Die kontinuumsmechanische Untersuchung der Lastübertragungsmechanismen zwischen den Rovings im textilbewehrten Feinbeton trägt wesentlich zum Gesamtverständnis des mechanischen Verhaltens des Verbundmaterials bei. Neben der Erfassung der gegenseitigen Beeinflussung sich kreuzender Rovings erfordert insbesondere die mechanische Modellierung und numerische Simulation von Bewehrungsstößen und Endverankerungen die Kenntnis dieser Übertragungsmechanismen. Die numerischen Simulationen sollen u. a. zeigen, welche Endverankerungslängen und welche Übergreifungslängen an Bewehrungsstößen erforderlich sind und wie die Querbewehrung die Rissbildung beeinflusst. / This paper concerns with the investigation of stress transfer mechanisms between yarns and concrete matrix and their influence on the overall behavior of textile reinforced concrete (TRC). This investigation considers textile reinforcement splices and textile reinforcement development lengths and carried out by means of Finite-Element simulations and fracture mechanic approaches. A first modeling procedure is made towards analyzing and investigating the damage mechanisms in TRC specimen under tension loading which are mainly characterized by matrix cracking and yarn pullout. This modeling approach allows for considering the yarn crack bridging which is a main characteristic behavior of TRC. In the same manner, 3D Finite-Element models are conducted for calculating the required reinforcement development lengths and the reinforcement overlapping lengths. The conducted approach takes into account different damage mechanisms observed in the corresponding experimental investigations which are also used for calibrating the modeling procedures. Moreover, the presented approach covers a wide range of required textile reinforcement overlapping lengths and development lengths and provides the corresponding ultimate loads.

In diesem Beitrag wird die Wasserabsorption und die Wasserpermeabilität von axial vorbelasteten Prüfkörpern aus textilbewehrtem Beton (TRC) und biegebelasteten Verbundprüfkörpern (Normalbeton + TRC) im gerissenen Zustand untersucht. Durch in situ Permeabilitätsmessungen wird das dehnungsabhängige Transportverhalten im einaxialen Zugversuch beobachtet und mittels eines analytischen Modells beschrieben. Es besteht eine ausgeprägte Abhängigkeit der Transportraten von Flüssigkeiten zu relevanten Risscharakteristika (Rissanzahl, Rissbreite). Weiterhin wurden Selbstheilungseffekte von feinen Rissen infolge einer zyklischen Wasserbeaufschlagung beobachtet. Die Feuchteverteilung in einer gerissenen Normalbetonprobe und einer Verbundprobe (Normalbeton + TRC) wird mit Hilfe der Neutronenstrahlradiographie zeit- und ortsaufgelöst dargestellt. Das Eindringen von Wasser wird anhand der Messungen qualitativ vorgestellt und diskutiert. / In this study water absorption and water permeability were tested on uniaxially preloaded, cracked specimens made of textile reinforced concrete (TRC) and cracked composite specimens (ordinary concrete + TRC) preloaded in bending. The influence of imposed strain on the permeation of water was observed in-situ by using uniaxial tensile tests and described by an analytical model. The transport values for the cracked material correlated with the cracks’ characteristics (number of cracks, crack width). Furthermore, the effect of self-healing phenomena on the transport properties of TRC was considered. The distribution of water in cracked ordinary concrete and cracked composite specimens was studied by means of neutron radiography which provided with a high spatial and temporal resolution. The penetration of water is presented qualitatively and discussed.

