LARGE DISPLACEMENT ELASTOPLASTIC ANALYSIS OF SPACE-TRUSSES

A formulation and a numerical solution procedure to perform the nonlinear analysis of imperfect space trusses is presented. The displacement method-based formulation is designed to model situations where physically and geometrically nonlinear effects are dominant in both pre- and post-collapse phases. The constitutive relations simulate local, elastoplastic buckling effects in thin-wall tubular members with initial geometric imperfections. The descriptions for the equilibrium and compatibility conditions are exact, valid for arbitrarily large displacements and deformations. Additional forces and deformations are used to preserve symmetry in the Lagrangian description of the governing system. Perturbation methods are adapted to the solution of the finite incremental problem. The external work rate is used as a step control variable. The numerical solution procedure is stable and capable of identifying and solving automatically the occurrence of critical points and the activation and deactivation of yield modes, while maximizing the step length in each increment.