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Rahmenbrücken in Verbundbauweise werden mit Spannweiten von über 60 m ausgeführt. Bisher wurde der Spannweitenbereich über 40 m aus VFT-Trägern mit geschweißten Trägern realisiert. Walzträger der Güte S460M sind in diesem Spannweitenbereich eine gestalterisch gute Alternative, bergen ein großes Einsparpotenzial im Konstruktionsstahl und bieten eine hohe Flexibilität in Hinblick auf die Schlankheit. Durch die großen Steg- und Flanschdicken sind dei VFT-Träger sehr robust. Der Aufsatz beschreibt die Konstruktion und beleuchtet wirtschaftliche und gestalterische Aspekte von VFT-Trägern aus Walzträgern.
Was bewegt Jörg Freitag?
(2014)
Vor der industriellen Produktion von Stahlträgern und Brettschichtholz boten Zahnbalken eine Möglichkeit große Auflagerabstände im Hoch- und Brückenbau zu überspannen. Verzahnte Balken sind aus heutiger Sicht als nachgiebig zusammengesetzte Biegeträger zu betrachten. Dabei wirken die handwerklich hergestellten Zahnverbindungen in gleicher Weise wie zum Beispiel Dübel besonderer Bauart. Der zur statischen Nachweisführung benötigte Verschiebungsmodul ist in der aktuell gültigen Holzbau-Bemessungsnorm DIN EN 1995–1–1:2010 nicht ausgewiesen. Somit ist es zurzeit nur durch eine versuchstechnische Ermittlung des Verschiebungsmoduls für die jeweilige Zahngeometrie möglich, statische Nachweise durchzuführen.
Structural Health Monitoring (SHM) of civil engineering structures is experiencing an increasing progress in the last decades. The present work focuses on the static behavior of a highway bridge due to environmental temperature effects. The goal of the present study was to test the applicability of the satellite-based synthetic aperture radar interferometry (InSAR) for deformation monitoring of a large, curved highway bridge and to compare the obtained results with alternative measurement techniques like classical geodesy surveying and with an advanced computer simulation. Such a comparison is quite rare and provides an important insight into the accuracy, efficiency and limitations of the InSAR technique in the context of SHM. Especially interesting was the question whether the InSAR technique is suitable for blind monitoring of a cluster of bridges in the region of interest. The present study shows that a pre-knowledge about each structure can be very important for a reliable interpretation of the InSAR measurement results. The second challenge of the study was to overcome several objective difficulties of combining and comparing quite different monitoring techniques that result from different sampling rates, measurement points and other specific features and sensitivities. Nevertheless, a suitable approach has been developed and implemented in the present study for the InSAR and total station measurements, providing new results and important knowledge about novel SHM techniques.
The German Association for Water, Wastewater and Waste e.V. (DWA) has published a new standard for the dimensioning, construction, and operation of constructed wetlands for treatment of domestic and municipal wastewater. The changes to the standard are based on a wide range of experience gained in recent years in Germany and Europe. For the first time ever, the standard has been officially translated and published in English. This paper summarizes the new standard for secondary treatment of domestic wastewater with classical one-stage unsaturated vertical flow (VF) wetlands, VF wetlands with lava sand for treatment of wastewater from combined sewer systems, and actively aerated VF and horizontal flow (HF) flow wetlands. Two-stage unsaturated VF wetlands treating raw wastewater (French VF wetlands), are also included in the new standard. HF wetlands are no longer described in the standard for secondary treatment of domestic wastewater. This does not exclude their application. Existing HF wetland systems in Germany may continue to be operated so long as effluent parameters are met and proper operations and maintenance is ensured. This paper gives an overview of the new design standard, including key information on wastewater type and loading, as well as primary attributes of each wetland design.
Composite dowels have opened new possibilities for engineers designing composite structures. The fundamental and most important characteristic of composite dowels is the shape of the cutting line. It is important to understand why only one particular shape of the cutting line is used in bridge engineering, while so many different shapes have been investigated by many researchers. The essential part of the process of developing composite dowels – the development of the shape of the cutting line – is presented in this paper. The influence of the steel web thickness is presented, and technological problems of steel fabrication are highlighted. The role of empirical experience from the first bridges, push-out tests, and finite element simulations is presented. Assumptions for numerical procedures are given. The distinction between the steel failure and concrete failure modes is introduced for composite dowels. The paper presents how the concept of “shape” was divided into “shape,” “ratio,” and finally “size,” and how, because of the fatigue problems in bridges, all the three factors have emerged to result in the form of shapes that can satisfy the requirements for bridges. Research leading to the invention of the first version of the clothoidal shape is presented.