INELASTIC TORSION OF STEEL I-BEAMS

A large twist rotation model for the nonlinear inelastic analysis of t he nonuniform torsion of I-section beams is presented in this paper. A finite-element procedure has been developed based on the model. The n onlinear equilibrium equations of beams in nonuniform torsion includin g the effect of the large twist rotation have been derived. The elasti c-plastic behavior of beams in nonuniform torsion is studied using the finite-element procedure and the results are compared with tests. It is found that I-section beams have much larger torsional capacities th an can be predicted by linear plastic collapse analysis, and that tors ional failure occurs not by the formation of a mechanism but by the te nsile rupture of the flanges. A method is proposed for calculating the full plastic nonuniform torque for practical design purposes.