This year 2024 we have tested 750 ground anchors; it is more of 6000 dynamic tests and more of 50 static tests. We have met numerous types of tie rods existing for 3 or 4 decades. Each new project involving old ground anchors is a highly formative adventure that leads to the re-discovery of methods that have sometimes become obsolete. The aim of these tests is to provide managers of retaining structures with the information they need to diagnose and support maintenance. Increasing the durability of these structures is at the heart of the approach. Putting the tie rods back under tension is one of the objectives, which needs to be clarified on the basis of the tests carried out.