A global analysis of a rack frame conducted using the Generalised Beam Theory (GBT) is presented. This study specifically focuses on a down-aisle frame, showing the particular characteristics of this type of structure, such as its perforated columns, semi-rigid joints, and significant second-order effects. The single-column simplified approach is applied, meaning that the entire rack is modelled with one single column and its adjacent half-beams. This approach substantially reduces modelling time and allows for very quick parametric studies while adequately reproducing the general 2D down-aisle behaviour. The GBT single-column model is first verified against a similar single-column shell finite element model used by the authors in previous research. Afterwards, the model is applied to study the effects of various factors influencing the results of a rack global analysis, including perforations, imperfection magnitudes and combinations, and sectional deformations. The nature of GBT allows for deriving clear conclusions on the influence of these aspects on structural behaviour. Furthermore, this article also aims to demonstrate the potential advantages of the theory for performing global analyses of these structures in both research and design.