Fatigue behavior of gusset plates subjected to out-of-plane distortions

Numerous bridges have used comparable lateral connection plates welded to either the web or flange to connect the lateral bracing system to the longitudinal girders. Cracks are known to grow in the weld end and the gap of the gusset weld. This condition is complicated by the high residual stresses developed in these severely restrained configurations and also by out-of-plane movement caused by the lateral bracing system. We have tried to evaluate the fatigue strength of several of these welded attachments and also to determine whether or not they can be affected by lateral constraints. It was found that the connecting lateral bracing to the web gusset had no influence on its fatigue behaviour. There was no detectable effect of connecting the lateral bracing members to the flange gusset plates. The effect of secondary stresses and displacements in the girder web due to lateral bracing connected to the gusset plates was insignificant as was the relative stiffness of the lateral bracing system.