Modellierung und Bemessung von dünnwandigen Platten- und Schalentragwerken aus textilbewehrtem Beton

Als Großdemonstrator des Sonderforschungsbereichs 532 soll auf dem Gelände der Fakultät für Bauingenieurwesen der RWTH Aachen ein Ausstellungspavillon mit einer Dachkonstruktion aus Textilbeton errichtet werden. Der Beitrag zeigt die automatisierte Bemessung dieser komplexen Tragstruktur mit Hilfe eines hierfür entwickelten numerischen Bemessungsstools. Die Auswertung erfolgt für alle Lastfallkombinationen nach DIN 1055-100 und unter Berücksichtigung der Reduktion der Tragfähigkeit der textilen Bewehrung infolge einer Umlenkung im Riss sowie einer Erhöhung der aufnehmbaren Textilspannungen infolge Biegebeanspruchung. Zur Ermittlung der Tragfähigkeit der Textilbetonschale wurden am Institut für Massivbau Dehnkörper- und Biegeversuche durchgeführt, die in Bewehrungsgrad und Dicke dem realen Bauwerk am Schalenrand entsprachen.Within the collaborate research center 532 at RWTH Aachen University the construction of an exposition hall with a double-curved roof structure consisting of textile reinforced concrete is currently planned. A numerical tool has been developed to calculate the necessary number of reinforcement layers. Further, the tool evaluates the characteristic stresses of the load case combinations in the ultimate limit state taking into account a reduction of the load-bearing capacity of the textile reinforcement due to alignment of the rovings in the crack bridge and a better activation of the inner filaments for bending induced tension. The resistance of the material has been determined in experimental investigations of tensile and bending specimens of the same thickness and reinforcement ratio as the planned shell structure

VOLUME FLOW UNBALANCES AND SHORTCUTS IN DECENTRALIZED AND CENTRALIZED VENTILATION UNITS – FIELD TESTS IN RESIDENTIAL BUILDINGS

Centralized and decentralized mechanical ventilation have become state-of-the-art in modern energy-efficient residential buildings. Calculations for the energy demand of buildings are done with nominal values of the ventilation units, assuming a proper function of the devices. The used ventilation concepts may be divided into two main categories- centralized and decentralized units and both come with advantages and disadvantages in terms of energy efficiency. In Luxembourg, a comprehensive field test has been performed in order to evaluate and compare their performance in practice. It could be shown that ventilation systems often do not meet the expectations. High unbalances in volume flows, high sensitivity to pressure differences and recirculation were measured in several cases. Only a proper installation and balancing of the systems can ensure an energy efficient function

Energy performance comparison of ventilation-based heating versus water-based heating systems in an efficient residential building

The application of air-based heating systems as a possible approach to reduce the construction costs in highly efficient residential buildings is becoming popular. Air-based heating systems have been well-known for their usage in passive houses during the past three decades. Available studies on such systems tend mostly to focus only on comparing exhaust air heat pump technology with conventional systems in efficient buildings. Moreover, most of the existing studies ignore the usual presence of the electrical heaters as backup. Besides, a comprehensive study and comparison between different air-based heating system concepts is still missing. In this study, four different air-based heating system concepts separated by the type of heat source of heat pump for heating and domestic hot water are defined. These systems are compared to four conventional heating system, including floor heating and direct electrical system employing dynamic annual simulations. According to simulation results, the systems with floor heating have shown the best system efficiencies and the lowest energy demand in comparison to the other systems. The main reason for this was the lower supply temperatures of the floor heating systems. Between the air heating systems, the system equipped with an outdoor air heat pump showed a better energy performance than an exhaust air system. The main reason for this could be attributed to the power limitation of exhaust air heat pump systems

Doppelt gekrümmte Schalen und Gitterschalen aus Textilbeton

Doppelt gekrümmte Schalen und Gitterschalen sind Tragsysteme, die, obwohl in Ihrer Wirkungsweise grundsätzlich verschieden, besonders für den Einsatz von Textilbeton geeignet sind. Aufgrund ihrer doppelten Krümmung weisen derartige Tragsysteme zahlreiche Besonderheiten hinsichtlich Formfindung, Lastabtrag und Herstellung auf. Anhand eines Ausführungsbeispiels von monolithischen Schirmschalen und Konstruktionsstudien zu Gitterschalen werden die Strukturkonzepte und ihre Auswirkungen auf das Tragverhalten, das Bewehrungskonzept und die Auswirkungen auf die Herstellung sowie die Bauteilfügung erläutert.Structural systems based on double curved monolithic shells or gridshells are both characterised by their good load bearing behaviour depending on the chosen geometry. Although both systems are different regarding their functionality they are suitable applications for TRC while taking advantage of the main constructive and design characteristics of the material. In describing an execution example of an umbrella-shaped shell-structure and design studies on gridshells the relation between structural concept and load bearing behaviour and the relation between the reinforcement concept and production as well as joining are discussed

