PSI - Issue 57

Mladen Lukić et al. / Procedia Structural Integrity 57 (2024) 550 – 559 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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• Partial factors : update of the partial factors based on a recent study (Maljaars et al., 2021) where the partial factors were calibrated so that fatigue verifications for Fatigue Load Models from EN 1991-2 (2003) – FLM4 for road bridges and LM 71 for railway bridges, using the Eurocode's tri-linear fatigue resistance curve – meet the target reliability values set by EN 1990 (2002). The resulting values of the global safety factor can be interpreted as showing uncertainties both on the traffic action effect – the partial factor on traffic action effect is currently equal to unity – and on the resistance. It was decided within TC 250/SC 3/WG 9 to keep the existing values of partial factors for fatigue resistance, especially as these factors are valid for all types of structures while the calibration has been done for road and railway bridges only. On this basis, Table 1 gives the recommended values of the partial factors for fatigue resistance with the adaptation to three consequence classes from EN 1990 (2002). In all cases, the consequence of failure of a structural detail should be deduced from its ultimate consequences: failure of the entire structure or not. The different application parts of Eurocode 3 need now to confirm the current value of the partial factor on fatigue action effect, or provide a new value for this factor. Table 1. Recommended values of the partial factors for fatigue resistance Design concept Consequence of fail Low consequence Medium consequence High consequence Safe life 1,15 1,25 1,35 Damage tolerant 1,00 1,15 1,25 • Hot-dip galvanizing : inclusion of the recommendations forsteel structures with hot-dip galvanizing (see Figure 3 for example) applying the nominal stress method. The particular provisions for such structures are given in the detail category tables for the nominal stress method, similar to design rules for weathering steels.

Fig. 3. Hot-dip galvanized structure (www.feuerverzinken.com)

• HFMI : inclusion of the recommendations for welded joints subjected to High Frequency Mechanical Impact (HFMI) treatment applying the nominal stress method. The particular provisions for such joints are given in Annex F. 3. Modifications of nominal stress method (main document)

3.1. Clarification of stress calculation

The calculation of nominal stresses has been improved in prEN 1993-1-9 (2022) to avoid misinterpretations, in particular for welds. The misleading illustrations in EN 1993-1-9 (2005) have been reworked. In contrast to the directional method of EN 1993-1-8 (2005), the relevant weld stresses  wf and  wf for fatigue have to be calculated at the weld throat that has been projected horizontally as shown in Figure 4. New rules explaining how to calculate the