Torsion of restrained thin-walled bars of open constant bisymmetric cross-section

Elastic and geometric stiffness matrices were derived using Castigliano’s first theorem, for the case of torsion of restrained thin-walled bars of open constant bisymmetric cross-section. Functions which describe the angles of torsion were adopted from the solutions of the differential equation for restrained torsion. The exact solutions were simplified by expanding them in a power series. Numerical examples were taken from Kujawa M 2009 Static and Sensitivity Analysis of Grids. . . 97, GUT Publishing House, and Szymczak C 1978 Engineering Transaction 26 323. Convergence of the solutions was analyzed using the matrices derived for torsion angles, warping, bimoments and critical forces.