Sandwichkonstruktionen mit Deckschichten aus dünnen Metallblechen und Stahlbeton stellen seit Jahrzehnten bewährte und wirtschaftliche Verbundkonstruktionen für Gebäudehüllen dar. Der Einsatz von dünnen Deckschichten aus textilbewehrtem Beton verbindet deren Vorteile und ermöglicht auch bei steigenden Anforderungen an den Wärmeschutz geringe Konstruktionsdicken. Der Beitrag berichtet über die Entwicklung von Ingenieurmodellen zur wirklichkeitsnahen Beschreibung des Tragverhaltens von Sandwichquerschnitten aus textilbewehrtem Beton, Hartschaumdämmkern und geeigneten Verbundmitteln. / Sandwich constructions made of thin metal sheets and structural concrete have been reliable and economic composite structures in the past decades. The application of thin-walled facings made of Textile Reinforced Concrete (TRC) combines the advantages of this construction and allows for slender construction thicknesses despite the progressing demands on thermal insulation. This contribution reports on the development of models, which enable the realistic mechanical description of the load-bearing behavior of the sandwich panels made of two TRC-facings and a core of polymeric rigid foam together with suitable connecting devices.

A model is presented to use normalized multi-linear tension and compression material characteristics of strain-hardening textile reinforced concrete and derive closed form expressions for predicting moment-curvature capacity. A set of design equations are derived and simplified for use in spreadsheet based applications. The model is applicable for both strain-softening and strainhardening materials. The predictability of the simplified model is checked by model calibration and development of design charts for moment capacity and stress developed throughout the cross section of a flexural member. Model is calibrated by predicting the results of Alkali Resistant Glass and Polyethylene fabrics. A case for the flexural design of Glass Fiber Reinforced Concrete (GFRC) specimen as a simply supported beam subjected to distributed load is used to demonstrate the design procedure.

A major distress mode in asphalt pavements is low temperature cracking, which results from the contraction and expansion of the asphalt pavement under extreme temperature changes. The potential for low temperature cracking is an interplay between the environment, the road structure and importantly the properties of the asphalt mixture. The thermal cracking performance of asphalt concrete mixtures can be evaluated by conducting thermal stress restrained specimen tests (TSRST) which is known to be correlated well with the fracture temperatures observed in the field. Although TSRST provides a good estimation of the field performance, it may be unrealistic to implement the obtained results in a design framework. On the other hand, recent studies showed Superpave indirect tension tests can be used to evaluate fracture performance (fatigue, moisture damage, low temperature cracking, etc.) of the asphalt concrete  mixtures. In addition, the obtained elastic and viscoelastic parameters from the Superpave IDT tests can be used as an input parameter to establish a design framework. The study presented in this thesis has a main objective to develop a framework using Superpave IDT test results as input parameters in order to evaluate the low temperature cracking performance of asphalt concrete mixtures. Moreover, the study aims to investigate micro-mechanically the low temperature cracking behavior of bitumen using atomic force microscopy (AFM) as a tool. The numerical model has been developed by integrating fracture energy threshold into an asphalt concrete thermal fracture model, considering non-linear thermal contraction coefficients. Based on the asphalt concrete mixture viscoelastic properties, this integrated model can predict thermally induced stresses and fracture temperatures. The elastic, viscoelastic and fracture energy input parameters of the model were measured by conducting indirect tension tests and the thermal contraction coefficients were measured experimentally. The proposed model has been validated by comparing the predicted fracture temperatures with the results obtained from TSRST tests. It was found that, while there is a quantitative discrepancy, the predicted ranking was correct. In the measurement of the thermal contraction coefficients it was observed that the thermal contraction coefficient in asphalt concrete is non-linear in the temperature range of interest for low temperature cracking. The implications of having non-linear thermal contraction coefficient were investigated numerically. In an effort to understand the effect of bitumen properties on low temperature fatigue cracking, AFM was used to characterize the morphology of bitumen. The AFM topographic and phase contrast image confirmed the existence of bee-shaped microstructure and different phases. The bitumen samples were subjected to both environmental and mechanical loading and after loading, micro-cracks appeared in the interfaces of the bitumen surface, confirming bitumen itself may also crack. It was also found that the presence of wax and wax crystallization plays a vital role in low temperature cracking performance of bitumen. / <p>QC 20120828</p>

