[en] The paper investigates the shear resistance of I-girders longitudinally stiffened by closed trape-zoidal stiffeners. It first reports on 4 full-scale tests performed at RWTH Aachen, on stiffened panels with strong closed stiffeners. As expected, failure in the subpanels has been governing. A devoted FEA shell model is then described and validated towards these results and other experimental sources. Parametric stud-ies led with the numerical tool help pointing out several aspects where the Eurocode 3 Part 1.5 recommenda-tions on stiffened panels in bending and shear may be improved.