The paper presents the results of an experimental program on welded steel I-beams, consisting of ten two-span plated girders with web stiffeners. By ar-ranging transverse stiffeners on both sides, the web was divided into four or eight rectangular sections with an aspect ratio of a/h=2.5. The h/t ratios of the web were between 175 and 350, and the b/t ratios of the flanges were between 8 and 40. During the laboratory tests the girders failed by the ten-sion field action at the internal support. In order to explore the shear buckling behavior of the tested girders geometrically and materially nonlinear anal-yses with imperfections were conducted on full-shell finite element models. Based on the validated numerical model a parametrical study was conducted on two-span beams with different geometrical parameters. With the results of the laboratory tests and the parametric study the accuracy of the shear strength formula and the interaction formula from the EN 1993-1-5:2024 is examined.