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. Fatigue evaluation of the use of weathering steel for bridges 5.1 Presentation of the weathering steels and of their use in France

According to standard NF EN 10025-5 [32], steel with improved resistance to atmospheric corrosion, also commonly known as weathering steel, is a steel to which a certain number of alloying elements, such as phosphorus, copper, chromium, nickel and molybdenum, have been added in order to increase its resistance to atmospheric corrosion by the formation of a self-protecting oxide layer on the base metal under the influence of atmospheric conditions. In the future, new alloys based mainly on steel and nickel are likely to be developed that will have a much better ability to form a protective patina than current weathering steels, but without the cost and difficulty of welding stainless steels. Present weathering steels are not new. The first experimental use of weathering steel on the French road network dates back to 1970 with the Treignac bridge in Corrèze. The Quarouble bridge ( Figure 30 ), which carries the A2 motorway near Valenciennes, was part of an experimental research programme launched in 1970 at the request of the steel industry [33] and could have provided information on the real fatigue behaviour in situ of weathering steel, but it was repainted in the late 1980s without any complaint from the steel industry.

Fig. 30: Quarouble bridge : former experimental W-steel bridge chosen for its redundancy after being repainted. The painting was decided to ensure fatigue reliabilty of the bridge during the late 80's. From the 80s to 2015, at the same time when the Quarrouble bridge was repainted as a precautionary measure: • Because the formation of a patina modifies the surface of the steel, it was mainly as a precaution against fatigue that weathering steels were banned in France between 1985 and 2015 for road bridges carrying heavy traffic and motorways [34]. • However, weathering steels were not banned for low traffic bridges where fatigue is not an issue, and many were built, such as this bridge over the River Gardon, designed by the authorof this article. It was built by the Richard-Ducros company in 1988.