Sheaths for Prestressed Concrete

A few decades have passed since the early ideas for prestressing concrete. Today the use of prestressed concrete is a tried and tested construction technique, indispensable for modern projects. The requirements for the prestressing processes are laid down in national and international regulations. This also includes the execution of prestressing work, including the applicable requirements for the companies that carry out the work and for specialized suppliers.

Accordingly, the requirements for sheathing pipes to hold prestressing steel are clearly defined and regulated in EN 523. Analogously to this European standard, the sheaths are subject to certain regulations relating to material and technical requirements. The high standards of quality of the HYDRA sheathing pipes are therefore maintained by monitoring through continuous production checks.

In order to document this quality standard independently, an extensive series of tests was carried out on the longitudinally welded pipes at the material testing institute at the University of Karlsruhe in 2008.
This affords us the chance and the security of applying the “CE mark” to HYDRA sheathing pipes in the future, and supplying our customers with the corresponding declaration of conformity.  This in turn has that advantage of allowing our customers to document the required quality accordingly to construction supervisors and approval authorities.

Shape of the Profile

By means of an appropriate design, Hydra sheaths allow for an easy and total filling of the cavities between the tendons and the sheath walls with compressed mortar. This guarantees corrosion protection for the tendons and the connection required for the transmission of force from the tendon to the sheath as well as from the sheath to the surrounding structural concrete.

Your Advantage:

  • Corrosion protection
  • High expenditures in time and money
  • Collecting of air bubbles to avoid their contact with the prestressing
  • Sufficent shearing connection by sufficient profile heigth
  • Short installation periods

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Longitudinally welded with narrow or wide groove

The wide spiral groove enlarges the sliding surface of thecorrugated sheath, thus allowing for a uniform support ofthe tendons. This will avoid increased friction during theinsertion and prestressing of the tendons and facilitate asteady sliding. Despite the high resistance to bending andtransversal load, the corrugation guarantees an excellentflexibility. The longitudinally welded sheath ensures thatno leakage will occur. Laitance is unable to intrude intothe sliding channel.The corrugated sheaths are subject to strict testspecifications and continuous supervision.

Designs

Type 7111
with wide groove, longitudinally welded

Range of dimensions:
from DN 21 to DN 98 in 5 mm steps


Material:
cold-rolled strip ST 2 EN 10139,
thickness tolerance EN 10140
optionally with special treatment for temporary corrosion protection

Storage length:
5 m; optionally with other lengths

Delivery: in bunches
with 20 pieces up to DN 55
with 15 pieces up to DN 70
with 10 pieces up to DN 85
with 5 pieces up to DN 98

Longitudinally welded with wide groove, heavy duty version

The heavy-duty version is a very appropriate solution whenever persons have to step onto the tendons during installation or sheaths with higher bending resistance are required, for example when empty sheaths are to be inserted into concrete. This sheath version reduces the effects of undesirable inclination deviations of the prestressing duct (wobble effect). In this respect, the values of the corrugated sheath 7211 are about three times higher than those of the standard version. Reinforcement by means of stiffening pipes is not required. For this reason, the heavy-duty version is an economical solution for tendons which are inserted after the concrete has been poured

Type 7211

Range of dimensions:
from DN 40 to DN 95 in
5 mm steps

Material:
cold-rolled strip ST 2 EN 10139,
thickness tolerance EN 10140
optionally with special treatment for temporary corrosion protection

Storage length:
5 m;
optionally with other lengths

Delivery: in bunches
with 20 pieces up to DN 55
with 10 pieces up to DN 85
with 5 pieces up to DN 95

Longitudinally welded with narrow groove, flat oval cross-section

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.

Type 7421

Material
cold-rolled strip St 2 EN 10139
thickness tolerance EN 10140
optionally with special treatment for temporary corrosion protection

Range of dimensions:
DN 40 x 21 bis DN 85 x 21

Storage length:
5 m; optionally with other lengths

Stripwound Sheathing Pipes

Design but partly also economic challenges require the use of larger tendons in prestressing. For this purpose, we offer stripwound sheathing pipes in the diameter ranges 100 mm to 150 mm. We can manufacture these sheathing pipes in wall thicknesses from 0.4 to 0.6 mm (partly 0.7 mm). They can therefore be used for almost all applications.

Type 7631

Material:
cold-rolled strip ST2EN 10139
thickness tolerance EN 10140
optionally with special treatment for temporary corrosion protection

Range of Dimensions:
DN 102 to DN 130

Delivery:
packaged in non-return
containers