Torsional collapse of thin-walled prismatic columns

Torsional collapse of thin-walled prismatic columns is studied analytically and numerically. Simple torsional collapse models are developed to predict the collapse behavior of square columns under large plastic rotation using energy method. By considering the combined effect of geometry and material, the onset of the sectional plastic buckling is predicted and the critical twisting rotation for sectional buckling is obtained. Next, an analytical expression is derived for the moment-rotation relation valid for rotation up to 180°. The analytical solution is shown to compare well with the numerical results. The solutions are then extended for rectangular and hexagonal thin-walled columns. Numerical simulations for rectangular and hexagonal columns are also carried out and the results are presented in this paper for the purpose of comparison.