Shear Carrying Capacity and Buckling of UHPFRC Panels

UHPFRC (Ultra High Performance Fibre Reinforced Concrete) is a mineral building material with brilliant material properties. Its extremely high strength and density cause a resistance against environmental effects as well as chemical and mechanical attacks, which is comparable with those of granite. Therefore Ultra High Performance Concrete (UHPC) shows a durability which is essentially higher than those of all concrete kinds known up to now. UHPC is to be considered not as an advancement of the high performance concrete, but as an independently developed new building material. It opens a new dimension in structural and architectural design. Light and elegant load-bearing structures made of UHPFRC could contain extremely thin-walled webs and/or panels. As a result of the crack formation highly non-linear material effects result in fibre-reinforced thin- walled panels. Within the scope of the applied project the shear carrying capacity and the stability (buckling) of thin-walled panels should be investigated by means of theoretical modelling and numerical simulation as well as by experimental investigations. The applied research project shows an indispensable condition for the implementing of UHPFRC in the practise in the form of innovative load-bearing structures and construction methods.

UHPFRC (Ultra High Performance Fibre Reinforced Concrete) is a tough and durable building material which offers big economical advantages for buildings of infrastructure. Its enormous compression strength allows for absolutely new design concepts - a change from heavy solid construction to thin-walled and elegant light weight structures. The load bearing capacity and the buckling of thin elements like panels have great importance for the structural analysis of such modern buildings like widely spanned bridges. New experimental set-ups had to be developed for getting a clear understanding of the complex failure mechanisms. A special loading control makes it possible to perform real buckling experiments in slow motion, although the buckling failure is in fact a sudden burst. Doing it this way, the experiment can be watched comfortably and deformations can be measured without putting the sensors at risk. Additionally, the forces inside the material must be known if one wants to derive theoretical approaches from the experiments. Because they cannot be measured, each experiment had to be simulated by the use of adequate engineering software. The development of the final theoretical formulae was carefully based on approved, physically fundamentals. Hence, the resulting theories are not only valid for the 30 large scale experiments but can also be applied to any other case of UHPFRC under shear load. Beside the intended aims further important facts with regard to the manufacturing of UHPFRC elements and its impact on the orientation of the fibres were found. A new non destructive measuring method for the determination of the fibre distribution as well as the fibre orientation in buildings was invented. This was the key for success in the context of the necessary quality inspection of building elements during the realisation of pilot projects. The following projects could be realised: Pedestrian Bridge Amlacherstraße in Lienz (completion 2009), Temporary Railway Bridge (Completion 2011) and the first big arc bridge for road traffic in the world; the Bridge WILD (Completion 2010). The practical experience as well as the scientific results will be contributed to guideline for UHPC design which is actually being elaborated at the Austrian Society for Concrete and Construction Technology (ÖBBV). The technical committee is chaired by Prof. Sparowitz. The research work of the Graz University of Technology on the development of the trend setting construction method with UHPC is honoured by the international scientific community. In Austria the UHPC team Graz was decorated with two reputable awards for engineers; the ZT Award 2007 and the Österreichische BAUPREIS 2008. The scientific achievements brought the famous DR.WOLFGANG.HOUSKA.PREIS 2008.