Maintenance and inspection of stay cables using prestressing steel at a German bridge

In the past all large stay cable bridges in Germany were built with locked wire ropes. For a new project, Ziegelgraben-Bridge crossing the "Strelasound", the contract award also had allowed offers with stay cables using prestressing strands for tendoring. Before executing the bridges with stay cables using prestressing strands special requirements for the life time of the bridge were defined to ensure the durability and sustainability of the structure. The exchangeability of a stay cable as well as of a single strand has to be possible. The possibility for load measurements has to be given. Ducts and corrosion protection systems shall be visitable. Exchangeability had to be verified with special tests. For load measuring direct (lock-off-test) and indirect methods (vibration analysis) were applied. For vibration analysis reference measurements were performed after completion of the bridges. As most of the ducts of stay cables using prestressing steel have an outer helix to reduce vibrations common methods for visual inspection with cameras had to be modified. After the test methods had been planned a maintenance manual was created which defines the inspection periods as well as type and number of tests for the inspection period. By this an effective maintenance of the stay cables with adequate durability and safety shall be guaranteed.