This paper presents the results of laboratory tests and numerical analysis for plate girders with partial height end stiffeners. Design rules for rigid end posts and non-rigid end posts are given in EN 1993-1-5:2006 but the shear resistance of partially stiffened webs is not mentioned. The use of non-tightly fitted stiffeners is hazardous due to insufficient investigations of the real behaviour. To discover this problem parametric studies on beams with different web slenderness are examined with the usage of advanced numerical simulations. The accuracy of the EN 1993-1-5:2006 standard design rule for partially stiffened beams is also examined. The results of the numerical simulations shows that the shear buckling capacity of girders is lower than the design recommendation where the height of the web stiffener is 25% of the web height. For girders with full height stiffeners the EN 1993-1-5:2006 standard leads conservative results.