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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The fatigue resistance curves of unwelded constructional details subject to normal stresses have been modified compared to EN 1993-1-9 (2005) to allow for a more efficient design. Such constructional details, including details with sharp notch effect,e.g. parent metalwith a bore hole, have a higher fatigue limit   D as the infinite life region starts already at 2 million stress cycles. Furthermore, unwelded details with light notch effect, for example the parent metal with mill scale, have a shallower slope parameter m = 5 as they exhibit a longer crack initiation phase.

3.3. Re-organisation of detail category tables

The detail category tables are the core of the nominal stress method. These tables have been completely editorially revised, as shown in Figure 6, with the more detailed illustrations in the draft standard compared to those in EN 1993 1-9 (2005). As a new user-friendly feature,an additionalcolumn with the weld symbols has been incorporated in the tables with welded constructional details to support and clarify the verbal description of the weld type.

Fig. 6. Example of a revised detail table for welded constructional details: Tab.10.4 in draft standard prEN 1993-1-9 (2022)

It is clearly stated in the draft standard that the last column of the tables only contains requirements that supplement the already existing requirements according to EN 1090-2 (2018) that, in general, have to be met by structures subject to fatigue. Therefore, the need for the weld quality B according to EN ISO 5817 (2014) is not repeated as this is a general requirement, given in Paragraph 8.2(2) of prEN 1993-1-9 (2022). Thus, only requirements that are beyond the weld quality B are mentioned in the last column of the tables (also valid for the detail category tables in annexes B and C). Lines at the bottom of the tables contain information how to treat the constructionaldetails of the table in case of hot-dip galvanizing, if necessary. This approach is already known in connection with constructional details made of weathering steels. 4. Major revision of hot-spot stress method in (Annex B) The hot-spot stress method is a local method, and the fatigue resistance can be characterised by a limited set of constructionaldetails. This method can also be used for unclassified constructionaldetails, not included in the detail category tables of the main document. The revision of this annex eliminates gaps identified in EN 1993-1-9 (2005) for computing the hot spot stress. This revision is strongly linked with the development of the new prEN 1993-1-14 (2022) that provides guidance on design assisted by finite element analysis. Together, they provide a coherent set of rules for the fatigue stress computation (given in prEN 1993-1-14), for choosing the detail category and making the