Heat exchanger tubes are commonly made from stainless steel.In a heat exchanger both the process fluid and the cooling orheating media can be corrosive. It is therefore important to beable to select materials that do not suffer from corrosion.Current methods in this area, however, suffer from limitationsand shortcomings. This thesis concerns corrosion tests forgeneral corrosion, dewpoint corrosion and stress corrosioncracking, respectively. For evaluation of general corrosion ofsuperduplex stainless steels in hydrochloric acid and sulphuricacid the importance of activation was studied. The results showthat activation has a great influence on the test result.Further the results indicate that experimental differences canbe the explanation for previously reported differences incorrosion resistance of superduplex stainless steel that havebeen attributed to the alloying with Cu and W. Furthermore, asimple test loop for testing stainless steels under dew formingconditions with a formed condensate of 1 % hydrochloric acidhas been developed. In the work constant strain and constantload test result have been compared and the observationsindicate that the differences can be explained by differencesin the relaxation properties of the materials. <b>Key words:</b>corrosion testing, heat exchanger, stainlesssteel, general corrosion, immersion tests, activation, stresscorrosion cracking, constant load, u-bends, relaxation,dewpoint corrosion / NR 20140805

Visualization is used for stainless steel container wall and lid cross section characterization. Two specific types of containers are examined: 3013 and SAVY. The container wall examined is from a sample of the inner container of a 3013 container. The inner lid cross section examined is from a SAVY container. Laser confocal microscope data and photographic data are used to determine features of the surfaces. The surface features are then characterized by various feature statistics, such as, maximum depth, area, eccentricity, and others. The purpose of this pilot study is to demonstrate the effectiveness of using the methodology to detect potential corrosion events on the inner container surfaces. The features are used to quantify these corrosion events. An automatic image analysis system uses this methodology to classify images for possible further human analysis by flagging possible corrosion events. A manual image analysis methodology is used to determine the amount of MnS on the SAVY container lid cross section. Visualization is an integral component of the analysis methodology.

Every website, computer and IT system have users who need to verify their identity throughauthentication. The most common form of authentication today is to apply an alphanumericpassword. Passwords are often based on biographical information that can be derived from the userhimself and common elements that are usually utilized while creating passwords are names, petnames, family related, and date of birth. While passwords today are often based on the individual'sbiographical elements, the police have problems cracking encrypted devices because it takes a longtime and is complex to identify the correct password among all possible combinations. This problemis the basis for the work and is the reason why this model for how biographical dictionaries should bestructured and contain is created. To design the model, a literature review has been carried outwhere elements have been defined and a structure formed. Interviews with IT forensics from thepolice and NFC were then held to refine the different elements and structure of the initial model andto create a reality anchor. The result of this work is a product in the form of a model that can be usedto create biographical dictionaries based on target people. The model demonstrates whichbiographical elements are relevant for finding potential passwords. The conclusion drawn is that themodel can facilitate the work of the police and IT forensics when it comes to cracking people'sbiographical passwords. By using a dictionary that is built with the model, time-consuming attackssuch as brute-force attacks or more general dictionary attacks do not need to be applied. / Till varje hemsida, dator och IT-system finns användare som behöver verifiera sin identitet genomautentisering. Den vanligaste formen av autentisering är idag att applicera ett alfanumerisktlösenord. Lösenord bygger ofta på biografiska uppgifter som kan härledas från användaren själv ochvanliga element som brukar användas vid lösenordsgenerering är: namn, husdjursnamn, familj ochfödelsedatum. Samtidigt som lösenord idag ofta bygger på individens biografiska element har polisenproblem att knäcka krypterade enheter på grund av att det tar lång tid och är väldigt komplext attidentifiera rätt lösenord bland alla möjliga kombinationer. Detta problem ligger till grund för arbetetsamt är orsaken till varför denna modell för hur biografiska ordböcker ska vara strukturerade ochinnehålla skapas. För att utforma modellen har en litteraturöversikt genomförts där element hardefinierats och en struktur formats. Intervjuer med IT-forensiker från polisen och NFC hölls därefterför att förädla den initiala modellens olika element och struktur samt att skapa enverklighetsförankring. Resultatet av detta arbete är en slutprodukt i form av en modell som går attnyttja för att skapa biografiska ordböcker utifrån målpersoner. Modellen påvisar vilka biografiskaelement som är relevanta för att hitta potentiella lösenord. Slutsatsen som dras gör gällande attmodellen kan underlätta polisens och IT-forensikers arbete när det kommer till att knäcka personersbiografiska lösenord. Genom att nyttja en ordbok som är uppbyggd med modellen behöver intetidskrävande angrepp som ”brute force” attacker eller mer generella ordboksattacker appliceras.

