Ensuring Existing Bridges are Safe and Strong with DYWIDAG Tendons
A highway bridge on an important regional highway was kept open during strengthening works thanks to DYWIDAG tendons. The new installation ensures that the bridge is safe, in line with updated standards.
The 200-metre-long highway bridge on the A46 in Germany connects the eastern Ruhr area with the Sauerland and Westphalia region. Comprised of two separate superstructures designed as a double T-beam bridge, an inspection revealed the bridge would require strengthening.
Load assumptions have been revised since the bridge was built, which meant that under the updated standards, the bridge would need to be reinforced to be considered safe. DYWIDAG was commissioned to supply and install the tendons that would provide the required strengthening. In addition, the tendons would need to be installed without any traffic restrictions on the bridge.
Wire EX tendons and unbonded bar tendons were installed. The Wire EX longitudinal tendons were arranged in pairs on both sides along the bridge beams. Some of these were anchored to the end cross-member and then to newly concreted anchor blocks. Meanwhile, 108 additional Type WS36 DYWIDAG unbonded bar tendons were used to actively tension the new anchor blocks to the existing beams and to reinforce the area of the end cross-member.
The Wire EX tendons and unbonded bar tendons were chosen for this project for several reasons. The longitudinal Wire EX tendons are prefabricated and delivered as a finished tendon on a transport drum, which avoids complex assembly work on site for a faster and less disruptive installation from below.
The unbonded bar tendons offered advantages as well. By using them in the anchor blocks, the prestressing force of the bar tendons can be easily checked at any time in the future, making inspections easier. Also, the DYWIDAG unbonded bar tendons are the only tendons on the German market that meet the requirements of ZTV-ING Part 3, Section 6, 4.3 (3) with regards to a permanently adhering, elastic corrosion protection material (shrink sleeve).
Despite the use of only mobile access solutions and the comparatively high structure height, the installation process was carried out very quickly and effectively. Traffic was able to continue using the bridge without any disruption, and the works were completed in the agreed timeframe.