Abstract
Fatigue assessment is of major importance for dynamically loaded steel structures. Increased operating loads and lightweight construction demands increase the requirements of steels considering the material strength used. Standards and guidelines specify fatigue classes for fatigue assessment that are independant of material strength, so there is no benefit regarding the use of high-strength steels in fatigue loaded structures. By using HFMI-treatment, the fatigue strength of welded joints can be increased and the potential of high-strength steels can be utilized. Therefore the research institutes involved have developed the DASt-guideline 026 which regulates the fatigue assessment of constructional details made of steel grades reaching from steel grade S235 to S700. An extension for steels up to a steel grade of S960 is pending and geometric imperfections exceeding quality level B of ISO 5817 are not covered yet.
The objective of the project is to extend the DASt-guideline 026 for high strength steels up to S960 and to investigate the influence of geometric imperfections on the fatigue strength of HFMI-treated welds. Therefore experimental investigations are carried out on constructional details with and without imperfections. Additionally various imperfections and their combinations are numerically investigated.
Previous investigations on steels up to steel grade S700 show an increasing effectiveness of HFMI-treatment with increasing material strength. Based on these investigations, the increase in fatigue strength for steel grades S700 to S960 will be quantified and the DASt guideline 026 will be extended to ultra-high-strength steels. The developed design recommendations will be verified with regard to the influence of imperfections and fatigue strength will be determined by a formula considering the extent of geometric imperfections. SMEs gain by a more economical design for fatigue loaded structures, which is enabled by the efficient use of ultra-high-strength steels.
Project Team
University of Stuttgart
Institute of Structural Design
Prof. Dr.-Ing. Ulrike Kuhlmann, Lisa-Marie Gölz, M.Sc.
Karlsruhe Institute of Technology (KIT)
Research Center for Steel, Timber and Masonry
Prof. Dr.-Ing. Thomas Ummenhofer, Dr.-Ing. Philipp Weidner
Fraunhofer Institute for Large Structures in Production Engineering IGP
Prof. Dr.-Ing. Wilko Flügge, Prof. Dr.-Ing. habil. Knuth-Michael Henkel
Project Funding
FOSTA e.V. / AiF
Project Start
01.01.2021