La presente tesis contempla el diseño de una gama de concretos de baja contracción, empleando cementos con adición de puzolanas, fibras de polipropileno y fibras metálicas para mitigar la fisuración, mejorando la durabilidad de las edificaciones. Para proponer los diseños se investigó cuáles de las contracciones son la que tienen mayor incidencia en la fisuración del concreto, siendo la contracción plástica y la contracción por secado las más importantes. Asimismo, se estudiaron qué variables son las que provocan la contracción y posterior fisuramiento, afirmando que son producidos por factores ambientales, los componentes del concreto y malas prácticas constructivas. En la primera etapa, se realizó la caracterización de los agregados (fino y grueso), realizándose ensayos como granulometría, absorción, peso específico, contenido de humedad y %pasante de la malla #200. En la segunda etapa se realizaron los ensayos en concreto fresco, siendo el de mayor importancia el ensayo de simulación de contracción plástica, para el cual empleamos la ASTM C1579. Para realizar este ensayo se fabricaron los paneles que simulan restricciones y se construyó una cámara en la que se controla la velocidad del aire, temperatura y humedad relativa. En la tercera etapa se realizaron los ensayos en concreto endurecido, siendo el más importante el ensayo de contracción por secado, para lo cual empleamos la ASTM C490. Para ello, se realizaron probetas rectangulares para la medición de la variación del cambio de longitud durante 31 días. Finalmente, se realizará el análisis costo – beneficio para demostrar la viabilidad de la propuesta. / This thesis contemplates the design of a range of low-shrinkage concretes, using cements with the addition of pozzolans, polypropylene fibers and metallic fibers to mitigate cracking, improving the durability of buildings. In order to propose the designs, it was investigated which of the contractions have the greatest incidence in the cracking of the concrete, being the plastic contraction and the drying contraction the most important. Likewise, the variables that cause contraction and subsequent cracking were studied, stating that they are produced by environmental factors, concrete components and poor construction practices. In the first stage, the characterization of the aggregates (fine and coarse) was carried out, performing tests such as granulometry, absorption, specific weight, moisture content and% passing through of the # 200 mesh. In the second stage, tests were carried out on fresh concrete, the most important being the plastic shrinkage simulation test, for which we used ASTM C1579. To carry out this test, the panels that simulate restrictions were manufactured and a chamber was built in which the air speed, temperature and relative humidity were controlled. In the third stage, tests were carried out on hardened concrete, the most important being the drying shrinkage test, for which we used ASTM C490. For this, rectangular test tubes were made to measure the variation of the change in length during 31 days. Finally, a cost-benefit analysis will be carried out to demonstrate the viability of the proposal. / Tesis

Today’s society is highly reliable on a working road infrastructure, which is because of collective efforts already built in terms of main net of roadways, and the attention is now paid to its service life primarily from a point of view of a climate change which is causing more frequent temperature extremes. This thesis sets its goal to perform basic tests for bitumen, especially ones dealing with low temperature properties, on types of bitumen usually used in out day to day world and asphalt mixtures made with those types of bitumen. The theoretical part talks about the basic definition of bitumen and studies performed on the similar issue. Practical part of the thesis is focused on performing the tests of bitumen and asphalt, which include but are not limited to, penetration test, softening point test, critical temperature detected by method by Fraasse and the bending beam rheometer and the test to set critical temperature of asphalt by using TSRST. At the end of the thesis the evaluation of results and its mutual correlation is performed.