Mr. Mattias Clarin is a Senior Design Specialist at Knowledge Service Center, SSAB Special Steels. He has an M.Sc. in Civil Engineering and a Ph.D. in Steel Structures from Luleå University of Technology. He has a background in design of steel structures with focus stability phenomena. The doctoral thesis was focused on Local Buckling and Patch Loading. During his +10 years at SSAB he has been supporting customers on how to use high strength steels of SSAB in the best way. This focusing on Fatigue (dynamic) and Static design, as well as general know-how and the approach to perform high stress design. He has more than 15 years of experience in education and research work in the field of Steel Structures. The education for external customers and internal employees and both national and international research work. He has a solid interest in helping and supporting customers by sharing knowledge and being a speaking partner in development work.

Preloading, or potential overloading early in the fatigue spectrum, may redistribute the local residual stress at the weld due to the stress concentration caused by weld geometry, thereby altering the joint’s fatigue strength. This study investigates the effect of preloading on the fatigue life of non-load-carrying circular flat studs made from S960 steel. Nominal preloading up to the material’s yield strength was applied to induce plastic deformation in the weld transition area. The preloaded specimens were then subjected to constant amplitude fatigue testing, and the results were compared with the fatigue life of specimens without preloading. The results indicate that preloading improves fatigue life, demonstrating a clear relationship between preloading and fatigue strength, which also highlights the benefits of high-strength steel in welded structures subjected to fatigue.