External Unbonded Post-tensioning System Using Threadbars

DYWIDAG’s external unbonded post-tensioning system using threadbars is an effective solution for strengthening a wide range of constructions. This system is particularly well-suited for strengthening against shear stress, with bar tendons arranged vertically outside the webs to replace missing stirrup reinforcement as needed. It is also commonly used for enhancing shear load capacity in bridges, pier caps and base anchorages, and the stressing of deviators and anchor blocks for longitudinal strengthening.

This system is also used for temporary applications such as pier head strengthening and bearing replacement, as well as for the temporary support of high loads.

Our system features two types of threadbars: WR bars with continuous hot-rolled thread, and WS bars with cold-rolled thread at anchorages and couplers. This allows for greater flexibility in design and installation, and ensures a high level of performance and durability. In addition, the bars can be re-stressed to maintain their original design capacity and extend the structure’s service life.

To protect against corrosion, we offer several options for our unbonded bar tendons, including injection with corrosion protection wax or cementitious grout, or heat shrink sleeves or DYNA Protect® bar (a double-layer, machine-wrapped corrosion protection tape), both supplied with PE ducts. This ensures that our system provides long-lasting performance and requires minimal maintenance over time. The maximum corrosion protection quality is achieved through prefabrication, which is an option for all corrosion protection options. However, on-site options are also available.

  • Threadbars available from 1'' (18mm) to 3'' (47mm)

  • Mainly suited to applications where the tendon profile is mostly straight

  • Low slip anchorages for low losses of pre-stressing force

  • Bars can be monitored with DYNA Force® monitoring , providing good structural monitoring options

  • Several corrosion protection options available depending on the application: heat shrink sleeve or DYNA Protect® Bar and PE duct; injection with corrosion protection with flexible filler, or injection with cementitious grout after stressing. For prefabricated options, factory controlled grouting with cementitious grout (DCP) is available.

  • Replacement, re-stressing and coupling possible

Main standards for steel nuances

Europe/ Asia/ Latin America: Y1050

North America: Grade 150 ksi

Europe/ Asia/ Latin America: ETA-05/0123, Z-13.72-50123 (Germany)

North America: Florida DOT approval. Post-Tensioning Institute System approval in progress