PSI - Issue 57

Gloria Hofmann et al. / Procedia Structural Integrity 57 (2024) 452–460 Hofmann, G.; Bartsch, H.; Kuhlmann, U.; Feldmann, M.

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in which the FAT class (or DC) of a detailwith several imperfections can be determined using a combination formula (Bartsch, 2023) In this way, the costly remanufacture of imperfect welded members can be avoided, resources can be saved and an important contribution to sustainability in steel construction can be made. 5. Conclusions and outlook The paper discusses different investigations regarding several influences on the fatigue resistance of important steel details, especially in view of the development of the new version of prEN 1993-1-9. The following main results can be summarized: 1. The experimental results on butt-welded joints both unmachined and ground flush show no statistical influence of the plate thickness, all tests within individual series have comparable fatigue strength regardless of the plate thickness. 2. Since the fatigue strength for the longitudinal attachments with a radius of r = 80 mm is the same as with a radius of r = 150 mm, the improved better detail category of 80 can therefore also be applied for smaller radii, as long as the end of the attachment is fully welded through and the transition ground flush. This allows material and weight to be saved and offcuts to be avoided. It is also possible to improve the detail category in general for longitudinal attachments with fully penetrated welds and weld transition zones ground flush. 3. Lack of penetration and root fusion are negligible in the load-carrying cruciform joint as long as the decisive detail is the weld toe. The weld root is then not decisive. For this purpose, a limit function can be defined depending on the weld geometry, above which a toe failure is to be expected and the root failure can be neglected. 4. In the case of transverse stiffeners (non-load carrying joint), even large air gaps in the form of the incorrect root gap for fillet welds show no negative influence on the fatigue strength. Based on these investigations, further analyses are planned for the future. To verify, whether the radius at the attachments ends can be omitted completely, the series of tests might be completed with attachments that are rectangular but still welded through and ground flush at the transition zone of the weld. In future releases, the fatigue class combination model (FCCM) (Bartsch, 2023; Bartsch & Feldmann, Fatigue Verification Concept for Details containing Weld Imperfections,2023) which is used to combine several imperfections in one DC, will be discussed in detail. Investigating important influences on the fatigue strength will continue to be an important field of research in steel construction in the future in order to make current regulations more economical and sustainable. 6. Acknowledgements The studies presented were carried out on in the frame of investigations in the research project (Feldmann, et al., exp. 2024). The project of the German Committee on Steel Construction (DASt) in cooperation with the Research Association for Steel Applications (FOSTA) was funded by the German Federation of Industrial Research Associations (AiF) within the framework of the program for the promotion of Industrial Collective Research (IGF) of the Federal Ministry for Economic Affairs and Energy. The research institutions would like to express their thanks for this. The contents presented here are also part of the dissertation by (Bartsch, 2023) and (Hofmann, in preparation) which are currently in progress. References Bartsch,H. (2023). Zum Einfluss von Schweißnahtimperfektionen auf die Ermüdungsfestigkeit von Stahlbauteilen - Dissertation (working title; in preparation). Institute of Steel Construction - RWTH Aachen University. Bartsch, H., & Feldmann, M. (2021). Numerical and databased investigations on the fatigue resistance of load carrying cruciform joints with gaps. Journal of Constructional Steel Research, 185 , 106843. doi:https://doi.org/10.1016/j.jcsr.2021.106843 Bartsch, H., & Feldmann, M. (2022). On the impact of undercuts and lack of penetration of cruciform joints from