Sub-lethal radiation enhances anti-tumor immunotherapy in a transgenic mouse model of pancreatic cancer

BACKGROUND: It is not uncommon to observe circulating tumor antigen-specific T lymphocytes in cancer patients despite a lack of significant infiltration and destruction of their tumors. Thus, an important goal for tumor immunotherapy is to identify ways to modulate in vivo anti-tumor immunity to achieve clinical efficacy. We investigate this proposition in a spontaneous mouse tumor model, Rip1-Tag2. METHODS: Experimental therapies were carried out in two distinctive trial designs, intended to either intervene in the explosive growth of small tumors, or regress bulky end-stage tumors. Rip1-Tag2 mice received a single transfer of splenocytes from Tag-specific, CD4(+) T cell receptor transgenic mice, a single sub-lethal radiation, or a combination therapy in which the lymphocyte transfer was preceded by the sub-lethal radiation. Tumor burden, the extent of lymphocyte infiltration into solid tumors and host survival were used to assess the efficacy of these therapeutic approaches. RESULTS: In either intervention or regression, the transfer of Tag-specific T cells alone did not result in significant lymphocyte infiltration into solid tumors, not did it affect tumor growth or host survival. In contrast, the combination therapy resulted in significant reduction in tumor burden, increase in lymphocyte infiltration into solid tumors, and extension of survival. CONCLUSIONS: The results indicate that certain types of solid tumors may be intrinsically resistant to infiltration and destruction by tumor-specific T lymphocytes. Our data suggest that such resistance can be disrupted by sub-lethal radiation. The combinatorial approach presented here merits consideration in the design of clinical trials aimed to achieve T cell-mediated anti-tumor immunity

Flächige Tragstrukturen aus textilbewehrtem Beton : Experimentelle und numerische Charakterisierung des Tragverhaltens, Bemessung und Herstellungsmethodik

Textile reinforced concrete (TRC) is an innovative composite material consisting of a fine grained concrete and a non-corroding textile reinforcement made of high strength carbon or alkali-resistant glass fibers. Due to the non-corroding textile fabrics thin-walled, light-weight structures can be constructed with TRC. In Germany in two collaborative research centers, one at RWTH Aachen University and the other at the Technical University Dresden, the new composite material was systematically investigated in recent years. Based on interdisciplinary research results experimental and numerical methods have been developed for material characterization giving a deeper insight in the complex material behavior of the new composite material.The high application potential of TRC in the construction industry has been demonstrated by various application examples ranging from large-sized facade elements, self-supporting sandwich panels to pedestrian bridges. Furthermore, the innovative composite has a high application potential in the field of strengthening of existing steel reinforced concrete structures. The material characteristics of TRC are also particularly attractive for filigree concrete shell structures as the flexible textile fabrics can be easily adapted to complex curved geometries. Due to their low weight TRC structures can be efficiently fabricated as precast elements and mounted on site. Compared to conventional steel reinforced shell structures using labor-intensive formworks the technical challenges arising in the context of TRC constructions shift to lifting, adjusting and coupling of the individual precast elements.As the dimensioning approaches developed within the collaborative research center mainly focus on linear structural elements such as truss and beam elements they had to be adopted to spatial structures and general loading conditions. Therefore a dimensioning approach for TRC shell structures with combined normal and bending loading has been developed. The underlying n-m interaction diagram is based on the cross-sectional strength characteristic of the composite. The nonlinear load-bearing behavior of TRC shell structures including stress redistribution has been investigated with a formulated anisotropic damage model. Starting point of the developed calibration procedure for the material model is the characteristic strain-hardening response of the composite material measured in the tensile tests. In order to provide a reproducible material characterization suitable test setups for TRC are needed. The developed experimental and numerical concepts are described in detail and exemplified for two TRC shell structures recently constructed at RWTH Aachen University. Furthermore, the fabrication technique applied for TRC shell structures is described differing strongly from the approaches used for conventional steel reinforced concrete. Especially the high positional accuracy within the cross-section of the filigree TRC shells requires innovative solutions