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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However, the study of Taras and Unterweger [18] of a thickness transition could be reproduced with weathering steel. The tapering shape results could be reproduced with k inside / k outside = 1,20 which is coherent with the application of the future annex D.4 of Eurocode 3 1-9. It is clear that the web and the flange have to be butt welded when tapering inside. Two ratio of the thickness variation ( 25/48mm and 48/70mm ) were studied to demonstrate the size effect. When the thickness variation is obtained by tapering outside (Case 1), which is the case of most bridges using weathering steel built in France for low traffic carrying bridges before 2015, the influence of the chancroid notchs remains small as shown in Figure 45. The Case 2 representing the tapering inside technique of assembly of the I girder is sensible to the weathering steel chancroid notchs when the flange and the web are butt welded in the transition zone. It is for instance the case for the Scyotte Bridge.

Figure 45: Summary diagram of the results of the Effective Notch stress method for thickness transition butt welds

These results can be used to assess existing bridges, for example using a confocal microscope to determine the H/R ratio. In the absence of further statistical data, a minimum H/R ratio of 0.400 seems reasonable for the design of a new bridge, as this detail is particularly important for a twin I-girder bridge. These results are usefull to assess existing weathering steel bridges in order to decide about the opportunity of blasting the patine and repainting the exposed surfaces. It was rightly suspected that the presence of other chancroid notchs near the studied chancroid notch that was located at the hot spot point could have a favourable effect on the results. The average distance between the chancroid notchs in formation observed on the Scyotte bridge is of 5mm and has be used for this study (Figure 46).