Re-anchoring during severing of historical tendons

Prestressed concrete bridges are increasingly being dismantled in Germany. The problem here is usually the insufficient knowledge of the properties of the materials used. In particular, it is difficult to determine the condition of the tendons and the grouting. In the course of dismantling, the cutting through of tendons away from the coupling joints can be advantageous for construction-related reasons. A prerequisite for ensuring the structural safety of the dismantling section is successful bond anchoring of the tendons with the surrounding grout, the duct, and the concrete. In addition to a good condition of the tendons and the grouting, sufficient knowledge of this bond behavior is therefore essential. However, information on the bond properties of the prestressing steel used in the Unterrieden viaduct could hardly be found in the literature. For this reason, investigations were carried out during the dismantling of the Unterrieden viaduct to determine the condition of the tendons. This included strain recovery measurements to determine the existing prestressing and tensile tests on prestressing bars, which were removed from the structure subsequent to the strain recovery measurements. Furthermore, bond specimens were taken from the bridge and tested in the laboratory in order to draw conclusions about the anchorage behavior of the tendons. These investigations are intended to verify the assumptions made in the dismantling planning.