ÖBV Guideline UHPC: New Aspects of Structural Design and Quality Assurance

The new Austrian UHPC guideline enables design and construction of material-efficient, durable structures made of UHPC for both new buildings and rehabilitation measures. The local fiber orientation is one decisive parameter influencing the post cracking tensile strength of UHPC and should be considered in calculating the characteristic value of the local post cracking tensile strength. The guideline offers two ways to determine the local fiber orientation, (i) theoretic prediction procedure considering the workability, the fiber content, the ratio between fiber length and width of the formwork, the way of concrete flow during casting, and (ii) a non-destructive measuring method. Specific partial safety factors cover the uncertainty of the method used. The essential way of a safe design of dry joints is to check the proof of decompression. The guideline presented considers the accuracy of flatness of the contact surfaces in this proof by changing the minimum of allowed compression stress depending on the flatness deviation of the contact surface. In order to ensure a homogeneous fiber distribution and that fiber orientation which has been used in the design calculations, a newly specified ratio between slump and flow time has to be checked experimentally.