Theoretical and experimental study on empty and foam-filled columns with square and rectangular cross section under axial compression

This article derives some theoretical relations to predict diagrams of absorbed energy and axial force versus axial displacement during the folding process in square and rectangular columns. By considering the folding wavelength as a constant parameter during the folds creation and using balance of internal and external energy and minimum principle in plasticity, final relations are calculated. Also, two different relations are introduced to predict the maximum folding force of the empty and polyurethane foam-filled columns with square and rectangular cross sections, by considering the interaction effects between column wall and foam-filler. Furthermore, some experiments were carried out on the empty and foam-filled metal columns and the experimental measurements were compared with predictions of the theoretical formulas that showed good correlation.