Only corrugated sheaths with small diameters can be used in slender prestressed concrete structures. Corrugated sheaths with flat oval cross-section are required for the application of multi-strand prestressing cables. Thus, the individual prestressing wires or strands cannot lie above each other during the prestressing process. The most important feature of the HYDRA corrugated sheaths is the continuous forming of rounded bends. This avoids the wedging of the strands in the corners so that every strand can be prestressed and anchored individually. In addition to the economic advantage provided by the application of prestressing equipment of low weight and easy use, there is the technical advantage of a helically corrugated sheath with longitudinal weld seam.
 


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