For about 50 years prestressing steels are used in Switzerland. They are in tendons, in fitted anchors and for some years also in stay cables. The level of internal prestressing steels is important for the structural safety, serviceability and durability of the relevant building and should be detectable and assessed. The options to non-destructively determine the corrosion state of clamping and anchoring systems are still relatively limited. Corrosion damage occurred in prestressing steels can gain valuable experience through the accurate evaluation of causation.
Detection, evaluation and assessment of corrosion damage to steel tension in prestressed and anchored structures and tie rods.
Compilation, documentation and development of the tensioning and anchor systems.
In the tendons as well as in the stay cables and anchors there are system-dependent constructive, material and version-related vulnerabilities. The existing damage led to a steady improvement in the systems.
Only in a few cases a single cause was responsible for major damage or collapse. Usually only carried out the sensitivity of the design and combination of different causes to damage or failure. External hazards are the environment or usability conditions (exposure side). Internal threats include weaknesses in the design and the actual corrosion protection system of tendons, stay cables and anchors (resistance side). In most cases there was a combination of several weaknesses in the design, when existing external hazard caused damage. This results in "damage chains", which often start by tendons with bond on the building surface and thus are most "visible".
Tendons, stay cables and anchors - Description of systems and findings from corrosion damage, Department of the Environment, Transport, Energy and Communication, Federal Roads Office, Report No. VSS. 588, August 2005.