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Torsional buckling of a cruciform column under uniform axial compression

from: Lecture 6.6.2: Buckling of Real Structural
Elements II, ESDEP WG 6 "Applied Stability", Univerza v Ljubljani

This paragraph is included on the website: "Instability due to torsional buckling can only arise in special circumstances. This buckling type is illustrated by means of a compressed strut composed of four identical outstands, giving a cruciform section (Figure 8); each outstand is a flat thin plate, liable to buckle because of the compression loading. If such a plate was simply supported along the column axis, it would buckle so that any line OA of the outstand, perpendicular to the longitudinal edges, would remain approximately straight, though rotating about point 0. Because the outstands are identical, they should each buckle at the same value of applied stress. It is thus possible to find a form of buckling in which any cross-section of the cruciform strut does not distort, but rotates about 0. The four outstands continue to meet at right angles so that the fact that they are joined rigidly along a common edge is not significant. This form of buckling, where the strut axis remains straight but sections rotate is termed 'torsional buckling'."

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