods were used to generate near threshold data. A crack-closure analysis was performed on both materials using the FASTRAN crack-closure model. The crack-growth-rate data for each material correlated very well and each collapsed onto a nearly unique curve in the low- and mid-rate regimes using the strip-yield model in the FASTRAN life-prediction code. For the 7050 alloy, a constraint factor of α = 1.8 was required, while for the 9310 steel α = 2.5 worked very well in correlating the test data over a very wide range in R values and rates from threshold to near fracture.