A modified design approach to the fatigue limit state for stud shear connectors in steel-concrete-composite members

Stud shear connectors transfer the forces from one composite layer to the adjacent one and thus represent vital elements for the load-bearing capacity of the structural member under consideration. In bridge structures, the fatigue strength of the stud shear connectors which are welded onto a steel member is especially important. Verification concepts for the fatigue strength have been developed and implemented in design codes, such as EN 1994. These design concepts generally refer to a single-stress steel-type verification format while the factual interaction of steel and concrete, resulting in flexure of the stud shear connector and in extreme, locally confined concrete pressure, is not considered widely. Studies (see Maeda et al. 1986, Leonhardt 1988 and Oehlers 1990) showed this influence to be substantial. In this paper a modified design concept considering the amplitude and mean stress level of the concrete will be derived. A concept for the corresponding application of safety factors will be provided.