PSI - Issue 57

Jacques BERTHELLEMY et al. / Procedia Structural Integrity 57 (2024) 872–903 J. Berthellemy / Structural Integrity Procedia 00 (2023) 000 – 000

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5.3 Change in recommendations in 2023 to re-introduce fatigue concerns It was decided to revise the recommendations so that the document to be adopted by consensus in 2023 would take greater account of fatigue. Three new main points were consensually added: • The maintenance of motorway weathering steel bridges requires much more attention than the maintenance of painted bridges. Maintenance costs are not reduced by the use of weathering steel but significantly increased, since every dust must be cleaned rapidly. Water stagnation and bird droppings are not permitted on weathering steel, for example. The result would be corrosion pits. The fatigue implications of this are discussed in section 5.5. • The Tables in Eurocode 3 Fatigue Part 1-9 that explicitly provide reductions in categories of detail that remained ignored in the 2015 French document, have been highlighted and explained. • Ludwig Kunz's work [36] on the fatigue of weathering steel was presented. The results of this work can be applied with the Clause 7.1(5) of the current French National Annex (2011) of [15] or with the future Eurocode 3 (2025) to re-evaluate some important weld categories by using the effective notch stress method of fatigue calculation. The result of patina formation is the appearance of chancroid notchs on the surface of the steel. The effect of this on fatigue is discussed in Section 5.6. 5.4 Evaluation of the Scyotte River Bridge case regarding fatigue The conditions of the two similar bridges over the river Scyotte and the river Saone, both recently built in 2017, showed that bridges made of weathering steel, and in particular the horizontal surfaces of the I -beams, require much more attention and maintenance than those made of painted steel. The large bridge over the Saône has been painted, while the bridge over the small Scyotte creek was carefully choosen for a new experimental use of weathering steel in application of the 2015 recommendations. The distance between these two similar bridges, if you set aside the anti-corrosion protection, is only about three kilometres. These bridges have helped to ensure that the revision of the recommendations has taken place in 2023. All the bird droppings that have accumulated since the bridges were built stick to the surface of weathering steal. Painted steel, on the other hand, has been made water-repellent through advances in paint technology, and rain is enough to wash off the surface and remove bird droppings.