Calculatingrestrained torsion of thin-walled open-sections beams

Abstract

When the cross-section of a open-section thin-walled bar is rotated around the bar axis by an angle accompanied by warping phenomenon, if the warping is prevented, there will be normal stress and shear stress in the bar to counteract the generated torque . it is called restrained torsion. The stress caused by restrained torsion generated in many cases significantly affects the total stress in the structure. Currently, the calculation of torsion in structures is often neglected and simplified leading to inaccurate reflecction of the structure’s behavior. This article summarizes the principle of caculating the restrained torsion of the open-section thin-walled beams along provides a specific examples for channel section beam according to Russian documents [1,2] to clarify the structural behavior and provide a basis for selecting appropriate cross-sections.

Keywords: Steel structure; thin-walled beams; warping torsion; restrained torsion; bimoment.