Internal Unbonded Post-tensioning System Using Monostrand

For superior corrosion protection and flexible installation in constrained spaces.

DYWIDAG’s internal unbonded post-tensioning system using monostrand tendons is a high-performance solution for improving the structural integrity and load-carrying capacity of concrete structures. It is used in buildings and parking garages where there is seismic activity. This system includes tendons consisting of bundled, greased and PE-sheathed monostrand tendons, and is typically used in building construction and for transversal post-tensioning of bridges.

The system follows the anchorage principles of bonded post-tensioning, but instead of grouting with cement grout, the tendons are protected against corrosion with grease or similar corrosion protection compounds in plastic sheaths. Double PE sheathing is available when the monostrands will be replaced or to satisfy special requirements. The use of grease, wax, or gel in a plastic duct provides excellent corrosion protection for the tendons.

The internal unbonded tendons are not rigidly bonded to the surrounding concrete, which offers benefits such as a low induced stress range, less fretting fatigue, easy monitoring of stressing forces, with re-stressing and replacement of the strands possible, if required. The tendons can be checked for stressing force using lift-off tests or built-in load cells, and can be re-stressed later provided the stressing anchors are accessible.

This system provides the highest quality of corrosion protection in prefabrication applications, as the corrosion protection is usually prefabricated with the tendon, delivered to site, and installed. Additionally, the system provides more favorable conditions for decompression checks and meets requirements for crack widths as on reinforced concrete members.

  • High-quality prefabricated Monostrands do not require additional ducts to ensure corrosion protection

  • Available for use with up to 37 strands for increased load capacity and greater durability

  • Customizable system with prefabrication or on-site production possible and curved or straight tendon profiles

  • No grouting operations required on site, for faster installation times

  • Additional PE sheathing for bridges in case the option for replacement is required

  • Diameters available include: 0.6" (15.2mm), 0.62” (15.7mm)

  • PE sheathing and corrosion protection compound provided to provide optimal protection against a wide range of potential damage mechanisms

  • Replacement, restressing and coupling possible

Main standards for steel nuances

Europe/ Asia/ Latin America: Y1770, Y1860

North America: 270 ksi low relaxed strand per ASTM A416

Europe/ Asia/ Latin America: ETA-03/0036 – ETA 19/0077 – Z-13.72 (Germany) – ETA-13/0814 – Z-13.2-2-95 (Germany) – Z-13.3-135 (Germany) – ETA-30/036

Industrial Buildings
Tank & Silos
Commercial & Residential Buildings