On fatigue strength of large-size bolt-assemblies in steel constructions under consideration of manufacturing and surface condition related impacts - part 1: state of knowledge

Manufacturing related impact factors significantly affect the fatigue strength of bolt assemblies used in steel constructions. The effects are taken into account very inconsistently in the design bases, depending on the normative reference used. Especially for bolt assemblies with large diameters, as they are commonly applied in large numbers at towers for wind energy plants, only a very limited experimental background for assessment of relevant impact factors has been available in the past. Part 1 of this paper presents the state of knowledge regarding the decisive influencing variables on the fatigue strength of bolts in steel structures. From this state of knowledge, the authors derive the basis for evaluating existing and (242) previously unpublished results from fatigue tests on axially loaded bolt nut connections up to nominal size M64, which are included in Part 2 of this paper. The focus is on the influence of size and surface layers, the influence of thread fabrication as well as the stress condition from the pulling assembly practice.