Idag är intresset för högpresterande betong (HPB) växande runt om världen då fördelarna är många, eftersom slankare, tätare, starkare och lättare konstruktioner kan tillverkas.   Detta examensarbete handlar om materialförsök och modellering för en typ av HPB som ska användas i husbyggnation. Arbetet inleddes med materialförsök i färskt tillstånd, där god gjutbarhet och konsistens eftersträvades. Utgångspunkten var från ett grundrecept med två olika ballastsorter (slaggballast med flygaska och krossballast från asfaltindustrin med silikastoft), vilka namngavs till pilotförsök 1 och pilotförsök 2. Vidare valdes pilotförsök 1 att provas i hårdnat tillstånd då det visades att det var mer ekonomiskt lönsam eftersom ballasten inte behövde siktas, lägre vct tillhandhölls och att flygaskan som användes i pilotförsök 1 är billigare än silikastoft som användes i pilotförsök 2. Resultaten efter 28 dygn för de materialförsök som utfördes i hårdnat tillstånd var: Tryckhållfasthet; 141,9 MPa Draghållfasthet; 7,0 MPa Böjdraghållfasthet; 10,0 MPa Elasticitetsmodul; 46,4 GPa Krympning efter 56 dygn; 0,5 ‰ Samtliga försök utfördes enligt svenska standarder (SS).   Dessutom vidareutvecklas och förbättrades ett redan arkitektoniskt gestaltat Attefallshus ur ett konstruktions- och hållbarhets perspektiv, där fokus låg på transport- och produktionsförutsättningar. Det resulterade i att horisontella avstyvningar tillades i väggelementen för att öka styvheten och minska risken för brott under transport och produktion. Huset är tänkt att produceras med prefabriceringsteknik. Avslutningsvis modellerades ett oarmerat väggelement i FE-programmet Abaqus under linjärt elastiskt tillstånd. Vid modelleringen användes de materialparametrar som erhölls från materialförsöken.  Det resulterade i att deformationer, spänningar samt knäcknings- och bucklingsanalys kunde redas ut. Väggelementen i huset klarar normenliga laster enligt modelleringen. / Nowadays the interest for high-performance concrete (HPC) is growing around the world as the benefits are many, for example slender, denser, stronger and lighter structures can be manufactured.   This thesis is about material and design experiments for a type of HPC to be used in building construction. The work began with materials experiments in the fresh state, where good workability and consistency were tried to be obtained. The starting point was from a basic recipe with two different aggregate types (slag aggregates with fly ash and crushed aggregates from the asphalt industry with silica fume), which were named as the pilot test 1 and the pilot test 2. Furthermore pilot test 1 was elected to be tested in hardened state as it turned out to be more economically profitable, had a lower vct, and that the flyash was cheaper than the silica fume used in the pilot test 2. The results after 28 days when the materials experiments were carried out in the hardened state were: Compressive strength; 141,9 MPa Tensile strength; 7,0 MPa Flexural strength; 10,0 MPa Modulus of elasticity; 46,4 GPa Shrinkage after 56 days; 0,5 ‰ All experiments were performed according to Swedish standards SS.   Moreover, an existing architecturally portrayed Attefallshus was further developed and improved from a design and a strength perspective that mainly focused on transport and production. It resulted in the horizontal stiffeners to be installed in the wall elements to increase rigidity and reduce the risk of breakage during shipment and production. The house is intended to be built with prefabrication technology. Finally the unreinforced wall elements were modeled in the FE program ABAQUS under linear elastic condition. During modeling the material parameters obtained from material tests were used in the model. Consequently, strain, stress and buckling analysis could be made. The wall sections in the house met the norm loads according to the model.

No description available.

The use of nanotechnology has become wide spread in all branches of science. Nanotechnology help us to understand microstructure and due to the world has started to produce new materials. One of many examples carbon nanotubes (CNTs). In diploma thesis I tried to find the way of successful introduction into concrete mixture. I was studying influence of CNTs and other nano particles and I was comparing them with referential samples (without CNTs). Also I tested the improvement of mechanical characteristics of concrete. The morphology of nano particles was studied using Scanning Electron Microscopy (SEM). The results show that introduction of nanoparticles to results in increasing strength and higher density. That is why High Performace Concrete so resistant and durable.

