A study of rectangular cross-section thin-walled beams under torsional, distortional and bimomental loads is presented. The assumed displacement field describes both torsional and distorsional behaviour, the shearing strain in the walls being taken into account. By a variational principle the equilibrium and boundary equations are derived and a physical interpretation of the natural conditions is given. A closed form solution is given with reference to the matrix form of the governing differential system together with a discussion of a sixth-order 'uncoupled' differential equation generalizing the BEF analogy. The present formulation shows that, in general, torsion and distortion are pair of coupled problems and a study of distortion without considering torsion would therefore not be legitimate. The comparison of the results predicted by the theory is in good agreement with experimental evidence. © 1990.
Mentrasti, L. (1990). Distortion (and Torsion) of rectangular thin-walled beams. Thin-Walled Structures, 10(3), 175–193. https://doi.org/10.1016/0263-8231(90)90062-4