Elastic-plastic responses of rectangular multi-cell beams under three-point bending

Thin-walled beams are widely applied in modern industrial products as structural or energy-absorbing components. They are often subject to bending loads and undergo large deformation. How to predict their elastic-plastic bending responses accurately by theoretical methods is still a quite challenging task. In this work, we propose a theoretical method to give more accurate solution on the elastic-plastic bending responses of thin-walled beams. Experimental tests of triple-cell aluminum alloy beams are first carried out, and numerical analyses are then performed. The nonlinear bending moment distribution of multi-cell beams along the span is revealed. Theoretical expressions are derived for elastic-plastic bending moments of multi-cell sections with 1 × m and 2 × m cells. The theoretical method to achieve the three-point bending responses of the multi-cell beams is then introduced, based on a large deformation three-point bending model. The conversion relations between the bending moment response and the force response are also provided. Finally, the effectiveness of the proposed method is validated by experimental and numerical results of multi-cell beams with different sectional shapes.