This paper presents the findings from experimental tests and numerical simulations on plate girders with various end post configurations. While EN 1993-1-5:2024 provides design rules for both rigid and non-rigid end posts, it does not address the shear resistance of partially stiffened webs. The use of partial-depth stiffeners faces risks due to the lack of thorough investigation into their mechanical behaviour. To explore this issue, small numbered experimental tests and large numbered parametric studies on beams with different web slenderness were conducted using advanced numerical simulations. The results indicated that the shear buckling capacity of girders is lower than the design recommendation when the web stiffener height is <50 % of the web height. For girders with full-height stiffeners, EN 1993-1-5:2024 yields safe results. The accuracy of the EN 1993-1-5:2024 design rule for partially stiffened beams was also evaluated and new and shear buckling design curves were proposed for girders with partial-depth stiffeners.