Derivation of a new fatigue class for top flange to web junctions of runway beams

In the course of the European standard harmonization the introduction of the Eurocodes in the technical approved area for steel construction led to a significantly more conservative classification regarding fatigue failure, especially for flange to web connections of runway beams in heavy smeltery cranes compared to former design experiences such as from DIN 18800 and DIN 4132. Actually these changes would lead to a doubling of the cross-sectional thicknesses, which e.g. also can result in web plates with extreme thicknesses of 80 mm. Execution as well as monitoring of such flange to web connections using full penetration teebutt welds are quite critical and could no longer be realized economically. Encouraged by the operators of such constructions and crane installations from the metallurgical industry, the aim was therefore to devise an amendment to the correspondent actual fatigue classification in the Eurocode. The basis for these efforts are crane runway girders designed according to the "old standard" and their damage behaviour for the notch detail "concentrated wheel load" at the upper neck weld. Some of these girders have been in use for decades and usually show no damage for this connection type, if the design is suitable according to previous standards. The investigations were accompanied by numerical simulations. The results are closing the experimental gap that has been existing and that so far has been bridged by experience and interpretation of single test results, justifying a modification of the rules in EN 1993-1-9 Table 8.10. 2019 The Authors. Published by Elsevier B.V.