There was developed a novel technological and constructive approach for the low-cost production of curved freeform formworks, which allow the production of single and double-curved fibre reinforced concrete. The scheduled approach was based on a flexible, asymmetrical multi-layered formwork system, which consists of glass-fibre reinforced plastic (GFRP). By using of the unusual anisotropic structural behavior, these GFRP formwork elements permitted a specific adjustment of defined curvature. The system design of the developed GFRP formwork was examined exhaustively. There were designed, numerically computed and produced prototypical curved freeform surfaces with different curvature radii. The fibre reinforced concrete had a compressive strength of 101.4 MPa and a 3-point bending tensile strength of 17.41 MPa. Beyond that, it was ensured that the TRC had a high durability, which has been shown by the capillary suction of de-icing solution and freeze thaw test with a total amount of scaled material of 874 g/m² and a relative dynamic E-Modulus of 100% after 28 freeze-thaw cycles.

Treten im Beton mehraxiale Spannungszustände auf, führen diese gegenüber einer einaxialen Beanspruchung zu einer signifikanten Änderung des Materialverhaltens. Neben einer festigkeitssteigernden bzw. -abmindernden Wirkung ergeben sich ebenfalls große Unterschiede im Spannungs-Dehnungs-Verhalten. Zur effizienten Konzipierung von Betonstrukturen unter komplexen Beanspruchungszuständen ist daher die Kenntnis des veränderten Materialverhaltens notwendig. Zur experimentellen Bestimmung des Spannungs-Dehnungs-Verhaltens eines Ultrahochleistungsbetons mit einer einaxialen Druckfestigkeit von über 170 N/mm² wurden mehraxiale Belastungsversuche an würfelförmigen Probekörpern durchgeführt. Die Untersuchung umfasste insgesamt 35 zwei- und dreiaxiale Spannungsverhältnisse unter proportionaler Laststeigerung mit vorrangiger Betrachtung von Zug-Druck-Druck-Beanspruchungen. Für die Einleitung der Zugbeanspruchungen in die Prüfkörper wurde eine neue Methode entwickelt, bei der mittels einbetonierter Schrauben die Belastung auf den Beton übertragen wird. Die Bestimmung des Verformungsverhaltens erfolgte im Inneren der Probekörper mit sechs tetraederförmig angeordneten Faser-Bragg-Gittern. Die somit direkt gemessenen Dehnungen ermöglichen die nachträgliche Berechnung der Komponenten des Dehnungstensors des Bezugskoordinatensystems. Für den untersuchten Ultrahochleitsungsbeton fallen die auf die einaxiale Druckfestigkeit bezogenen mehraxialen Festigkeitswerte mit zunehmendem hydrostatischen Druckspannungsanteil der Beanspruchung geringer aus als bei Normalbetonen. Weiterhin weist das Verformungsverhalten eine größere Sprödigkeit gegenüber Normalbetonen auf, so dass auch unter dreiaxialen Druckspannungszuständen die Probekörper schlagartig versagen. Aus den gemessenen Spannungs-Dehnungs-Linien werden neben den maximalen Festigkeiten die Festigkeitswerte an der Elastizitätsgrenze, der Affinitätsgrenze sowie beim Volumenminimum der Probekörper bestimmt. Zur Approximation dieser charakteristischen Werte wurde eine Grenzflächenbeschreibung entwickelt und an den Versuchsergebnissen kalibriert. Des Weiteren erfolgte die Zusammenstellung einer Datenbank mit in der Literatur verfügbaren mehraxialen maximalen Festigkeitswerten von Betonen mit einaxialen Druckfestigkeiten von 10 N/mm² bis 180 N/mm² und die Kalibrierung des entwickelten Modells zur Grenzflächenbeschreibung in Abhängigkeit der einaxialen Druckfestigkeit. Die bei der Kalibrierung der Grenzfläche für einzelne Betonfestigkeitsklassen bestimmten Freiwerte hängen dabei stark von den vorliegenden Versuchsdaten und