Construction details of bridges often exhibit a multi-axial stress state under non-proportional fatigue loading due to the geometry and loading situation. Design models (e.g., DIN EN 1993-1-9) inadequately reflect the fatigue behavior of these structural details and loading situations and often result in non-conservative service life predictions when applied to the existing rare test data. However, the test specimens inadequately reflected the specific construction details of bridge construction.

Therefore, the currently running FOSTA research project P 1658 will carry out multiaxial fatigue tests with cross-sections and loading situations adapted to bridge construction. The two-phase model developed at the RUB will be extended for the consideration of non-proportional stresses and will form the basis for analytical-numerical simulations considering cyclic, elastic-plastic material properties. As a result, the enhanced design concepts are validated, the influence of scattering input variables is evaluated using a probabilistic model, and simplified calculation methods and design tools are developed. In addition, common construction details are assessed and, if necessary, optimized variants are developed.