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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The principles of 3D-volume modeling presented here were developed at Cerema for the European research program Precobeam. These principles made it possible to find by calculation the classes of fatigue of the Eurocodes based on experimental results as presented in [11,12,13,14]. It produces good results for fatigue classes under 71 MPa. In this case the class of detail is obtained with the Woehler model used in Eurocode 3, EN 1993-1-9 [15] represented by equation (1):

( eq. 1 ) where p is the probability of crack initiation during the used cycle and 100 MPa is the stress range of the cycle presented in Figure 5. 2.3 Recalculation example of poor fatigue design using cope holes Several bridges were built after 1987 with important thickness transition coinciding with a cope hole, then in this case according to [16] 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 words the only stress concentration factor recommended in 1996 was the only effect of the eccentricity of the flange according to P. Corfdir in [17]. Right category of detail was proposed by Taras and Unterweger [18] and adopted in Eurocode 3. These formulae are not valid in the case of cope holes. Fatigue damage in the particular case of cope holes has recently been calculated using the "hot spot stress method" [19]. Fatigue damage was assessed according to various parameters, in particular variation in the thickness of the bottom flange.

Figure 6: A1 Overpass and its important thickness transitions at a cope hole built in 1991.

2.4 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 the author and the present paper recommended a box girder bridge as it was explained later in [20],[21],[22]. 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 transverse flanges, this mechanical schema leads to important thickness