speziell vom Wertebereich der hydrostatischen Spannungsanteile der maximalen Beanspruchungen ab. Die Approximation des Spannungs-Dehnungs-Verhaltens der mehraxial beanspruchten Probekörper erfolgt mittels eines schädigungsbasierten Materialgesetzes. Hierbei wird für den anfänglich isotropen Beton zum einen eine lastinduzierte isotrope Schädigung und zum anderen eine lastinduzierte orthotrope Schädigung angenommen, die von den auftretenden Hauptdehnungen abhängig ist. Mit dem entwickelten Materialgesetz werden sehr gute Übereinstimmungen mit den gemessenen Spannungs-Dehnungs-Linien erreicht, so dass sich ebenfalls eine gute Vorhersage der maximalen Festigkeitswerte ergibt. / Concrete under multiaxial stress states shows significant changes of the material behaviour compared to uniaxial loading. Besides strength increasing and decreasing effects, also great differences in the stress-strain behaviour occur. In order to design concrete structures efficiently concerning complex stress states, the knowledge about the modified material behaviour is necessary. To determine experimentally the stress-strain behaviour of an ultra high performance concrete with a uniaxial compressive strength of about 170 N/mm², multiaxial loading tests on cubic-shaped specimens were carried out. Altogether, the investigation contained 35 biaxial and triaxial stress ratios under proportionally increasing load with primarily tension-compression-compression loadings. Applying the tensile load on the specimen, a new method was developed, which uses screws embedded in the concrete to transfer the loading. The deformations were measured by using six tetrahedron-shaped arranged Fibre Bragg Gratings inside the concrete specimen. Subsequently, with the directly measured strains the components of the strain tensor of the reference coordinate system could be determined. For the investigated ultra high performance concrete the increase of the multiaxial strength, referring to the uniaxial compressive strength, decreases compared to normal strength concrete with the increasing hydrostatic stress component of the load. Moreover, the deformation behaviour shows an increased brittleness compared to normal strength concrete, so that even under triaxial compressive stress states the specimens fail abruptly. Besides the ultimate strength, from the measured stress-strain curves the strength at the proportional limit, at the limit of affinity as well as at the minimum volume of the specimen is determined. To approximate these characteristic values, a description of a hypersurface is developed and calibrated with the test results. Furthermore, a database with multiaxial ultimate strength values of concretes with uniaxial compressive strengths between 10 N/mm² to 180 N/mm² available from literature was compiled and a calibration of the developed hypersurface model depending on the uniaxial compressive strength was carried out. Thereby, the obtained values of arbitrary parameters of individual concrete strength classes depend severely on the available test results, especially on the range of values of the hydrostatic stress component of the ultimate strength. The approximation of the stress-strain behaviour of the multiaxial loaded specimens is carried out by means of a damage-based material law. For this purpose, concerning the initially isotropic concrete, a load-induced isotropic and orthotropic damage depending on the principle strains is assumed. With the developed material law, very good accordance with the measured stress-strain curves could be achieved, so that also results in a good approximation of the ultimate concrete strength.

No description available.

