| Abstract: | Influence of wall thickness on the fatigue behaviour of welded X‐joints of circular hollow sections. The current version of EN 1993‐1‐9 stipulates different notch classes for the design of fatigue loaded constructions based on the nominal stress concept. Annex B of EN 1993‐1‐9 also outlines the design referring to the structure stress concept, but includes no specifications for the evaluation of the structural stresses (e. g. extrapolation path) nor detailed classification for specific fatigue loaded hollow sections. More extensive specifications for the application of the structure stress concept with detailed calculation formulas graphs and extrapolation points are given in CIDECT‐Design Guide No. 8, for example. For the design of such welded steel constructions for fatigue, there are different methods, that can be applied. In order to handle the size effect, different recommendations can be found in literature to reduce the predicted fatigue life of plates and tubes with increased thickness. For example in the current DIN EN 1993‐1‐9 wall thickness correction factor for plates exceeding t > t0 = 25mm is given, i. e.: SR = SR,D (to/t)0,25. For welded hollow sections, DIN EN 1993‐1‐9 limits the range of validity to wall thicknesses t ≤ 8mm and 12,5mm respectively and the diameters of circular hollow sections to d ≤ 300mm and to edge length of rectangular hollow section b ≤ 200mm. In the scope of the FOSTA research project P 801, the Labor für Stahl‐ und Leichtmetallbau of the University of Applied Sciences Munich, conducted investigations on different notch cases of welded hollow sections with the outcome of assessing the influence parameters of welded hollow sections. |
