Serielle Stückfertigung von Bauteilen aus textilbewehrtem Beton

Serial Batch Production of Building Members Made of Textile Reinforced Concrete Within a research project production techniques were investigated to produce building members made of textile reinforced concrete in a batch production. Laminating, casting, spraying and spinning techniques have been evaluated as well as a combination of these methods. In the beginning the main focus was the production and manufacturing technique with the adjustment of fine grained concrete and fabrics to the respective production technique and the development and choice of distance holders. In order to investigate the manufacturing technique specimens were comprehensively produced by means of selected production techniques. This contains the choice of an adequate production technique, the design of the selected building members, the production of the utilised fabrics as well as the production and testing of the building members. This procedure was carried out for the production of elements of an integrated formwork and spun concrete tubes.     

Longitudinal shear in composite steel and concrete trusses

The distribution of longitudinal shear along an interface between steel and concrete of composite trusses is generally highly non-uniform, exhibiting peaks above truss nodes (unless after plastic redistribution). The investigation presented here examines experimentally the behaviour of two steel and concrete composite truss girders, using perforated shear connector to reach full shear connection. Experimental results have served to calibrate the non-linear 3D numerical FE model formulated using ANSYS software package. More than 30 variants of shear connections of a simple truss with Vierendeel panel at midspan have been studied, having various load–slip relationships obtained from previous research. Distinctive peaks of shear flow in the connection above truss nodes have been found within elastic behaviour–especially important for connectors loaded in fatigue–followed by plastic redistribution in plastic region. Comparison of the numerical results with proposals given in Eurocode 4 and influence of shear connection densification above truss nodes are discussed in a detail. Finally, some recommendations for practical design are presented.     

Theoretical Investigation of the Radiation Pattern From LEDs Incorporating Shallow Photonic Crystals

A theoretical approach based on coupled-mode theory is presented in order to determine the radiation pattern of LEDs incorporating a shallow photonic crystal. From this, a fundamental limit for the directionality of the diffraction of a single guided mode is given. Additionally, the Fabry-Perot resonances are shown to have significant impact on the directionality of diffracted light. For a realistic green-emitting InGaN LED in thin-film configuration the optimum reciprocal lattice vector is derived in terms of absolute diffracted intensity and directionality within a limited acceptance angle. The latter can be as high as 1.8 times the directionality of a Lambertian emitter. Furthermore, the spontaneous emission distribution between guided modes heavily influences the diffracted intensity.     

Local Equilibrium and Nodule Formation on Al‐TRIP‐Aided Steel Surfaces During Intercritical Annealing

Several advanced high strength steels were intercritically annealed at a dew point of ?5°C. Afterwards, surface morphology was investigated by scanning and transmission electron microscopy (TEM). In Al alloyed TRIP‐aided steels, nodules of metallic Fe containing traces of Mn could be proven by TEM analysis. To clarify the mechanism of origin, several further annealing trails were done and finally a new component of the occurring heterogeneous gas/metal reaction during intercritical annealing was postulated. It is concluded that neither the diffusion mechanism of the alloying elements nor the stress gradient between stress‐free surface region of the internal oxidation front nor the oxygen partial pressure dominates alone the selective oxidation process. It is suggested that the reactivity of the considered surface, its local surface chemistry and the local thermodynamic equilibrium should be taken into account in greater detail. Preferred dissociation points of absorbed water vapor could lead to a local increased oxygen partial pressure. With this, a nanoscaled oxidation/reduction process could be initiated.     

Nanostructural analysis by atomic force microscopy followed by light microscopy on the same archival slide

Integrated information on ultrastructural surface texture and chemistry increasingly plays a role in the biomedical sciences. Light microscopy provides access to biochemical data by the application of dyes. Ultrastructural representation of the surface structure of tissues, cells, or macromolecules can be obtained by scanning electron microscopy (SEM). However, SEM often requires gold or coal coating of biological samples, which makes a combined examination by light microscopy and SEM difficult. Conventional histochemical staining methods are not easily applicable to biological material subsequent to such treatment. Atomic force microscopy (AFM) gives access to surface textures down to ultrastructural dimensions without previous coating of the sample. A combination of AFM with conventional histochemical staining protocols for light microscopy on a single slide is therefore presented. Unstained cores were examined using AFM (tapping mode) and subsequently stained histochemically. The images obtained by AFM were compared with the results of histochemistry. AFM technology did not interfere with any of the histochemical staining protocols. Ultrastructurally analyzed regions could be identified in light microscopy and histochemical properties of ultrastructurally determined regions could be seen. AFM-generated ultrastructural information with subsequent staining gives way to novel findings in the biomedical sciences. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc.     

Zur Entwicklung und zum Einsatz des Liquid‐V‐Dampers zur Tilgung von vertikalen Brückenschwingungen – Teil 1 – Mechanische Grundlagen und Wirkungsweise

Die Kenntnis über das dynamische Verhalten von Bauwerken gewinnt immer mehr an Bedeutung. Dies trifft insbesondere auf Brücken zu, die durch den Einsatz von hochfesten Materialien sowie komplexen Computerprogrammen schlanker und leichter denn je geplant und gebaut werden können. Dadurch wird die Berücksichtigung dynamischer Kriterien in der Planung und Bauwerksüberwachung unumgänglich. Eine Möglichkeit der Minimierung der auftretenden Schwingungen ist die Anordnung von Schwingungsdämpfern am Tragwerk, die bis dato hauptsächlich in der Form des Masse‐Feder‐Dämpfers realisiert wurden. In diesem zweiteiligen Beitrag soll der alternative Einsatz von Flüssigkeitsschwingungstilgern in V‐Form (Liquid‐V‐Damper) gegen vertikale Brückenschwingungen speziell für den Einsatz bei Fachwerkbrücken dargestellt werden. Dabei wird der Schwerpunkt im vorliegenden ersten Teil des Beitrages auf die mechanische Wirkungsweise gelegt, der zweite Teil beschäftigt sich mit den zugehörigen Versuchen sowie der praktischen Anwendung der Tilger. Auf die baupraktische Einsatzmöglichkeit der Liquid‐V‐Damper wird dabei ein besonderes Augenmerk gelegt. Development and use of the Liquid‐V‐Damper against vertical bridge vibrations. Part 1 – Mechanical basics and mode of operation. Nowadays the acknowledgment of the dynamical behavior of structures, in special for bridges, becomes more and more important because of the use of high strength materials and complex computer simulations. Due to that reasons these structures can be planed and build more slender and light weighted than ever. So the consideration of dynamical effects in the planning phase and the structure monitoring is indispensable. One possible method to reduce structural vibrations is the arrangement of dampers on the structure. The common type of dampers is the mass‐spring damper. In this two‐part paper the alternative use of tuned liquid column damper (Liquid‐V‐Damper) against vertical bridge vibrations in special designed for truss bridges is presented. The presented first part concerns with the mechanical mode of operation, the second part will present the corresponding testing series and the practical tuning of the damper. Special attention is paid to the practical use of the Liquid‐V‐Damper.