Das Institut für Tragwerksentwurf (ITE) und das Institut für Baustof e, Massivbau und Brandschutz (iBMB) der TU Braunschweig bearbeiteten in der ersten Förderperiode des SPP 1542 „Leicht Bauen mit Beton“ gemeinsam das Teilprojekt „Entwicklung neuartiger Verbindungen für geometrisch komplexe Flächen- und Stabwerkselemente aus UHPC“. Schwerpunkt waren umfangreiche Untersuchungen zu geometrisch komplexen und hochpräzise hergestellte trocken gefügten Stoßverbindungen für dünnwandige UHPC-Bauteile zur Übertragung von Druck-, Biege- und Scherkräften. Zur Verbesserung der Zugtragfähigkeit und des Nachbruchverhaltens wurde im Forschungsprojekt stahlfaserverstärkter ultrahochfester Beton (UHPFRC) verwendet. Die einzelnen Arbeitspakete waren entsprechend der Expertisen der beiden Institute aufgeteilt. Während sich das ITE insbesondere mit der Entwicklung der Bauteil- und Fugengeometrien sowie dem Schalungsbaus befasste, lagen Planung und Umsetzung der experimentellen und numerischen Material- und Bauteiluntersuchungen in der Verantwortung des iBMB. [Aus. Einleitung) / The Institute of Structural Design (ITE) and the Institute of Building Materials, Concrete Structures and Fire Safety (iBMB) of the Technical University of Braunschweig worked together in the f rst funding period of the SPP 1542 “Concrete Light” on the subproject “Development of novel jointing systems for complex beam surface and spatial elements made of UHPFRC”. The focus was on extensive investigations of geometrically complex and high-precision dry-jointed connections for thin-walled UHPC components for the transmission of compressive, bending and shear forces. Steel f bre reinforced ultra-high performance concrete (UHPFRC) was used in the research project to improve the tensile strength and post fracture behaviour. The individual work packages were divided according to the expertise of the two institutes. While the ITE was particularly concerned with the development of the component and joint geometries as well as the formwork construction, the iBMB was responsible for the planning and implementation of the experimental and numerical material and element analyses. [Off: Introduction]

Dieses Projekt widmete sich einer neuen Bauweise für stabförmige Drucktragglieder aus ultrahochfestem Beton (UHFB), die - als UHFB-Rohre mit Stahlrohren ummantelt - hier als Hybridrohre bezeichnet werden. Durch eine äußere Wickelverstärkung aus kohlenstofffaserverstärktem Kunststoff (CFK) werden die beiden, für sich alleine betrachtet ausgeprägt spröden Hochleistungsmaterialien UHFB und CFK so kombiniert, dass sie zu besonders leichten Bauteilen hoher Tragfähigkeit mit ausgeprägt duktilem Versagensverhalten zusammengefügt werden. [Aus: Motivation und Zielsetzung] / This project was dedicated to a new construction method for rod-shaped support elements made of ultra-high performance concrete (UHPC), which - as UHPC tubes coated with steel sheets - are called hybrid tubes in this report. Through an exterior wrapping-reinforcement made of carbon fibre reinforced plastic (CFRP), the two high-performance materials UHPC and CFRP, which are distinctly brittle when viewed on their own, are combined in such a way that they form particularly light components of high load-bearing capacity with profound ductile failure behaviour. [Off: Motivation and objective]

Die vorliegende Arbeit befaßt sich mit der experimentellen Analyse des Tragverhaltens von Hochleistungsbeton unter mehraxialer Beanspruchung. Dabei wurden sowohl die zwei und die dreiaxiale Drucktragfähigkeit als auch das Verhalten unter zweiaxialer kombinierter Druck Zug Beanspruchung untersucht. Für die Analyse kamen jeweils drei Betonfestigkeitsklassen zum Einsatz, C 55/67, C 70/85 und C 90/105. Innerhalb der durchgeführten Versuchsreihen wurden sowohl die jeweiligen Bruchlasten als auch die Spannungs Dehnungs Beziehungen ermittelt. Die Ergebnisse dieser Untersuchungen wurden mit denen verglichen, die an Normalbeton gewonnen wurden. Aus diesem Vergleich wurden Schlußfolgerungen für den Einsatz von Hochleistungsbetonen abgeleitet. Zur mathematischen Beschreibung des Tragverhaltens von Hochleistungsbeton wurden für die untersuchten Beanspruchungsregime Näherungsfunktionen angegeben. / The subject of this paper is the experimental analysis of the behavior of High Performance Concrete under multiaxial loading. Thereby the behavior under bi- and triaxial compression as well as the behavior under combined compression-tension stresses were examined. Three concrete grades were examined, C 55/67, C 70/85 and C 90/105. Within the test series, the ultimate loads and the stress-strain-relationships were determined. The results of the examinations were compared to the results which are already known for normal strength concrete. From these comparisons conclusions for the usage of high performance concrete were made. For the examined states of stress mathematical approximations are specified.