PSI - Issue 38

Jacques Berthellemy et al. / Procedia Structural Integrity 38 (2022) 428–446 Jacques Berthellemy / Structural Integrity Procedia 00 (2021) 000 – 000

432

5

1.3. Other examples Use of weathering steel for bridges

In the case of box girders, weathering steel can be used as soon as the the bridge is far enough away from the sea. However for Double-I bridge decks the effect of pits of corrosion due to birds nesting on the flanges can create stress concentrations and initiate fatigue cracks [11]. The prudent 1985 French recommandations [12] were changed in 2015 [13] by the same bureaucrats without serious consideration for the fatigue question. Of course, I am in favour of using weathering steels but with precautions in case of 2xI girders and heavy motorway traffics. Examples of poor fatigue design for a I-girder bridge For the following A1 overpass near Paris presented in Fig. 7, both Professor M. Virlogeux and I recommended a box girder bridge. I-girders were however adopted. The number of spans is different for each girder. Among other problems e.g. at the intersection of longitudinal and transversal flanges, this mechanical schema leads to important thickness transitions for girders with limited spans. W. Hoorpah notes in [14] that he was in the contractual obligation to justify the cope hole detail in Fig. 8 according to the 71 MPa class category.

Fig. 7: Wrong and right conception for the A1 overpass. The box solution was actually built in Avignon. The central box girder solution was considered impossible by the local administration, but could be built shortly after at an other place facing a similar problem. However, many other bridges were built later with important thickness transition coinciding with a cope hole, then in this case according to [15 ] at 3.2.3 “no evidence exists according to the Eurocodes for an additional penalty of the thickness transition”. The only “penalty”, which in other word s the only stress concentration factor recommended in 1996 was the effect of the eccentricity of the flange put in evince by P. Corfdir in [16].

Figure 8: A1 Overpass and its important thickness transitions at a cope hole built in 1991.