PSI - Issue 57

Philipp Ladendorf et al. / Procedia Structural Integrity 57 (2024) 589–597 Ladendorf, Herion, Winkler, Dürr / Structural Integrity Procedia 00 (2019) 000 – 000

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The mean fatigue strength of the fatigue tests is shown in Fig. 10, confirming the numerical results regarding the conventional RHS-K-joint (series G) and the variants 1 and 2, which both show a higher mean fatigue strength. Variant 3 shows a slightly lower mean fatigue strength than variant 2, mainly due to irregularities caused by the weld quality and a lack of penetration in the vicinity of the slotted braces, where a fatigue crack growth originated from the weld root. The potential of the gusset-plates is represented by test series F and the truss specimens, which contained outward running weld seams at the ends of the gusset-plates. This led to a relocation of the Hot Spot in the area in front of the stiffness transfer caused by the gusset-plate. To investigate the fatigue crack behavior of the weld root and the potential of in- and outward running welds, a succeeding research project is about to start at the end of the year 2023. But as conclusion, gusset-plate variant 2 shows an adequate fatigue strength when compared to the necessary fabrication effort. 5. Conclusion This paper presents the results of a systematic numerical parametric study conducted on five RHS-geometries and three CHS-geometries containing three variants of gusset-plates in direct comparison to the same conventional K-joint geometries. Moreover, the experimental results of the underlying research project P1442 are presented. The numerical study shows the beneficial use of gusset-plates for the load-cases AX and IPB for most of the investigated RHS-K-joints. Since the investigated CHS-geometries already show a lower SCF-level for the conventional K-joint, the benefits of using gusset-plates at CHS are not as high as at RHS. The experimental results, expressed as mean fatigue strengths, confirm the results of the numerical investigation. Since the weld quality of some single joint specimens left room for improvement, the use of outward running welds of the truss specimens showed great potential. This potential is going to be investigated in a succeeding research project with the goal of optimized weld seam geometries for the common fatigue detail longitudinal stiffener as well as for shape-optimized hollow section X- and K-joints. Acknowledgment We gratefully acknowledge the Research Association for Steel Application (FOSTA e.V.) for funding the project P1442/32/2019 S 0024/10258/19 via the Foundation for Steel Application Research. The project has been carried out at the Centre of Competence for Tubes and Hollow Sections (CCTH), Karlsruhe and at the University of Applied Sciences, Munich. Special acknowledgement is given to the hollow section suppliers for providing the materials, the manufacturing companies for fabricating the specimen and for the invaluable and fruitful discussions with all members of the project committee during the various project meetings. References Herion, S., 1994. Räumliche K-Knoten aus Rechteck-Hohlprofilen, Dissertation, Universität Karlsruhe. Herion, S., Hrabowski; J., Ummenhofer, T., Ladendorf, P., Pijpers, R., 2020. Erweiterung der Ermüdungsbemessung von K-Knoten mit Spalt aus RHP und KHP auf hochfeste Stähle und dickwandige Profile”, Abschlussbericht FOSTA P 1132, Forschungs ereinigung für Stahlanwe n dung e.V., Düsseldorf, ISBN 978-3-946885-73-3 Herion, S., Fleischer, O., Hrabowski, J., Raso, S., Valli, A., Mastropasqua, A., Bononi, E., 2017. Laser Tube Cutting – comparison of new types of K-joints and their SCF with standard solutions. 16th International Symposium on Tubular Structures (ISTS 2017), Melbourne, Australia. CRC Press Balkema, Leiden, The Netherlands, pp. 215-222. Herion, S., Fleischer, O., König, D., 2014. Comparison of different configurations of thick-walled K-joints with gap made of RHS and CHS. Proceedings of the 24th International Offshore and Polar Engineering Conference. Busan, Korea. Herion, S., Hrabowski, J, Ladendorf, P., Dürr, A., Winkler, M., 2023. Erhöhung der Ermüdungsfestigkeit von Hohlprofilanschlüssen aus hochfesten Stählen durch formoptimierte Knotenbleche, Abschlussbericht FOSTA P 1442, Forschungsvereinigung für Stahlanwendung e.V., Düsseldorf, final release pending. X. L. Zhao; S. Herion; J. A. Packer, 2002. Design Guide for circular and rectangular hollow section welded joint under fatigue loading / CIDECT - Comité International pour le Développement et l ’É tude de la Construction Tubulaire, TÜV-Verlag.