ABSTRACT
This article will describe the latest developments in external post-tensioning (PT) tendon replacement. Before updated grouting specifications and standards were issued and implemented, grouting of external PT tendons could lead to an increased risk of the occurrence of defects such as voids and inhomogeneous grout quality. These defects can lead to corrosion of the high-strength strands which can cause broken tendons. Once a broken tendon is found in a structure, inspections are carried out which might conclude to replace existing external tendons that are of insufficient load capacity.
The article will particularly focus on current de-tensioning techniques to de-tension existing tendons. External PT tendons inside concrete bridges can differ in size, number of strands per tendon, and in length. The larger the size and the longer the tendon, the more energy is captured in the tendon and special care needs to be taken to de-tension the tendons safely. Different de-tension techniques will be described as well as a specialist high-speed dynamic analysis to simulate the behaviour of the tendon in case of sudden release with the large stored energy.
In countries such as the US, France and the UK, grouting defects have gotten a lot of attention for some time. We now see also more and more projects in other countries around the world where tendon replacement is required. Actual project examples will be described in the article.
