Fatigue of Thin-Walled Plate Girders

For thin-walled plate girders, the factors to prevent fatigue cracks due to out-of-plane deformation of the web under in-plane loading are presented. The cracks are caused by plate-bending stress which is generated by out-of-plane deformation of the web. It is shown that for girders in bending, the deformation-induced cracks do not occur below the allowable fatigue stress range for the cracks at the end of vertical stiffeners which are classified as stress category C in the AASHTO Specifications. It is also shown that for girders in shear, the shear buckling strength for a rectangular plate with simply-supported conditions along the four edges gives a conservative guideline for the prevention of the deformation-induced cracks.