Fundamentplatten aus Stahlbeton und Stahlfaserbeton. Experimentelle Untersuchungen zur Gebrauchstauglichkeit und Tragfähigkeit

Reinforced Concrete and Steel Fibre Reinforced Concrete Rafts Experimental tests on serviceability and ultimate loading performance Houses and residential buildings are increasingly built on rafts instead of strip foundations. The main advantages of rafts are more efficient excavation works and easy concreting of the rafts itself. The use of steel fibre reinforced concrete slabs offers economic advantages if there are no special requirements on service ability such as water tightness or crack limitations. At Aachen University of Applied Sciences a comparative experimental study on the load carrying behaviour of rafts made of concrete, reinforced concrete and steel fibre reinforced concrete was carried out. The tests have proven steel fibre concrete as suitable material for rafts in case of sufficient stiffness of the subbase. In case of special requirements on service ability, reinforced concrete or combined fibre and bar reinforced concrete should be used. In that case stresses should be calculated based on the elastic theory.     

Bauteile aus Stahlfaserbeton und stahlfaserverstärktem Stahlbeton

Mit der zu erwartenden Einführung der Richtlinie “Stahlfaserbeton” des Deutschen Ausschuss für Stahlbeton (DAfStb) entsteht für den Verbundwerkstoff Stahlfaserbeton ein neues, breites Spektrum an zusätzlichen Anwendungsmöglichkeiten. Durch die Wirkung der Fasern im Beton können nach Überschreitung der Betonzugfestigkeit nennenswerte Kräfte zwischen den Rissufern übertragen und bei der rechnerischen Erfassung des Tragverhaltens berücksichtigt werden. Im Aufsatz werden Vorgehensweisen, Hilfsmittel und ein auf Tabellenkalkulationen und Optimierungsmethoden basierendes Programm zur Biegebemessung und Verformungsabschätzung von Querschnitten und Systemen aus Stahlfaserbeton und stahlfaserverstärktem Stahlbeton entwickelt. Grundlage sind die bekannten Bemessungsansätze und ‐hilfsmittel für Stahlbetonquerschnitte. Die Anwendung der Hilfsmittel – auch für Verformungsabschätzungen auf Basis nichtlinearer Verfahren – zeigen zwei Beispiele. Structural Elements of Steel Fibre Reinforced Concrete with or without Bar Reinforcement Tools for Design and Deflection Estimations according to the Guideline “Stahlfaserbeton” by DAfStb The expected release of the guideline “Stahlfaserbeton” by ‘German Committee for Reinforced Concrete’ (DAfStb) offers a wide application range for the composite material steel fibre reinforced concrete (SFRC). Due to additional steel fibres in concrete considerable tension forces can be transferred between crack edges after reaching plain concrete's tensile strength. These forces can be accounted for in calculation of load bearing capacity. Adapted from common design methods and tools for plain reinforced concrete new procedures, tools and a computer application – based on spreadsheet analysis and optimisation methods – for SFRC are presented in this article. These allow for both bending design as well as deflection estimation of crosssections and structural systems made of SFRC with and without additional rebars. Their application – also in case of deflection estimation using non‐linear methods – is demonstrated in two elaborated examples.     

Möglichkeiten der Bemessung von Bauteilen aus Glas

Methods for design of structural elements made of glass. The application of structural elements made of glass became more common and nowadays appear to be standard. For the design of such elements legal conditions and background have to be obeyed. In addition knowledge about design rules and – for special problems – alternative methods and technical background is necessary. In this paper the past and present regulations and related questions for design of structural elements of glass are presented. Finally an outlook for future design methods and regulations in context with the modern concept of partial safety factors is given.     

Ermüdungssichere Bemessung vorgespannter Ringflanschstöße unter Berücksichtigung von Flanschimperfektionen

Fatigue design of preloaded ring flange connections taking flange imperfections into account. The fatigue life of the bolts in preloaded ring flange connections may drastically drop when there are gaps between the flange contact surfaces before preloading the bolts (“flange imperfections”). Preloaded ring flange connections are often used as site joints in tower‐like steel structures, e.g. in tubular towers of wind turbines (WEA). The fatigue‐detrimental effects of flange imperfections have been comprehensively investigated at the University of Essen. The conclusions to be drawn from it with regard to a fatigue‐safe design are described and commented in the present paper, based on the relevant rules in the new DIBt‐guidelines for WEA. Two calculation models are presented how to take flange imperfections approximately into account in the fatigue design. For the redeveloping of a site joint, which during erection turns out to be too imperfect, the method of packing the gaps is discussed.