Geometrical imperfections of compressed chords in truss girders generate loads on the transverse roof bracings which are connected to the truss girders. The real distribution of this load is contrary to the model presented in the EN 1993-1-1 standard. The influence of the shape of the truss girder with geometrical imperfections on the load of transverse roof bracing has been numerically analysed in this article. The most commonly used shapes of truss girders as well as selected geometrical parameters have been considered. The obtained research results were used to determine the load acting on roof purlins and bracing rods in a typical hall structure.