In this study, the effect of hole reinforcement on the buckling behaviour of thin-walled structures mostly used in aircrafts is investigated under combined loads. A fuselage floor beam with real dimensions is used for the buckling analysis, and a parametric study based on several loading scenarios is considered. Investigated structures include different ratios of hole diameter to reinforcement width (d/w), ratios of reinforcement height to web plate thickness (h/t), and the aspect ratio of the web plate (a/b). The material of the thin walled structure is Al 7075 series. The commercial finite element analysis program, ABAQUS, is used for buckling analysis. The loading scenarios such as compression, shear, and bending, as well as combined loading are considered using a validated finite element model. For the selected range of geometrical parameters, buckling loads and allowable buckling stresses are computed. Furthermore, compression, shear and bending rates are calculated, and the interaction curves are plotted with the help of data obtained from the finite element studies. The effect of loading scenario on the buckling strength is compared for beam without a hole, with a hole and with a hole plus reinforcement cases. The main goal of this study is to provide engineers graphical data that can be used to check whether or not a structure will fail under several defined load cases including combined loading.