The paper considers the elastic critical load of longitudinally unstiffened I-girders subjected to a localized load of variable length in the plane of the web. In the current regulations, the contribution of the patch load length and the flange thickness is not considered for calculating the elastic critical load. The influence of the boundary conditions on the vertical edges of the loaded panel on the value of the buckling coefficient is presented. An improved expression for the calculation of the buckling coefficients of longitudinally unstiffened I-girders is proposed
