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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of HFMI cannot be taken into account accordingto the 2023 draft project of the fatigue part 1 -9 of Eurocode 3 in its Annex F (Note 2, part 5). However, after about ten years it will be economically impossible to completely remove numerous pits and avoid their regarding their disastrous effect regarding fatigue.

Fig. 36: Corrosion Pit According to Lieurade Cetim / 1998 [40] The main challenge in fatigue monitoring bridges made in waethering steel is to ensure that corrosion pitting that could initiate fatigue cracks, does not occur. No serious research has been carried out on this subject: Fatigue tests after exposure to bird droppings, as in real life, are still needed. The fact that there are no proven ruins is not a proof for the future, because a rupture can occur 30 or 40 years after the construction due to the addition of the time of formation of the pits plus the time of initiation of the fatigue crack!

Fig 37-a: Pit FEM model

Fig 37-b: Pit FEM result: Map of the fatigue cracks initiation probabilities

The Effective Notch Stress Method procedure with Code_Aster provides a detail category of 60 MPa instead of 125 MPa forthe usualsteel surface.This is a reduction by a factorof about two of the same order as in 2.4 and 2.5 which confirms that the formation of such pits has to be avoided.

5.6 Fatigue behaviour of weathering steel even in the absence of pits Ludvík Kunz and al. studied chancroid notch formations at the surface of W steel in normal conditions The specimens were exposed for more than 20 years in central Bohemia in a rural countryside.