Abstract
For the box beams which compose the frame structure of a vehicle, and consist of thin plates, an approximate expression are derived from the knowledgement of the shear buckling stress, and the exact expression from the energy methods under compressional force assuming the coupling of the adjacent plates. The accuracy of these expressions is investigated as compared with the results acquired in the buckling eigenvalue analysis by the finite element method (FEM). As the results, the difference of compressional buckling stresses between the approximate expression and FEM is less than about 6% as for the aspect ratio of the cross section between 0.3-1.0.
