Browsing by Author "Hofmann, Gloria"

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Open Access
Influence of the geometry of butt welds and longitudinal attachments on their fatigue resistance
(2023) Hofmann, Gloria; Kuhlmann, Ulrike
Many constructions, such as wind turbines, bridges and crane runways, are cyclic loaded so that fatigue failure may occur. Therefore, in the course of the revision of Eurocode 3, two research projects funded by AiF-DASt re-investigate the classification of constructional details of EN 1993-1-9. This paper focuses on the geometrical influence on the fatigue resistance of butt welds and longitudinal attachments. First, the influence of the plate thickness on butt welds was investigated. Both a meta-study based on test results of various research projects and our own test series on butt welds up to 80 mm thickness led to interesting conclusions. Furthermore, the influence of the length and radius of longitudinal attachments on the fatigue resistance was investigated. By experiments and numerical analysis, clarification has been sought whether the transition radius larger than 150 mm or the ground weld toe is decisive for the improvement of the fatigue resistance. Since previous meta-studies could not provide a clear result on the influence of the longitudinal attachment length, this was also investigated. A database established in the projects allows to integrate and assess the specified details of butt welds and longitudinal attachments in the context of the overall approach in EN 1993-1-9.
Open Access
A statistical assessment of the fatigue strength improvement of butt-welded joints by flush grinding
(2023) Braun, Moritz; Baumgartner, Jörg; Hofmann, Gloria; Drebenstedt, Karl; Bauer, Niklas Michael; Bakhschi, Hadi; Kuhlmann, Ulrike
All major rules and guidelines include fatigue design (FAT) classes for flush ground butt-welded joints. These FAT classes vary between FAT110 and FAT155; however, in the majority of cases, the underlying database and specimen-related details are unclear or unknown. This study evaluates 1003 fatigue test results gathered from various literature sources and tries to relate the fatigue strength improvement to typical specimen types and test conditions. To this goal, statistical methods based on correlation analysis are employed. Next, proposals for updates of rules and guidelines for flush ground butt-welded joints made of steel are established by determining new FAT classes and a suitable slope exponent. In addition, an overview of design standards and recommendations is given and main influencing factors are discussed.
Open Access
Steel and composite bridges : enabling sustainable solutions
(2024) Kuhlmann, Ulrike; Arnim, Mareike von; Gölz, Lisa‐Marie; Hofmann, Gloria; Knecht, Wigand; Mönch, Simon; Pourostad, Vahid; Stempniewski, Lena
Sustainable bridges are characterised by three main aspects: saving resources by an efficient construction, allowing for a lifelong use of bridges by optimal detailing in view of fatigue and flexible design concepts for strengthening and adapting to changed user requirements. After a short introduction in the assessment of sustainability for bridges, an overview on recent bridge research in view of sustainability is given. The key point of efficient construction in future is the use of high strength steel (HSS): basic research and adaptation of rules are needed for welding of matching and mismatching connections. Joints and their relevant failure modes are to be investigated before hollow sections of HSS can be used in a wider range. And for steel and composite bridges, optimised plate buckling rules may serve for more efficiency in construction. Bridges are designed for a service life of 100 years. This can easily be achieved and even exceeded if the detailing is realised in view of fatigue. Research on welded details such as butt welds or joints of tubular bracings will be presented. Welds can be improved by post‐weld treatment such as high‐frequency mechanical impact (HFMI) treatment. Fatigue is also a key issue when steel and concrete or timber and concrete are combined for composite bridges. Reinforced composite slabs without prestressing require a fatigue verification for the transverse shear also in areas with cracked concrete. The notch forms an efficient connection in timber‐concrete composite (TCC) bridges, where, however, little has been known up to now on the fatigue behaviour.