This paper aims at investigating the patch loading resistance of steel plate girders with triangular cell flanges. In this study, the patch loading resistance is computed nonlinear finite element analysis considering large displacements, elastoplastic material behavior, initial geometric imperfections, and residual stresses. The numerical model is validated against experimental works taken from the literature. Thereafter, an extensive parametric analysis is conducted in order to investigate the influence of various geometric parameters such as the location in the web and flange as well as the thickness of the plates that forms the triangular cells, and the panel aspect ratio on the resistance of the stiffened girders. The results show a significant increase in the resistance.