PSI - Issue 19

Mladen Lukić / Procedia Structural Integrity 19 (2019) 655–664

662

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Author name / Structural Integrity Procedia 00 (2019) 000–000

not to be on the agenda. The proposed curves can be seen in Fig. 4 reuniting the new drawings of curves for normal stresses, normal stresses in trusses and shear stresses. These drawings were included in the First draft of the new EN 1993-1-9, identified as prEN 1993-1-9 (2019).

Fig. 4. Shapes of fatigue strength curves proposed in prEN 1993-1-9 (2019)

The key benefit of this revision of fatigue strength tables and fatigue strength curves will be removing all the possible constructional detail identification doubts. Its output would be enlargement and modification of Tables 8.1 to 8.10 in EN 1993-1-9 (2005), as well as the redrawing of fatigue strength curves. 2.2.9. Sub-task 9: Execution classes Certain execution requirements are given in Tables 8.1 to 8.10 of EN 1993-1-9 (2005); however, their drafting took place before the introduction of the first version of EN 1090-2 (2008). Those requirements are generally difficult to compare to the execution classes given in the latter (the same applies for EN 1090-2 (2018)). Clarification is thus needed to check out to which extent EN 1090-2 (2018) rules are sufficient or whether modified execution requirements, in line with execution classes (for welded structures together with revision of EN ISO 5817 (2014)) and of fitness-for-service criteria, need to be developed. An important point here is to determine the basic execution class necessary to obtain detail categories in the fatigue strength tables. Different parts of Eurocode 3 do not have the same opinion on that question. The dominant idea seems to be that EXC3 is needed, but some parts as well as EN 1090-2 (2018) consider that for some detail categories EXC2 would be sufficient. This topic is only at the beginning of its consideration. The key benefit is expected to be harmonization of execution and design by taking into account execution classes for constructional details subjected to fatigue in their classification. Something like that has already been done in EN 1999-1-3 (2007). Its output would be clarification and modifications of Tables 8.1 to 8.10 in EN 1993-1-9 (2005) in respect to execution. 2.2.10. Sub-task 10: Multi-axial fatigue There is a rule in EN 1993-1-9 (2005) for the combination of normal and shear stress ranges which differs from rules given elsewhere (e.g. IIW, DNV). Recent research could provide a more consistent and harmonized approach for the combination of stress ranges. New information on multi-axial fatigue rules need to be brought in line with the corresponding sections in EN 1993-2 (2006) and EN 1993-6 (2006). The fundamental work of this sub-task is expected to be undertaken by others. The Project Team will only need to review and incorporate this material into the subsequent drafts of the standard, adapting it when necessary to ensure that it is consistent with the rest of its work. The key benefit is expected to be an improved multi-axial fatigue verification criterion (or criteria) to avoid unjustified oversizing or useless expenses. Its output would be modification of the current clause and new clauses if needed.