Fatigue management of the Midland Links, UK steel box girder decks Available to Purchase

The Midland Links motorway viaducts, carrying the M5 and M6 around Birmingham, UK have been subject to a regular programme of assessment, repair and strengthening since 1989, after corrosion problems, primarily due to chloride contamination, were first detected in 1979. A number of the longer spans comprise multiple steel and concrete composite box girders and some of these superstructures are supported by steel box girder cross-beams. Assessment showed areas of very high overstress in the web plate at the locations of internal bracings. These overstresses affected ultimate, serviceability and fatigue limit states and arose because of poor detailing of the cross-braces and stiffeners. Acoustic emission sensors were installed to determine if the predicted fatigue activity was actually occurring and elastic shell finite-element (FE) modelling was undertaken for an improved determination of stresses. Plastic redistribution was considered to demonstrate adequate ultimate limit state (ULS) performance and an analysis was undertaken with potential fatigue damage modelled to prove the structure would not collapse with such damage at the ULS. In situ strain monitoring was undertaken to calibrate the FE results, improve the predicted fatigue life and allow preparation of a long-term strategy for managing and monitoring fatigue activity using a damage tolerant approach.