For the assessment of existing riveted railway bridges, the German railway provides guideline 805 for estimating residual lifetimes and calculating safe inspection intervals. Safe inspection intervals are calculated using tonnage factor diagrams. Crack propagation calculations determine these tonnage factors within the framework of linear elastic fracture mechanics under various input configurations. These calculations are based on an assumed or measured crack and future traffic. The recent revision of the guideline, aimed at harmonization with the Eurocodes, also included a recalculation of these tonnage factors. This paper presents the methodology employed in determining tonnage factors, along with the assumed input parameters. Crack propagation calculations and two subsequent regression analyses lead to the tonnage factors and, finally, to the determination of model limitations. Resulting diagrams of tonnage factors for different fracture mechanics models and traffic compositions are presented, including curves for heavy traffic not covered by the guideline. Generally, heavier traffic yields lower tonnage factors, implying shorter safe inspection intervals. However, exceptions are noted for certain span lengths in the upper range investigated. Additionally, the assumed dynamic factors and load distribution by the rail are discussed in detail, providing comparative insights through calculations deviating from guideline 805. In summary, the revised results in this paper enable users of guideline 805 to determine safe inspection intervals without fracture mechanics knowledge, thus ensuring that potential crack growth does not lead to component failure between two inspections.
