Life extension of pre-damaged existing crane runway girders

Crane runway girders are subjected to cyclic loading and must therefore be designed against fatigue failure. For existing structures, however, there are no standards for handling pre-damaged components at the end of their calculated lifetime. The Institute for Material and Building Research of the University of Applied Sciences Munich examines different approaches on how to deal with existing welded steel structures. The research project addresses the following questions:

How can pre-damaged components without visible cracks be strengthened?

How can components with visible cracks be repaired in a fatigue-proof manner?

How can pre-damaged components be reinforced through a low-notch application of steel cover plates?

In order to answer these questions several numerical and experimental investigations are carried out. Different innovative fastening techniques like lockbolts, adhesives and self-tapping screws for attaching reinforcement cover plates are tested on small and large specimens. Within this paper the research project will be presented and previous results on components without visible cracks will be summarized.