Flexural-Torsional Deformations of Imperfect Thin-Walled Columns with Continuous Bracing

Columns with initial crookedness and twist are analyzed. Continuous elastic restraints resist bending and twisting as the compressive load is increased. The thin-walled columns are linearly elastic and deformations are small. Numerical results are presented for three examples of pinned columns with half-sine initial imperfection shapes. The first two are singly symmetric, a Cee section and a Tee section, with torsional bracing. Flexural-torsional coupling occurs between the twist and bending in the strong direction. The third example is a doubly symmetric I section with lateral bracing on one flange. Flexural-torsional deformation involves twist and bending in the weak direction. The effects of axial load, bracing stiffness, and relative orientations of the imperfections are investigated. Also, the stiffness required to restrict the twist to be a certain proportion of the initial twist is determined, which could be useful for designing compression members connected to sheathing.

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