In September 2000 the DAfStb issued a technical recommendation for the experimental assessment of structural safety and usability of concrete structures. By now, the influence of pavement or floor layers and of other factors on the load carrying capacity is not known exactly. In this thesis, it has been investigated how road pavements, the geometry and bridge caps reduce the actions on concrete bridge structures and how these influences should be taken into account in the experimental evaluation of the bending capacity by an additional test load increment. In co-operation with a local authority in Stralsund, Germany, comprehensive loading test could be performed at an abandoned concrete bridge with prefabricated girders. Between loading cycles, the pavement has been stepwise disassembled. In addition, the ultimate load of the structure as well as of an individual girder has been determined in fracture tests. By means of a hybrid analysis, i.e. a numerical simulation supported by experimental data, the influences of the pavement layers have been determined. These results were verified by experimental observations obtained in past bridge tests. The influence of the pavement layers on the load carrying capacity appeared to be as high as 28% at the maximum for the bridges investigated. Since the loading vehicle BELFA has been completed in March 2001, test loads can be applied now self-securing to bridges in the so-called large load circuit, i.e. the structure is loaded including supports and foundation. The technical concept, the principle and possible applications of the BELFA are described. The results presented will allow to determine the additional test load increment for compensating the influence of pavement layers, structural geometry and bridge caps in future experimental safety evaluations. For this analysis, the exact geometry of the structure, the thickness of the pavement layers as well as their material properties, especially the modulus of elasticity, have to be known. Guidelines for the analysis procedure as well as for simplifying assumptions are given. / Experimentelle Nachweise der Tragsicherheit und Gebrauchstauglichkeit von Betonbauwerken sind seit September 2000 in einer DAfStb-Richtlinie geregelt. Der Einfluss mittragender Aufbauschichten und anderer Faktoren war bisher quantitativ unbekannt. In der vorliegenden Arbeit wurde untersucht, wie Straßenbeläge, Bauwerksgeometrie und Kappen die Beanspruchung der Tragkonstruktion von Massivbrücken mindern und im experimentellen Nachweis der Biegetragsicherheit durch eine Überlast zu berücksichtigen sind. In Zusammenarbeit mit dem Straßenbauamt Stralsund konnten an einer Fertigteilträgerbrücke Belastungsversuche mit sukzessivem Rückbau des Fahrbahnaufbaus sowie Bruchversuche am Gesamtsystem und an ausgebauten Fertigteilträgern mit Ortbetonergänzung erfolgen. Mit Hilfe der hybriden Statik, also der Modifikation und Evaluation von Rechnungen anhand experimentell erlangter Messwerte, wurden die Einflüsse der Aufbauschichten quantifiziert und durch Auswertung weiterer Brückenbelastungsversuche verifiziert. Der Einfluss der Aufbauschichten betrug bei den untersuchten Brücken bis zu 28%. Seit der Inbetriebnahme des Belastungsfahrzeuges BELFA im März 2001 können Versuchlasten auch im großen Kräftekreislauf, d.h. am Gesamtsystem einschließlich Auflager- und Gründungssituation, selbstsichernd aufgebracht werden. Die Entwicklung des BELFA, seine Funktionsweise und seine Einsatzmöglichkeiten werden erläutert. Mit den Ergebnissen dieser Arbeit ist es zukünftig möglich, die notwendige Überlast bei Belastungsversuchen zur Kompensation der Einflüsse aus Straßenbelag, Bauwerksgeometrie und Kappen mit genauem Aufmaß der Bauwerksgeometrie und der Schichtdicken sowie mit ingenieurmäßigem Abschätzen der Materialkennwerte (E-Moduli) hinreichend genau zu bestimmen. Handlungsempfehlungen geben Hinweise zur generellen Vorgehensweise sowie für vereinfachte Rechenannahmen.

With continued feature size reduction in microelectronics and with more than a billion transistors on a single integrated circuit (IC), on-chip interconnection has become a challenge in terms of processing-, electrical-, thermal-, and mechanical perspective. Today’s high-performance ICs have on-chip back-end-of-line (BEOL) layers that consist of copper traces and vias interspersed with low-k dielectric materials. These layers have thicknesses in the range of 100 nm near the transistors and 1000 nm away from the transistors close to the solder bumps. In such BEOL layered stacks, cracking and/or delamination is a common failure mode due to the low mechanical and adhesive strength of the dielectric materials as well as due to high thermally-induced stresses. However, there are no available cohesive zone models and parameters to study such interfacial cracks in sub-micron thick microelectronic layers. This work focuses on developing framework based on cohesive zone modeling approach to study interfacial delamination in sub-micron thick layers. Such a framework is then successfully applied to predict microelectronic device reliability. As intentionally creating pre-fabricated cracks in such interfaces is difficult, this work examines a combination of four-point bend and double-cantilever beam tests to create initial cracks and to develop cohesive zone parameters over a range of mode-mixity. Similarly, a combination of four-point bend and end-notch flexure tests is used to cover additional range of mode-mixity. In these tests, silicon wafers obtained from wafer foundry are used for experimental characterization. The developed parameters are then used in actual microelectronic device to predict the onset and propagation of crack, and the results from such predictions are successfully validated with experimental data. In addition, nanoindenter-based shear test technique designed specifically for this study is demonstrated. The new test technique can address different mode mixities compared to the other interfacial fracture characterization tests, is sensitive to capture the change in fracture parameter due to changes in local trace pattern variations around the vicinity of bump and the test mimics the forces experienced by the bump during flip-chip assembly reflow process. Through this experimental and theoretical modeling research, guidelines are also developed for the reliable design of BEOL stacks for current and next-generation microelectronic devices.

The diploma thesis is focused on the evaluation of mechanical fracture parameters of concrete after exposure to high temperatures. In the introductory theoretical part general principles of fracture mechanics with the concentration on a linear elastic fracture mechanics and non-linear fracture models for the concrete are summarized. The meaning of the three-point bending fracture test used for determination of fracture parameters is also explained. Further the influence of high temperatures on the partial components of concrete and general modeling of temperature loading is described. The practical part is concerned with the evaluation of fire experiments on the concrete panels including numerical simulations using GiD and ATENA software. The evaluation of data obtained from the three-point bending test carried out on specimens with initial stress concentrator taken from concrete panels is a main part of the diploma thesis. The values of modulus of elasticity, effective fracture toughness, work of fracture and fracture energy are determined from the measured F–d and F–CMOD diagrams after their proper corrections in the GTDiPS application. The evaluation of the selected mechanical fracture parameters was performed by StiCrack software using effective crack model and work of fracture method and DKFM_BUT software using the double-K fracture model. Finally, the attention is paid to the analysis of the obtained data.

The purpose of dissertation is the analysis of the calculation of fracture parameters using Double-K fracture model for quasi-brittle specimens with the stress concentrator loaded by three-point bending or wedge splitting. To calculation of these parameters was used the developed DKFM_BUT software in Microsoft Excel application with using of Visual Basic programming language. Furthermore, the adequate shape functions and compliance functions were introduced for the selected wedge splitting test configurations. Main part of this dissertation is the series of comprehensively implemented and evaluated fracture experiments on specimens from advanced building materials, while the attention was paid to the analysis of experimental data. Finally, the selected results obtained using mentioned software support were presented and discussed.