Geometric nonlinear analysis of asymmetric thin-walled beam-columns

The geometric nonlinear analysis of structures comprising members of asymmetric thin-walled open section is investigated. The geometric stiffness matrix for a thin-walled element is derived, incorporating second order nonlinear strain terms in the governing energy equations. The derived stiffness matrices are used to predict bifurcation loads of a number of structures. An updated Lagrangian formulation, coupled with the numerical arc-length technique, is employed to trace the non-linear load-deflection paths up to the maximum load. Numerical examples of the load-deflection behaviour of eccentrically loaded and restrained unequal angle beam-columns are presented.