External Unbonded Post-tensioning System Using Strand

Efficient strengthening and repair without disrupting the existing structure.

Our external unbonded post-tensioning system using strand tendons is the perfect solution for infrastructure projects that require strengthening and repair. This versatile system features tendons that are guided outside the concrete cross-section and either run straight between the end anchorages or are deflected at cross beams, saddles, and other structural components.

Our system is designed for maximum performance and durability, featuring individual PE-coated strands which are bundled in a PE pipe or wire bundles in grease-, wax- or gel-filled sheaths. This ensures that our system provides long-lasting protection against corrosion and requires minimal maintenance over time.

One of the key benefits of our external unbonded post-tensioning system is that the tendons are solely connected to the structure in the anchorage and deviation zone; there is no rigid bond to the surrounding concrete. This offers several benefits, including a low induced stress range, less fretting fatigue, easy monitoring of stressing forces, and the ability to re-stress or replace the tendons if required.

There is a growing trend of using epoxy filled and coated strands in external post-tensioning tendon. It provides higher durability and fatigue resistance. The tendon can be inspected inside the box of bridge easily and can be replaced easily.

Our system also meets the requirements for crack widths as on reinforced concrete members.

  • Available for use with between 3 and 55 strands for increased load capacity and greater durability

  • Tendon diameters of 0.6" (15.2mm), 0.62” (15.7mm) available

  • Anchorage zone without helix possible, for easy connection of the tendon to the anchorage, and reduced likelihood of damage to the helix during installation

  • Tendon profile can be straight or curve

  • Tendons are inspectable, providing good structural monitoring options

  • On-site production of even very long tendons possible

  • Electrically isolated version available for improved safety

  • Stress measurement with DYNA Force® possible

  • Corrosion protection provided by filling with flexible filler, and cementitious grout in a PE-duct

  • Replacement and re-stressing possible if filled with flexible filler

Main standards for steel nuances

Europe/ Asia/ Latin America: Y1770, Y1860

North America: 270 ksi low relaxed strand per ASTM A416 and ASTM A882 for epoxy coated strand