Determination of stresses in welded connections of railway bridges with the finite element method and global-local approach

Resumo

Steel bridges are used due to their large spans with reduced self-weight, and therefore, are widely used for expanding the Brazilian railway network. However, due to the cyclic loading acting on the structure, and their limited damping capacity, the dynamic effects must be evaluated. In addition, due to the cyclic loading, the effects of fatigue must be considered. In bridges, fatigue failures account for most of the damage and collapse of structures. Thus, techniques are proposed for assessing their service life, considering fatigue failure effects. Fatigue life assessment can be performed considering the history of stresses acting on the structure, and obtaining stress history data using the finite element method yields more accurate results compared to normative methods, but it requires an extremely refined mesh to obtain adequate stress values. Therefore, this study presents a strategy for obtaining stress histories with the passage of a vehicle on a railway bridge using the commercial software Ansys Mechanical APDL v. 2020R1 and Python routines to assess the fatigue life of connections. A global-local methodology is proposed, in which a model of a bridge span using shell and beam elements is developed and subjected to the passage of a vehicle. Its displacement results are then transferred to a local connection model developed with solid elements, to determine stresses for future use in assessment of fatigue life.