箱形断面梁のねじり座屈の近似解法

概要

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Recently, high strength steel material is used increasingly for plates which constitute the frame structures of vehicles. Since these plates become thinner, the buckling on the plates has been recognized as an important issue for automotive industries. In this paper, the expression is derived to obtain simply the shear stress on plates at torsional buckling for the box beams which represent the frame structure. Assuming the deflection shape of the buckled plate simply supported on all sides and the right angle at four corners, the precise expression is derived based on the energy method. However, this expression is complicated and hard to use easily. Therefore, the approximate expression is proposed by the knowledge from the aforementioned derivation. The accuracy of that expression is investigated as compared with the results acquired in the buckling eigenvalue analysis by FEM. As the results, the difference of shear stress at torsional buckling is less than about 5% as for the aspect ratio of the cross section between 0.4 - 1.0.