The efficiency of the technique of strengthening existing structures using Ultra High Performance Fibre Reinforced Concrete (UHPFRC) has been investigated in this study. The uniaxial stress-strain relationship in tension and the compressive strength characteristics have been determined by direct tensile and compressive tests respectively. These results have been used for the constitutive modelling of UHPFRC. The model in tension is consisted of several linear parts, including strain hardening followed by a significant post crack energy absorption softening branch. Finite Element method has been used for the modelling of strengthened reinforced concrete beams with UHPFRC layers and a parametric study has been conducted on beams strengthened with UHPFRC layers and jackets. The efficiency of this technique is highlighted and the performance of strengthened beams with UHPFRC layers is compared to respective specimens strengthened with additional concrete layers reinforced with steel bars. by superior mechanical properties. Kang et al. (2010) and Yoo et al. (2013) examined the effect of the steel fibers amount on the flexural strength of UHPFRC and it was found that the flexural strength increased with the fiber volume ratio while the ductility was decreased. Kang et al. (2010) presented an inverse analysis to determine the tensile fracture model of UHPFRC and a trilinear tensile fracture model of UHPFRC tensile softening model is proposed.

Full-Scale Experiment Bridge WILD -Design of an UHPC Arch Bridge based on ExperimentsThe outstanding durability of UHPC makes this material predestined for the construction of bridges. In Austria UHPC is introduced into the practice of road bridges through the realisation of the bridge WILD. The cross section of the arch, which spans 70 m, is just 6 cm thick and doesn't contain any passive reinforcement. The design is based on international recommendations on the one hand and on specific experiments on the other hand. This paper deals with the evaluation of two full-scale laboratory tests. The setup is configured for getting a broad field of results as it is necessary for approval tests. In this way, all critical design states, which are also determined by calculation, are investigated experimentally. Furthermore, the experiments cover secondary effects, which don't have any verification through practical experience but can clearly be seen in FE-results. The test results are carefully interpreted and explained by the use of simple mechanical models. The final examination of the results is figured out by means of comparison between calculation and experiment.

Special Features of Material and Structure in the Application of UHPC for Bridge Construction exemplified by three Pilot ProjectsSince 1997 nearly 30 bridges have been built worldwide using UHPC (Ultra High Performance Concrete). Due to the high performance of UHPC, especially owing to its strength and durability properties, this material is predestined for engineering structures and as a result also for bridges. Common design philosophies in concrete construction can not easily be adapted to this new material. The consistent incorporation of the properties and special features of this new material as well as the demands for sustainability lead to filigree, flexible and modular buildings. Therefore the design philosophy can be classified between concrete and steel constructions. Considering the complete life-cycle costs, such constructions permit economical buildings with an eminent benefit for the national economy. After general consideration, the special properties and the new insights gained are exemplified based on experiences during construction, dimensioning and implementation of three different pilot projects in Austria. Warum UHFB im Brückenbau?Seit dem Bau der ersten Brücke aus UHFB 1997, der Sherbrooke Pedestrain Bridge in Quebec -Kanada, wurden mittlerweile weltweit mit steigender Tendenz fast 30 Straßen-und Fußgängerbrücken aus UHFB mit Druckfestigkeiten zwischen 130 und 200 MPa realisiert [1]. Es gibt vielfältige Gründe, die einen Einsatz von UHFB -hier im Speziellen im Brückenbau -herausfordern. Festigkeit und Gewicht

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