Three-point bending collapse of thin-walled rectangular beams

Three-point bending collapse is an important energy absorption mechanism of thin-walled beams subjected to crash loads. However, currently, there are still no theoretical methods available to predict the response of the beams under such load condition due to the complicated deformation features and influencing factors. In this paper, a detailed investigation on the three-point bending collapse of rectangular beams is performed. Quasi static three-point bending tests are conducted first for thin-walled rectangular tubes. Numerical simulations are then performed by nonlinear finite element code LS-DYNA to investigate the bending responses. Parametric studies are carried out for thin-walled rectangular beams to investigate the influences of the span, the cross-sectional geometrical configurations and the diameter of the punch on bending responses. Results show that the geometrical parameters have great influence on the deformed shapes, force and bending moment responses of the beams. Finally, the bending responses of rectangular beams in experiment and simulation are compared with Kecman's model, which is proposed for pure bending. Big deviations are observed and hence a theoretical method basing on Kecman's model is proposed to predict their bending responses under three-point bending. Comparisons show that the proposed theoretical method can well predict the bending moment response of thin walled rectangular beams under three-point bending.