Significance of distortion in thin-walled closed beam section design

Torsional and/or bending rigidities have been used as the key performance measure in conventional beam section design practice. The goal of this investigation is, however, to show that a so-called distortional rigidity also affects significantly the section shapes especially in the design of thin-walled closed beam sections. Though several investigations have analyzed complicated deformations of thin-walled beams such as distortion and warping, this paper is perhaps the first report to show how the design of thin-walled beam section shapes is affected by the additional consideration of the distortional rigidity. To illustrate this, several beam section optimization problems are considered.