Non-linear non-uniform torsion of thin-walled beams

A theoretical and experimental investigation is made to study the non-linear behaviour of thin-walled elastic beams of open sections subjected to non-uniform torsion. The differential equations describing the behaviour and the associated boundary conditions are presented. A perturbation solution is carried out to obtain the torque-rotation characteristics and also the axial strain distribution. The accuracy of the perturbation solution is checked against a numerical solution of the governing equation.A set of experimental tests on two I-sections is carried out to verify the theoretical calculation. It is shown that the torque-rotation behaviour exhibits a hardening non-linear characteristic. The agreement between theory and test results is reasonable.