Thin-walled cold-formed built-up members are often used in rack storage structures due to their advantages such as the strength-to-weight ratio and their stability behaviour. To form such built-up sections, single sections are connected with intermediate fasteners – with or without packing plates – to prevent the single members from buckling independently. Being so, the cross-section becomes at least symmetrical in one axis. The effect of these intermediate connections is considered in some international standards such as the American and the Australian ones, but is neglected in EN 1993-1-3. The only available rules in Eurocode are found in EN 1993-1-1, but their extension to cold-formed thin-walled sections could be questionable. This paper presents investigations conducted on the validity and applicability of the existing design rules provided in EN 1993-1-1 for determining the buckling resistance under pure compression of a built-up member consisting of two back-to-back thin-walled U profiles, accounting for the effects of the shear stiffness. To achieve this, a number of parametrical numerical studies on these type of members have been conducted with ABAQUS software. The numerical results have been then compared with the analytical ones given in EN 1993-1-1. Finally, recommendations for the design of such structural elements are provided. This study takes place in an ongoing project funded by SPW project entitled ACTIONS: “Advanced Eurocodes Compliant Tools for Industrial Optimized Innovative Structures”, involving STOW group, GDTech and CRM companies, as well as the University of Liege.