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A evolução dos concretos utilizados nas últimas décadas deu origem ao Concreto de Alto Desempenho (CAD), que tem, entre suas características, alta resistência à compressão e baixa permeabilidade. Com o desenvolvimento dos produtos químicos utilizados na construção civil, em especial os superplastificantes e superfluidificantes, a utilização desse tipo de concreto tornou-se cada vez mais freqüente pela possibilidade de se obter uma mistura suficientemente trabalhável utilizando-se fatores água/cimento menores do que 0,35. Devido à sua microestrutura mais homogênea, esse tipo de concreto apresenta um comportamento mais frágil do que os concretos convencionais, exigindo uma melhor caracterização do material. A partir do final da década de 70 começou-se a aplicar os conceitos da Mecânica da Fratura para análise do comportamento de estruturas construídas com esse tipo de concreto. Como em algumas situações a resistência nominal de peças de concreto diminui com o aumento de suas dimensões, houve a necessidade de se considerar o efeito de escala das estruturas a fim de se obter níveis de segurança mais adequados no seu dimensionamento, o que justificou a utilização da Mecânica da Fratura. Neste trabalho a energia de fraturamento foi obtida experimentalmente pelo método do trabalho de fraturamento e pelo método do efeito de escala, por meio de ensaios estáveis de flexão de três pontos em amostras de concreto de alto desempenho com entalhe. Foi também desenvolvida a simulação numérica de uma viga com entalhe, analisada pelo método dos elementos finitos e empregando-se na modelagem constitutiva os conceitos da Mecânica da Fratura aplicada ao concreto. As vigas foram moldadas e ensaiadas no Instituto Politécnico do Rio de Janeiro (IPRJ) da Universidade do Estado do Rio de Janeiro (UERJ) na cidade de Nova Friburgo. Os ensaios foram realizados com controle de deslocamento da célula de carga. Foram ensaiadas três séries de 12 vigas, com quatro dimensões diferentes, geometricamente proporcionais, e três amostras para cada dimensão, totalizando 36 vigas. As alturas utilizadas para as vigas foram 38, 76, 152 e 304 mm, e sua espessura foi mantida constante igual a 38 mm. Os corpos de prova cilíndricos, para caracterização da resistência à compressão do concreto, foram moldados no IPRJ e rompidos no laboratório de engenharia civil da UERJ, na cidade do Rio de Janeiro. Os concretos utilizados apresentaram resistência à compressão média de 70 MPa. / The evolution of the concrete mixes used during the last decades gave birth to the High Performance Concrete (HPC), which, among its main characteristics, presents high strength and low permeability. With the development of chemical products used in civil engineering constructions, mainly the superplasticizers, the use of this kind of concrete has become more and more frequent due to the possibility of obtaining a workable mixture with a water/cement ratio lower than 0.35. Due to its more homogeneous microstructure, the HPC presents a more fragile behavior than the conventional concrete, demanding a better characterization of the material. At the end of the 1970s, concepts of the Fracture Mechanics started to be used for the analysis of the structural behavior of concrete structures. As the nominal stress of the material decreases as the size of the structure increases, it became necessary to consider this size effect in the analysis in order to obtain more suitable levels of security. This fact justifies the use of the Fracture Mechanics in the structural analysis of concrete structures. In this work, the fracture energy was experimentally obtained using the work-offracture method and the size effect method by performing three-point bend tests in HPC notched beams. It was also developed a numerical simulation of the tests, performing the analysis through the Finite Element Method and applying the concepts of the Fracture Mechanics of Concrete into the constitutive model. The notched beams were molded and tested at the Polytechnic Institute of the State University of Rio de Janeiro (IPRJ/UERJ), located in the city of Nova Friburgo. The tests were controlled by the vertical displacement of the load cell. Three series of twelve beams with four geometrically similar sizes were tested. Three samples for each size were cast, making an amount of 36 beams. The beams were 38, 76, 152 and 304 millimeters high and the width was kept constant equal to 38 millimeters. To characterize the concrete compression strength, 100x200 millimeters cylinders were molded at the IPRJ and tested at the UERJ civil engineering laboratory in the city of Rio de Janeiro. The tested concretes presented a medium compressive strength of 70 MPa.