Buckling and post-buckling behaviour of selected cold-formed C-beams with atypical flanges

The paper deals with cold-formed C-beams the cross-section of which is modified when compared to a classical one. The reason of the modification was to increase the stiffness of the beam as well as to increase its buckling and limit load. Different shapes of flanges were proposed in order to investigate their influence on the buckling load, buckling shape and the limit load of the beam. The main investigation was performed with the use of the finite element method thanks to which the models of beams with different cross-sections and of different thickness and length could be taken into account. Linear and non-linear numerical calculations were conducted. Additionally the beams with selected cross-sections have been manufactured and investigated experimentally. The results obtained this way serve as a reference point for the numerical results. Based on the results obtained from numerical investigation it can be seen that the modification of the flange may increase the buckling and limit load of the beam significantly. Moreover, the analysis of these values reveals that after the loss of stability the beam may bear the load which is larger than the buckling load up to 50% before the limit load is reached. The discrapencies between the results of FE analyses and the experimental data are acceptable and are discussed in the manuscript. Some indications for further investigations are provided.