This paper presents findings from tests and numerical simulations conducted on plate girders with varying end post configurations. Although EN 1993–1–5:2024 provides design guidelines for both rigid and non-rigid end posts, it does not cover the shear resistance of webs that are only partially stiffened. Partial-depth stiffeners pose potential risks due to the limited research into their mechanical behaviour. To investigate this issue, tests and parametric studies were per-formed on beams with differing web slenderness using advanced numerical simulations. EN 1993–1–5:2024 provides reliable estimates for fully stiffened beams, while new shear buckling curves have been proposed for partially stiffened beams.