Derivation of Torsion Formulas for Multiply Connected Thick-Walled Rectangular Sections

The paper presents an approximate theory leading to expressions relating torque, shear stress, and angle of twist for the torsion of multiply connected thick-walled rectangular hollow sections. Simple formulas are derived for singly connected sections which are shown to be reasonably accurate for design purposes. In the Appendix, a numerical example illustrates the application of the theory to a multiply connected section.